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Coolant Loss

Cliff883

By Cliff883
in Ask A GM Technician

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Cliff883 Enthusiast

Cliff883

Posted
Posted

I have a 1988 GMC Sierra slx with a 305 motor with 182,000 miles. I was having an issue with coolant loss over the winter. but could never find it. It was about half a quart or so a week. From like may until last week I have not lost any fluid at all. I have been using the heater or defroster in the mornings now and coolant is dissapearing again. Any ideas? Any help would be greatly appreciated.

Cliff883 Enthusiast

Cliff883

Posted
  • Author
Posted

I actually haven't noticed a coolant smell. And if I don't lose any coolant if I am not using my heater or defroster, isn't it not likely going to show on a pressure test?

jrod332 Enthusiast

jrod332

Posted
Posted

I thought the same thing with my truck. Usually with a pressure test your putting more pressure into the system then the the system will do itself. You want to force the coolant to come out wherever the leak is. If there is a tiny pin hole that isn't visible that you will never get enough pressure to show a leak.

cwendel4 Enthusiast

cwendel4

Posted
Posted

I do not remember if your year has one or not, it has been awhile. Does your truck have a heater control valve? It would have a vacuum line connected to it and be between the water pump and the heater inlet in the heater hose. If the leak is only when you use the heat and you don't smell coolant, the valve could be leaking only when open. The coolant then drips to a place where it does not burn or pool on the ground.

 

Had a 77 fulsize pontiac that had a leak from the heater nipple. Everytime it started to leak, it would drip onto the exhaust manifold and I would smell the coolant burning.

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

the tester has areas on it for the pressure cap you have,yours is a 15 pound ,pressure it up to that ,and check the interior carpet on passenger side ,heater core MAY have crapped out on ya

Cliff883 Enthusiast

Cliff883

Posted
  • Author
Posted

Well i did find a leak from the thermostat housing, took care of that. Checked it again and it held at 15 so I will check in a couple days to see if there is any more loss.

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