Several issues
 

I just bought a 1999 Gran Am SE. The car keeps overheating and dont know why. My husband put in a new water pump, thermostat, and fan switch. The fans never come on for some unknown reason. We know that they work because he put straight power to them. What does the temp need to be before the fans actually come on? The other problem we are having is the car is idiling rough when you are just sitting there at a light and when you take off it seems to bog down and then it is fine. It back fires every now and then. Does anyone know what could becausing this problem also? Also when you step on the gas it hesitates too.:banghead:banghead

Sound like the LIM ya'll?

Could you please tell me exactly what that is?

Eesh.....sounds like you bought a car that is suffering from the infamous LIM leak. Check the oil to see if it is 'milky'. Also, check the coolant reservoir(tank) to see if the coolant is contaminated with oil. If you can't see inside the tank to check the fluid level, then you need to see a mechanic ASAP.

My husband checked and there is no oil in the reservior tank and the oil is not milky.

Do you see any kind of smoke coming out of the exhaust. Like a white color IIRC. It might be a cracked head.

Does the car rev at around 2000 rpm when you let it idle in reverse?

No smoke coming out of the tailpipe at all. I never paid attention to where it revs when it is in reverse.

I was just trying to determine whether you have a vacuum leak at the manifold. I bought my Grand Am for dirt cheap from an owner who had just got the LIM gasket replaced and the car was still running bad so he wanted to get rid of it. It turns out the mechanics at the shop he took his car to didn't do put the intake manifold back properly and ripped the fuel injector o-rings, causing a vacuum leak.
I don't understand why your fans don't turn on. It could be a temp sensor problem or a bad relay, maybe a fuse. Have the hubby check the fuse box in the engine bay. If the previous owner of your car experienced the LIM leak, there is a chance a component in your cooling system has been damaged. I would think the thermostat is stuck closed, but since that was replaced I don't know if I can help any further. Good Luck!

My husband thinks there is a leak at the manifold just like you said. Do you know at what temp the car will get to before the fans kick on? I appreciate all your help.

The PCM commands Low Speed Fans ON under the following conditions:

The engine coolant temperature exceeds approximately 106°C (223°F).
The A/C refrigerant pressure exceeds 1310 kPa (190 psi).
The vehicle is shut off when the engine coolant temperature is greater than 140°C (284°F) and system voltage is more than 12 volts. The fans will stay ON for approximately 3 minutes.


The PCM commands High Speed Fans on under the following conditions:

The engine coolant temperature reaches 110°C (230°F).
The A/C refrigerant pressure exceeds 1655 kPa (240 psi).

Also, is the Service Engine Soon light on? If it is on, I would try to drive to the nearest Autozone and have them check what code is trigging the SES light. If there is a vacuum leak at the manifold, the SES light should come on. If there is a fluid leak at the manifold, the light might not come on at all.

The service engine soon light it not on at all. We have the stock PCM should we get a new one so the fans come on when the car is off to cool it down?

It says to use DEX cool is that a special coolant we need to use?

Probably not a good idea right now. The stock PCM is not very likely to go bad and be the cause of your problems. Something else is going on. I would first confirm whether your fans are turning on when your car starts to overheat. You know the fans themselves work, but are they being 'told' to turn on during operation.

Well if they arent being told to work when they are suppose to what would be causing that?

The stock fans go on LOW speed at 223 I think.
and possibly HIGH speed at 240-250ish.

Also may want to look in to a head gasket leak.
LIM doesn't tend to cause a car to overheat... just loses oil/coolant.

Heads are basically a few steps past the LIM... not that hard really if you can follow basic directions ;D

With the motor running, open the hood at look at it.
Down the sides of the motor, if there is anything leaking out.. It's a LIM leak more than likely.

When you shut the car off, listen for a hissing noise.
It will be very faint. But it will be there if your headgasket is leaking.
(the car does have to be pretty warm for it to do it)

What method did he use to put the power to them?

edit; Did you buy it from a dealer? or a private person?
Might be able to lemon law that sucker.
Since getting it fixed at a dealer is basically 1/3 the price of the car.
I know I got mine used from a dealership (that only sold lexus/volvos and such.. so this car was dirt to them) and they gave me a 30 day warranty on it from anything that goes wrong or was wrong.
Not that I would have taken it back to them if there was... since they were such jerks... but that's another story ;x

2nd edit; When it's overheating, how hot does it get? Does the red light come on? How many times has it overheated to the red (if it does go that high)...
May want to tear it down to the heads and have them resurfaced anyway if it happened a lot... They could have gotten warped or something.
But if it bogs down you may have something leaking down there and not be getting enough compression.

Might want to replace the coolant temp sensor. I would've done that before replacing the water pump because those usually aren't bad unless they are leaking coolant from the drip hole under the pulley and you can see that.

If you replace the temp sensor and it's reading the temps correctly, and it's still over heating, then it's probably either a bad head gasket/warped head, or a plugged radiator.

Question... how hot does it get on the temp gauge when it over heats? As hass said it has a red zone and the warning light should come on if it gets up there. Does it lose coolant when it does this? If it does this regularly and the fans don't work, you should be getting some type of DTC code and a check engine light.

Just for your reference, it is normal for these cars to run around 210-220. The stock thermostat doesn't open until 195. The computer doesn't turn on the first fan until 223 degrees F (106 C) and off at 217 F (103 C). It turns the second fan on at 232 F (111 C) and off at 226 F (108 C). If you aren't seeing temps over that, the fans won't turn on and it's not over heating. If you are seeing temps over that, and the fans still don't turn on, check the underhood junction box. There are several fuses and relays in there that operate the fans.

The water pump was replaced because it went bad. I dont understand why they make these cars to get so hot before the fans kick on. I know when it gets a little past 200 it will overheat and all the coolant will be all over the place. It just seems that the fans arent coming on like they should. But if it has to reach that temp before they kick on then I guess that would be the reason. The radiator isnt clogged because we flushed it thinking that might be the problem and it was fine. Let me ask this does the Dex Cool coolant make a difference from regular coolant?

No warning light comes on because it never goes into the red when it is overheats.

Many newer cars are designed to run hotter so as to be more efficient and cleaner burning.

As for dexcool, the big issues is never, under any circumstances, should you ever mix dexcool and regular antifreeze. You can put regular antifreeze in, but ONLY after a full cooling system flush. I don't know about you, but I have found it difficult to even find conventional antifreeze any more. Mostly I just see the yellow type that supposedly will mix with either regular or dexcool.