Grab a beer, sit back, relax it's a long one...

Over the last 3 years I've been battling random overheats with this thing. Heres the deal with the cooling system.

93 TA / 185k.
Radiator is 2 years old.
Water pump is 2 years old.
Condenser is 2 years old.
Gutted cat <--- plugged it caused overheating
Thermostat is 4 weeks old.
Electric fans work
Radiator shroud is intact.
Air dam is intact.
Gone through numerous radiator caps

It drove 800 miles with no problems from seattle to northern nevada. Passed Battle Mountain and it started creeping up to 220* on the gauge and started bubbling out the overflow. From then on, it was random pull offs, cool downs, and top offs. The last 45 miles were with the heater on, windows down and going 65mph. Anything faster and it would creep up and overheat again.

I took it to a FINDLAY chevy for a diagnostic. They said before they address the overheating I need to spend $2600 to seal the oil pan leaks so they can see the possible coolant leaks. Riiiiiigghhhhtt.....I said its unrelated please focus on the coolant system. They later say they couldn't do a pressure test and determine the leak because the machine they use couldnt seal to the radiator. So they suggested a new radiator with all new hoses for $1600 before they can do a pressure test. I denied service and left.

Ok, I can understand the rad neck maybe warped causing an eventual pressure leak and boil overflow. But I need a 2nd opinion. I'm skeptical of all shops but remember Pep Boys treating me and my family right. So yesterday I take it down to one. I tell them everything about it and how Findlay Chevrolet couldn't replicate the problem. Today Pep Boys calls back. To my shock they cant replicate the problem. The pressure test was good and so is the radiator. They couldn't find any leaks. I asked them if they drove it. He said the tech drove it 3 or 4 miles and nothing. Before it would hit 220 within that time.

I still have to pick it up and ask some more questions, but at this point im completely dumbstruck with this thing. Any ideas? I need it to get home 1000 miles away and I'm getting conflicting reports on this thing.

Imput would be greatly appreciated. Could a tiny head gasket leak over 3 years cause these problems and wouldnt a pressure test find out if it had one? But it wouldnt be intermittent, it would be constant.

-Kevin.

 

Thermostat failing toward the closed position and causing restriction? Since it is relatively new, maybe it is not so good. It is also an easy thing to replace.

Sorry you have problems on the road.

 

Thanks. I dont doubt it. But to its discredit, I saw coolant circulating after the overheating started. I cant imagine it failing only sometimes.

Could a block in the heater core cause overheating? Only when it starts boiling out do I get a coolant smell. Usually with the windows down. But never a damp carpet. I asked about it, Pep Boys wants $570 for what I could do under for around $100 in an hour or so.

I'm taking it to a 3rd shop tomorrow for a third opinion.

 

When you saw coolant circulating, how hot was the system? Did you observe any bubbling and spurting at the fill neck?

 

I did see bubbling and spurting. Then it calmed down and just circulated. If I turned the fans off, by 220* it was flowing out the fill neck of the radiator.

 

Sit back its a long one:

1) Take your water pump off and flush your block 4-5x on each side- that’s 8-10x total. (I wasn’t able to pull the block drain/knock sensor).
2) Flush your heater core 4x and GENTLY back flush the heater core 4x.
3) Flush your radiator 4x
4) Replace water pump with a new AC Delco 252701 (its Chinese now)
5) Replace thermostat with new AC Delco 131100
6) Replace radiator cap with new AC Delco RC94

Do a 40% old fashion green antifreeze with 60% distilled water. I can’t stress enough the importance of a proper bleeding (nose of car in the air, running, defroster on high- use a bleeder tool kit they are less than $50) opening the bleeder screws when refilling.

Drive with the AC or defroster on since your fans work. Unless you have a blown head gasket if you follow that to the letter it will cure your problems.

My 94 Z28 typically runs 185-186* here in Ohio. Our 90-94* days the car runs 187-188* according to the approximate gauge reading after I replaced those parts with that EXACT procedure.

I run full synthetic oil don’t know if it helps or not. Who knows probably not.

 

I appreciate the long post, but I'm traveling through Vegas to Phx from seattle. I don't have tools or a garage to perform work. So I'm at the mercy of a shop that can find the problem.

 

Update. I picked up the car and drove it to overheat and brought it back. They were able to get a positive pressure test. Indeed the fill neck was warped. So they threw in the new radiator, i made it back to seattle, and all is right with the world.....err not really.

 

Glad you're on the road again, but sorry you had to spend extra money.