I just brought my 90 GTA out of storage. After cranking a few times she fired up and idled perfectly. Let it idle for a while, the radiator fan came on when warm, then after about 33 minutes I noticed the temperature gauge was reading high... i looked closer and realized that the temperature needle was pointing JUST BEFORE the red-line zone on the temp gauge. I quickly shut the engine down. I really hope I didn't cook the block. Any ideas whether I did or didn't?

Right after shutting down the engine I start hearing a periodic steaming of hot coolant (like water on a hot iron) coming from the radiator. Then steam starts to rise from the radiator (just a puff of steam really). Suddenly I realize green coolant is drizzling out from under the radiator. I could see a little bit of coolant leaking down the side of the radiator. It was hard to pinpoint where the coolant was leaking from as everything is covered up. The coolant reservoir was full to max line. I suppose dirt could have built up in the radiator cap, preventing it from venting?

Any ideas what could be happening to my coolant system?

Could it be something like the water pump isn't working so isn't circulating coolant properly? Or is this impossible?

Could it be a stuck thermostat?

Oddly enough this happened to my motorcycle a while ago. I started it up after it sat for a while... it idled for a while... then overheated and started spewing hot coolant.

What is going on here?

 

you have 1or 2 fans? could be a bad tstat or rad cap could also be a weak pump

 

Figure out where your coolant is leaking from. Even if the engine overheats, it shouldn't leak fluid, it should just expand into the reservoir. If it's overflowing the reservoir, the reservoir is overfilled.

If the plastic tanks on the radiator have cracked, you may need a new radiator. Or your cap could be faulty, or not completely installed. Find the leak and fix it.

 

2nd Drew, find the leak and make sure the system is sealed up and the cap is good(maybe replace it just to rule that out). Air in a low coolant level system can make temps skyrocket in a hurry because depending on where the sensor is it could be measuring steam temp.

Weak pump maybe? Find the leak, fill 'er back up and drive it around a little so it is not idling and that rpm will help get the coolant circulating if the pump is getting weak.

Thermostat fail? Very possible, probably easiest to replace it. They are cheap and since you are auto draining now its probably dry, cheap insurance too.

If you are filling your overflow tank to the point of overflowing itself and it is where the Full Cold mark is when it is cold, you could have bigger issues but I don't think that is what you meant when you say overflow is full, right?

 

Yes it could be that,.... but with any luck the T-Stat is just stuck closed after staying closed the whole time it was in storage. If it was suck closed I'm sure the high temps caused a lot of excess pressure too. ( might have caused the little leak you found. <Tighten clamp a little more ?? Fingers crossed >! )

* Be sure you're using a properly rated Radiator cap.

You can feel the upper hose during warm-up & just about always easily tell when the T-Stat opens up ( 'cause it gets real hot real fast. ) I'd run the car @ idle again and this time feel the hose,..... if you don't feel the T-Stat open by the time the temps reach just under the coolant red-line, replace the T-Stat. You should also watch for any leaks too while doing this test; best to have a helper to watch the temp gauge too; they can call out the temps so you know almost exactly when it's about to open. ( as long as the gauge is OK and you know the T-Stat rating ! )


Good luck !

 

Not totally sure... I want to say 2 though. I think when the engine is hot and the A/C is on, then the second one is supposed to come on IIRC.

 

seems to be exactly what happened. Would anyone know how to replace a T-stat on a 1990 GTA 305/5.0 TPI (time to dust off my chilton's)? Anyone know what the stock radiator cap pressure is? Sure seems like it was leaking at the actual radiator. All that sizzling steaming hot coolant sound was coming from the radiator I'm thinking. But if the T-stat was stuck closed then the radiator should have been cold, right? My coolant reservoir should be filled to the correct level.

 

Remove the two bolts that retain the waterneck, lift out the old thermostat, clean gasket surfaces, drop in new thermostat, apply new gasket, anti-seize liberally on the waterneck bolts, torque to spec.

*You may need to remove things before you can get at the waterneck bolts. Use your best judgement. Avoid stripping or breaking the bolts. Be prepared to tighten them a hair to work them loose before backing them off. If they bind, use plenty of penetrating fluid (PBlaster) and work them back and forth until they come out, as in left 1/2 turn, right 1/4 turn, left 1/2 turn, right 1/4 turn, repeating until done. Might also be a good idea to clean the threads of the bolts and in the intake before going back together with anti-seize. Did I mention that sometimes the bolts stick like a melon farmer?

 

Thanks for the tips. I like your technique for undoing tough block bolts. I should have checked youtube U sooner... looks like they may have some install vids for a t-stat third gens.

Update: Finally replaced t-stat. No more overheating.

 

You could also be seeing what happens when a car sits for a period of time. Things rot or rust out and just enough pressure could cause little (or big) leaks. Radiators, rubber hoses, steel lines all rust from sitting. He could have a pinhole leak in his radiator from just sitting and the pressure from the coolant was enough to expose it when the thermostat opened or didn't open. I would also check your radiator hoses to make sure that they still have some strength in there hose wall to apply pressure to the coolant to help the coolant fight the heat. They shouldn't be mushy (easy to squeeze). They should have some resistance to them still. If not, may want to replace them as well.