1. Home
  2. Automotive Technologies
  3. 87 Supra Overheating, HELP!!

87 Supra Overheating, HELP!!

My 87 Supra started overheating lately. I had a similar problem with an 84 Toyota a long time ago where I ended up replacing pretty much every part in the cooling system and it still kept overheating.

Anyways, here's the situation and maybe someone can shed some light on this without me blinding replacing stuff.

  1. There are no leaks in the system.

  1. It can idle for a long time without overheating, but problem happens when I start driving (pretty much at any speed, even 30-40 mph in the city).

  2. When it overheats, I can hear the water boiling and steam starts blowing out of the overflow. Eventually, the cooling system gets pretty low from losing water through the steam.

  1. The heater quit working at the same time. I'm not sure what this part is, but it's a small fan that sits next to the large fan on the radiator. That small fan is not moving. Is this connected to the heater?

  2. I flushed the system.

  1. I pulled the thermostat out and hot water is coming out of the engine OK, I believe.

  2. When I flushed the system, I did not notice any oil in the water (does that mean the head gasket is probably not blown?)

  1. The car has 164K on it, and has never had a cooling system problem that I know of (I've had this car since 80K). However, I'm not sure if this car had the defective head gasket replaced during the recall.

Basically, what's happening is the hot coolant in the radiator isn't getting cooled off properly. I think it might be a fan clutch or the radiator? Is there a sure way to test?

Thanks all,

Michael

Reply to
Michael
Loading thread data ...

The additional fan is for the A/C and should come on when the A/C is switched on. Have you pressure tested the system confirming that there are no leaks ? It appears as tho the air flow thru the radiator is being restricted due to debris clogging the fins in the radiator or A/C condenser which sits in front of the radiator. You mentioned that the thermostat was removed........put it back ! With no thermostat the coolant will flow too fast thru the system to effectively exchange the heat produced by the engine. On the same note thermostats are prone to failure and have caused catastrophic failure in many a motor, what i recommend is removing the valve and spring assy. from the center of the thermostat, this will create a restrictor plate that allows for constant flow of coolant thru the system at a rate comparable to that of a fully open thermostat. As far as the heater not working the cause could be the lack of a thermostat or the heater control valve is not opening or the blower fan is inoperable. One way of checking for a blown head gasket is to pull the spark plugs and inspect them, usually the gasket will fail between two adjacent cylinder and those plugs will be clean because the steam entering those two cylinders tends to decarbonize the chambers. Another possibility is the coolant and/or steam holes in the head gasket have become clogged or rusted up causing a overheating problem. You confused me when you mentioned a fan clutch because if you have electric cooling fans there is no fan clutch, however if you do have a fan clutch you should feel a strong breeze from the fan when the motor is at operating temperature, the clutch uses a bimetal spring that expands and contracts according to temp. and this is what causes the clutch to cycle the fan on/off. If it uses electric fans as i suspect the fan/fans are switched on/off by a thermal ground switch that is usually mounted in the intake manifold or possibly the cylinder head. You can bypass the switch by removing the ground wire from the switch and attaching it directly to ground, this will enable the fan/fans to run when the key is switched on. The only sure way to test the system is take it to a shop and have them pressure test the cooling system.

-- Mad Dog

"Michael" wrote in message news: snipped-for-privacy@posting.google.com...

Reply to
Mad Dog

Yes, the system was pressure tested at a shop. There were no leaks. They wanted to replace the radiator & water pump, but I wasn't convinced that was the problem.

Reply to
Michael

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.