Hey y'all - new poster here. Have been all over the internet with this problem, dawned on me this may be the best place to look for help.

Yes, another "no heat" quandry.

2000 Blazer LT (loaded) 4.3L 130K miles

2nd year with no heat. So far, I have:

replaced thermostat (3X)
complete flush (numerous times)
replaced water pump (found leaky weep hole)
flushed heater core (numerous times)

Findings so far: only thing that has worked is flushing the heater core. However: both hoses are equally hot - both before and after flush. Also, the only thing that comes out is a little AF then clear water. Have never seen any gunk, goo, etc. and flow is good. I've more or less ruled out a plugged geater core. After flushing, heat only lasts for 15-30 mins, then goes cool again.

Have also noticed that A/C comes on (sometimes) when car is started. Does NOT do this every time, just once in a while. Problem at panel?

Also - have tried removing/replacing radiator cap - air heats up, but only for a short time. Is this pointing towards an air bubble in the system? I wonder if disconnecting the hoses to flush the core is also "burping" the system. Hmmm...

Any ideas? Wally

 

This sounds more like a controls issue. Does it have Auto air?

Mine has that and when it is on the AC is an all the time. Make sure when you change the direction of the air flow, ie. dash, floor, defrost, it is actually changing. Can you here it change when you move the **** from heat to cool and back?

 

Hey samuknow! Yup, it's the AUTO kind, but all of the air flows seem to be working properly. I just noticed the A/C coming on by itself the other day - the "no heat" has been a problem for quite a while.

None-the-less, I'm going to have the control panel thoroughly checked.

Thanx!

 

Recently did a coolant flush on my truck and still didn`t have heat. Then took the heater core hoses off and did a separate flush of just the heater core. Better, but still very faint. Drove the passenger`s side up on a ramp and let it get up to temp with the rad cap off. Then let it cool and refilled overflow tank. Did this 1-2 times (allowing engine to cool between) and now have blazing hot heat on command as it should be. With all the hoses coming off and openings that allowed air in I wouldn`t be surprised if you do have air trapped in there somewhere. Do you hear any gurgling as you drive it and/or when you really get on the gas?

And what temp t-stat did you put back in it?

 

Sam - just read your post again - and, more specifically, you asked about hearing it switch from "heat to cool". Good question - I tried listening for it yesterday, and I honestly didn't hear anything. I'm just not sure if it indeed wasn't switching, or if I just couldn't hear it.

How "loud" (for lack of a better term) is the blend door switch?

 

Triple - I think you're on the right track. It's sure acting like it has a bubble in it somewhere. Especially (as you pointed out) I've disconnected/reconnected hoses like crazy. I'm going to try the up-on-a-ramp trick to try to get the air out.

Don't really hear any gurgling - but then again, haven't really been listening for it.

Mechanic put in the thermostats - not exactly sure what temp they were, but I'm pretty sure they're correct - temp guage is consistantly 200-210 which is where I believe it should be.

Thanx!! Wally

 

I barely hear a change when adjusting the blend. But I can hear it.

An air pocket is a good thought also.

Keep us posted.

 

I recently replaiced the thermostat and still no heat. I plan to flush the heater core out as soon as the temp gets above freezing again but I think I will try this before I rip the hoses off anyway. If it doesn't work then I will flush the heater core and then try this again.

 

I've been going through the same thing for about 2 weeks, except I had heat up to 160 w/ a 195* stat that wouldn't go no higher did all as you did, everyone tells/told me it was air, stayed normal for 1 day now back in the same boat again, being that the heater hoses are just about equal to the highest point, I'm gonna buy the Prestone flush & fill kit with the T. And use that T to gradually bleed the heater line when it's up to temp. Just maybe I'll be able to release this pocket of air under pressure slowlywherever it is and put this to bed. I'm tired of playin around with this bleedin b/s. I've had the truck up overnight,cap off, the only time it came up to temp 195* I had to race it while the cap off and a/f spilling as it warmed.

 

Well, I put the pass side up on a ramp and tried this out. Still no heat. Every once in awhile I will get a little bit of heat and then nothing but cool air. I have no way to measure the temp but I get the same cool air when on all speeds. I guess I will have to wait till a warmer day and flush the heater core. hopefully I wont have go thru replacing the heater core. I only have a hanes manual, That thing is a joke.