Is it my heater core?

1991 Suburban, very little heat blowing out of vents, even blocked off the grill while driving to see if I could build up heat. Temp gauge never gets above middle hash mark between 100 - 210, front floor board not wet or any other obvious signs of a coolant leak.

Thermostat sticking open?

Any thoughts appreciated.

Its usually the culprit. make sure everything else under the hood is hooked up and functioning like the T-stat and hoses

Thx.

The 86 K10 I had in high school had those exact same problems. Bad thermostat. Replaced it and never had another bit of trouble.

I am going to start with the thermostat first.....6.00 at local auto parts store. Then move to the heater core if it isn't the "stat".

Thx for the input.

Get the fail safe ones they are a couple bucks more but they always fail in the open position instead of the closed position. No cooked engine to worry about

If it's not the stat try flushing out the core with a garden hose.

Sent from the dust in front of you!

do both heater hoses get hot?

Well this took all day:

MadOgre said:

Get the fail safe ones they are a couple bucks more but they always fail in the open position instead of the closed position. No cooked engine to worry about

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Ended up costing about 12.00, but nice to know it should fail in the open position if it goes.

350runner said:

If it's not the stat try flushing out the core with a garden hose. Sent from the dust in front of you!

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Oh dear God was this horrible. When I bought the suburban this past March I would have thought I checked to see what the coolant looked like. Must not have because the coolant looked like the Red River....When it's RED!

I flushed everything out until I got clear water. I saved the debris so I could make my own roll of sandpaper at a later date.

Water pump looked like it had been leaking as there was rust colored crap from the weep hole and down the front of the engine, as had the T-stat housing.

So I put on a new water pump as well as a 195 degree T-stat, and of course new coolant.

Replaced the lower radiator hose, top one looked good.

Passenger side of the radiator had the same rusty crap from where the end cap meets the fins. Guess I'll start looking to see about getting a new radiator for the ol' beast.

marks86 said:

do both heater hoses get hot?

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Yes, both got hot. Air is now warmer (not saying much), but nowhere close to being warm or hot.

If nothing else our sons got to play junior mechanics w/ me.

Man I wish I could afford a place on the red river I'd stay fishing all day.... yea sounds like it was super clogged up I'd run one of those yellow bottle of radiator flush through and see what that does. Then I'd start looking into the AC/heat blend door in the duct

Sent from the dust in front of you!

350runner said:

Man I wish I could afford a place on the red river I'd stay fishing all day.... yea sounds like it was super clogged up I'd run one of those yellow bottle of radiator flush through and see what that does. Then I'd start looking into the AC/heat blend door in the duct

Sent from the dust in front of you!

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I was expecting to see a mud cat pop out of the dang thing at anytime.

Lol!

Sent from the dust in front of you!

I find the RED GM dexcool anti freeze coolant works better then the old green stuff. I kept having T-stats fail until I switched to the red. I have never had one fail since switching to the red.

Even if your heater core is not leaking it still may be well beyond operational.

If you have coolant at the proper level and your engine warms to operational temp, Your heater core hoses are plumbed in the correct fashion and you still have no heat then I would say you need a new core.

All that crud is from your core/radiator and is probably plugged up good. You would need to reverse flush it by taking both hoses off the engine side and using a good pressured garden hose to back flush it and then the other way and then back flush again until you get nothing. If you have done that and still no heat then you need a new core.

I drove it to work and back today (80 miles round trip) and the air was a little warmer than the outside air. Next day off is Tuesday so I'll see about changing the heater core then.

Again, thanks for all of the input.

I wouldn't use DexKill but that's me.

I'd clean out everything around the heater core. Not sure if you can access it by taking out the blower or not. I had a 7 lb. box of crap when I cleaned mine out. Leaves and sticks can get in there and cause poor heat. The temp came up to about 75-80 at the vents before, after it was over 115.