[weapon]

This is the updated version with a little tweakage to the process...the original was done last year and things have been added and changed as needed.

For some time, I have been using 1971 Caprice heatercores when I wanted to use 2-4 120mm fans for some serious cooling power. The problems with that core (barbed fittings that are a royal pain to get out and odd shaped holes punched into the top tank) led me to search for a different core.

After scanning through tons of heatercore specs, I decided to give the heatercore for the 1977 Pontiac Bonneville (with a/c) a test run if the price was right. A quick call to autozone confirmed that it was a heatercore that they normally stock and with a great pricetag of $17.99 this one looked like a sure bet for replacing my caprice cores for future mods. (Note: AutoZone has since had an unusually high number of the b'ville cores with brass tanks instead of the copper ones - check all of your local auto stores for the best price and make them pull it out of the box before you buy it - the copper ones have a color much like that of a new penny - I will add pics and a better description of how to tell them apart a little later)

Quick run down of the specs:
10-3/4" X 5-5/8" X 2" w/o the tanks
about 12-1/2" X 5-5/8 X 2" with the tanks

To put the size into perspective, this is the '77 Bonneville core with two 120mm fans laying on top of it:

Almost perfect...

On to other good points of this core:
One of the best things about this core are the holes in the tanks for the fittings. They are not odd-shaped oval disasters like the ones that are punched into some cores. Instead, they are almost perfectly round and their size makes the switch over to barbed fittings much easier than you would expect.

Pic of the top tank with the factory tubes:

^nice round holes -- that are the same size.

As I mentioned earlier, the caprice cores that I had been using started causing problems as the tubes were barbed -- they are almost locked into the tanks and it is very hard to get them out without cutting, drilling and some torch work -- when they are gone, they leave nasty oval punchouts that are a PITA to seal up properly. Due to the barbs on the factory tubes, if you try to heat them up and yank them straight out, it will tear the brass on the tanks - another headache. I halfway expected the tubes on the '77 Bonneville to be barbed like those on the caprice cores but this is not the case -- a little torch work and some vise grips gets them right out.



^1st fitting came out cleanly with just a little solder residue left.
For those that have never taken a torch to one of the heatercores: you have to be careful with where you apply the heat. The top tank is held on with nothing but solder. If you overheat the tank, that sucker will come right off and it is very hard to get it back on without leaks.

To avoid overheating, I 1st filled the heatercore with cool water. Then I wrapped most of the top tank in soaking wet paper towels (check the above pic). Just to make sure I had everything covered, I then wrapped the core area with a insulating plumber's wrap -- several water soaked paper towels would work in place of the wrap. [This is overkill - if you are careful, filling the core with water is more than enough to protect the fins from the heat. Laying a few soaking wet paper towels on the top tank can help avoid some problems with leaks on the seams of the tank though]

Once you have the tank protected from excessive heat, apply heat with the torch directly to the tube where it enters the tank -- like this:

^If you look in the right hand side of the (fuzzy) pic, you can see vise grips locked onto the tube. Once the solder starts to melt, try moving the vise grips side to side a little - once all of the solder becomes liquid, a bit of side to side action and a straight pull with the vise grip will pull the tube out cleanly.

both tubes out with no problems:


On to the really nice bonus you get with this core -- the pre-drilled holes are perfect in size for a 3/8" -18 NPT tap. If you buy 3/8" NPT x 1/2" barbed fittings, this is a piece of cake. Just thread the existing holes like so:


Then screw in the barbed fittings. To make sure there are no leaks whatsoever, you can add some JB Weld to the threads and then let it dry or use the torch a little more and silver solder the fittings in place.

Before sealing the fittings in place it looks like this:


A tweak for better waterflow through the core:

If you look at the pic, you can see that the fittings are screwed in and they are ready to be soldered...but the ones that are in place have had the threaded section cut down (Dremel + high speed cutoff wheel) to prevent any flow restrictions.

On the far tank, one of the 3/8"npt x 1/2" barbed fittings in its original form is setting on top of the tank to demonstrate the possible problem -- when it is screwed all the way into the tank, it would be very close to the back wall of the tank -- in between the tanks you can see the section of thread that was cut off with the Dremel.

I just threaded the fittings in as far as they would go, marked em with a sharpie (sharpie mark still readily apparent on the threads of the fitting that is screwed into the 1st tank) and then cut them off leaving 3-4 full threads before the sharpie mark. That gives me a little more clearance and no concerns about overly restricting water flow.

To do this correctly, you have to screw the fittings into the tank and then mark them as each top tank is just a little different and that will change how much you have to cut off. If you cut the threads too short, you will have to run down to the auto parts store, buy some new ones and start over.

Tweakage for looks:
I cut 2 panels out of 22 gauge brass sheet and silver soldered them to the sides of the core - they are approximately 2" wide x 10.75" long. Once they were cut and propertly soldered to the core, I cleaned everything up and added primer and black paint to get this:

No more wavy sided look.

[weapon]

Pics of the finished '77 Bonneville core with the shroud I built and a couple of 120mm fans in place:



It has gaskets between the shroud and the core and gaskets between the fans and the shroud to make sure there is no air leakage. the gaskets are made from Vapco cork tape (basically the same stuff that chipcon calls "sealstring" in the prommie kits). Thin neoprene gaskets or the like also would have worked but i had a lot of cork tape left over from my last phase change build so I just used that.

It is fairly hard to tell in the pics, but the paint on the shroud and the core match up almost perfectly -- the angle makes them look like slightly different shades because of the metallic in the paint. When they are viewed from the same angle, they match.

[weapon]

Painting the core:

1. Scrub down the sides, the top tank and the bottom tank with cast aluminum wheel cleaner (basically acid) and a brass brush - rinse it off with lots of water and let it dry.
2. Lightly rough the sides and tanks with 400 grit wet/dry paper, once again, rinse with lots of water and dry off with lint free paper towels or terry cloth.
3. 2 mist coats of Duplicolor adhesion promoter as per can instuctions.
4. 2 coats of Duplicolor Hi-Build sandable primer, lightly sand between coats with 400 grit wet - if you sand thru the primer and hit metal, add another primer coat.
5. 2 coats Duplicolor Primer Sealer
6. 2-4 coats of Duplicolor Enamel paint
7. 2 coats Duplicolor clearcoat.

Let dry for about 5 days minimum if you go with the above painting scheme - putting it in out in direct sun light for a day or two will help speed up the drying. Just make sure you bring it in before it gets dark outside or the paint will likely get cloudy.

Another way to speed up the process.
1. steps 1-4 as above.
2. skip step 5 from above.
3. 2 coats of Duplicolor Truck and Van paint in whatever color you like.
4. 2 clear coats.

Bake the core in an oven at 125 deg F for 1-2 days.

[weapon]

When you go to get the heatercore, make them pull it out of the box before you buy it. If you have already bought it and it is the wrong one, see if they will exchange it as most of the brass tanked cores are much more difficult to mod correctly.

How to tell the right one from the wrong one?
check the pic:


Both heatercores are for the same model - the '77 Bonneville with a/c.
The one on the left is clearly brass-sided with brass tanks where the one on the right has copper sides and tanks. I slipped up once and didnt check and that is how the brass one wound up in my collection.

Other ways to tell them apart -
The copper cores usually have the extra ridge that runs down the side of the core where the brass ones just have the flat ridges running side-to-side on the side panels.

The bottom tank on the copper core is usually a bit flatter and wider than the bottom tank on the brass core. The brass cores usually have a bottom tank that has a rectangular block like section on the bottom tank (check the pic). The copper tanks often have a much more rounded center section on the tank.

Both cores had the same markings on the box so definitely make them break open the box and check the core before you buy it. The tubes on the brass-sided ones I have seen are not as easy to mod as the copper ones. If there is an Advance auto store near you, check there - I haven't seen any of the brass sided ones from Advance as of yet.

My Nikon is temporarily out of service or I would have the shroud building section of this finished. The part to get the Nikon back in action should be here with in a week -- so the shroud building section is coming soon.

Side note: a properly built shroud adds more than a 40% increase in the cooling ability of a heatercore.

[weapon]

Originally Posted by Bad_CEKTOP

Nice, I've seen this over at xtremesystems, the 77 Bonneville cores are $50 CDN here in Canada, when I get the chance to swing by a store I'm gonna pick one up.

Great guide.

Thanks.

The other versions of this thread have gotten fairly messy over time so I thought it would be a good idea to consolidate it into one neat post that didn't require reading 4-5 pages to get all of the info. That and I updated the info as needed.

More info:
Soldering in the fittings. The solder used can make this process fairly simple or a pain in the arse. AutoZone carries an acid core solder that is great for heatcores. It is about $5 and it melts at a fairly low temp so you don't have to get the top tank super-hot to properly solder and seal the new fittings.

I normally use a bit more expensive version of silver solder for all the soldering I do but it is pretty much overkill for a heatercore. If anyone is interested in overkill, get Harris StayBrite8 and use it with Harris StayClean flux. It becomes liquid at 535F and it rated for around 11,000psi shear strength and 15,000psi on joints.

Torch for the heatercore mod:
Just about any propane torch will work. I used one of the Berzomatic torches that comes in the Plumber's Kit from WalMart for the first core I modded. That kit is still available with the same torch and it is around $20 with a tank of propane included.

Since then, I started using a BerzoMatic TS4000 torch and that is the one in the pics. It burns a bit hotter than the regular propane torch so it gets the job done a little more quickly. It will also work with MAPP gas so it occasionally gets put to use when I am building waterblocks or phase change evaporators.
pic of some serious heat:


pic of another modded '77 bonneville core in my bro's two room H2O system:

[Bad_CEKTOP]

I deleted my post so it wouldn't split yours up
Thought's I'd get away with a repost later but you caught me.

[thorilan]

quick question for ya. do you think you could convert it to single pass if you got more than 1 chamber for the top half and modded it. maybe even make it like a spilt loopso 2 in 2 out ?

oh and great work btw

[weapon]

Originally Posted by Bad_CEKTOP

I deleted my post so it wouldn't split yours up
Thought's I'd get away with a repost later but you caught me.

Originally Posted by thorilan

quick question for ya. do you think you could convert it to single pass if you got more than 1 chamber for the top half and modded it. maybe even make it like a spilt loopso 2 in 2 out ?

oh and great work btw

I have converted a couple of them - the first one I did the easy way -I just added a center-mounted exit fitting on the bottom tank. So that one had two inlets and one outlet. Surprisingly enough, that didn't really screw up the flow thru the core.

I recently got a hold of another core that is pretty much screwed for all practical purposes (fin damage) but the tanks are fine. So, I plan on using the tanks off of that one to make one core that is dual-chamber, single-pass and then I will use the bottom tank with another core to make one that is single-channel, single-pass. Basically, I am just going to switch the tanks so each core with have the same tank on top and bottom, then I'll mod the fittings as required.

It can't be any harder than brazing two '77 bonneville cores together like I did to make the monster-core:

that was about a 9.8 on the pain-in-the-arse scale....nothing quite like a core that will take eight 120mm fans though.

[pelikan]

Excellent guide. Well written, clear and thorough.

[weapon]

Originally Posted by pelikan

Excellent guide. Well written, clear and thorough.

thanks.

Heat exchangers for watercooling have become a minor obsession for me.
I still pick up a different core or other rad now and then just to see what mods can be done to any particular model. Between core modding and building phase change, I manage to burn a good deal of time but it is always worth it - just when I think I have squeezed all I can get out of a core a new mod pops up that increases the performance. The heatercore mod for the '77 bonneville is the end result of a lot of tweaking and testing of different cores and as far as I can tell, it by far and away produces the most bang for the buck.

I have tested the '77 bonneville with various mods and shroud designs against most of the major commercial rads and it eats their lunch for a good deal less money. Besides, there is always a certain satisfaction in coming up with something yourself.

edit: there is a new core I am playing with that is just a little smaller than the '77 b'ville core that looks like it will perform within .5 C or so. It might even match it on most systems. More info on this one after I test it a bit more.

I will continue to build on this thread with the performance info gained from my modding exploits. Right now, it is just about the best, if not the best, heat exchanger you could ask for in a straight H2O loop -- but I think I can still make it a little better.

shroud building and flow mod info will becoming as soon as I finish it and get some solid test results.

sneak peak at the shroud:

that was a few hours on the CAD proggie...the results are better than I could have hoped for though.

[slater3333uk]

Ive seen this somewhere before. Have you posted this guide on another forums?

Why do you think a copper core is better? Brass is much easyer to work with and brass cores still have copper finns so cooling ability is uneffected?

How did you braze the cores together without the solder melting and the core totaly disintigrating? i guss you must mean solder

Nice guide

slater..

[weapon]

Originally Posted by slater3333uk

Ive seen this somewhere before. Have you posted this guide on another forums?

Why do you think a copper core is better? Brass is much easyer to work with and brass cores still have copper finns so cooling ability is uneffected?

How did you braze the cores together without the solder melting and the core totaly disintigrating? i guss you must mean solder

Nice guide

slater..

there were various versions of this up in several forums - well, most of it anyway....some of the stuff in this thread is new.

The primary reason I suggest going with the copper core over the brass core involves the tubes on most of the brass tanked bonneville cores I have seen. They use a different method to lock the tubes into the top tank on the brass versions and it is really difficult to get them out without damaging the tanks. They are pretty much locked into the tank with a bit of a crimp and a barb - the last one I ran into like that took the torch, a dremel, a tubing cutter and a drill just to get the factory tubes out. If it weren't for that, I wouldn't have a problem with them.

the monster core...nope - I meant brazed That took alot of water, a good deal of heatsink paste and some very careful fluxing and heating. I built a jig of sorts to hold both cores in the right alignment out of weld steel and then I clamped everything in place and did the seam in 1/2" sections with safety-silv 45 and staysilv flux (2 more of my favorite products from Harris ) Once I had a solid attachment between the cores, I switched to staybrite 8 and resoldered the seams on the fins. Royal PITA material but it is leak-free.

[ukdan]

nice guide, just one tip, when cutting the thread for the barbs, coat the tap with grease so that most of the swarf sticks to the tap and doesn't go into the core itself.

[Xplos!ve]

what temps are you getting with that huge 8 fan thing?? <-watercooling newb

[BlueMan]

Weapon - have you ever tested/tweaked a Fedco 2-342 (GDI 399090)?

[weapon]

Originally Posted by ukdan

nice guide, just one tip, when cutting the thread for the barbs, coat the tap with grease so that most of the swarf sticks to the tap and doesn't go into the core itself.

that's a good idea - I usually just flip the core over and blast it out with water after I'm done with it. seems to have the same end result. anyway, there usually isn't a whole lot of shavings left after the tapping as the holes are slightly larger than 9/16" which is the size normally used with a 3/8" NPT tap.

Originally Posted by BlueMan

Weapon - have you ever tested/tweaked a Fedco 2-342 (GDI 399090)?

I have one from a '70 on my bench right now. I am working on fittings that will get a little more flow out of it (hopefully). I also have one from another year model of bonneville that I am modding (a little smaller than the '77 b'ville but it will still take dual 120mm fans). As soon as I get all of them modded and shrouded, I plan to plug 'em into my current system to see how they compare to the latest version of the '77 bonneville core.

[@/2ct!<]

bah, hurry up lol I want to know which one, I hear great things about both.

[BlueMan]

Just so you know, weapon, I was able to attach my tubing to the pipes on the 2-342 without any kind of barbs - just boil the tubes and stretch them over. I imagine you can't get better flow than that!

[weapon]

well, there is one thing I don't like about the Fedco 2-342 (GDI 399090) - it has oval shaped punch outs for the tanks. That isn't that big of a deal to fix as I came up with a solution for that in the past. Anyone else's 2-342 have round holes where the tube enters the tank or are they all sporting the oval ones??

why fix it as opposed to just cutting off the pipes?
They pinch the inlet and outlet down to a narrow channel on both the inlet and outlet. If my damn nikon wasn't temporarily out of service, I'd post pics of the tank with the tubes removed so you could see the shape of the tubes where they enter the tanks - a little weapon moddage will get the flow on this one up a bit. I might have to do a brief how-to on modding this sucker.

anyway, I am going to put together a plexi shroud for it tonite and finish the inlet and outlet mods. I'll post pics when I get my nikon up and running.

EDIT: an old and somewhat crappy drill bit (9/16" honkin' bit) decided it had enough of my nonsense and broke at the shaft mid-core mod. Needless to say, scratch one Fedco 2-342. On the bright side, I will have some really cool pics of the guts of a heatercore when the nikon gets back in action as I went ahead and dissected this one with the dremel armed with a fiber reinforced cutoff wheel -- the number of layers of copper that are packed between the flow channels in these things is downright amazing. I'm still fairly shocked the bit snapped -- it must have already had a crack in it from drilling tops for waterblocks as there is no way the thin metal in a heatercore tank should have even slightly phased it.

of course, that bit was older than dust...

Anyway, I promptly called the local auto stores and found another 2-342 and it has been modded with 1/2" female theaded fittings (even if it ended up being a 40 minute round trip to get the core). After the slight setback, I only managed to get the top plate for the shroud cut but it is ready to have the side panels added. I cheated and used plexi b/c it is quicker and easier than the metal route. I am trying to decide if I am going to be lazy and just make a box style shroud or a nice, highspeed venturi design. Leaning towards the venturi at the moment.

side note: if you plan on having the shroud on the same side and the inlet and outlet on the 2-342, you will be a little cramped for space - the core area is 240mm long --- a dig thru my 120mm fan collection turned up 2 that are 238mm when stacked back-to-back. That doesn't leave much room for error as you only have about 1mm on either side of the fan cutouts. The inlet and outlet tubes are packed in there fairly tightly as well (especially if you add 1/2" threaded female fittings). If you mount the shroud on the opposite side, it would be much easier.

[Bad_CEKTOP]

weapon, have you tried fitting the 77 B-ville core into a 5 1/2 bay? My bays are all railed and are 6" wide with about 1/8 inch internal indents for rails on each side. Just wondering how much clearance there will be, you have it down as 5 5/8.

[weapon]

without a shroud a '77 b'ville core should fit in a 5 1/4" bay.

quick comparison -
a TDK burner I have sitting here is right at 205mm long x 147mm wide x 43mm thick -- this drive has a little bit of play in the fit in most cases. Anyway, the length usually isn't an issue unless you have a very tiny case so let's narrow it down to the width and depth. The bare '77 b'ville core I have handy is right at 144mm wide and 50mm thick. So, will it fit? It's hard to say - in my experience, there is always some dimensional differences in the sizes of 5.25" bays based on who made the case. If the top 5.25 bay in your case is like those in a lot of cases, it will have a bottom rail to support a 5.25" device but there isn't a top rail -- most of them just open up to the top of the case and rely on screws to hold the top device in that slot. Check your case to see if it is made like that - if it is, you should have plenty of clearance for the b'ville core. Then all you have to do it figure out how much room you have for the fans and if an extremely thin shroud would fit in there or if there is some other logical way to get a decent amount of airflow thru the core.

got any pics of the case?

[Bad_CEKTOP]

It's the CM Stacker. The bays are larger than normal, I couldn't mount my fan controller with regular screws because of this. The width of the bay is 151mm, not sure if 7mm will be enough because of the rail holders. I was hoping to fit 4x120mm in push/pull in there. hmmm.... I think I can take it back if it doesn't fit anyway, it's just an auto part.

[Silver]

Good seeing you again. Shelved the phase for now and have just about got the box built on a dual 77 core. Am looking to keep the rad out temps under 22c at exit of second rad. Going with 5 ys tech 120x38s as on the box they are pretty quite and unobtrusive. Rheo, psu and temp guages to be moved into the new box. Idling right now w/1.7v at 3700mhz, in temp 22.6 out temp 21.9 (2.8c).

[Rpkole]

Very good guide only prob i had was i filled the heater core all the way up before i put the heat to it and the steam kept putting out my flame :-p but other than that it went great

[weapon]

Originally Posted by Silver

Good seeing you again. Shelved the phase for now and have just about got the box built on a dual 77 core. Am looking to keep the rad out temps under 22c at exit of second rad. Going with 5 ys tech 120x38s as on the box they are pretty quite and unobtrusive. Rheo, psu and temp guages to be moved into the new box. Idling right now w/1.7v at 3700mhz, in temp 22.6 out temp 21.9 (2.8c).

sup silver? I just caught your PM over at xtreme - lol. this is an interesting cross-forum communication pattern we have developed. I think it now runs across about 5 threads and 3 different PM boxes.

I'm still working on the 2-342 core - I killed my dremel (again) and ran out of time tonight or it would already be in the testing phase. Also, I'm waiting on a wye fitting and some new thermisters so I can test out dual '77 cores in parallel. The monstercore is still in a holding pattern as I once again got diverted by another project -and I then went back and modded it a bit more. I will get it hooked up and tested before long though.

EDIT: progress
The shroud (while not exactly pleasing to the eye) is now mounted on the 2-342 heatercore with dual 120s and its pretty much ready to go. I just cranked out (well torched out) some new inline temp sensors that should have zero affect on flow levels but read the water temps right before and after the heatercore. I also added threaded fittings to the end so I can swap out the size of the brass barb that is plugged into it if I need to and they should allow fairly quick swap outs between the different heatercores for testing. Since I have a modded Caprice core here I think I will throw it into the mix with the '70 chevy truck single pass (aka 2-342) and the '77 bonneville (aka 2-302) I can post info on how I made the inline temp sensors if anyone is interested.

Also, I got my other thermisters lined out so I should be able to get accurate readings from the air going into and coming out of the core as well as ambient temps, etc. Now that I have all this stuff correctly setup, I have to let it set here and collect dust as I have to go to work. damn, I hate when that happens.

[pelikan]

I'm interested in how you made the water temp sensors. Thanks.

[Silver]

Yeh, post it for me as well. I am using the sensors on the vinyl lines with closed cell encompassing it. I am particularly interested in the monster rad. A possible solution that I have at least entertained. I presently have 6 of the ys techs (120x38) available for use on rheostat. Now the present setup using two of these fans on a box with one rad allows for a piece of paper (normal full sheet) to be pulled to the rad with a mighty slap. I believe I am approaching max air flow with these fans. I then placed this paper over the rad and of course you can hear the fans pull down. As I pulled the paper to the side of the rail, the fans picked up again about an inch and a half from the edge of the rad. This would indicate to me that I can do with another 10 percent or so of air flow. I will go with 5 of these fans on the new box with the duals I think. This would give a max theoretical flow of 625 cfm in free air.

[weapon]

getting an inline temp sensor into the loop - a how-to within a how-to thread.

the stuff I used -
--a small section of 1/2" ID copper pipe (available at almost any hardware store) - for setting up one inline sensor, you only need a piece about 2" to 3" long
--a 3/4" to 1" long piece of 1/4" OD copper tubing - the piece I used was from a hookup kit for an ice maker but it is also used in refrigeration. This is also available at lowes, home depot, etc. - The OD of the tubing I used was 1/4" but the ID is what is important. The ID should be just large enough to where you don't have to force the thermister through it.
--plumber's goop, jb weld or any type of good epoxy
--2" section of heatshrink tubing that will slide over 1/4" OD copper tubing
--prewired thermister or you can run to radio hack and wire up one.

in the tools department:
power drill with a 1/4" drill bit
dremel with cutoff wheel or copper tubing cutter
a sheet of 400 grit 3M wet/dry
cheapie propane torch from a plumber's kit at walmart (alternate route using JB Weld for the torchless masses )
acid core solder from autozone or wherever you can find it
lighter or match (using the propane torch on heat shrink tubing is an amusing way to waste your time but it rarely results in anything other than a small charred piece of material that was once heatshrink tubing)
6 pack of beer (not optional so quit thinking it might be )

on to the pics -
the primary components:
http://pages.suddenlink.net/weapon/images/itmp1.jpg

a pic of the thermister inserted thru the 1/4" OD copper tubing
http://pages.suddenlink.net/weapon/images/itmp2.jpg
when you position it for mounting in the tube, only the white tip on the end of the thermister should be sticking out of that section of copper tubing.

prep steps - coat the tip of the thermister with a thin coat of clear epoxy or a couple of coats of clear nail polish - the thermisters I used already had a decent coating on them from the factory but it never hurts to be sure.
- use the 400 grit sand paper to smooth out the ends of the 1/4" OD section of copper tubing and the ends on the 1/2" ID section of copper pipe.

the next steps are so basic that I didn't think pics would be required but I will add some in here just in case my ramblings are less than clear:
1. Take the section of 1/2" ID copper pipe and drill a 1/4" hole in the very center of the tube.
2. Insert the 1/4" OD piece of tubing into the hole so that when viewed from the inside of the 1/2" pipe, it is flush with the inner wall of the pipe surrounding the hole (pic of how this should look shortly)
3. Either fire up the torch and use the acid core solder to solder the 1/4" piece of tubing in place and then let it cool down to room temp or glob on the JB weld and let it dry overnight.
4. Coat the thermister (except for the white tip) with plumbers goop or jb weld from the blue area near the tip of the thermister all the way up the thermister wires (I ended up coating about a 1" section up the wires).
5. Insert the thermister thru the 1/4" copper tube until the just the very tip is poking into the inside of the 1/2" ID copper pipe. Then force some more JB weld or Goop in around the wires as needed to entirely plug up the 1/4" tube. Prop it place somewhere and let that dry. Now, drink the 6 pack of beer as you will have nothing better to do for a few minutes and we're through playing with power tools and torches.
EDIT: DO NOT use regular silicone for filling up and sealing the inside of the small copper tube that contains the thermister wires - I just tested another one that used silicone instead of an epoxy or goop and it isn't strong enough to hold - well - it isn't strong enough when you are using a pump that is rated for 1140pgh at least. On the other hand, since goop or JB weld is strong enough for the flow and head of my RLQO pump, unless you are using something with more head and flow, you should be plenty safe with either.
--Also, one slight tweak to the process - after you have slipped the thermister in thru the 1/4' OD copper tube and you have added the goop or the epoxy you can take a pair of pliers and lightly crimp the top of the 1/4" OD copper tube to where it is not quite touching the wires running thru the channel. After the goop or the epoxy has dried, it will be pretty much locked into place as the crimp on the end will be much smaller than the diameter of the goop/epoxy plug that is in the copper tube.
6. slip the heatshrink down the wires and over the 1/4" copper tube section - the heatshrink should be a few millimeters longer than the section of 1/4" copper tubing - it will provide some support for the wires so they don't get roughed up by the edges of the copper tubing.

1/2" ID tygon or clearflex will fit over the ends of the 1/2" ID copper pipe with a little effort. If you want an inline sensor that is a little more user-friendly when it comes to getting your tygon or clearflex onto it or that will allow you to switch out barbed fittings, you can get copper pipe fittings at lowe's that are 1/2" ID copper pipe on one side and 1/2" NPT female thread or 3/8" NPT thread on the other. These have to be soldered onto the 1/2" ID copper pipe or JB Welded in place with a nice thick layer so they should be added immediately after step 3 above.

On to the pics with a little explantion to tie them into the text instructions:
This pic shows how the 1/4" OD copper tubing is attached to the 1/2"ID copper pipe:
http://pages.suddenlink.net/weapon/images/itmp3.jpg
^as you can see in the pic, I had already ran the thermister thru the copper tube and gooped it and the wires. The ridge around the base of the 1/4" copper tube is a solder bead.

This one shows the inside of the 1/2" ID copper pipe and how far the 1/4" copper tube should protrude into the flow channel. While the lighting isn't spectacular by any means, you can also make out the outline of the tip of the thermister and you can see the rounded area beneath it from the sealant I coated it with before I ran it thru the 1/4" tube.
http://pages.suddenlink.net/weapon/images/itmp4.jpg

pic showing how it looks after the heatshrink is added over the 1/4" tube to support the wires from the thermister:
http://pages.suddenlink.net/weapon/images/itmp5.jpg

pic showing a 1/2" ID x 1/2" NPT threaded female fitting (mentioned above) with a 1/2" NPT brass barb next to the bare 1/2" ID pipe version of the inline sensor:
http://pages.suddenlink.net/weapon/images/itmp6.jpg

If your system is in an exceptionally hot or cold room, you can insulate the copper pipe with standard 1/2" foam pipe insulation (lowes or home depot) to make sure the sensor is not thrown off by the effects of external air temp on the copper housing of the sensor.

This setup places the tip of the thermister in direct contact with the water running thru the loop so it should provide accurate temp readings when the thermister is plugged into any decent temp monitoring device. With a nice bay mounted temp unit, you can check your water temps with quick glace at the front of your system.

Note on size: The bare 1/2" copper pipe versions can be scaled down to where they are less than 2" long - all you really need is enough space to insert the 1/4" copper tube + enough space on each end to clamp down your clearflex/tygon/vinyl tubing. the bare pipe version also has the advantage of being extremely light weight so you can add them just about anywhere in the cooling loop. If you are worried about them shorting something out if you move your tubing around, after your tubing is clamped to them, you can coat the copper areas with liquid electric tape (also available at lowes, home depot, autozone, etc.)

[arabarabian]

That was a very well writen, concise article. I found it to be very enlightening. I am trying to put together a good cooling solution for a dual Opteron system that is pretty silent so you just hit a bulls eye with that one.

[Neco]

Jesus, who needs 8 fans when the core is that big ? haha

Ever test it passively ?