1983 Celica Supra heating up over along period of time

[Pender]

Hi, Im a new owner of 83 L-type. When i bought my car the original owner said it was heating up on big hills but fine any another time. So i got it home and replaced the rad cap and coolant, which both needed it. So now i warm it up at idle and the gauge gets to about 1/2 and all seem great, Ill let it idle for 20min or more and no change. Once i get out on the road it takes about another 20 mins for the temp to start to creep up to just before the break in the white line on the temp gauge. Ive own other older toys and never had a problem like this , can anybody help or tell me where to start. Thanks
77 celica coupe
80 toyota 4x4
83 celica supra

[ZZT231]

Could it be a sticky Thermostat or that your radiator is loosing pressure?

[CELICA XX]

A few quick fix ideas: (assuming your radiator & water pump is alright)

1. Low on coolant?
2. Thermostat?
3. Pockets of air in the system?

[John X]

Just some shots in the dark:
maybe a clog in the radiator somewhere?
maybe a clog in one of the hoses?
maybe the thermostat isn't openining all the way?

Ususally its the other way, ie: it overheats sitting still but is fine when its moving...hmmm...

-John

[AJ]

or bad fan clutch as well.

I would replace the thermostat with a Toy one, and the fan clutch.

Or worn impeller on the water pump, although not likely.

[Square]

The fact that it only overheats under load leads me to believe that it is your radiator/water flow. To check it, I would remove the thermostat completely, and drive it and see if it still happens. When you say you are driving it arond, I am assuming that you are moving at 40MPH or greater (thus ensuring a large flow of air through the radiator). If that is the case and it still slowly overheats with no thermostat, then I would say that your radiator is getting old and becoming inefficient. That would explain why it is strong enough to keep the motor cool at idle, but not under load.

[rumptis]

I had this same problem and it ended up being my Radiator. I took me over a year to finally figure that out do yourself a favor and just change it.

[Pender]

Thanks for the posts, anything helps. If flushed and burped my rad but there seems to be no difference, I read that the heater contol valve on the firewall could also be the problem. I bypassed it , no difference. My buddy with an 84 mk2 says its my hg, he says its very common on these cars. But im leaning toward the rad. Anyways ill keep working on it thanks for the help. by the way this car is wicked

[rumptis]

I also figured it was my head gasket even though doing tests didn't show anything else. I went ahead and decided to put a 6m in and still had the same problem. The Rads are well known for cloging up. I did everything to flush it out and as far as looking it and running water through it, it seemed just fine. But now I can run it as fast as I want and sit in traffic on very hot days and it hardly goes above half way at most.