OK everyone and anyone who can help - my turbo GSR is giving me all hell when it comes to keeping cool for more than about 20 min of driving.

I decided I had a blown headgasket initially (MONTHS ago); replaced HG. When head was off I checked for cracks and warps and everything seemed fine and dandy. Before this I couldn't drive 5 minutes - after HG replaced it was as it is now... fine if I baby it, but if I try to pass or accelerate or anything silly like and drive for more than 20-25 min then it starts overheating.

I've tried:

new thermostats (2 or 3 - currently Jackson Racing 160F)

drilled 6 x 3/16" holes in thermostat

new radiator caps (3)

redline water wetter w/ all distilled and with 50% coolant

checked water pump - was replaced about 12000 miles ago and is in perfect condition

pressure tested radiator; no leaks

In any case when the car starts heating up, running the heater full blast keeps her cool even if I drive pretty hard.

I still kind of suspect a warped cyl head is allowing the HG to leak but perhaps less than before; the only check for this I've heard is to run the engine with the rad cap off. Before I replaced the HG I could see bubbles coming up the filler neck when I did this. Now I don't see the bubbles but the coolant DOES gradually overflow the filler neck if I idle it without the cap on.

One question I don't know the real answer to: does coolant ENTER the radiator through the UPPER hose or the lower hose?

When I had original headgasket problem I used a lot of "stop leak" aluminum powder type products in hopes that my coolant loss was through a leaky radiator (and at dad's advice) and now I'm wondering if this stuff has completely blocked flow thru the radiator in places and this back pressure is why the radiator overflows when the cap is off. Of course if the coolant flow is the opposite direction from what I'm thinking that wouldn't work. Right now I'm running some heavy-duty radiator flush in hopes that it might break up some of the stuff, just in case this is what's going on. Dunno if it will help but worth a shot.

Thanks for any help in advance.

 

warped cylinder head...i am having the same problem myself right now...either switch the head or take the current one to the machine shop and have it decked another thousandth

 

Unless you are losing alot of coolant, your head may not be the problem. Did you try replacing your radiator? It might have some blockage in it. I recently replaced my radiator. I got a brand new one from a local shop for $150. One last thing, the top hose is the return hose(coolant returns to radiator) and the bottom hose is inlet hose(where the coolant flows out of the radiator and into the engine.)