1996 Chevy Blazer Thermostate question

Tiny
FRIARBARB
  • MEMBER
  • 1996 CHEVROLET BLAZER
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 119,000 MILES
I replaced the thermostat housing (it had developed a pin hole leak) and thermostat on my 96 Blazer, had the cooling system flushed.

After I did this, the engine temp gauge would steadily rise to around 240-250 for a few minutes then fall back to around 190 degrees. I checked the coolant resevoir and it is full, but there was not alot of coolant in the radiator itself.

I replaced the thermostat again and refilled the radiator. Same thing will happen. Tempature will rise to around 240 degrees, then fall back to 190 degrees in a few minutes.

Could I have another defective thermostat?
Could the radiator pressure cap be defective, not allowing coolant from the resevoir to flow back to the engine?

Robert
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Monday, June 16th, 2008 AT 10:13 AM

6 Replies

Tiny
MASTERTECHTIM
  • MEMBER
Your air bound. Run vehicle with the cap off until it warms up and all of the coolant will get sucked low in the radiator then fill the radiator itself and you will bea all set. There are no other problems just air bound. With the cap off and it running it might bubble out of radiator until the thermostat opens and then go empty real quick. This is normal, wait until you see it go empty then fill it. If your uneasy about this method then fill the radiator and let it get hot like it is now then let it cool and then refill radiator and repeat process until all the air is out. You cant fill a empty radiator from the overflow, it just wont work. Let me know how you make out
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Monday, June 16th, 2008 AT 11:07 AM
Tiny
FRIARBARB
  • MEMBER
Tim,

Did as you advised and it worked fine for a bit. Then went for a short drive and the tempature climbed back to around 240 degrees. After a few minutes, temp dropped back to around 190 degrees.

When it cools off a bit I will check the radiator again and repeat the process you described previously.

Could this be an on going problem?

Thanks again.

Robert
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Monday, June 16th, 2008 AT 11:36 AM
Tiny
OBXAUTOMEDIC
  • EXPERT
Hello,

Not to step on any toes here, but to ad to mastertechtim. May I suggest jacking up the front of the vehicle as high as you can Safely Do. As everyone knows Air will Rise to the Highest Point. So if there is air in the engine and you jack it up it will work it's way toward the front of the engine were it will be easier to expel.
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Monday, June 16th, 2008 AT 2:46 PM
Tiny
MASTERTECHTIM
  • MEMBER
These engines bleed out pretty quickly. This wont be a on going problem, just one more time adding coolant should do it. This system has a heater core bypass that goes to the top of the radiator and pushes the air through the system pretty fast. Keep us posted.
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Monday, June 16th, 2008 AT 4:08 PM
Tiny
FRIARBARB
  • MEMBER
Tim,

Problem solved. Opened the radiator this morning, after cooling off all night, and it was full. Ran around abit and tempature settled in at around 190 degrees.

One question if you have the time.

Why, when the radiator was low on coolant, didn't any from the reservoir get siphoned back to the radiator?

Thanks again for taking the time to help me out.

Take the rest of the day off.

Robert
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Tuesday, June 17th, 2008 AT 4:02 PM
Tiny
MASTERTECHTIM
  • MEMBER
With so much air in system it does not build up enough vacuum when its low to pull the coolant in. When its full it only takes a little vacuum pressure to pull it in. For example when pressurizing a coolant system thats half empty it takes alot of air volume to fill in the void but when its full, only a little pressure is needed. Anyways happy motoring
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Friday, June 20th, 2008 AT 4:17 PM

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