Chevy & GMC Vans

Well, I've had the intake manifold gasket, t-stat and water pump replaced, just in time for winter to rear her ugly head. Unfortunately, all that is coming out of the vents is air at approximately 76º. This is while the ambient air temps are in the 60s. I really don't look forward to winter if this is all the old girl can muster, as we do experience sub-arctic temps here in the winter. And yes, I have replaced all the old, corrupted vacuum lines.

Any ideas?

A stuck heater control valve? If the vacuum hose that goes to it is good.

Anti-freeze level good? (I remember having no heat in mine and this was the cause. Also had a trickling water sound coming from the dash area.)

Coolant level is at top of radiator with overflow tank still good and with proper level there, too. Remember, too, that I've replaced all the corrupted vacuum lines.

I think it may be a stuck HCV. I've left the heat on scorch now for the last few days and the temps coming out of the dash have been steadily climbing. Perhaps it was running all these years with leaking head gasket that may have caused the HCV to stick. The temps coming from the dash vents now are above 100º, so this bodes well. (I used to drive reefer, so I stuck my reefer thermometer in the dash vent to monitor the heat output.)

I'll let you know as this progresses. Right now, Ma Nature is cooperating by keeping the temps in the reasonable range. But, then again, this IS Montana and our weather here is definitely fickle.

I recently had to replace the heater blend door actuator. It contains an electric motor, circuit board and some gears. If you remove the engine cover, it is on left side of the interior A/C heater box under the dash. It's easy to see with the engine cover removed. With the key on rotate the heat control knob and you should see the actuator move thru it's full range. Mine had a broken nylon gear inside.

Thx. Will check it out.

mdmead wrote:Anti-freeze level good? (I remember having no heat in mine and this was the cause. Also had a trickling water sound coming from the dash area.)

This would have been my bet as well, especially in light of all the coolant work you mention having done lately...make sure there is NO air in the system

1, take the rad cap off
make sure overflow is at the proper level

2, crank her over, turn the heater on full blast, and let the t-stat open,...be ready with a jug of ready mixed coolant, the level may drop in the rad if there was air in the system, if there was no air then you should have nice hot air blastin from the vents...the level of coolant will slowly start to rise in the rad if so, put cap back on.

I burped the old girl. Initially, the coolant was at the very top of the rad with little, if any, in the overflow tank. I even stuck a thermometer in the coolant to monitor the temps. The temps in the radiator AFTER the t-stat opened never climbed above 130º. But, there is SOME heat coming out of the vents now, even though it doesn't climb above 100º.

All the vacuum lines are good and the t-stat is a new 195º.

It would seem that the temp coming out of the vents should be better than that.

The 2 coolant hoses going to the heater core should be quite hot once the van is warmed up. If not, gotta go back from there. If they are hot then the heater core is a possible problem.

Took Klementine back to the mechanic today. I had to pay more money down on the massive funds charged for his labour. While there, I complained about lack of heat. He offered to flush the heater core; I figured, why not If the problem didn't lie there, then, at the very least, I have eliminated one possible problem. Well, he flushed it out and VOÍLA! I now have heat!

The beginning temp at the dash vents was 30º C. After the flush/blow out, it is now 60º C! Lots and lots of toasty air comes out.