Question about 1998 Pontiac Sunfire

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Pontiac sunfire overheating

I have a 2.2l 1998 Pontiac sunfire that is overheating...It started out running a little warmer than normal, Then it started where it was getting into the yellow (ran at normal temp when idle) Then it progressed to full fledge overheating, I replace the themostat thinking that maybe it was sticking closed...That didnt work...then I replaced the waterpump...Nothing changed...My oil isnt milky (no antifreeze mixed)...Sometimes the heat in the cab will work fine then all the sudden it will stop and thats when it begins to overheat...almost as if the coolant stops flowing...The top radiator hose builds up with lots of pressure then it starts blowing antifreeze out of the reserve tank...Any help that can be offered will be greatly appreciated...I describe the problem to the best of my ability...If you need anything else checked just ask (rad fan is working also)

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  • Anonymous Jan 29, 2009

    I have the same problem, 2000 Pont Sunfire , no heat and starts overheating, Im thinking the heater core is plugged up. Checked the hoses and only one hose coming out of the core is Hot. I think i will change the core and see if thats the Prob.

  • ruger32 Jan 30, 2009

    I am having overheating problem on 98 sunfire. Will run fine for 25 to 30 miles, then overheat. Lots of coolant coming out from somewhere, can't find source. Have replaced heater core that was leaking, that's when overheating problem started. Then replaced t-stat. Didn't help. I was wondering if it might be something as simple as the cap on coolant reservoir not holding 15 lbs. of pressure

  • Anonymous Mar 29, 2009

    mine was doing the same, i found a few holes in the rad hose, as i went to the yunk yard to get another one i discovered that this problem is quite common. thsat probably where your coolant is coming from, a leaky rad hose. but alas, my overheating problems dont end there.

  • zjayz101 Apr 10, 2009

    I also have a 98 pontiac sunfire Im having the exact same problem I also changed the water pump, t stat and when that was done Istarted it up and the engien would violently shake and now there is no water left in the resovore and the car wont start also there is the smell and smoke frome the exoust coming from the resavore tank i really do belive that the head gasket is blown !!!!!!

  • JayJays_Dad Apr 28, 2009

    my 97 sunfire has that mist from the reservoir tank, it keeps overheating, and now a worse leak from somewhere around the reservoir. it was leaking from the water pump before so i replaced it and the thermostat, but now it leaks [elsewhere]. even after i fill the reservoir it still overheats.

  • soulmate_des
    soulmate_des Jan 24, 2013

    your head gasket is leaking air from the motor into the rad and heater core.take the thermostat out and drill a 1/8 size hole in it right beside the little center opening brass centerpiece on the thermostat.this will release pressure in your motor and solve your problem.it works for me,try it.

  • soulmate_des
    soulmate_des Jan 24, 2013

    TAKE OUT THE THERMOSTAT AND DRILL A 1/8TH HOLE IN IT WHERE THE COOLANT GOES THROUGH IT,PUT IT BACK IN AND YOUR PRESSURE PROBLEMS WILL GO AWAY,IT WORKED FOR ME.

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I have your fix, Disconnect your Heater Core hoses and flush out the Heater Core or replace it. The coolant has to pass through the Heater Core before it gets to the Thermostat. GM designed the cooling system this way to speed up in-cab heating.

Posted on Jan 31, 2011

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For the last 3 years, i fixed about 12 of these 2.2 motors of sunfires and cavaliers. For some reason the cylinder head get warped and tends to damage the head gasket. From there on overheating progressed and aggravates the situation. Air leaks into the coolant chanel and further deteriorating engine cooling effect. To fix the problem, took the cyl-head and had them machined. So far all of the motors i've done never had the same overheating problem.

Posted on Apr 09, 2010

  • soulmate_des
    soulmate_des Jan 24, 2013

    MOST SUNFIRE WHICH PRESSUREIZE ARE A COMMON HEAD GASKET PROBLEM.THE AIR GOES INTO THE RAD SYSTEM AND PRESSURE THE THERMOSTAT TO STAY SHUT AND OVERHEAT,DRILL A HOLE IN THE THERMOSTAT AND PUT IT BACK IN,THIS WILL WORK IN MOST CASES,AS IT RELEASES THE PRESSURE FROM THE HEAD GASKET LEAK.

  • dark_439
    dark_439 Jan 30, 2013

    are you sure about this? will it still be safe to opperate? mine started overheating a while ago, i changed the t-stat and it kinda seemed fine for a bit, the coolant light still comes on every now and again eventhou it is filled to the right amount. the Rad stays cool, the left hose that comes from the t-stat housing down to the rad is cold, but the top hose on the right side is warm, and the rad itself is cold, havnt noticed the fan come on either???

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In the summer 2008 I had my entire cooling system replaced. About ten days afterwards the overheating problem disappeared only to return in the summer of 2010. To make a long story short, it was the cooling fan relay that needed to be replaced. Now the car is running like a champ! - Bob the finder www.bobthefinder.com

Posted on Aug 19, 2010

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I had a similar problem with a 98 sunfire 2.4l. The first thing I did was check to see if the fan was running, and it was, but it seemed to be coming on and off at the wrong times. If you look at the fuse box under the hood on the drivers side there are a few relays on the side closest to the firewall. A quick way to check if the relay is the problem is to swap the cooling fan relay with the heater fan relay since they are identical. If it solves your problem then you know you need a new relay. It worked for me.

Posted on Aug 20, 2010

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  • Pontiac Master
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I'd take the radiator out and flush it in both directions. If that makes a difference, flush it out again. also,There is a possibility that cylinder pressure is driving coolant out of the head, into the cooling system, from either a bad head gasket or crack in head itself. Check electrodes on plugs for signs of coolant. I'd do the radiator thing first though. There are tests a shop can do to find the head problem... The rest is up to you!

Posted on Jan 03, 2009

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Mine overheated gradually into the yellow & finally into the red. Changed thermostat...still in the red. Have to purge air out of the pressurised system..purge valve near thermostat in line. Air in heater core causes it to blow cold. Water pump new only 3 years ago. Nothing leaking this stone. Considering testing & changing temperature sensor

Posted on Nov 12, 2016

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SOURCE: 2001 Pontiac Aztek Overheating. Replaced

Sounds like you have a clog, or a collapsed hose. Try flushing the system.

Posted on Feb 28, 2011

salsaurbana
  • 56 Answers

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

LowJulz01
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SOURCE: pontiac sunfire overheating

hello! I had the same problem with my 2000 Pontiac Sunfire... there might be one of these 2 problems with it.... maybe the Heater Core is jammed and the coolant dosen't flow thru the engine to cool it off, or the water pump is defective.... does the heating works or not? if yes, the water pump is defect, if not, the heater core is jammed, try a ''radiator hose cleaner'' (sold in Napa's or Carquest..) it will act as a kind of ''decloaker''.. if works, good! 15$ solution... if not, replace Heater Core... ~150$

Posted on Jan 15, 2012

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