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Jerry, Master Mechanic
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1997 Pontiac Sunfire: Replaced water pump and heater core..antifreeze

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1997 Pontiac Sunfire continues to have cooling problems. Replaced water pump and heater core twice, but still loses antifreeze.

Hello and welcome to Just, Super mechanic here. About your vehicle.


The first thing that you want to do is check the cooling system for any exhaust gases. There is a tester for thas that you can gt from Autozone for about $20.

If there are any exhaust gases in the cooling system, that will cause more pressure than desired and will probably allow the engine to burn coolant.

If there are, then there would be an internal engine problem, like a head gasket or head. Of course, you will want to make sure that the system is full and the cooling fan(s) are working as well as the pressure cap holding pressure. Thanks

Jerry and 4 other Car Specialists are ready to help you
Customer: replied 9 years ago.
The head gasket was checked and so were the hoses and the thermostat and all are OK. The coolant simply leaks(overflows) and the mechanic can't seem to find the cause. It seems worse when the air conditioner is used, plus you can smell coolant when you're sitting in the passenger compartment.

I know that there was a GM service advisory concerning cooling problems with 1997 Sunfires but I can;t seem to find it.

I found the one I think you are talking about. Here it is, see if that helps.

File In Section: 6 - Engine

Bulletin No.: 67-62-04

Date: December, 1996

Coolant Loss, Visible Coolant Leakage, Low Coolant Lamp On, or Coolant Odor, Caused by Coolant Leakage (Install a New Thermostat Gasket)


1996-97 Buick Skylark 1996-97 Chevrolet Cavalier 1997 Chevrolet Malibu 1996-97 Oldsmobile Achieva 1996-97 Pontiac Sunfire, Grand Am

with 2.2L, 2.4L Engines (VINs 4, T - RPOs LN2, LD9)

Built before October, 1996


Some customers may comment about engine coolant loss, low coolant lamp on, visible coolant, or a coolant odor from the engine compartment. Some owners may be unable to distinguish the coolant from transmission fluid due to its orange color.


Some 1996 and 1997 J and N model cars equipped with 2.4 Liter (VIN Engine Code T RPO LD9) engines may exhibit coolant leakage at the joint where the radiator outlet pipe is connected to the coolant pump cover. In addition, some of these vehicles may exhibit leakage at the joint between the cooling system air bleed pipe and the coolant outlet. On 2.2 Liter engines (VIN Engine Code 4 - RPO LN2) coolant leakage may occur between the thermostat housing and the coolant inlet pipe.


On vehicles exhibiting leakage at the thermostat gasket joint, install a new thermostat gasket with part number 24576633, using procedures outlined in the Engine Cooling Section on the Service Manual.

If any of the previously noted conditions occur, first inspect the vehicle per the Engine Cooling Section of the applicable Service Manual. If no other cause is found for the condition, proceed with step 2.


2.Inspect the joint between the radiator outlet pipe (thermostat housing on 2.2L engines) and the coolant pump cover (coolant inlet pipe on 2.2L engines) for signs of leakage. Pressure or dye testing may be necessary in some instances.


3.If any signs of coolant leakage are noted, replace the thermostat gasket using the procedures in the Engine Cooling Section of the Service Manual.


4.If the thermostat seal has been replaced with part number 24576633 and there continues to be leakage between the radiator outlet pipe (thermostat housing on 2.2L engines) and the coolant pump cover (coolant inlet pipe on 2.2L engines), replace the thermostat housing on 2.2L engines or the radiator outlet pipe on 2.4L engines.
Important: Do not attempt to install any seal other than 24576633 into this joint! If an attempt is made to install a thicker seal, the flange on the radiator outlet pipe will be distorted when it is tightened creating an additional leak. If any attempt has been made to repair the leak with a thicker seal, the thermostat housing on 2.2L (RPO LN2) engines or the radiator outlet pipe on 2.4L (RPO LD9) engines should be replaced to prevent leaks caused by distortion.


Important: DO NOT REPLACE 82°C (180°F) 1996 THERMOSTAT WITH ANY OTHER THERMOSTAT. If poor heater performance is noted, follow diagnostic procedures in Section 1A of the appropriate Service Manual.


In some instances of poor heater performance, 1995 91°C (195°F) thermostats have been installed in 1996 2.2L LN2 and 2.4L LD9 engines. The 1996 thermostat used for the inlet thermostat system is unique and cannot be replaced with a thermostat from an outlet side thermostat application.

If a 1995 91°C (195°F) thermostat is used to replace a 1996 82°C (180°F) thermostat, the following conditions WILL occur:

^91°C (195°F) (1995) vs. 82°C (180°F) (1996) will cause the 1996 2.2L LN2 and 2.4L LD9 engines to run hotter at low RPM.


^A lighter spring in the 91°C (195°F) (1995) thermostat will allow the thermostat to be pulled open by coolant flow at higher RPM, causing the engine to run too cold and will cause poor heater performance at highway speeds.


5.On vehicles equipped with the 2.4 Liter (VIN Engine Code T RPO LD9) engine, inspect the sealing of the joint between the coolant outlet and the cooling system air bleed pipe.


If any leakage is noted, replace the coolant outlet, GM P/N 24575259, air bleed pipe, GM P/N 24574205, and "0" ring seal, GM P/N 24573057. Use silicone based lubricant, GM P/N 12345579, when installing the new air bleed pipe and seal into the coolant outlet.



Customer: replied 9 years ago.
I'm not a mechanic, I program computers, but I'm tired of my wife complaining about her car always smelling like antifreeze and then having to nag our mechanic about the problem. Our mechanic specializes on Imports and has done a top notch job with my Camry, but maybe this Sunfire is just not his cup of tea. Anyway, your answer seems plausible to me so I'm going to Accept It, but if you can think of anything else that can be causing this continuous cooling situation then I'd sure appreciate your help.

Our mechanic blamed GM's Perma Cool antifreeze for ruining the water pump at 32,000 miles, and then contributing to the heater core problems. The NAPA replacement heater core began leaking around 1,000 miles after the install so he replaced it with a genuine GM heater core free of charge. That was around 2,000 miles ago. The heater did perform poorly this winter and took forever to warm up even though the antifreeze level was right where it should be. Even though it's a 1997 it only has 58,000 original miles on it and has been a real pain. It seems to go through shock mounts(lots of pot holes on our roads) real easily as well. Anyway thanks for your help.
Your welcome. The only other thing that I could think of would be, (and I would imagine that your tech has already checked) the radiator for clogging. One way to see would be when the engine is rather hot, check for any cool spots in the radiator's core. You can use a gun type of thermometer, but I always use my hand, (old school) and if there are any cool spots whatso ever, the radiator would need to be either cleaned out really good or replaced. Thanks
Customer: replied 9 years ago.
Thanks again - I'm going to click on reply to send this Thanks Again and then Accept.
Take Care...