What now?? Overheating Celica

[killerkane]

I have a 1987 Celica GT, however the engine was replaced with a Camary engine... I think early 80s vintage.

This Celica has an overheating problem. I've flushed the cooling system mulitple times. I've replaced all the cooling system I could - from the radiator to the thermostat [and checked the water pump]. The car still overheats.

It is always the same, whether I am idleing or driving at 70 mph: the temp gauge gets to normal operating temp [about 1/4 the gauge] and stays steady for 5 to 10 minutes. Then it starts getting hotter until it completely overheats. It is almost as though a switch goes off and tells the engine to overheat.

Oh yeah, when it does get hot, I've tried spaying the radiator with water, and that does cool the car down, so I don't think there is a blockage in the engine anywhere.

Any ideas?

[lloydjv]

Check these things:
Make sure there are no obstructions to the radiator's cooling fins.
Be sure your radiator cap is on tight and there is no air in the system. Air will not allow the cooling system to pressurize and properly circulate the coolant.
Check the fan for proper operation and make sure it is in good condition.
If you know how, check for proper circulation, other wise run it to your local mechanic and have him or her pressure test the system.
And I am not certain if you have one, but check the coolant temperature switch as well.

[killerkane]

Thanks. Could be air in the cooling system. How do you make sure it is all out?

Then again, as soon as I spray the raidator with water the engine cools. Seems like the cooling system is working.

Anything that could cause the engine to output excess heat?

[Pineapple]

Is your fan working? Does the system hold pressure? ie does top hose get hard when car is hot.

[killerkane]

I checked the hose, in fact I replaced the top with one that hard white hose made of plastic for testing. The one that has a pressure measure attachment. It showed no negative pressure.

Yep it holds pressure. In fact once the temp gauge goes past the middle the cap starts releasing steam.

My impression is the cooling system works, unless it blocks temporary. I think it may be the engine putting out excess heat.

[killerkane]

What could cause the enginee to start outputting excess heat??

I noticed a few vaccum parts seem to be missing... could it run too lean and such?

[Pineapple]

Looks like your cap releasing too early. Mine start releasing to overflow after 3/4 way up the gauge. The system need a few psi pressure to prevent coolant from boiling. How much psi you got when its warm? Did you fill up the rad after it overheat? Usually you'll lose coolant after overheat. My problem was easy, new rad.

[GT4Thug]

i had similar with a fiat with an engine swap, the engine was higher than the rad and kept making vapour locks within the engine that cause overheating when driven hard....

it then forced the water out of the expansion through thte pressure cap, then as it cooled it drew 'MORE' air into the system exaggerating the problem...

double check again for air locks just in case , run it to temp with the rad cap off and see if further air circulates to the rad after the thermostat is open.

the way i cured it was to drill a very small hole in the thermostat, this allowed 2 things

1) a cooler engine
2) air to be forced out from behind the thermostat by the small amount of water passing thru before it is opened

that also agrees along the lines of pinapples theory as a little loss of coolant makes a big difference

Thug!

[87CelicaGTS]

I have the same problem with my 87 gts, I put in a brand new radiator and thermostat and hoses and it is overheating still.. but when I turn off the car and get out I hear a hissing noise like there is a pressure leak somewhere under the hood and it is a really loud hissing noise. I cant visualy see where the pressure is leaking which makes me worried. So I know it is not holding enough pressure to push the water through the motor and cool it off.

[fredk]

OK, a slow building heat may indicate a blown headgasket or cracked head, try this, get it full of water, get a funnel that you can cram into the radiator that will seal in the filler neck and will hold a good bit of water, just dont hit the fins with it or break the neck, almost fill the funnel, start it up, you might see some air come out during warm up, just keep it pretty full, it might push some water out when the thermostat opens, just dont freak. Right after the first fan cycle or hit it with a garden hose if it starts to boil, put your hand all over the finned surface of the radiator while the motor is still running and it should be hot ALL OVER, if it is cold near the bottom or at one side it IS OVER for the radiator. All my toyotas the fan comes on before or near boil so you may have a fan turning too slowly or the sensor is going bad, continue to look at the water in the funnel and look for a pretty constant stream of tiny bubbles, or if it is real bad, you might have larger bubbles of a NEVER ending stream, this is cylinder compression getting into the cooling system somehow. If it pushes water out of the funnel on a pretty regular cycle, you are having circulation problems, a thermostat acting up or a water pump impleller rusted away and a small hole drilled into the thermostat body goes a long way to getting rid of trapped air. Just remember this, the radiator has to get ALOT hotter than the air going through it to get rid of the engine heat fast enough, you should not be able to keep your hand on the fins or in the cooling fan airsteam for very long, also check for a missing air dam that might be missing under the bottom edge or dirt in the fins