Need more heat

[L31MaxExpress]

I had a similar issue with my Express van except it was with the a/c. The evaporator was half covered in leafs and plugged with these things that come off sycamore trees. I only discovered it because it corroded the evaporator and the evaorator started to leak. Replaced the core and only then did I notice how much the airflow had been restricted.

 

[TechNova]

I had some problems with a little heat moving to no heat as the truck ran for awhile.
I pulled the left block drain and left knock sensor and back flushed the block with a garden hose.
I then back flushed the heater core separately.
There was a lot of debris, rust etc that came out of the block.
I have good heat now.
The debris was plugging the core. I think it would settle out until I ran the truck again stirring it up.

 

[nhyrum]

I had some problems with a little heat moving to no heat as the truck ran for awhile.
I pulled the left block drain and left knock sensor and back flushed the block with a garden hose.
I then back flushed the heater core separately.
There was a lot of debris, rust etc that came out of the block.
I have good heat now.
The debris was plugging the core. I think it would settle out until I ran the truck again stirring it up.

I've flushed the block already, I had to do freeze plugs and everything was good. With the plugs out I stuck my fingers in and everything looked and felt good. I ran a few jugs of radiator flush as well. I've flushed the core, both directions, multiple times. The core gets hot

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[L31MaxExpress]

I've flushed the block already, I had to do freeze plugs and everything was good. With the plugs out I stuck my fingers in and everything looked and felt good. I ran a few jugs of radiator flush as well. I've flushed the core, both directions, multiple times. The core gets hot

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Sounds like you have isolated your issue to inside the heater box.

I would still try a new thermostat to see if that temperature cycling stops though.

 

[454cid]

.... and what I grew up calling helicopters.

Maple tree seeds?

 

[Schurkey]

The heater in my truck isn't the greatest. Last fall I replaced the water pump, thermostat with a 205 for the winter, and hoses going to the heater core, and back flushed the core multiple times. The year before that, before I owned the truck, the heater core was replaced at a shop

This fall I replaced freeze plugs, so the coolant has been flushed and replaced with new, I've put new, or hoses and fittings, including that one everyone hates, and a piece of card board over the grille. I've got the 4.3, and iirc, the same radiator is used for the 350(truck is a 95) the thermostat is functioning, I've verified with my own two eyeballs, and I can verify with the temp gauge, that is pretty accurate, even though it's just a gauge. Once "warm" and driving, the temp will climb to the 210 mark, the thermostat will open, and the temp falls to the 155 ish mark, then repeat. And even at the 210 mark, the heat at the vent isn't super warm, but enough to keep the cab warn ish, but even boring l blowing right on my feet, it never gets to where they're uncomfortably warm, or result even just warm.

I've checked and verified that the blend door actuator works, and that the door moves.

Any way to get more heat from her? Winter is about to really settle in, where days won't even get above 0F, so I would like to be able to get my feet warm

I thought I had a problem with the heater on my '88 K1500. I wore a snowmobile suit to work, 30 highway miles away from home. Needed snowmobile boots to keep my feet warm-ish.

Turned out--after a couple of years of suffering, replacing the heater core, and adding a 205 thermostat--that the heater was working just fine. The foam-rubber (foam plastic?) seals on the heater box were so decomposed that I was getting enough cold air infiltration to cancel out the heat. The cold air was pouring out under the dash, passenger side.

Replacing the crappy GM seals with strips of generic home-improvement-store rolls of foam tape resulted in a cab that will roast me out of the truck at -20F unless I turn the heat down.

It's not a job for the faint-of-heart. Steering column comes out, dash swings down, then you fight and beat the plastic heater box out. It's no fun at all. I replaced ALL the foam seals, but the critical one was the one connecting the underside of the metal "firewall" plenum area to the plastic box that the heater blower fits into.

Completely worth-it, though.

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Note the pine needles and other leafy crap stuck in the heater core. This is after I've removed all the "easy" debris.

I'm suspicious of your thermostat. I have the sense that it's "sticky". But check for cold-air infiltration first.

Another issue would be folks that have opened-up the door panels, and failed to re-install the plastic sheeting that seals cold air out.

Y’all ever drop a room temperature (say 70 degrees) stat in a pot of boiling water? It takes a 1-2 minutes to fully open up. I tested one once, thought my stat wasn’t opening.

Not the thermostats I use.

Also possible that the blower side of the box is full of debris which is blocking airflow over the core. My truck spent the first 25 years of its life in the Pacific Northwest and when I replaced the blower a couple months ago the box was 3/4 full of pine needles. Both heat and AC work much better now.

Common as dirt.

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My in-laws had some nut-bearing trees--almonds or walnuts or somesuch. They stored the nuts in the garage.

Rodents got into the garage, packed the heater box of the Buick full of whatever nuts they could stuff in there. I have no idea how they got into the heater box, just that that's what the shop found when they took it all apart.

 

[nhyrum]

I thought I had a problem with the heater on my '88 K1500. I wore a snowmobile suit to work, 30 highway miles away from home. Needed snowmobile boots to keep my feet warm-ish.

Turned out--after a couple of years of suffering, replacing the heater core, and adding a 205 thermostat--that the heater was working just fine. The foam-rubber (foam plastic?) seals on the heater box were so decomposed that I was getting enough cold air infiltration to cancel out the heat. The cold air was pouring out under the dash, passenger side.

Replacing the crappy GM seals with strips of generic home-improvement-store rolls of foam tape resulted in a cab that will roast me out of the truck at -20F unless I turn the heat down.

It's not a job for the faint-of-heart. Steering column comes out, dash swings down, then you fight and beat the plastic heater box out. It's no fun at all. I replaced ALL the foam seals, but the critical one was the one connecting the underside of the metal "firewall" plenum area to the plastic box that the heater blower fits into.

Completely worth-it, though.

You must be registered for see images attach

Note the pine needles and other leafy crap stuck in the heater core. This is after I've removed all the "easy" debris.

I'm suspicious of your thermostat. I have the sense that it's "sticky". But check for cold-air infiltration first.

Another issue would be folks that have opened-up the door panels, and failed to re-install the plastic sheeting that seals cold air out.



Not the thermostats I use.


Common as dirt.

You must be registered for see images attach

My in-laws had some nut-bearing trees--almonds or walnuts or somesuch. They stored the nuts in the garage.

Rodents got into the garage, packed the heater box of the Buick full of whatever nuts they could stuff in there. I have no idea how they got into the heater box, just that that's what the shop found when they took it all apart.

That sounds like something I'll do after it warms up (or if I move into a house with a garage). Replacing the upper heater box part would fix part of my problem, the clip part that holds the heater core is busted, and that's part of that upper piece.

I don't think I necessarily have an issue of cold air infiltration, unless it's in the heater box area, since the air coming out of the vents is probably only about 85-90 degrees. I'm now beginning to think it has to be leaves and crap in the way.

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[Hutchinson]

Schurkey, just curios, what do you mean “not the thermostats I use” ? I took my stat out, when I first dropped the HT383e in, and tested it - I then got a 165 degree and a 180 degree stat and tested them the same. They took around a minute to “fully” open up. Just curious bud,....am I missing something? I ended up putting the 180 in,....I know people say, the 195 is best, but for me, I just like the 180.

 

[Schurkey]

I wound up with an entire case of (now discontinued) thermostats in an eBay purchase. I've sold some to folks on a Pontiac forum; and before I put them in the shipping box, I drop 'em in a pot of boiling water. I want to verify they'll open so there's no problem with a "factory defect".

The thermostats tend to be fully open MUCH faster than the "1--2 minutes". I'd have said "30--40 seconds".

Even the "normal" Stant thernostats have opened quicker than "1--2 minutes" when dropped in boiling water.

 

[df2x4]

Since we're talking thermostats...

Personally I'm not a big fan of Stant. I know some people love them but I have had one of them fail less than a year from the install date. I run OE GM/ACDelco (The OEM part number, not the "Professional" series) 195 degree themostats in both of my trucks and they've been flawless. Replaced both of them (factory ones were fine, more of a peace of mind thing) about four or five years back and they're still going strong. They're more expensive at about $14 each but for something that lasts so long I don't mind paying the little bit extra.

Part number for both of my '97s (C1500 4.3L and K1500 Suburban 5.7L) is 12632948.