Question about 1999 Pontiac Grand Am GT

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1999 Pontiac Grand Am Overheating

Hello,
I just purchased a 1999 Pontiac Grand Am with a 3.4 liter motor.

The coolant system seems to run dry, I have bled the air several times and changed the thermostat. It will run fine for a little while then the heater stops blowing hot air and the radiator air starts blowing cold, the temp runs up to 250 + I've heard that the head gaskets can blow out on these motors, is this one of the things it does when the head gaskets are bad ?

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  • daviddean Aug 20, 2008

    Yes. I have had the intake gasket replaced, but engine is still overheating.

  • laurtawney5 Dec 23, 2008

    do you think it could be thermastat, head gasket, and is it expensive. i only have 85,000 miles on it. should this be happening so fast?

  • oceanblu2004 Dec 29, 2008


    I am having the exact same problem and I have replaced the thermostat, the water pump, and I am still having the problem. I replaced the head gasket a few years ago which cost me over $1,200. We haven't checked the heater core hose yet, but we will try that next.I have had nothing but problems with my car. There are some car repair shops that will check out your car for free, that way you will know if it is even worth fixing before you put a lot of money into it. Good Luck!

  • gconley45 Jan 31, 2009

    I had the head gasket replaced, thermosta, radiator, water pump. The car runs okay until the motoe gets hot. The heater starts blowing cold air and comes out the over flow. The hoses were checked.

  • gconley45 Jan 31, 2009

    In my earlier posting I stated what we replaced on a 1999 grand am 3.4 for the over heating. We replaced the head gasket, radiator and radiator cap, cooling temp sensor, hoses,belt, water pump and the thermostat twice. The resouirer looked fine no cracks. The water was still comming out the over flow and the heater would start blowing cold air. We finally raplaced the resouier because there was nothing left. "Problem solved" Hurray!!

  • gupetto Mar 27, 2009

    the car keeps blowing the water out of the overfill at about 200 to 220 degrees and steaming constantly out of the bleeders a ton of air after i already bled it. this happend two weeks ago to i changed the antifreeze and bled it and it lasted for two weeks now its doing it again. what do you think?

  • alizw Apr 14, 2009

    At first it seemed that my car was leakin water out of the bottom of the water overflow. Now is just is overheatin but it is holdin water now, not sure what the problem is just not wantin to spend 8 hours changin out the water pump if is is something else? ANY SUGGESTIONS... please help
    lil chic wit a grand dam


  • elexbre Apr 26, 2009

    My 99 grand am gt has been leaking coolant for about 2 months then it had leaked coolant in my oil. they say it is my head gasketbut i have no idea how to fixit or how much it would round abouts in parts

  • Gerardo Melendrez Sep 20, 2013

    yes it is the head gasket

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13 Answers

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I had the same problem on my 1999 Pontiac GA 3.4 litre. Replaced a bunch of stuff. It just kept pushing the coolant out the overflow once the temp got to 200 + like to drove me nuts. Ended up being that reservoir. If you measure the O.D. of the cap(brand new cap) and the I.D. of the reservoir filler neck there is no way it will seal(even tried to fit a different type cap,no luck). The system has to be able to build pressure or the coolant will boil out at 212. Causing the coolant to be pushed out the reservoir. Why? you say or How? did the filler neck increase in size. I dont know but GM has write ups about this problem. They say sand it with a piece of sandpaper to smooth it. Maybe someone sanded it way to much?? Around $40 bucks and I was on my way. Hope this helps someone.

Posted on Apr 11, 2009

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  • Jtrevino2134 Aug 29, 2011

    Thanks.... Had this problem with my 99 Pontiac grand am.. Changed radiator, heads, gaskets, thermostat,waterpump, and still couldn't stop the water from comming out of the overflow line. I read this yesterday and changed my reservoir this morning and walah.. It works fine now . So I recommend for people having this problem change the reservoir first it's only 36$ .. Thanks again

  • szakacs87
    szakacs87 May 31, 2012

    I have changed evrything heads,gaskets,temp sensor,thermastat,radiator,upper and lower manifold were cracked so i changed them 2 i even took a another coolant resivor from another car and it kept overhaeting drain all thr fluids out the resivor So i get on here today and read evryone's post so i went and spent the 36 dollors at autozone and got a brand new resivor and walla 700 dollors later every thing is fixed and im cruisin in my gt this was the best birthday present ever thank u CHRIS BURRESS

  • szakacs87
    szakacs87 May 31, 2012

    I have changed evrything heads,gaskets,temp sensor,thermastat,radiator,upper and lower manifold were cracked so i changed them 2 i even took a another coolant resivor from another car and it kept overhaeting drain all thr fluids out the resivor So i get on here today and read evryone's post so i went and spent the 36 dollors at autozone and got a brand new resivor and walla 700 dollors later every thing is fixed and im cruisin in my gt this was the best birthday present ever thank u CHRIS BURRESS

  • Deann Engle Mar 05, 2014

    Im very happy 4 you I hope my grand daughters problem is that simple way be4 700,00.But its doing the same thing yours is doing,She just spent her lifes savings on it at an auction..

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My 99 grand am 3.4 keeps overheating I dont see water leaking and I still have to put water everytime I use da car, fans work brand new water pump raidiater flush and srill overheats can someone help..

Posted on Sep 11, 2011

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My car overheats the fans dont turn on when it overheats i have changed everything i have got told it was

Posted on Feb 28, 2011

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I'm having the same problem, and maybe I'm a little over-emotional, but i kind of want to hang myself. I've had EVERYTHING changed, the water pump, the thermastat, the coolant tank itself, the hoses, and the head gaskets have been replaced TWICE since I bought the piece of garbage, It makes me sick, I drive about 10 blocks to work everyday and ten blocks back (in a small town) and I have to fill the coolant tank every morning!!! GM can eat my ****, not a nice thing for a lady to say, but seriously, who's the moron that came up with this car? NOTHING BUT PROBLEMS! I'm glad Pontiac is dead.

Posted on Jul 15, 2009

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I just had that problem, its a intake leak! i just got that fixd on my car, i also would check on getting the belt fixd if its old i mean replaced! because it could not be working properly and be causeing the water pump not to work as well.



Posted on Apr 30, 2009

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The :Pontic Grand Ams and many GM cars have defective cooling systems.GMC installed "Dexcool in may of their models about 5-10 years ago. There's a class action suit that GmC agreed to pay out on soon. click decool.com

Posted on Apr 12, 2009

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Ya, these 3.4 engines along with the 3.1 engines are known for blowing head gaskets, most will will not make it to see 100k miles without a head gasket blowing.
And your overheating problem is pretty much text book effects of the head gasket going, although it could be other things - given that motor chances are its the head gasket - and NO you do not have to have milky looking oil for the gasket to be broken- it would all depend on where it broke, and the extent of the break. but if you keep driving it while letting it overheat - you will end up warping the heads and causing a larger gap for the antifreeze to leak into the oil (thats what causes the milky oil), chances are the car will no longer want to run after that.
You can purchase a $40 cooling system pressure tester to confirm it - they sell them just about everywhere , its attatched to the cap where you put in the antifreeze - you pump pressure into the system and see if the pressure can be kept, keep a eye out for leaks while doing this.

Posted on Apr 09, 2009

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Yes it sounds like its already blown check your oil, and see if its gray

Posted on Aug 22, 2008

  • bmbxiii Dec 01, 2010

    hey ppl mutsy here to help you out and there are 2 main overheating problems ether your reservoir or the the problem that is always happening with these 3.4s overheating is the lower intake gaskets..you see GM put out these motors with totally weak factory lower intake gaskets where the coolant channels will surely leak or worst, mix with the oil..and believe when i say it is a pain to change if you dont know what your doing..i dont what GM was thinking with this defect..hope this was helpful so fix it or just buy a ford ;)..

    musty

  • justinkeaton
    justinkeaton Dec 17, 2012

    my 99 grand am overheats..NO HEAT BUT I LET IT IDEL FOR ABOUT 20 MIN AND IT WAS 3/4 OF THE WAY ON THE TEMP GAUGE I PUT IT IN REVERSE BACKED OUT 10 FEET IT GOT REAL HOT..HAS NEW THERMOSTAT..THERE JUST SEEMS TO HAVE AIR IN THE LINES I BROKE THE BLEEDER LOOSE AND JUST AIR COMES OUT NO COOLANT.COULD IT BE THE WATER PUMP FOR RADIATOR??NEED HELP PLEASE!!

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Make sure the fan comes on. The plug can get corroded by salt or the relay in the fuse box that turns it on can fail and this is the easiest thing to fix. Rule out the hoses, water pump and the tank where you add more coolant before considering the head gaskets because it's so expensive. The hoses, heater core and possibly the water pump could go bad in this much time. If the previous owner replaced the hoses without scraping the old rubber stuck on where they were connected, they may be fine but will leak by the ends. You shouldn't drive the car in case it is the gaskets because it can make it worse.
I would clean the engine bay with Engine Brite spray and rinse off the radiator. Don't spray Engine Brite on the radiator or wires. Then you can warm it up after it's dry and see where the coolant is coming out easier. Look around the hoses, clamps, water pump and the overflow tank and its hose, the radiator cap, and on and under the radiator for antifreeze. You can buy a hand air pump at an auto parts store that replaces the radiator cap to force the leaks to show up without running the car. A heater core can also leak due to using red antifreeze or nor replacing it often enough and the coolant can end up as a sticky sweet smelling spot on the carpet or drip under the car behind the engine area. Once air leaks inside the cooling system, it expands, pushing out coolant faster still, so the loss isn't steady. When the level drops enough, steam forms and touches the temperature sensor which is usually way below the highest water level. You will notice the temperature gauge shoot up in less than a minute from whatever to over 240 degrees. By this time, there has already been steam in the top of the engine since this is higher than the sensor. Since steam doesn't cool on contact like water does, these spots get even hotter while it is running, warping the flat surfaces that the gaskets are wedged between, which might cause just a new gasket replacement to fail if driven like that for too long. When your heater doesn't work, it has dropped to the level of the water pump, which is spinning dry. The water pump seals are lubricated by the antifreeze, so this is bad and if you've been only adding water because you ran out of antifreeze, it's worse. Most antifreeze they sell for at least 10 years is actually 1/2 water. Almost all water in the system causes steam to form easier even if it is full. So what I'm saying is check it periodically later, even after you fix any leaks.

The gaskets have to leak in one or more of 4 places.
1.Between a cylinder and a coolant passage: Water doesn't burn and may foul the spark plug. The engine may misfire enough to turn on the check engine light and the exhaust may smell sweet or with unburnt gas. On a cold engine and a full radiator, take off the radiator cap and start it. Look down in the radiator for clear or white bubbles of exhaust smoke coming up that smell like exhaust.
2. To the oil returns: This can happen with manifold or throttle gaskets which are cheaper to replace. Coolant gets inside the engine oil. The oil will look slightly creamy to like coffee or chocolate milk. The bottom of the oil fill cap may have water drops on it even when hot and smell both sweet and like gas. The car may suck some oil or water through the intake and it will show in the exhaust and foul the spark plugs.
3. To the edge of the engine: Coolant will run down the outside of the engine and smell sweet when it evaporates off it's heat.
4. Between 2 cylinders. It won't necessarily lose coolant, but the burning will blow back and forth across the gasket between the cylinders, eventually warping and melting the aluminum between them. You'll know because it will lose power and come on in seconds to minutes. If you shut down right away, it will just burn the gasket.

Posted on Nov 08, 2016

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My car does this exact same thing we were kinda thinkin the heatercore cuz it keeps getting air in the lines somehow we have to bleed it everytime we leave and about 3 times just going 16 miles into town .so we bypassed it today if it over heats again then we know its not that and if its not that then im pretty sure its the resivour tank cuz we can harley get the cap on n off its really hard to get off n on gotta use pliers to turn it and its a new cap lol if its not that then head gaskets lol

Posted on Feb 14, 2013

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I had the same issue with coolant running out of the overflow, it was not the tank and it wasn't an intake gasket, it was as simple as a 9 dollar radiator cap. If they go bad the cap won't hold the pressure like it should allowing the coolant to go through the tube and onto the ground. Good Luck!

Posted on Aug 13, 2010

I had the same problem check the heater core hose they get pinched so coolant can flow.

Posted on Oct 08, 2008

There is a bleeder valve. look on top of water pump housing you'll see a tube about 1" in diamater with one tube about 3/4" that runs across the front of engine. It looks like a brass plug. It takes a 5/6 wrench or socket. open it and let the air excape

Posted on Sep 15, 2008

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SOURCE: 1999 Pontiac Grand Am Overheating

It is probably the problem. To make shure that need to change the gaskets, one of the symptoms use to be thet the temp rises when you are running at speed 50+ average, where is supposed that the car gets a lot of air due by the speed and nobody thinks that will be overheated.

Posted on Nov 19, 2008

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