Can You Help Me Stop Overheating?!! Options

[JohnnyWadd]

Hey, guys. I'm about to embark on a project to help a friend figure out why her car is overheating. It's a 1992 Talon 2.0L Non-Turbo. She knows I'm a DSMer (though she doesn't call it that), so she enlisted my help. I took five minutes to look at it, but I didn't get very far into it, yet. I figured I'd post what I know so far and see if someone can give me a little insight as to what to look at. Maybe that'll make it a bit easier on me once I do dive in.

Anyway, the girl called me and told me that someone had told her that the water pump was out. I asked her how sure they were, and she said they were positive. So, I asked her if it was leaking any coolant from anywhere. She said "no". In my experience, a bad water pump leaks because the seal usually goes bad. Could it still be the water pump, even though it's not leaking? I've never seen a water pump just stop circulating. Hell, even when they leak, they usually still circulate, don't they? And the bearing can't be seized up. Since it's run by the timing belt, I'm sure it would've shot that bitch out of there, then I'd be in major trouble.

So, I went to the car and started her up. I only let her idle for five minutes in the driveway. I never took her out on the road. As she sat idling, sure enough, she started to get hot. As the temperature rose, though, I noticed that the cooling fan never kicked on, even though the guage approached the red line. I decided to try and jump that temp switch to see if I could kick that fan on. I know there are a couple of temp sensors on that car. The only one I messed with is the one on the thermostat housing. Is that the right one? Is that the switch that's responsible for cycling that cooling fan off and on? If not, where is it? On the radiator?

Anyway, I disconnected the plug and tried to jump across it to kick the fan on. Nothing happened. I them messed with the circuit breaker for the fan on the fuse block. Took it out, then put it back in. Still nothing. I plugged the temp switch back in and kind of played with the wires a bit, but still was getting no love from it.

Then, as I was going around to the driver's side to make sure I wasn't running it too hot, the fan kicked on all by itself. Seemed a little late to me. I felt like it should've been running much sooner. It had been running for quite a while and hovering near the red before it decided to comply. Not sure if it started because of what I'd done or not. Anyway, I watched the guage, and it dropped to a more reasonable level, but then it decided to start rising again. I decided to kill it before I got it too hot. Then we be really screwed.

So, what do you guys think? I think that there's something wrong with that fan or the switch or the relay. I don't think the pump is bad. If that water wasn't circulating, I don't think the temp would've dropped at all when the fan kicked on. That is, unless the temp sensor for the guage is near that fan, and it was reading the temperature of the coolant near where the fan was cooling it down. But, then if it wasn't circulating, the coolant in the radiator wouldn't be hot at all, right?

I'm a little confused. I'm guessing if it was strictly the fan, it would run much cooler at highway speeds, right? You know, with air passing through the radiator. Let me know what you guys think. As soon as I get a chance, I'm going to dig deeper. I'll post what I figure out.

Thanks for reading this, and I thank you in advance for any advice you might be able to give.

Jon

[JohnnyWadd]

All right, guys... I think this car might have much bigger problems, and maybe I shouldn't have dropped $450 on her. I've owned it for two days, and already thinking I should kick myself in the ass for squandering my cash.

First off, I decided to pull the thermostat out of her to see if I could keep her cool while running down the road. And, before you ask, no I wasn't planning on leaving it that way. I know it's not good for the car to run it without a thermostat. Anyway, the first thing I noticed is that there was about 1/8 inch of gunk on the thermostat all the way around the opening. I didn't think it was motor oil, but to be sure I ran down to a local radiator shop to ask them what they thought it was. The guy told me what I thought he would. He told me that he thought it was stop-leak. Like Bar's or something similar. Evidently, this thing started leaking, and rather than fix the problem correctly, someone threw a bunch of stop-leak in the cooling system.

So, this presence of gunk leads me to believe that the inside of the radiator looks the same.

Anyway, after I took out the thermostat, I decided to take her for a drive and see if she ran hot. At first, she did okay. It ran for a couple of miles (city driving) at normal operating temperature. By that, I mean that without a thermostat, it ran at the temperature it normally runs at with a thermostat, not less, as it should have if the thermostat were the problem. I let her idle while talking to the radiator guy. It still did fine. Then, when I started coming back home, it started getting way worse. The guage pointed to the start of the red line, so I shut her down. I decided to limp her home by starting her, getting her up to the speed limit, then shutting her down, taking her out of gear, and coasting down the side streets. I made it home this way without overheating her.

So, anyway, there's no water in the oil pan, and no oil in the cooling system. However, the radiator guy told me that what these things do when the head gasket goes bad is leak between the combustion chamber and the coolant system. So, the compression increases the pressure in the cooling system, forcing coolant out (usually by creating new leaks in the cooling system). The only upside is that I can find no evidence whatsoever of cooling system leaks. Not surprising, considering that there's an eighth of an inch of stop-leak in there.

So, let me give you my logic, now. If you guys see a fault, point it out. If you have another idea, shout it out. If you agree, give me some words of encouragement. I'm thinking one of two things: bad head gasket; or so much stop-leak inside the radiator that neither the fans nor the air coming in at driving speeds can begin to cool the water. Since there is no coolant/oil exchange between the oil and cooling ports, I'm thinking that with a compression test, I'll be able to tell if the pressure is leaking back into the cooling system. Also, if I did a compression test with the radiator cap off, wouldn't I see bubbles shooting up through the water at the filler hole? Pressure will release at the point of least resistance. If I have the cap off, that will definitely be the point of least resistance.

If I find no head gasket woes, I would think that I can assume that the stop-leak is the culprit. Is there anything that I can run through there to get rid of all that shit? I don't think that just flushing it will drive that stuff out. If not, I'll just replace the radiator and see if that helps it run cooler. No, not with a new one. I'm not going to take that big of a chance.

One more thing of note. When under load, there's a bit of a rattle coming out from under the hood. Can't tell where it's coming from. It doesn't do it when I rev the engine. Only when under load. Not sure what it is. It's not really a knock. Not loud enough. Like I said, it's a bit of a rattle. You know, it almost sounds similar to the rattle a diesel engine makes when operating normally, though not near as loud. What do you guys make of that?

Thanks again for your help, fellas. I appreciate anything you can give me.
Jon

P.S. I hate all forms of stop-leak. They're evil. They should be eliminated to force people to actually fix problems that arise rather than just putting a band-aid on something that needs a tourniquet. I think that they were invented by and for people that want to mask a problem before they rip off the next owner of their car.