Vacuum Sealing T-line (on inlet)?

Ok, a bit of a catchy title. But I couldn't think to call it anything else.

I was able to bleed my system in about 30 minutes with my setup (thread is here: http://www.ocforums.com/showthread.php?t=345384).

You'll note that the T is "before" the pump. I explain the reasoning for that in that thread (never heard of bleeding "after" pumps, in all other liquid systems it's "before" the pump. that doesn't make sense to me when someone here says after).


What I'd like to ask is: Did anyone else notice the amount of vacuum/section the D4 pump (or alike pump) does when used in this fashion (on the inlet, not the outlet)?

With the T-line full and open/vented to atmosphere, when I flip the pump on it draws the fluid level down about 5"! That's 5" of 1/2" ID tubing. Now some might say that's an idea of the restriction I have in the system. But with the very large 120x3 radiator and using the largest-nozzle in the TDX plate, I don't see restriction getting any more then any one else out there (at present).

Now something I noticed: When you kick the pump on, there's a small delay before it gets going (about a 1/2 second to a 2nd). Even with the system fully bled.

I removed this delay, and squeezed in even more fluid, by:

1) bleeding the system completely

2) venting the t-line to atmosphere

3) turning the pump on, letting it suck down the fluid in the t-line

4) filling the t-line to the max, while pump is on and fluid is sucked down

5) Sealing the T-line up. I do this with a plug like this:




This causes a slight amount pressure in the system when turned off. I'm not sure of the adverse effects from this, but the fact of using a t-line on the inlet side of the pump to create this seems ideal to me to keep air out of the system for some time.

What do you guys think? I'll let you know the long term effects in a few months.

I do the same thing with no adverse affects, I don't see nearly 5" with a mag3 though.


by the way, why are you under the impression that everyone puts the t-line or resevoir someplace other than the pump inlet? we know that it's much more convienient to have it right before the inlet to assist in filling.

crimedog said:

I do the same thing with no adverse affects, I don't see nearly 5" with a mag3 though.


by the way, why are you under the impression that everyone puts the t-line or resevoir someplace other than the pump inlet? we know that it's much more convienient to have it right before the inlet to assist in filling.

Click to expand...

Ah. In my research, I ran across two setups and people giving advice such as "Make sure to place it on the onlet of the pump". So I took it as advice across all water setups.

That makes more sense, as I did see a few setups with the same D4 pump I have on the inlet. But only saw the post(s) giving advice for the outlet. Ah, so it was just "those" rouge posts.

What I'd like to ask is: Did anyone else notice the amount of vacuum/section the D4 pump (or alike pump) does when used in this fashion (on the inlet, not the outlet)?

Click to expand...

The waterlevel in my T-line drops ~1.5cm when i turn on my D4.

Interesting... your water level sure drops a lot when you turn the pump on. I happen to have my T-line between my core and block and I observed the reverse effect; when ON the water level rises a little bit--about 1 cm max. I've sealed my T-line with the system off, so that it is pressurized when on.

Haven't noticed any drawbacks from the position of the T-line, by the way.

My D4 has a T-line before the pump, and coolant levels barely drop at all when I turn the pump on. If your system is properly bled, it would seem to me like your coolant levels should not drop at all; because there is no place in your loop for more coolant to go, and liquids do not compress any significant amount even at high pressure. I imagine that if your T-line is after your pump, you might be able to get coolant to overflow when the pump turns on; but that's speculation on my part.

I also always seal my system with negative pressure. That way if I have a leak, air will leak into the loop, rather then coolant leak out. I also like to give room for thermal expansion of the coolant, something I've found can be quite significant (I've seen my coolant levels rise 2+ inches at high coolant temps with an unsealed loop).

Edit: grammar

How do you get negative pressure into the loop? squeez a tube before capping?

I'm wondering the same thing. Its closer to nominal-pressure-sealing the tee line. If you fill the tee line w/o the pump on and cap it, its at normal outisde pressure when its off, then at negative when it sucks the water down. In this instance, you're just allowing it to remain at [close to] normal pressure when operating, and at possitive pressure when it's off.

I would surmise that it'd be best to run at negative pressure when bleeding (cap w/pump off) since the negative pressure should allow the air form bubbles easier, then operate at nominal pressure (cap w/pump on) to prevent disolved air from coming out of solution.

I turn my radiator fan off and let my processor temp rise as high as I feel comfortable, then squeeze a tube and cap it. Then I turn the radiator back on, the coolant cools off and contracts and I get negative pressure

not sure if this is 100% correct, but i was thinking about this yesterday. the loop is pressurized (by the pump obviously,) and when something is put under pressure it's volume decreases. t-line level going up and down is more than likely an effect of a high pressure loop.

crimedog said:

not sure if this is 100% correct, but i was thinking about this yesterday. the loop is pressurized (by the pump obviously,) and when something is put under pressure it's volume decreases. t-line level going up and down is more than likely an effect of a high pressure loop.

Click to expand...

Possible, but liquids don't compress that much. However, eduncan has a LOT more tubing then I do, and after doing some tests, I get a half inch drop in my coolant level. So its possible that the large fluctuation is a result of lots of tubing.

EDIT

Also this means more fluid to move, and that means more work for the pump. This is probably why your pump takes time to get up to speed (mine starts instantly.)