Question about 1998 Pontiac Sunfire
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)
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
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
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
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
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
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
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
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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