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Relieve Pressure

Posted: Fri Jul 28, 2006 6:42 am
by sfyamr1
Hi, everyone! When I replaced my expansion tank for the fifth time in nearly as many months 3 years ago, I realized that the biggest problem seemed to come from pressure. The old one, albeit one of those crap aftermarket plastic jobbies, was simply bursting and swelling from pressure and heat.

So, it dawned on me that if there were a way to relieve the pressure without risking any spray-out, it just might help the new one last a little longer than 3 months!

My answer? I broke out the drill (always a good start ;-) )and drilled two small relief holes right through the rubber gasket and metal retainer of my cap. The hole is small enough that the rubber recovers enough to eliminate any spray, but the holes let out enough air to keep pressure from trying to detonate the tank.

The results? Unbelievable. Over three years on and it looks like new. No kidding! I can't believe it, either. I have experienced absolutely no cooling problems whatsoever (live in LA, where it's routinely 90+), and no drips, or leaks at all.

It's worth a try, before you spend a chunk of $$ on a metal one.

I can take pics, if anyone wants to see what I did.

Posted: Thu Aug 03, 2006 4:48 am
by Keith
You need the pressure in the system to raise the boiling point of the coolant. Drilling a hole to reduce this pressure is not a good idea as the tank is part of the pressurized system. It may have worked for you, but I wouldnt recommend anyone trying this.

Posted: Thu Aug 03, 2006 6:42 am
by x-rad
It would probably be better if you had somehow weakened the pressure relief spring in the cap(slightly better control than two holes).......

As stated above, decrease in pressure equalls decrease in boiling point. So at sea level (1atm), pure water boils at ~100C. If you are using pure ethylene glycol, ~200C. Under containment, you can raise the boiling point and increase the heat capacity of the fluid producing better engine cooling(as long as you can also remove the heat from the fluid).

I always use 'pure'(which of course is not 'pure') antifreeze and my temps stay about 180C. As a side note, I used to drive a turbo car with no thermostat. Improved cooling and flow, but you had to wait a little for everything to warm up....

Sfyamr: I would like to see the pics....

I had a friend who used to solve his problems with a drill and sabersaw...until he tried to put speakers into the metal deck behind the headrests of a TR7 and found the gas tank....

Posted: Sat Oct 28, 2006 6:04 am
by constantinemacris
can we still order tanks

Posted: Sat Oct 28, 2006 8:14 am
by Sporttunergtv6
iap sells them.

Posted: Sat Jan 20, 2007 1:49 am
by Alfettish
Can we still buy these expansion tanks?

Posted: Sat Jan 20, 2007 4:28 pm
by tImBoWe

Re: GTV6 expansion tanks by Canton Racing Products.

Posted: Thu Jun 18, 2020 5:53 am
June 2020

There is a group buy for these tanks, now made by Moroso, going on at

See this link: ... 16.695668/