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Steve
Steve, Auto Service Technician
Category: Car
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Experience:  25+ yrs experience as a professional working technician; ASE L1 master technician
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97 Pontiac: overheating..replace water pump, radiator, hoses

Customer Question

I have a 97 Pontiac transport van that keeps overheating. I have replace water pump, radiator, hoses, therostat and it's still over heating. What is my problem?
Submitted: 11 years ago.
Category: Car
Expert:  Steve replied 11 years ago.

Several possibilities come to mind:


(1) Cooling fan problem? The electric cooling fans should be running long before the vehicle overheats, and always when the AC compressor is turned on.


(2) Proper mixture of antifreeze and water? Having a 50/50 mix is very important. Antifreeze boils at 270 degrees or higher, while water boils at 212 degrees. Cooling fans do not come on on most GM products untill around 220F. Therefore, if you have mostly water in your cooling system, it will boil over long before the cooling fans come on.


(3) Head gasket leak allowing hot exhaust gasses to enter a cooling jacket. There is a quick simple chemical test a garaage can do to check for this if it is suspected. A sign of a head gasket problem would be bubbles appearing in teh radiator neck while the engine is running, a coolant overflow bottle that keeps filling up and not drawing back into the engine when it cools off (because the gas displaces coolant), or if the previous radiator appeared to fail from overpressurization (bulged or failed tanks).

Expert:  Steve replied 11 years ago.

Note also: this engine requires a air bleed procedure to be performed after it is filled, to remove trapped air. If this is not done, the vehicle will overheat. ALso, make sure the system is full.


Here is the fill procedure, and I will post the bleed procedure for you also...



  1. Close the radiator drain valve. Reinstall all engine block drains.
  2. Remove the coolant recovery reservoir and empty. Flush the reservoir with clean water, drain and reinstall


  1. Slowly fill the cooling system through the radiator neck using the following procedure:



    • If the coolant system has been flushed, first add 100 percent ethylene glycol in the amount listed in the illustration for the appropriate engine cooling and heating option. Then slowly add clean water to the system until the level of the coolant mixture has reached the port of the coolant temperature switch. Wait for two minutes and recheck the level of the coolant mixture, add clean water if necessary to restore the coolant mixture level to the port of the coolant temperature switch. Install the coolant temperature switch. Then slowly add clean water to the system until the level of the coolant mixture has reached base of the radiator neck. Wait for two minutes and recheck the level of the coolant mixture, add clean water if necessary to restore the coolant mixture level to the base of the radiator neck.

NOTE:



  • When refilling the engine cooling system, add three engine coolant supplement sealant pellets, GM P/N(NNN) NNN-NNNNor equivalent, and GM approved new Ethylene Glycol Coolant DEX-COOL(R) GM P/N(NNN) NNN-NNNN
  • If the cooling system is being refilled ONLY (no flush), a 50 percent ethylene glycol and 50 percent clean water mixture should be used to fill the system. Fill the system until the level of the 50/50 mixture has reached the port of the coolant temperature switch. Wait two minutes and recheck the level of the coolant mixture, add a 50/50 ethylene glycol/water mixture as necessary to restore the coolant mixture level to the port of the coolant temperature switch. Install the coolant temperature switch. Fill the system until the level of the 50/50 mixture has reached the base of the radiator neck. Wait two minutes and recheck the level of the coolant mixture, add a 50/50 ethylene glycol/water mixture as necessary to restore the coolant mixture level to the base of the radiator neck.


  1. Install the radiator cap making certain the arrows line up with the overflow tube.
  2. Close all air bleeds. DO NOT over-torque the air bleed valve.



    • The air bleed valve is made out of brass.


  1. Fill the coolant reservoir with a 50 percent ethylene glycol and a 50 percent clean water coolant mixture. The proper amount of this mixture to be installed into the coolant reservoir is listed below:



    • All engines Add 2.4 liters (2.5 quarts) of a 50/50 mixture of ethylene glycol and clean water to the coolant recovery reservoir.

CAUTION: The low coolant indicator lamp may come on after this procedure. After operating the vehicle so that the engine heats up and cools down three times, if the low coolant indicator lamp does NOT go out, or fails to come on at ignition check and coolant is at the level indicated in step 3. If at any time the "TEMP" warning indicator comes on, immediate action is required.

NOTE: The freeze protection of the engine coolant after the engine heats up and cools down three times using a thermohydrometer to ensure proper freeze -37°C (-34°F) protection. Obtain the coolant mixture for the inspection from the base of the radiator neck, NOT from the coolant recovery reservoir.






Expert:  Steve replied 11 years ago.

I cannot for some reason seem to locate teh bleed procedure in the databases i have available to me, although the refill procedure mentions a brass bleed valve on this engine.


If your vehicle has air bleed valve<s> they would be found on the water outlet where the top radiator hose attaches, and possibly one on the water pipe in the water pump area. If you have bleed valves, run the engine up to operating temperature with the radiator cap in place, and then slowly open the bleeder screws and wait untill you see a steady stream of cooant flowing out (indicating all air has been purged) before closing it.


I hope this information is helpful; if so, clicking my accept button would be greatly appreciated... thanks!


Customer: replied 11 years ago.
Reply to Steve7654's Post: Thank you, XXXXX XXXXX taken my van to the shop and they told me it was the head gasket leaking from the inside just like you said. I appreciate your help.

Tari

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