How to Give a Waterblock a Brain (Cap) Transplant

Detailed How-To for waterblock soldering – Owen Stevens

Many of you may remember my second article on a home made spiral waterblock ,Tales of a ‘Shade Tree’ Machinist Revisited – My Homemade Water Block Mark II.

Well I was looking for a way to improve on my second generation spiral waterblock and I started thinking about the internal features that might help the flow ‘turbulence’ or mixing. I theorized that a few strategically placed surface imperfections might be able to improve the performance. I recalled seeing a water-water heat exchanger on a web site that touted its internal ‘herring bone’ surface as a great benefit to its performance.

I decided that I wanted to make a new waterblock!

I started to get a material list together and so on, but being as it was getting close to the holidays and had just spent $100 on a new GeForce 4 Ti 4200 video card, I was a bit short on hobby funds. Then the idea struck me – why not take apart my old spiral waterblock and use it. I actually had some ‘spare’ ¼” copper plate that would work just fine – I was in business!


Here’s the original waterblock before surgery. A wimpy little cap and tiny 3/8″ fittings – not for long. <<Insert Maniacal Laugh, ha ha ha!>>

PII Case Diagram

My first step was to remove the hose barbs for a little inspection. Nope, not shiny new copper any more.


Man those were some short threads in the original 1/8″ copper top! Maybe 2 and a half turns, yikes! This block definitely needs some help.


Prepped and up and ready for surgery. Hold still, will yah! This won’t hurt a bit!


Well, a butane scalpel can be a bit hot I suppose…


Ah, the solder is starting to melt and flow.


On the verge of letting go… see how the base is twisting.



Note: This is very, very hot, so make sure you have the proper safety gear: Heavy leather gloves, eye protection, and a leather apron is good too.


Well, our patient has been successfully ‘parted’ from its old head. Notice how I caught it in a bucket of water – I’m good! Or actually, it just happened to fall right into it – did I say I’m lucky too!


Here’s the old top – notice the residual solder spiral from the original assembly. And of course, the corrosion in the former channel.


Now the part we want is the old base. It needs a bit of clean up though, lots of black corrosion/oxidation.


A close up shot of the channels.


Now I want to make this the new top and create a new base, so I transferred the spiral to a piece of graph paper and taped it to my copper base stock.


And I started drilling little ‘dimples’ to disrupt the flow. Remember to always drill between the lines.


Further along the spiral. Man, this is a time consuming process!


Ah, finally done drilling happily along the path. I used a smaller bit in the center to try for a bit more ridges.

More Drilling

Next I needed to drill the inlet and outlet holes. Nurse, prep the patient.


You might feel a little ‘pressure’. I drilled with a wood backing block, that’s where the wood chips come from. It’s a good idea to have a backing block if you don’t like holes in you cross vise base.


The holes are now tapped for the threaded hose barbs.



Now assembly – first you clean the surfaces – OK, I didn’t clean the channel that well, so sue me – I’ve got malpractice insurance right?


Here is how the base and top align. Note the dimples are at the inlet.


Next smear a lot of paste flux on the base and top.


The solder I use is silver based, which is good, but it also melts at a higher temperature than more tin based solders, which takes some getting used to – ie it takes longer to get the block hot enough to melt it. (Didn’t I say in my last article that I was going to buy an oxy-acetylene torch,? Oh well, maybe Santa will bring one!)


Here the bits are clamped and beginning to heat up.

Clamp 2

The trick to soldering copper is to get it hot BEFORE you touch it with the solder… so hot that the solder melts when it touches the copper. That way, it ‘flows’ into the fluxed joint. Notice that I put the solder on the top and it is flowing down inside the block edge.


Now fully soldered, our transplant is almost complete. A little air cooling post-op is recommended before handling or inserting fittings.



Here it is sawed to size and cleaned up with my latest find inserted – ¼” pipe thread by ½” hose barb nylon fittings! I pay less than a dollar a piece for these at a Marine supply store! Yes, yes, it is a bit ‘rough’ on the one edge, but I’m not about looks – it’s what’s inside that counts! (Oh yeah, the inside was pretty filthy too…)


The base lapped as much as my patience would allow that day. (Hey I made a joke! Get it – Dr.’s patients vs. my lack of patience…)


I am hoping that the thicker ¼” base will help to ‘smooth out’ the temperature profile in the base.


And here it is – the finished product installed and ready to be ‘plumbed in’.

A new block is born from the remnants of an old one. In use, it seemed to cool just as well as my Multi-hole waterblock – 24C room, 26C water, read by an indoor (room) outdoor (water) thermometer, 28C CPU at load, read by internal diode reader (thanks Hoot!). C/W = very low but hard to determine. If pressed I would say 62.8W for my XP 1600+ at load which leads to a C/W of a ridiculous .06 (BillA don’t even start :).

Well I hope you enjoyed my little ‘operation’ – I know I did!


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