99 Chevy S-10 No Heat

billcu

billcu

Head Moderator
Staff member
My Brother's truck has little or no heat. It seems like it's a blend door problem. The thermostat has been replaced and the coolant is full. The truck runs fine otherwise.

Is anyone familiar with this system?

Does anyone know of a site like this where I could search for a solution?
 
Thanks Bud.

I checked out the site. I couldn't find anything about heater problems.

I was hoping it was a common problem like on the Gen 2 Mark VIII's, but I guess not.

Looks like I'll just have to tear into it myself. It seems like the heat control knob isn't connected to anything. I'm not sure if it's cable operated or vacuum. I guess I'll find out one way or another.:err-what?:
 
How long has he had the truck? If kinda new (to him), I wonder if previous owner had a leaky heater core and fixed it by routing the heater hose right back into the block instead of thru the heater? I've done that to keep a vehicle going...but it was summer in NY.
 
He's had it for a few years now. There is some heat coming out but not much. Sometimes it works better too, so I don't think that it's bypassed, but I'll check to make sure.

The temp gage shows normal according to that site that you gave me.
 
Next thing that comes to mind is to double check coolent level. Ya know how we have to fill our Marks thru the filler neck and NOT the overflow tank? As I haven't had a GM product since 85, I don't really know. I do know if a radiator doesn't have enough coolent, no heat! As you can see, I'm just guessing now....ask the question at that site I found.
 
Thanks again Bud. I will check that out for sure, but there was never an overheating problem or strange gage movement so I'm thinking that's OK.

I did post my question at that board. So far I've got one reply, that I should flush the heater core.

I'm a little hesitant to flush it though, as I've heard horror stories about leaking heater cores after a flush job. What I'll do is probably disconnect the hoses at the engine side and just pour some coolant into the hoses and see if it looks restricted first.

I should also check to see that the valve to the heater core is opening. Does this valve open when vacuum is applied or is it normally open?
 
I think what I'd do first is to make sure that the core is able to flow. Remove the in/out hoses from the engine end and simply blow through one end to see if there's a restriction and go from there. Air in=air out!
 
Success!

I flushed the heater core today, and the heat works great.

Thanks Bud, for the website and other suggestions.

I' ll get my brother to join that site. It's a pretty good site, except for the horrible pop up ads.

I'm glad that we don't have that here.:big-grin:
 
Get that great GM feeling with genuine GM parts or two engines which ever costs less,Oh Im sorry Mr.Godby this unit is ten days out of warrenty
 
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