94 burb heater trouble

[jpg-94burb]

I have a 94 5.7 burb with a heater problem. I have very little heat comming out of heater. I have replaced the heater core, t-stat, water pump, rad cap, and had the cooling system prof flushed. There just seems to be not enough flow going through the heater core to get a good amount of heat through it. If you sit and squize on the heater core inlet hose you can see that a lot more water and heat will go through it. With the cap off you just see a small amount of flow through it. After all this being changed, now my temp guage will move from 200 to 160 and continue this all day. it has been 2 weeks since I have done anything to it and still no heat or stopped movement on temp guage. Any help would be great.

[J-Ri]

If the guage is accurate, it sounds like the new thermostat is bad. I got 3 bad ones in a row for my car. Will it get hot if you leave it running at about 1500 RPM with the vehicle not moving?

[jpg-94burb]

Tried 3 t-stats, and still does it. I can get a little heat out at 1500 rpms. The t-stat is working correctly because we checked it (the repair shop) using a infered temp guage. Even they are stumped. There is just a small amount of flow that is getting there to where the heater core gets its water from. We even did a pressure check for leaks in the entire system and it held 18psi with no leaks. The temp guage moving is the least of my worries now that I know that it is not over heating, I just want some heat. Is there possibly somewhere else that i could get water for the heater from, like the freeze plug?

[2000CAYukon]

If the hoses to the heater core are both warm then the issue is not coolant flow but air flow thru the heater core.

The actuator for the door to the heater core may not be working.

If the flow thru the heater core is the issue, then the water pump could be bad or a clogged hose or passage.

//2000CAYukon

[jpg-94burb]

no trouble with the door act, still having trbl, warmer heat with rec on but heat still goes away with the truck at idle. when you turn on blower motor the return hose goes cold slowly. just can't get any flow through there. we even bypassed the core and still saw very little flow on the line. could there be something wrong where th inlet line ties into intake or is there another place that i could chenge to hook up the inlet side of the core and plug the intake side?

[777stickman]

It really sounds to me like there is air in the system. I did a water pump, t-stat and intake gasket replacement 3 years ago on my '98 K2500 sub. 2 weeks later I was still having heating problems and a fluctuating temp gauge. So I started driving it about 20 miles and then parking it uphill over night. Next day add some coolant to the recovery tank and do the same thing except park it down hill over night. Took about another week and all was good. If you have rear heat make sure you turn that on while driving.

Good luck........Steve

[jpg-94burb]

thanks for the info, i'll try anything now. Been dealing with this for 2 weeks now. if you would look back later to see if this helped. Thanks again!!!!

[jpg-94burb]

Finally it's fixed. the whole problem was with the quick connect line on the intake manifold. The thing is made of pot metal and had actually disolved and clogged itself almost shut. be careful removing this thing because it is very easy thing to break off in the intake and then you will have more trouble than you had at first. Another piece of advise is to not replace it with another one just like it, just buy a treaded hose fitting that will go directly to the heater hose and you shouldn't have any trouble. The only reason for the quick connect is for the factory during assembly. this is one of those repairs that cost $300 to fix a part that actually cost me $2.50. Still it did stump 4 different repair shops and several machanics. So don't fall into the same trap that happened to me.