Cant stop overheating

[heister00]

Hello, this is my first post and i need desperate help. I have an 1988 Toyota Supra 7MGE (non-Turbo). My problem is my engine overheats. It used to overheat quick so i changed the thermostat, refilled, and "burped" the cooling system. That helped to a certain extent. Now it overheats slower. If just idling it takes about 30 minutes. If i am driving it takes about 12 minutes. I also changed both hoses, radiator cap, coolant (obviously), and the thermostat housing. There are no leaks either. When i am driving even when it gets to hot temps. the car runs perfect. Another thing i noticed is my Oil Pressure Gauge is normal at first but after about 3-4 minutes of driving it indicates a loss of pressure. The oil level is where it should be and again there are no leaks. If anyone can help me out please do so, i would appreciate it.

[TcmaBoy]

Alright, so you are not losing coolant? Your levels stay constant? Are you getting a white cloud out of your exaust? If so, what does it smell like? Is there coolant in your oil? Is there oil in the coolant? With the engine running remove the radiator cap and check to see if there are bubbles comming out of the radiator. Have you checked compression?

If your motor is good then I would use some coolant system cleaner. Given the age of the vehicle you may have deposits in your water jackets. Use some of that cleaner. It will flush things out and should bring your temps down.

[heister00]

OK, yes my fluid levels stay constant. There is no white cloud that comes out of my exhaust. About checking for coolant in my oil or vise versa, how do i go about checking that. I have already left the radiator cap off with the engine running and got all the bubbles out. No i have not checked the compression reason being it starts, idles, accelerates, and runs fine even when "supposedly" overheated. I say supposedly because one of my friends suggested my sensor is faulty. I know he doesnt mean the water temp sensor cause i just put a new one in. I dont know where the sensor that sends the signal to the gauge is or i would replace that. Another thing i read on the forums is about the guard that goes under the engine. I have not put my guard back on and supposedly that makes a difference. It said it makes a difference because the air flows through the bumper and under the car as opposed to right into the radiator when the guard is on. Is this true? If so would that cause it to overheat slowly? Now about my oil pressure, why would that drop after a couple minutes of driving?

[KimMG]

Start your car
Let it idle to operating temperature
Turn off
If you have an electric fan, disconnect the battery
Feel the radiator for cold spots (clogs)
Make sure your radiator fins are clear from obstructions (debri, bugs)
Is the fan working? How old is the water pump? (the vanes on old pumps wear away and don't circulate too well)

[heister00]

Well, i will have to do the check for cold stops. My question though is there are 2 fans a big one on the left and a little one on the right. The big one on the left spins constantly. The little one i have never see even move. What is the smaller fan for and would that be my reason for overheating? As for obstructions on the radiator fins, there are none. I also have no clue how old the water pump is. Thanks again for the input.

[83_CELICA]

my car does the same thing. its an 88n/a. no white smoke, but it overheats and it compression tested perfect. no leaks, no bhg, but still a big problem

[TcmaBoy]

Is it actually boiling over, or is the gauge just indicating hot? This may be tied to your fault code.

[83_CELICA]

it usually ends up boiling out of the overflow tank. it wasnt driven for about 6 months. but there's still no smoke or smell of it. and compression test was good. and i dont know where the coolant temp circuit is in the car! help!

[heister00]

Originally Posted by 83_CELICA

it usually ends up boiling out of the overflow tank. it wasnt driven for about 6 months. but there's still no smoke or smell of it. and compression test was good. and i dont know where the coolant temp circuit is in the car! help!

I found out what my problem was. It was the simple thing: my radiator cap. Change it. If the cap cant hold pressure it will send the hot coolant in to the overflow and boil out. It also lets air into the system which heats up faster than the coolant. the vacuum in the coolant system escapes also. Trust me spend the $8 - $10 and change it. I did and no more overheating for me.

[TcmaBoy]

The little things will get you every time.

[gelcol]

I've change the cap ,radiator, and still overheats
I'll try to run it slowly temp goes down.

[Brian R.]

Try flushing your system. See the following article:
http://www.cygnusx1.net/Supra/TechTi...ent_flush.aspx

You may need a new thermostat.