1986 Other GMC Models heater

Tiny
BOLEXI
  • MEMBER
  • 1986 GMC
Heater problem
1986 Other GMC Models 4 cyl Two Wheel Drive 128, 00 miles

I have a gmc diesel 40 box truk (ISUZU) and the heater will not get hot, gets luke warm. I had checked the temp of the radiator fluid with a thermometer and after 7 miles of driving and then idling for 20 minutes the water was only 140 degrees. I also have over half the radiator covered with cardboard I opend the thermostat housing and tested that water and it was only 140 degrees also. I then replaced the thermostat and still the same problem.
Saturday, December 15th, 2007 AT 2:57 PM

1 Reply

Tiny
MHPAUTOS
  • MECHANIC
  • 31,937 POSTS
Hi there,

You may have a blocked heater core or a faulty heater tap that is not opening fully, check the flow through the heater core and the operation of the tap controller and the heater tap.

Mark (MHPAUTOS)
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Sunday, December 16th, 2007 AT 5:08 AM

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