Hey folks, I have a problem.

My wifes van overheats, but only when it's very hot outside AND the air conditioning is on. It doesn't overheat at all when the a/c is off, no matter how hot it is outside; and it doesn't overheat when the a/c is on if the temperatures outside are moderate (80ish or less).

We haven't done anything to it yet, except I took it to a car wash and tried to spray out the a/c condenser. I don't know how good a job I did because it was difficult to get a good angle of spray to the condenser inside the engine compartment. Must not have been too good a job, considering the problem still exists.

The only possible connecting repair we've ever done was last year the fans started staying running all of the time, even when the vehicle was off. We replaced the fan relay and that problem was fixed. This a/c overheating problem existed before that relay went out, and continued to exist after we replaced it. Needless to say, I don't think the relay is the problem, but I thought I'd mention that repair since it's an associated component.

Anyway, any thoughts on what it could be? I've thought that maybe the radiator is old/corroded/clogged and incapable of handling the excess heat load from running the a/c on an extremely hot day. I don't know though, I'm a backyard mechanic, at best, and every new problem is a learning experience for me.

Any help would be greatly appreciated! Thanks!

 

well, does the Fan come ON when you over heat? maybe try a Thermostat.
it is possible that your radiator is clog. You can try flushing it out. Just disconnect both radiator hose, and run water thru it.

 

If all else fails to correct the overheating don't forget the water pump. I had an overheating problem and it turned out to be the water pump. The impeller was loose on the shaft.

 

Yes, the fan runs. Do they have different speeds they run at, or is it just an on/off type setup? If they have different speeds I have no clue how I would tell whether or not it was running at varying speeds.

 

The fans turn on at ~ 220 deg at 30% speed. Speed increases as the temps rise. The only way to detect fan speed I know of is with A DRBIII scanner at the dealership. If your fans are indeed turning on with the A/C on, I would agree with a corroded radiator or weak pump.

 

Ok, I changed the radiator and the thermostat. I'm not sure if it's fixed or not because here in Indiana today is a beautiful temperate day and not hot enough outside to cause the problem if we use the air conditioner.

I do have another question now though.

When I pulled the thermostat housing I discovered that the old thermostat had basically fallen apart and the pieces of it were just lying about in the bottom of the housing.

It's the lying about part that disturbs me. Given that the coolant system is pressurized and flowing, shouldn't the parts have migrated elsewhere? I mean the water pump should be forcing the water through the system and moving the stuff around, right? Or am I just retarded?

How would I even know if my water pump was working? It doesn't leak, and the weep hole isn't seeping any water, so how would I know if the pump was actually moving the water? Or is that just a given?

I don't know, any help would definitely be appreciated.

 

As I mentioned earlier, check the pump. Even though it is not leaking the impeller could be loose on the shaft. That was the problem on my van.

The only way I know to check it is to take it off.

 

One check for the pump, though not absolute, is to take off the rad cap, start the engine and watch for coolant flow about 5 minutes after starting a cold engine.

 

well, if you Heat works, that means water pump is pumping fine. Heater core needs constant coolant to circulate to stay HOT.
since you said your thermostat has fallen apart, that's probably your problems.