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Thanks for the info - OK, so it's probably not the cap. I was kind of afraid of that, since 21 psi seems to be a pretty healthy pressure retension value. Also, if the cap's spring were weak, the coolant would flow out the overflow, probably creating a puddle, which isn't happening.
I haven't pressurized the system, because I wanted some input as to what value to which to pressurize it. I will probably do that tomorrow after work. I did look under in the passenger side footwell for signs of wetness on the carpet, but it's dry. I also looked under the dash on the passenger side, and didn't see any sign of wetness near the heater core area. And I'm not seeing signs of a white color to the exhaust, but then again, since the problem only happens under the stress of a track session, I wouldn't notice it. Other people at the track haven't pointed this out to me, so I'm going to assume it isn't the happening. I'm going to rule everything out before I even consider that a brand new head gasket is the problem, as this seems like an extremely remote possibility, especially since I can smell antifreeze.
Tap a pressure gauge into your cooling system; probably easiest to go right into the water neck. Watch the gauge when on the track. You will learn a lot.
The tests that have been recommended may not show a combustion leak (into the cooling system) in a static setting, but monitoring the pressure while you're experiencing the issue will likely expose a compression leak.
Report back what you find. Bear in mind that the water pressure generated by the water pump alone will exceed the pressure cap release point. This is not an issue, and will show as rise/fall consistent with RPM.
Major, unambiguous progress. I got under the car tonight, and for the first time since the symptoms started months ago, I saw signs of residual coolant on the bottom of the engine, near the front. So it's definitely getting worse. Thinking it's the water pump, I removed the upper belt cover, and removed the bolts for the bottom belt cover, but I couldn't see any signs of residual coolant on or around the part of the water pump I can see. So I pressurized the system, using a hand-pump unit I rented from Autozone. Nothing happened up to 15 psi, so I gave it a few more pumps, in an attempt to simulate the pressure seen in the system under full throttle acceleration on a hot Texas summer day at the track. At 16-17 psi, I heard a loud "Pop!", accompanied by coolant gushing all over the garage floor, in the same area where I had seen residual coolant when I first got under the car. So, the good news is that the leak is definitely external, and I won't need to pull the head anytime soon.
But the amazing/depressing thing is that even with a huge, highly visibly leak I can create at will, I can't pinpoint exactly where it's coming from. The inside of the lower belt cover is totally dry, as is the radiator, so the water isn't bursting rearward out of a leak in the radiator. I'm afraid I'm going to have to take the belts off (I just replaced them a few months ago) to get a better look, and even then, it may be difficult to diagnose whether the leak is coming from within the pump itself, or whether part of the gasket has blown out, and if so, why? I'll definitely test the tightness of the water pump bolts before I remove it to see if there may be an issue with the threads in the block that hold the pump bolts. Any other pointers on how to best proceed going forward would, as always, be greatly appreciated.
Last edited by Cloud9...68; 06-30-2015 at 03:44 PM.
That is why I test with system filled with air and soap in a spray bottle.
Draining the coolant can be a mess. I just open the drain two turns and leave the cap on then walk away...coolant trickles down the raised seam on the batwing and into the catch pan. It takes an hour but no mess and no waste.
But the problem is that there's so much stuff in the way of the area I think the leak is coming from that I can't pinpoint it, despite the fact that it's an enormous leak. I have to think it's either the water pump itself, or the interface where the pump mates to the block, but without removing the belts and the rear plastic belt cover, it's going to be heard to tell where the leak is coming from. I've changed the belts on this car so many times I could do it in my sleep, so I'm just grateful it isn't the head gasket.
This ended up taking much longer than I had expected, but in the end, the source of my coolant leak was about a simple and trivial as it could possibly have been. It had nothing to do with the head gasket, water pump, or even a hose. The leak was coming from where the short hose that connects between the heater control valve, and the metal coolant pipe running above the exhaust manifold, connects to the HCV. It wasn't even the hose itself (although I ended up replacing it anyway) - it was just the fact that the clamp I had used was a little larger in diameter than it needed to be, so when I tightened it, it ended up somewhat oval, and wasn't applying clamping force evenly around the hose. Literally a sub-one dollar fix.
Unfortunately, when I did the pressure test, I interpreted the source of the leak as coming from the water pump area, so I took off the belts to inspect the pump, and of course found no sign of a leak coming from it, so that appeared to be a huge waste of time. Except it may have ended up being a blessing in disguise, because I discovered that the circlip that retains the pivoting arm for the tensioner was in pretty bad shape, and I also managed to squeeze one of the o-rings into the arm's pin, which I had never had any luck with before, so the timing belt assembly should work more reliably now.
But the moral of this story is to not assume the worst when you have a problem. Keep looking for the simple stuff, until you're sure you've ruled it all out, before proceeding to the more difficult and expensive stuff.
Coming home from work today, I decided to give the old girl a workout, she replied in return with this:
Going to wait to remove the clamp as the engine is still hot, $.70 fix and she's good to go another round tomorrow.
I ran her hard, she puked in return.
Same issue as your coolant leak, this coolant hose clamp is no good and caused the coolant to run out, see the white overspray of the coolant on the header.
06-29-2015, 09:04 AM
