: '94 STS is overheating

09-18-06, 10:44 AM
My '94 STS has started overheating, changed the radiator, thermostat, cap, checked all hoses, flushed system, and checked pump, (was good). left fan does not come on unless the A/C is on , then both fans come on.
driving the car causes the overheating to happen faster.
what could be the cause?

09-18-06, 03:12 PM
Be sure the purge line is clear and flowing. Do a search for overheating and/or purge line. It has been discussed many times in detail.

09-18-06, 04:29 PM
I have a 94 Seville that I thought was overheating. When starting the car cold, it would heat up till it reached ~175 degree's and then it would go into overheat condition. It turned out that it wasn’t overheating, but had a bad ECU. I initially replaced the temp sensor hoping it was going to be a cheap fix, but ended up replacing the ECU. If you know how to get the onboard diagnostics running check PCM code P04. The reading would jump from the 50's to 196. If the temp sensor circuit is working correctly it should never make large jumps. Before doing any more work, check to make sure no codes are set in the onboard diagnostics.

09-19-06, 08:51 AM
I did check the codes, hoping for the Temp sensor to be bad, but there was no codes, I reset all the systems to clear any possible code current or history, and ran the car, still overheated, and still no codes.

What is the purge line? the upper radiator hose seems to be very hard, like it's under high pressure. but the cap is new tested and good, so pressure should be about 15~16 psi.

Could a clogged heater hose cause this?

The local mechanic seems to think it is a blown head gasket, (he has not looked at the car yet).

thanks again for the help.

09-19-06, 10:05 AM
The purge line is the 3/8" line that runs from the pump housing to the top side of the surge tank. It's job is to purge air from the system. Pull the line at the surge tank with the engine running (cold, so as not to burn yourself). There should be coolant flow. The flow will be relative to RPM. If there is coolant flow, the line is clear, quickly push it back on and tighten it down. If not, then shut down, locate and clear the obstruction.

09-19-06, 11:12 AM
On my car there is a hose/pipe that goes from the water pump cover, around the engine, to the bottom of the purge tank, via a tee, the other side of the tee has a hose connected to the heater core, the other side of the heater core has a hose connected to pipe that runs around the engine back into the water pump assembly at the back of the engine.
So the hose on the bottom of the tank is the one in question?

09-19-06, 12:05 PM
While I am not intimately familiar with the '94, that does not sound right. Every purge line I have seen '97, '99, '02 & '03 has the purge line entering the surge tank on the side, near the top (above the coolant level).

09-19-06, 01:57 PM
on both of my '94s there is a hose on the bottom, and the small hose just under the cap to direct coolent to the ground when the cap lets any through.
I will re-check both the hose at the bottom of the tank, and the heater hose.

09-25-06, 12:43 PM
I took the car to a pro, and he did all the test to check for a blow head gasket, and he said the engine was fine, but he did not understand the car overheating. I told him that I replaced the radiator with a used one, he then had it removed and cleaned.
overheating problem is fixed.
so, the problem was a combination of crack water pump cover, stuck thermostat, bad radiator cap and a clogged radiator.
gland that is over, but it cost a lot to find that all out.
thanks for all the help.

09-25-06, 01:02 PM
Good to hear

09-25-06, 04:32 PM
Wow! I guess the good news is it was still cheaper than a head gasket job. Glad you got it fixed.