overheating problem

I have a 99 Grand Am 3.4L engine with 98,000 miles on it.

A couple days ago it started overheating. I am able to drive the car for about 10 or 15 minutes at normal operating temperature and then the temperature slowly starts to creep up. Only one time was it able to get so hot without me noticing that the temp light came on.

It is not leaking any coolant except through the overflow after it overheats. I replaced the thermostat. I am going to try the air bleeding procedure that xeroinfinity has posted.

Any other suggestions would be great, it seems so odd to me that I am able to operate at normal temp for a while before the overheating starts, and it is consistently like this.

sound like a failing water pump

I'm agree, when a my car overheating i will check first the water pump, most of the time this is the problem. Try to check it out. If no changes at all ask advice from the expert or mechanic.

I did not get much air out and it did not make any difference. I have no reason to believe that the cooling capacity of the radiator could have diminished due to damage or clog so I also think that a failing water pump could be the problem.

I don't know a lot about these pumps, is it just that the impellers get worn or something. That is what I am suspecting as it seems the cooling capacity has just dropped marginally in this case. I am excited that a new one is like $20. I will most likely pick one up today and install today as it looks very easy to get too, probably easier than the thermostat was.

before you replace the water pump, check out:

http://www.automotiveforums.com/vbulletin/showthread.php?t=1012323

See if your system comes up to pressure after 10-20 minutes. No pressure = problem. Check reservoir cap (~$5 to replace); get coolant system pressure tester (some auto parts stores loan them out) and do the pressure leak-down test.

the pump itself isn't hard to replace, provided that you can get to it
However... beware that usually the pump is driven by... the timing belt/chain!

Since you would be messing with it, you might want to also change the belt/chain, specially if it's a belt!

replace t-stat, pump & cap.

I did a flush with one of those bottles for flushing the coolant system. That made no difference. For now I am just running it with the fans on all the times and it does fine. I just have to turn the A/C on when I first get in the car to turn the fans on and then they stay on and they keep the temp down. I bought the water pump but didn't put it in yet. I think I will put the pump in this weekend just to see if that will make the difference.

Do these pumps get worn down some how or lose pumping capacity slightly at some point?

So you mean the fans do not turn on when the coolant is hot?

The sequence should be: cold -> heat up -> thermostat open -> heat up -> fans turn on -> cool down -> fan off -> heat up -> fan on ... and so on

if the fan do not turn on, then possibly that the "electronic" thermostat has failed.

I first assumed that the fan was running as expected

The fans on this car turn on when the car gets to 223 degrees or when the pressure in the A/C lines is above a certain point which basically turns the fans on once you turn the A/C on.

So, have you checked to see if it holds pressure?
My take is that water pumps usually fail by leaking, not by losing the ability to pump. Does your heater work? If you run it for 5-10 mins and turn on heater, do you get hot air? If so, your pump is OK.
Nothing should be coming out of the overflow until the pressure is >15psi; unless the reservoir or cap is bad.

Replacing the water pump at 98K miles is a good idea, I'm just concerned that it might not be the cause of your immediate problem.

I'll check out the cap. It doesn't screw on very well, feels like it is all cross threaded and you have to turn it a million times to put it on all the way. Maybe I should just buy a new cap.


I think I will do that before I put the water pump in just to see.

Cap did not work, car is still overheating. Time to put the water pump in now.

Replaced the water pump, that did not fix it.

A close friend who is also a mechanic had been telling me since the beginning that this is a sign of a blown head gasket so we changed that today as well as all other gaskets. Still overheating.

Very unhappy about this.

So far I have replaced thermostat, water pump, expansion tank cap, and all gaskets. I have no ideas. I think I need a new car.

A blown gasket would cause coolant leak and/or exaust in the coolant, causing bubbles. the leak would cause the coolant to leak out, to be burned or to mix with the oil.

I'm starting to wonder if the problem could be... electric...
Like a faulty temperature sensor...

Pressure test results?

http://cgi.ebay.com/ebaymotors/Snap-On-Cooling-System-Pressure-Tester-Snap-Coolant-/180518527170?cmd=ViewItem&pt=Motors_Automotive_Tools&hash=item2a07be20c2

I have not done a pressure test. Although I did replace the cap so pressure is not being lost through that.

It appears though that my cooling problem is directly related to the appearance of air being introduced into the coolant system somehow. I am pretty sure there is no other way for that to happen other than coming from the exhaust gases. Since all the gaskets were just replaced yesterday I am thinking it could be a crack in the head although nothing was seen.

Is there a brand of stop leak that someone would recommend over others?

It sounds like the air being introduced into the cooling system is steam, from boiling coolant. Coolant boils at a much lower temperature when it's not under pressure. Most cars cooling systems will run at 7-10 psi after warm-up. Parts of the engine (near cumbustion chamber) get really hot, and will boil coolant unless its under pressure. I'd really check the coolant reservoir, cap, and hoses attached to it for pressure leaks. The reservoir itself may have a fine crack in it, typically where the top and bottom halfs are pressed together. The caps have a rubber o-ring that can get crimped/twisted. A new reservoir = $40; or get one from a parts yard. I had one that leaked from around the cap; it wasn't the cap but the reservoir itself.

If its not the reservoir, it may be that some coolant passages are clogged (even though you did the flush). If the heater isn't working, it may be a clog in the heater core.
Are you running Dexcool in it? Dexcool has a tendency to gunk up (brown waxy gunk)when some air gets into the system, which is why its so important to bleed the air out. It will also form a real nasty gunk if it's mixed with regular "green" coolants. Do you know maintenance history, if coolant is dexcool, or was switched to green stuff? Many people have switched from dexcool to green coolant, but you really have to flush out all the dexcool before introducing the green stuff.
I'd stay away from stop leak stuff, if there's a clogged passageway causing the problem it sure won't help. Do you see coolant leaking anywhere? White smoke / coolant in the oil / etc? Once the air is bled out, there's nothing but liquid coolant in there and you should see it leaking out as the engine warms up, if its a leak. The only place where "air" can leak out is the upper part of the coolant reservoir/cap.
Hope this helps.

I sit there with the car running and bleed valve open and the temp will be at 200 and then water will stop coming out of the bleeder and the temp will start rising. Straight water boils at 212, 50/50 boils at 257 I believe. The air will start to form well before it ever gets close to those temps regardless of which I am running in the car.

I believe I have thought of a simple enough way to check the coolant pressure though and I will do that tommorrow before I use the stop leak,


It has not been running dexcool for at least the last 25,000 miles since I have owned it. Before that I really don't know.

As I said I have already replaced the cap but I will check the pressure being held in the reservoir. I didn't do anything to it today.

I am thinking that if I somehow connected the bleeder valve to the expansion tank that it would then have a reservoir for constantly venting off all of the air that forms in the system and that would give me a way to continue driving it for a few weeks until I have time to replace the head if that is the problem.

Well I did my pressure test and it didn't seem like the system was holding pressure so I went to advance and borrowed the coolant system pressure testing kit it most definitely was not holding pressure. With the help of a little soap it is obviously coming from the neck where the cap goes on. Time to find a new expansion tank tomorrow at the junk yard.

Hopefully this fixes the problem, thank you skeeter. You were right all along.....I hope.

try some Teflon tape around the treads of the reservoir.

sounds like the thermostat

I thought about maybe trying some tape of sealant of some sort but I am going to check the pick and pull too I think. Maybe I will give some teflon tape a shot tomorrow morning before I head out to the junk yard.

I thought about maybe trying some tape of sealant of some sort but I am going to check the pick and pull too I think. Maybe I will give some teflon tape a shot tomorrow morning before I head out to the junk yard.


i have teflon tape on mine, and no problems it stays in place even when you remove the cap. Its part of the tread now trust me

3100, it seems like the leak is actually right through the plastic and not around the threads. Maybe it is through the threads though actually now that I think about it. I am going to try the teflon tape first thing. Man these caps go on hard enough already though.....We'll see.

The threads are only there to hold the cap in place, not to hold pressure. It's the rubber o-ring that forms the seal between the inside neck of the reservoir and the cap. If the o-ring doesn't seal (twisted/out-of-round, or because neck is scored or out-of-round) pressure will leak into area above o-ring, which leads out to the overflow hose. That's what happens when the pressure gets over 15psi: the cap has a pressure-relief valve built in that lets pressure through, it comes out slots in the cap above the o-ring and goes out the overflow tube.

The cap shouldn't be so hard to screw on; it's a sign of trouble. Try lubricating the o-ring with wd-40 and see if it goes on easier. But I'd still get a new reservoir.

6$ reservoir from the junk yard. Now the system holds pressure, too bad it still overheats though.

I think it was on the inside by the o-ring that it was leaking.

I put the bars leak in last night, time to go find out if it works now.

Still not working.

sound like a gasket problem now. I would retest the pressure on the cooling system and see if the pressure leaks down. If it does might be a gasket faliure, causing the cooling pressure to leak down?

I already replaced all the gaskets. They really didn't look that bad. I had a friend with me that is a mechanic and he said that he doesn't believe the head is warped at all. So I think maybe there is a small crack in the head that is big enough to allow exhaust gases at pressure to go through but not big enough to allow any liquids through it.

I created a rig that connects the bleeder valve above the water pump to the overflow tank. So that it can vent off air constantly by itself. That was not enough to fix the problem. Now I am going to remove the thermostat and see how it runs like that. I'm not really in the mood to replace the head if I don't know that that is the problem.

A quick check to see if its a heat-problem vs. head-gasket problem: when engine's cold, squeeze the radiator hose; should be easy to squeeze. Start engine; squeeze hose some more.. If pressure builds rapidly in hose (within a minute or two), it's pressure leaking in from the cumbustion chamber. If it takes 7-10-15 minutes to build up, (and levels off at 7-10 psi), it's normal.
I know it's a PITA with the 3400 cooling system. I ended up draining out the coolant and flushing/bleeding several times, and re-using the coolant since it was getting expensive. When you had the heads off, did it look pretty clean inside, or all gunked up?
I'd flush the bejeezus out the system, with heater on full;
Also, the radiator could be clogged so that even a new pump can't circulate coolant properly. Have you used the drain plug in the bottom of the radiator to drain the coolant? Did it just flow right out, or was it clogged up. If the drain plug is clogged, it a sign that lots of debris can build up at the bottom of the radiator. You might want to flush the radiator itself; take off the top and bottom hoses and flush it out with a garden hose.

Is there a drain plug on this car? I never saw one. I have just been draining it from the radiator hose on the passenger side that is near the bottom. The system has been flushed and I am pretty sure pumping through the radiator isn't the issue although I have not back flushed with a garden hose which I did think about doing, I just never got around to it yet.

Right now I am shopping for G6's. They seem to be about the only reasonably priced used car on the market.

I got the Grand Am back into driving condition with my constant vent system and no thermostat. Good enough to get me to the auto dealers I guess. I will probably be trying the back flush in the near future and if that doesn't work I think I will be shopping for a used head. Thanks for all the help, I was surprised that it wasn't holding pressure before, and even more surprised when it wasn't my problem. This has probably been the most mysterious problem I have ever had with a car.

Like lots of things, it's a pain-in-the-a##. It's on the front, bottom, driver's side corner of the radiator; a good pic is at:

http://www.automotiveforums.com/vbulletin/showthread.php?t=936788&highlight=radiator+drain+plug

the picture shows an original plug; since they break a lot you may have an after-market one that is usually black with "butterfly wing" which you twist to open it up. As in the linked picture:
"To loosen the radiator drain all you need is a tool like in the pic below. This is a 1/4" drive socket handle. Insert into center square of drain plug and then just turn 1/8-1/4 turn counterclockwise. The drain plug does not need to be removed."

If you've got the butterfly-wing, you can twist it by hand. These plugs are easy to break. I broke mine and then replaced it with one from A-Zone. My radiator was so clogged up on the bottom that I was able to drive to the store without a plug; and take the old broken plug in to compare to the replacement. The plug works as a valve to open/close a passageway to let the coolant drain out the bottom of the radiator. If it's clogged, use something like a plastic ty-wrap to jam up in the passageway, hopefully that will unclog it. Even as I write this I'm starting to feel like strangling whoever designed it.

Hi, you might want to check your exhaust system for clogging. Why? because clogged cat will not allow hot exhaust fumes to escape from engine on time and engine will heat up faster

Did you try bleeding the air out of the system again? These vehicles are very hard to get all the air out of them. Leave the radiator cap off and let it run for 10-15 minutes and see if any bubbles appear (as long as it dont overheat severely while your waiting). Also, when you replaced the head gaskets, did you check/clean the cylinder heads or the block? You could have a cracked head or block.

any updates? did you check exhaust for abnormal back pressure?

did you ever scan the dtc codes? replace reservoir tank with the cap? did you ever resolve this?