1994 GMC Yukon Heating issues

Tiny
CHICO03
  • MEMBER
  • 1994 GMC YUKON
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
I have no heat and I've replaced the thermostat heater core and water pump. Checked hoses for blockage or collapsing. Checked and replaced fitting. Checked hvac actuator. Still no heat. Replaced antifreeze. Truck will get to temp about 195 to 210 then drop down to about 150. Used a temp gun to check Temps on everything. Put cardboard in front of radiator. Covering half and nothing. At idle it will blow cool air but when put under load the air warms up. But not hot. At a loss please help.
Wednesday, October 21st, 2015 AT 10:47 AM

3 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
It shold be a 195 degree t stat, check to see if both hoses get hot when engine warmed up. It may have an air lock in system so check radiator cap. Check for a vacuum leak at one of motors and see if vacuum is going to any of them.
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Friday, October 23rd, 2015 AT 6:36 AM
Tiny
CHICO03
  • MEMBER
  • 2 POSTS
Only the hose from the back of the intake gets hot not the one going to the water pump. I just replaced the t Stat and made sure it's a 195. I have a new r cap just haven't put it on.
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Friday, October 23rd, 2015 AT 6:41 AM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Your heater may be plugged then as both hoses should be hot. Check for blockage in hose to pump or maybe an air lock causing problem. Check radiator cap as it may not be building any pressure.
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Friday, October 23rd, 2015 AT 6:51 AM

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