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Overheating

Tiny
JONATHAN57818
  • MEMBER
  • 1989 GMC C1500
  • 6,000 MILES
I put a 16 pound cap for my radiator on my 1989 GMC Sierra 5.7l and it began to overheat and leak antifreeze from the cap. Why is this happening should I put a higher psi cap or lower?
Tuesday, January 26th, 2016 AT 7:46 PM

6 Replies

Tiny
JOHNNYT73
  • MECHANIC
  • 924 POSTS
Have you replaced the cap? If not then it sounds to me as if the seal is bad and or it is not working and allowing the coolant to boil.
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Wednesday, January 27th, 2016 AT 6:34 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Could be a bad head gasket as well if it overheats. Putting compression into coolant.
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Wednesday, January 27th, 2016 AT 6:37 AM
Tiny
JONATHAN57818
  • MEMBER
  • 4 POSTS
I replaced the cap and put an new 18 pound. It still heats up to 230 and it returns to 190 but doesn't spill or seem to be overheating. I'm just wondering why the 16 pound didn't work?
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Wednesday, January 27th, 2016 AT 10:31 AM
Tiny
JOHNNYT73
  • MECHANIC
  • 924 POSTS
Was the 16 psi cap the original? I would check your thermostat as well. Plus make sure you are bleeding the cooling system and getting all the air out of the system.
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Wednesday, January 27th, 2016 AT 10:33 AM
Tiny
JONATHAN57818
  • MEMBER
  • 4 POSTS
The 16 psi was new and my thermostat Is also new and how would I know if air is problem?
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+1
Wednesday, January 27th, 2016 AT 11:48 AM
Tiny
JOHNNYT73
  • MECHANIC
  • 924 POSTS
If you are overheating with no leaks, and you didn't on purpose try to burp the air out of the system. Did you bleed the system after replacing the thermostat?
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Wednesday, January 27th, 2016 AT 11:57 AM

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