Flaky heat & no heat in the rear

[nopower65]

My 95 burban decided to unleash a nasty prank-- and of course waited until the coldest weather of the year! The heat comes & goes (as in all the heat goes away) and I have NO heat in the rear, unless the rpms' are 2500 or higher.

We cannot find any leaks, had the system flushed and new coolant added (spent a hour in the shop waiting for them to complete the "burping" of air process) and it still isn't putting out heat consistently (in the front) or at all in the rear.


Any ideas?

TIA :confused:

[Spindrift]

Did you check the thermostat for proper operation?

[Keith Richards]

I,ve been having a similar problem with my 98 2500 since i bought it.It seems to be an electrical connection with mine. When it turns off on me (always when it's freezing)what I do is take off the plastic dashboard cover,disconnect the wire where it plugs into the fan speed setting,clean it and reassemble.It only takes 2 or 3 minutes and sometimes this half assed method will fix the problem for months,sometimes days but it always works.Someday I would like it fixed right but I'm lacking funds.Maybe your problem is the same?

[jimcreek]

does your temp gauge come up to operating temp this is the way mine is set up and i suspect yours is the same.
your evaporater is on one side of a damper door and your heater core is on the other side of the damper door and electronic motor sits on top of this damper door and moves to open the heater core side as heat is needed.
the electronic motor is controled by the temperture control on dash.
so if your thermostat is working correctly your heater core always stays hot even in the summer and your cab temp. is controled by how far the damper door is opened one way or the other.

[nopower65]

I'll look into the damper door. Now the damn thing is causing other problems. I put a thermostat in, temp won't hold steady. Runs to about 190, stays there for a while, then will take a mad dash to about 215, sometimes come down in a minute or tow, last night stayed there. I shut it off, it promptly ****d green all over the snow. (Of course, it's 2 degrees here). And the heater still has a mind of its own. Sometimes I have heat, sometimes I don't-- no correlation with what is going on with the temp. Have no heat at all in the rear zoen (Suburban).

What's up with this???

HELP!!

[jimcreek]

you should be able to see the heater hoses going into the cab through the fire wall check while warm (not hot ) to see if both hoses are warm if so it has to be damper door.

[nopower65]

I checked the heater hoses under the hood. Sometimes warm, sometimes not. Return line is significantly cooler.

Does this point to a water pump problem? Or worse?

[kowsoc]

This might be a long shot but I have heard of the impeller on the water pump shaft coming loose spinning freely, therefore not moving coolant. This would explain the overheating you had...you could have got a defective thermostat though. Check the hoses heading into the cab as mentioned to check for proper circulation.