Overheating Problem

[Benm109]

OK, here's the story. It's kind of long.

On Wednesday my car overheated. The temp usually stays at 220 but on the way home that day it went up to 260 (which is redline) and stayed at that temp as I tried to get home ASAP (I'd rather the car overheat for 3-4 minutes than leave it in a parking lot by itself). The SES light came on, too (the codes were 43-EST problem and 53-charging over voltage). 6 hours later that day I started the car, let it idle, and then took it for a quick spin. I came back to the house and let it idle. It then started surging, slowly then more and more and then just died. Two minutes later I started the car again, drove it in the garage, and left it alone.

Now today I put on a new thermostat and gasket (because it was slowly leaking) and a new EGR vacuum solenoid and cleaned the EGR valve (I think that caused the surging). I took the car out for a drive and then drove back to the house. The temp was at 220 but was rising slowly till it got to about 250. All of the time I was watching the fan. It never came on. I shut the car off after it got to 255. The fuse for the fan is fine, I checked it.

Now, my questions are: Does anyone know what my problem might be? Shouldn't the fan come on at around 220? Thanks very much in advance.

[TraceZ]

First I'd test the fan by hotwiring it, then I'd replace the fan temp sensor. I believe in your car there are 2 temp sensers... One for the guage and another for the PCM and fan. There is also a fan relay you can check on.

Does it overheat on the highway when driving at 55 or higher? If not, I'd say fixing the fan should fix your problems.

[Benm109]

How would I go about hotwiring the fan to check it?

[Dave M]

If it overheats on the highway when you should ave plenty of air moving through the radiator, you may have a blockage in the system or debris in front of the radiator or missing airdam, etc. But that wouldn't explain why the fan didn't come on. I agree with TraceZ. If the fan itself is good, replace the switches and/or sensors.

[Benm109]

Also, the fan did come on when the car overheated on Wednesday. I am not sure exactly when it kicked in but after it overheated if I had the car key on, engine off the fan would turn on.

[TraceZ]

Originally posted by Benm109
How would I go about hotwiring the fan to check it?

Unplug it and jump it to the battery.

[Benm109]

Cool, I'll try that ASAP.

[Detroit_Bird]

What's your coolant look like? 91 should be a nice bright green- if it looks brown or muddy there's prolly rust in it and it might not be doing it's job, and/or you have rusty failing components in the system that could be causing the overheat condition.

[Benm109]

It still nice and green. It's fairly new coolant, too. I rebuilt the engine about a month ago so I put some new coolant in it. The radiator is clean on the front, too, because I checked that.

[Dave M]

How many times have you driven it after the rebuild when it hasn't overheated? Was it driven everyday for the last month with no problems, or was this one of it's first trips since the rebuild?

[Benm109]

Yes, it was driven everyday since the rebuild. It is my daily driver and Wednesday was the first day I ever experienced overheating. I have had the car for about six months now.

[Benm109]

I'm going to attempt to hotwire the fan to see if it works. Is there a risk of cross polarizing it (hooking it up backwards, - to + and + to -)? I tried to trace the wires but both go into the wiring harness and then dissapear and they are both black wires. I don't want to ruin it if it is not bad.

[Mr Nice Guy]

On my 95 Formula I had a problem with the fans not turning on by themselves. They would only come on when the AC was on. Do your's come on with the AC. I think mine was probably a temp sensor since running the AC causes the fans to come but I ended up wrecking it before I fixed it. As a temporary fix I would put the AC on in traffic if it got hot. I never had a problem on the highway though.....Good Luck.........Later

[Benm109]

I never tried turning on the AC to see if the fan came on. Any idea about if the fan motor will get cross-polarized?

[Mr Nice Guy]

I would guess that if you got the wires reversed it'd prolly just run backwards but I'm not sure. There are instructions for a manual fan switch as well. Try www.installuniversity.com it should be on there somewhere. Good Luck.......Later