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Heater blowing luke warm at best

With a single T-stat setup (1994-95), it's pretty well mandatory to use the genuine ACDelco thermostats... none of the others (including Stant, RobertShaw, etc) seem to properly engage the bypass diverter.

Most people indicate the 2-T-stat systems are more forgiving, but these trucks like lots of flow, so I'd go with the genuine ACDelco or RobertShaw thermostats, if it was me. I've also seen some of the cheap ones blow a rubber (the seal around the body of the thermostat) and plug things up.

It's not like these trucks are very forgiving in the heat/cool dept...
 
JiFaire said:
With a single T-stat setup (1994-95), it's pretty well mandatory to use the genuine ACDelco thermostats... none of the others (including Stant, RobertShaw, etc) seem to properly engage the bypass diverter.

Most people indicate the 2-T-stat systems are more forgiving, but these trucks like lots of flow, so I'd go with the genuine ACDelco or RobertShaw thermostats, if it was me. I've also seen some of the cheap ones blow a rubber (the seal around the body of the thermostat) and plug things up.

It's not like these trucks are very forgiving in the heat/cool dept...
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I know they have the robert shaw style at autozone. I guess that is the route I will take. Any place that is reasonably priced to get them?
 
Then wouldn't I run the risk of going to jail for contributing to the delinquency of a minor?
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Nope - I've never even been in a mine.
BTW - If you send personal checks I'll have to hang onto the boxes till the checks clear.

Have a good one Rodd :)
 
Hey I have a question. If the rear is blowing hot, why would it be the thermostats? If you want to change them Rodd give me a call, I put GM ones in my truck and I don't think I spent $70 on the pair. If they haven't been done it would be good PM anyway. Or swing it by the shop and we'll check it wth a heat gun at the sensor and see what it reads.
 
I just had an interesting experience today. Haven't been "here" for a while, but thought this would be of use to those who experience the same symptoms I had. Since a bought my truck, almost 4 years agoa, it had medeocre(spelling?) heat. Couldn't figure it out, cleaned out the core fins, changes stats, changed coolant etc. The one thing I never did until today was flush the heater core. Why not, I'll never know, because that did the trick. I just used a funnel, a water jug and a low pressure air hose, doing a reverse flow flush for the first 2 or 3 times. What do you think happened? Well, pieces of rubber came shooting out. Yep, you heard right. The one piece said "towards radiator" on it. Pieces of the old therm. gasket. I repeated this step over about 4 times, finally getting a clear result. I tell you what, now she heats! Never had to turn the heat down before, but today, on the drive home I did. I am a happy man. I guess the rubber was too big to fit throught the core, and slowly plugged up the flow.
 
Thanks for the tip guru. I still havn't found time to fix my issue yet. If you have any pics that would be great.
 
Guru, where did you do the flushing from? You make a good point that it's probably a good idea to do this - even if for no other reason than good PM.

Like Rodd, I have a Burb, so I'm sure our underhood arrangment is a little different, though. I mean, you don't have a "T" by the firewall, right?
 
Rodd said:
Thanks for the tip guru. I still havn't found time to fix my issue yet. If you have any pics that would be great.
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Sorry, no pics, my buddy dumped the culprit junk before I could.

As far as the flush goes, most people use a garden hose, but I didn't have that luxury. I removed the line from the therm housing.( I have the DIY quick connect deletion mod). I added about 6 feet of clear hose to that aluminum line and ran in into an empty pail. I removed the return line from the core to the rad at the rad and flushed from there back through the core. This pushed all the crap back out the way it came. The coolant flows from the therm housing into the rad, by passing the thermostats. Don't use to much pressure. If you have a puddle of water in you truck, you may have blown up your heater core. Don't need to panic about this happening, just be careful if you have to use air pressure.
 
DennisG01 said:
Guru, where did you do the flushing from? You make a good point that it's probably a good idea to do this - even if for no other reason than good PM.

Like Rodd, I have a Burb, so I'm sure our underhood arrangment is a little different, though. I mean, you don't have a "T" by the firewall, right?
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Not sure, this may be a 'if its not broke, don't fix it' item for me. Albeit it aids in cooling a tad, but if she's already a little weak from being 12years old... I hate when good PM turns into "I wish I hadn't".

LOL, Washing the engine compartment in a different vehicle has done that to me before, and now I'm scared to. .
 
Matt Bachand said:
Not sure, this may be a 'if its not broke, don't fix it' item for me. Albeit it aids in cooling a tad, but if she's already a little weak from being 12years old... I hate when good PM turns into "I wish I hadn't".

LOL, Washing the engine compartment in a different vehicle has done that to me before, and now I'm scared to. .
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Well, that's a good point, too. Otherwise, pick from the below:
:mad2:
:eek:
:sad:
:yikes:
etc, etc.

I think I'll try it, though. Heck, mine's only 11 years old! :smile5:
 
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Do these trucks have a blend door under the dash? Once upon a time, your heater heat was controlled by a valve in the input coolant line to the heater core. Most vehicles nowadays lack this valve, so coolant constantly circulates to the heater core, and the warm air is controlled by a blend door somewhere between the heat and AC core that allows air to pass through the heater core or not.

Many times the levers, cables, or vacuum servos that control the blend door stop working, which does not allow you to get any air through the heater core.
 
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