Heat Issues

[Justin Fleming]

For some reason it seems I can not get any heat out of the truck. Basicly I have to block the front radiator and drive the truck for 10 miles and it will come up to 220. If I slow down or come to a stop it cools right back down extremely fast. I can let the truck run at idle for 20+ minutes and the needle never come off the 100 mark. It almost seems as if the thermo stat is stuck open. It is not old at all and I know they can fail. What I have noticed is after driving for a while and I stop and shut the truck off I can hear gargling in the coolant system and I am not sure what causes that. I cant really tell even where it is coming from either....

 

[dyeager535]

Pretty much has to be a thermostat issue IMO. This of course, assumes that however you are measuring temp is correct.

Even if the fan clutch was locked up, the thermostat would stay shut and the engine temp would be whatever the t-stat is rated for.

Your truck doesn't have a "heater shutoff valve" does it? I wasn't aware until recently that any of our trucks got them, but basically it cuts coolant off to the heater core based on the selection on the heater control head in the cab.

You may be hearing noise from the cooling system because there is no pressure being built up (from the coolant expanding) to expel the air.

 

[Justin Fleming]

Pretty much has to be a thermostat issue IMO. This of course, assumes that however you are measuring temp is correct.

Even if the fan clutch was locked up, the thermostat would stay shut and the engine temp would be whatever the t-stat is rated for.

Your truck doesn't have a "heater shutoff valve" does it? I wasn't aware until recently that any of our trucks got them, but basically it cuts coolant off to the heater core based on the selection on the heater control head in the cab.

You may be hearing noise from the cooling system because there is no pressure being built up (from the coolant expanding) to expel the air.

I dont beleive I hvae a heater shutoff vavle. I would assume it would be inline of the rubber heater core line in the engine bay and I do not have anything. Is that a correct assumption?

 

[dyeager535]

Yes, that would be correct. I've never physically seen one on the trucks, but I've seen the part listed.

For the cars that vintage they had a vacuum line that ran to it, which controlled the valve opening/closing, I assume trucks would have been setup the same way.

 

[ryoken]

stuck therm...

 

[4xcrazy]

Yes, that would be correct. I've never physically seen one on the trucks, but I've seen the part listed.

For the cars that vintage they had a vacuum line that ran to it, which controlled the valve opening/closing, I assume trucks would have been setup the same way.

I have that vacuum line and valve on my '89 Burb.

 

[frankin5]

Do you have Factory rear heat.

 

[4xcrazy]

If you're asking me, not factory. I believe the previous owner ran coolant lines all the way back and installed some sort of heat exchanger up in front of the ac evap unit. No hot water gets supplied to front of rear unless the heat selector is over to warm/hot selection.

So for my rear heat, I turn the heat selector to hot and then turn the rear fan switch on.

I have a dual heater vacuum switch in the garage for dual heaters, it actually has 4 ports, 2 feed and 2 return, mine was a single with one feed and one return, just simply had a Y-splitter in line to the those feeding and returning.