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Anyway, I have a Grand Am 2003 V6. It only has 80k miles. My car ran great when I got it(used), but at some point it began to have minor temperature problems. It would always run a little bit hotter than it should. This basically just meant I couldn't keep it idling forever. At some point I took a drive for about an hour and the vehicle was running fine. I got to where I needed. On my way back home though it overheated. It didn't blow up or anything because I caught it in time, but it hit the redline. I checked it and it had no coolant at all. I let it cool off and filled it up with water and there weren't any leaks and it drove fine after that except for the before mentioned idle-overheating problem. This was about 2 years ago.

I ran over a deer a few months ago though and now the problems are worse. It was discovered that one of my fans was burned up, so that could have been the previous problem. Now though, the radiator has been replaced and both fans work and now it stays hotter than usual just driving. The temperature it usually should be at is about 200F. It now commonly stays about 205 and can get as high as 225 with just normal driving(note, 260F is red line)

One more unique thing about this. If my engine is at about 205 when I park, if I turn off my car and leave it for about 15 minutes, when I come back and start it, it will usually be about 215 or so. Basically, noticeably hotter after turning it off and back on.

I've checked for leaks -- There may be a very small leak somewhere. But it shouldn't be anything to worry about because I fill it up with about 2 cups of coolant or so after 3 or 4 months. So it's a small leak, if not just evaporation. And of course, I've checked to make sure I have enough coolant and that it's mixed properly.

And the only other thing(which is getting fixed soon) is that my air conditioner lines are ran wrong with one of the lines right against a heat shield on the engine, but that shouldn't affect the temp of the car should it?

So what could be the problem? I don't expect to fix this myself, but I'd love to be able to suggest to a mechanic maybe what the problem is instead of them tinkering around for a couple of very expensive hours.

Edit: I don't know how I forgot to mention this, but there is a hissing coming from my engine. I thought it was from my A/C(which is normal?), but I'm beginning to think it's not. Basically, I can hear a hissing that appears to be coming from within the air vents in the interior. The hissing is particularly loud when idle or braking and goes away completely while doing hard acceleration with it getting more and more quiet with the harder I press the accelerator.

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Hotter after sitting briefly is normal. The coolant continues to absorb heat from the hot engine, while not having any airflow for cooling. Shouldn't be too extreme though, should only climb to near what the oil temperature is (under normal conditions 10-30 degrees difference is typical). –  Brian Knoblauch Jul 7 '11 at 18:49
    
@Brian ah ok then. Scratch that off I suppose, still don't know why my car gets warm by normal highway driving though –  Earlz Jul 7 '11 at 19:40
    
Under which circumstances does the temperature go up to 225 while driving? What sort of speeds? –  Timo Geusch Jul 7 '11 at 20:38
    
@Timo any speeds. Usually when going slower though like 25 to 50 MPH. My engine usually runs right above 200 when driving 65 MPH –  Earlz Jul 11 '11 at 18:13
    
@Timo and it seems basically random. Going uphill and lots of starts and stops make it seem to heat up quicker, especially with it being summer. But really not doing any hard driving like up a large mountain or anything like that. Just normal city driving mostly is when it seems the worst –  Earlz Jul 11 '11 at 18:15

6 Answers 6

My 2001 aztek with 120000 miles was overheating badly. Radiator had a leak and was replaced. Still overheating with new thermostat. Bottom line dexcool ate head gaskets up. Was losing Antifreeze thru cylinder. Replaced head gaskets and put in standard Antifreeze. Runs great.

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You see, the problem with runnning with straight coolant--a don't know how that fad got started in the previous century--is that coolant has relatively little heat capacity; whereas water has very much (near tops) heat capacity--for which reason, the main coolant during summer driving is water, not antifreeze. The main purpose of commercial coolant/antifreeze (along with radiator cap) is to raise the boiling point and lower the freeze point of the water--that plus imparting anticorrosion qualities to the water. Because of water's and of antifreeze's separate and distinct advantages, the 50:50 water:coolant mix is typically found to provide the best compromise of advantages and disadvantages, for the widest range of average weather conditions... for all makes and models.

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up vote 3 down vote accepted

This actually ended up being a very simple problem. Something so simple that I'm almost in disbelief.

My car has been running nearly straight antifreeze.(I'd say about 90% anyway) Everyone I'd talked to locally has said it should run even cooler doing that... but they're wrong. I emptied my expansion tank(not the radiator itself) and filled it with straight water. After a day of running it and letting it mix my car is now back to running at 200F and doesn't get hotter while idling or anything.

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First, if it runs hotter during slower speeds (the 25mph-50mph you mention), I would think this is a sign that you're not getting enough airflow through the radiator. This might be a fan issues, but it might also be some other obstruction that prevents sufficient airflow.

You said you hit a deer and had the radiator replaced as a result. I would check or get someone to check both for a vacuum leak (the hissing might indicate a vacuum leak although it shouldn't go away if you rev the engine harder unless it's a turbo- or supercharged car) and also check if all the ducting to the radiator (if your Grand Am has some, I would expect it to) and the undertray under the engine is present. If they've been damaged and haven't been replaced, this can mess up the airflow in interesting ways and can easily contribute to less airflow through the radiator.

Unless you live in a desert climate like I do, I wouldn't expect the sort of coolant loss you describe - it's quite a lot and evaporation of coolant were a problem we'd all be constantly filling up coolant :). In fact I'd worry about that even in the climate I live in.

I'd start with getting the ducting checked out and the cooling system pressure tested - every decent shop has the kit for the latter and if it doesn't hold pressure for a reasonable amount, you've got a leak somewhere and need to get that fixed first.

Edit: Given that you mention that the radiator was replaced with a used one, there is a chance that it might be partially blocked or at least not flow as well as it should. Flushing out the blockages depend how bad they are - you might be able to flush it out with the right sort of chemicals but there's no guarantee. The easiest way to find out if the radiator is suffering from blockages is to warm up the car properly until the radiator hoses get hot and then see if there are areas of the radiator that remain cold. Don't touch the radiator for that, either hover the palm of your hand half an inch over the surface or use an infrared thermometer. If there are blockages you should notice a difference in temperature.

Chances are that if the blockages are severe enough to affect the running temperature, it's time for a new radiator. Get a new one from a reputable shop this time, it's a lot cheaper than having to fix a head gasket that blew because the engine overheated.

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I checked my coolant yesterday and it's still to the rim. I last filled it up a few months ago, so I'm going to say it's not leaking at any practical rate. But yes, I'll have the vacuum checked as well as the radiator pressure tested and give an update back here –  Earlz Jul 12 '11 at 18:31
    
Also, I'm sure this is probably normal, but no matter how hot my car might get, all I ever have to do to get it back down to the regular 200F is turn on the heater for about 3-5 minutes. Afterwards, it will slowly heat back up again depending on the driving I'm doing, but I can always at least keep it from getting too hot or staying hot –  Earlz Jul 12 '11 at 18:32
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@Earlz, That would be another indicator that the radiator isn't providing the necessary cooling capacity - you're basically using the heat exchanger of the heater as an additional radiator. If you hadn't mentioned that the radiator was new(ish), the symptoms would look like a partially blocked radiator. –  Timo Geusch Jul 12 '11 at 19:48
    
well it's a possibility. It wasn't a new radiator, it was a salvage from a car exactly like mine. I would think that the person who repaired it would've checked for blockages when installing it but seeing all the other things he didn't do or did wrong, I wouldn't doubt that to be a problem. Just out of curiosity, if there is a blockage in a radiator does it usually require getting a new radiator or can they be flushed out? –  Earlz Jul 12 '11 at 20:01
    
I've updated the answer, short version is you might need a radiator or you might be able to flush out the blockages, but I wouldn't put money on the latter. –  Timo Geusch Jul 13 '11 at 1:41

The hissing might be a vacuum leak, have your mechanic look into that.

When car runs hot or gets close to overheating, it is extra taxing on several parts of the engine and cooling system. There could be gasket that is leaking or a water pump that is close to failing, or you could just have a bad thermostat, but it sounds like the problem might be worse.

I would suggest getting it looked at soon, as running it hot might cause more problems.

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for the hissing, is it possible that this is just a coincidence? The knob broke off on the fan control of my air conditioner and now I have to change which vents are open with pliers(on the small metal stick that was attached to the knob). Whenever I turn the knob with the pliers the hissing can either get louder or quieter and at some point I can barely hear it. –  Earlz Jul 12 '11 at 19:03
    
@Earlz, in that case it could just be leaking vacuum controls in your air vents or something related. –  jzd Jul 13 '11 at 10:53

Have you replaced the thermostat and or the coolant temperature sensor. I have had a car which I thought was overheating have a bad coolant temperature sensor and there was actually nothing wrong with it. If that doesn't fix it I would replace the thermostat which is cheap and easy in most cars.

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Yes, I've considered that and I'll probably end up doing that before doing any other costly checks/repairs. –  Earlz Jul 11 '11 at 18:12
    
Also, you may want to see my edit –  Earlz Jul 11 '11 at 18:21

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