Engine overheats on highway with AC on

[DOUBL3 D]

Alright so the car heats up really fast when you start it, I'm not sure if that's normal for these cars or not. Anyway the car ran fine but heats up to this afterawhile.

But come down to around this

And then goes to this

The car has 96,200 miles, had the head gasket changed at 55,000 miles, a fluidyne aluminum radiator, and not Toyota red coolant (will be changing this soon). It should also be noted that the aircon doesn't work well when it heats up. Car doesn't currently have shrouds (have them but need to go to the dealership to get bolts).

 

[Nick M]

Get the shroud. Do you understand why an air conditioner will put more heat in the coolant? And if you do, then you understand why there are extra fans? The shroud pulls air over the entire core, rather than a small spot in front of the fan. I would check to see that temp and high pressure switches close, and the fans turn on. At speed, you don't need much in the way of the fans with the ram air effect. That makes me think something is wrong with the radiator. That would be typical of one that is old and rusted on the inside. Perhaps there is a little more you aren't offering up in information to have the symptom of an old radiator with newer one that is very high quality.

 

[DOUBL3 D]

Get the shroud. Do you understand why an air conditioner will put more heat in the coolant? And if you do, then you understand why there are extra fans? The shroud pulls air over the entire core, rather than a small spot in front of the fan. I would check to see that temp and high pressure switches close, and the fans turn on. At speed, you don't need much in the way of the fans with the ram air effect. That makes me think something is wrong with the radiator. That would be typical of one that is old and rusted on the inside. Perhaps there is a little more you aren't offering up in information to have the symptom of an old radiator with newer one that is very high quality.

I'll check the inside of the radiator when I do the coolant flush and then study up on the coolant system so I'm a little more well versed in the area. How would I see if the temp and pressure switch closes?

 

[Poodles]

Has any work been done on the AC? It's not going to blow cold when it starts to overheat as the system shuts off to save the motor.

 

[DOUBL3 D]

I don't believe so. It usually blows ice cold air, however when the engine heats up (like in the top pic) it seems to stop blowing cold air

 

[NewGen]

Could the mechanical fan be having issues? I know sometimes they get warn out and don't have any resistance left when you spin them causing the car to run warmer.

 

[DOUBL3 D]

Could the mechanical fan be having issues? I know sometimes they get warn out and don't have any resistance left when you spin them causing the car to run warmer.

How would I check this?

 

[jonahs_supra]

does the condensor fins/passage look clean?
if they're clean then i would suspect as Nick M. stated
install fan shroud...its the main cooling fan for radiator and condensor

 

[NewGen]

How would I check this?

The way I was brought up (not saying this is right so don't flame me). With the car off and it's cooled down. We use to spin the fan to see how much resistance it had. If it spins freely and has no resistance it could be your problem. I do agree though having no fan shroud is definitely an issue also.

 

[DOUBL3 D]

does the condensor fins/passage look clean?
if they're clean then i would suspect as Nick M. stated
install fan shroud...its the main cooling fan for radiator and condensor

I have a fan shroud just not the ones underneath the radiator or fog lights.

The way I was brought up (not saying this is right so don't flame me). With the car off and it's cooled down. We use to spin the fan to see how much resistance it had. If it spins freely and has no resistance it could be your problem. I do agree though having no fan shroud is definitely an issue also.

I'll go check this out and report back

 

[DOUBL3 D]

Alright so I drove her around town today and her heat was normal, was totally fine. I'm gettig bolts from the dealership tomorrow to put the fog light shrouds on as the po didn't bother to put them back on. I need to see if there is a shroud for underneath the radiator to

Will update tomorrow

 

[jonahs_supra]

I have a fan shroud just not the ones underneath the radiator or fog lights.

i dont have any underneath shrouds on my car
i would check condensor fins for cloggage/restricting air flow

 

[DOUBL3 D]

i dont have any underneath shrouds on my car
i would check condensor fins for cloggage/restricting air flow

I'll look up how to do that tomorrow, air con is something I'm not well versed in. Thank you for your help

 

[IJ.]

Turn the AC off on the highway... fixed

 

[DOUBL3 D]

Turn the AC off on the highway... fixed

That's what I did Sunday on the 6 hour drive. Just another excuse to take off the roof

 

[IJ.]

If the Undertray and blockers are missing there's your issue @ HighWay speeds.

 

[DOUBL3 D]

I don't believe if I have an undertray. What I have are parts 53138 and 53139 from the EPC (see link below), though they aren't currently on my car. I went to the dealership to get bolts today for the two said shrouds/blockers but they were closed. Looks like ill do it tomorrow

http://www.cygnusx1.net/Supra/Library/EPC/291410/catalog.aspx?F=5301&P=1

 

[S.A. supra]

Would a open or no thermostat. Do the same thing? Not keeping the coolant in the radiator long enough? I had a problem with over heating once a long time ago and when I was checking the car out. The previous owner didn't put a thermostat in. I just can't remember when the symptoms occurred. I want to say it was on the highways in the summer time.

 

[IJ.]

I don't believe if I have an undertray. What I have are parts 53138 and 53139 from the EPC (see link below), though they aren't currently on my car. I went to the dealership to get bolts today for the two said shrouds/blockers but they were closed. Looks like ill do it tomorrow

http://www.cygnusx1.net/Supra/Library/EPC/291410/catalog.aspx?F=5301&P=1

There are a bunch of smaller blockers around the Rad that are lost over the years on these cars as people don't understand just how important they are.

Would a open or no thermostat. Do the same thing? Not keeping the coolant in the radiator long enough?

Possibly, resident time in the rad is important (more a SBC issue) but I don't think the 7M waterpump moves enough water for it to be the issue (bugger all flow at idle and cavitation at high rpm)

 

[Dan_Gyoba]

Personally, I check the fan clutch right after shutdown, while it's hot. At that time, the clutch should have enough resistance that it takes a little effort to spin, and should NOT spin freely after you push the blades (ie: the fan comes to an immediate stop when you let go instead of pinwheeling.)

I'll also check when cool, that it's easier to spin, so that I have some indication that the clutch is doing what it's supposed to.

My last fan clutch failed in such a way as to have locked up entirely. Wow was that noisy...