Intermittent Heat?

99 Blazer LS, 4dr 4WD. Bought this vehicle last December and loved how much heat this thing could put out. Then when Spring came obviously I didn’t use the heat much and didn’t notice anything wrong but then the other day I caught a chill and went for max heat and there was virtually no heat available. A bit warm but that’s it. So today I check it and max heat appears to be back! Vehicle was at operating temperature in all cases. Is there some reason heating capability would change so sporadically? Anything to check? (No changes have been made to the vehicle since I bought it other than oil)

Also, regardless of where my fan, temp, and vent settings are at, when this vehicle downshifts to pull a hill, I get air out of my mid-level vents. Is this common?

Thanks

Where is the temp gauge sitting when the engine is up to temperature and completely warmed up?

Just shy of 200.

Get your cooling system and heater core triple reverse flushed.

Get your cooling system and heater core triple reverse flushed.

:lol2: What the hell is "triple reversed flushed" haha...

Does that mean 3 coolant flushes at $100 each ?? Please explain....

:lol2: What the hell is "triple reversed flushed" haha...

Does that mean 3 coolant flushes at $100 each ?? Please explain....


They forward and reverse flush the heater core three times.

They did it to mine at the dealer.

They forward and reverse flush the heater core three times.

They did it to mine at the dealer.


Huh....didn't know that....sounds like a good idea though.....!!! Power flushing that way would get any crap out of the heater core for sure...

No so much power flushing, but reversing the flow direction of the flush to dislodge more debris and crud.

Had a similar situation, the problem was merely a clogged heater core. The coolant had crystallized in there and blocked it. A little compressed air did the trick but it's a good idea to have it flushed as mentioned.

Which leads us to another thing - the reason the heater core clogged was a faulty radiator cap. So if this is in fact the same problem you are having, check the radiator cap after flushing the heater core and replace if necessary (might be a good idea to jsut replace it anyway, they are cheap).

Also be sure to completely refill the cooling system when you are done.