Caprice Heating Problem, help...

Hi,

I got a problem with my heater unit in my 90 Caprice Classic Station. I had to change the Heater Valve witch is located under the hood. It has a Valve for the hot water to circulate through the heat changer (i don't if i discribed it right).
Anyway, after i changed that valve my heater won't stay hot, when i turn on the heater.
The vacuum line to the vlave also works fine. It first gets warm, but after a few seconds it just turns cold. I can do that all the time. It never stays warm. cold air is OK, anything else is fine and works, just the heater has this annoying Problem.
Can anyone help me please. I already bleed the air of the system, but don't know if theres still air inside, but i don't think so.

Sorry for my bad english.

Regards

Hi,

I got a problem with my heater unit in my 90 Caprice Classic Station. I had to change the Heater Valve witch is located under the hood. It has a Valve for the hot water to circulate through the heat changer (i don't if i discribed it right).
Anyway, after i changed that valve my heater won't stay hot, when i turn on the heater.
The vacuum line to the vlave also works fine. It first gets warm, but after a few seconds it just turns cold. I can do that all the time. It never stays warm. cold air is OK, anything else is fine and works, just the heater has this annoying Problem.
Can anyone help me please. I already bleed the air of the system, but don't know if theres still air inside, but i don't think so.

Sorry for my bad english.

Regards

Defective new valve, maybe?

If all else fails, you could remove the valve and just replace it with a straight plastic pipe, so the antifreeze runs through the hose all the time. Just tape off the vacuum hose somehow so it doesn't suck air in. I believe the vacuum hose is there to close the heater valve when the air conditioner is on.

Defective new valve, maybe?

If all else fails, you could remove the valve and just replace it with a straight plastic pipe, so the antifreeze runs through the hose all the time. Just tape off the vacuum hose somehow so it doesn't suck air in. I believe the vacuum hose is there to close the heater valve when the air conditioner is on.


OK, i will try that. The vacuum hose is to change between cold and hot air. You can check it easy. If you turn on the heat, there will be underpressure constantly (you can check that with your finger tip on the vacuum hose), if you put on cold air, the underpressure is gone. so if you do this, the valve opens and closes. but it also might be there for closing the heat valve, if AC is turned on.
Do you think that could be a damaged valve? I mean because of that strange behavior, that i first have warm air and after a few seconds it changes.
I mean the valve is open permantly (cause i am always trying to heat) and the water hose is also pretty hot, so i don't think it could be the valve

OK, i will try that. The vacuum hose is to change between cold and hot air. You can check it easy. If you turn on the heat, there will be underpressure constantly (you can check that with your finger tip on the vacuum hose), if you put on cold air, the underpressure is gone. so if you do this, the valve opens and closes. but it also might be there for closing the heat valve, if AC is turned on.
Do you think that could be a damaged valve? I mean because of that strange behavior, that i first have warm air and after a few seconds it changes.
I mean the valve is open permantly (cause i am always trying to heat) and the water hose is also pretty hot, so i don't think it could be the valve

Is the hose between the valve and the heater core getting just as hot as the hose that feeds into the valve from the engine, when you have the heat on?

So the heat was working fine before you changed the valve?

Why did you change the valve? Was it leaking?

Is the valve installed correctly?

i distroyed the valve by coincidende, so i had to replace it. Every hose is hot. The one from the valve to the heater core is very hot. the hose going back to the engine is warm, but never hot. I don't know whats up with the heating unit. the hole system is not leaking at all.

OK, I cleaned everything and had a look at the whole heater system. I need some help with the heater control valve.
I think there is the problem.
If i turn on the heating and put on hot, there is no Underpressure from the hose. If i put on cold, there is underpressure constantly.

OK, if the Membran of the heater control valve doesn't have underpressure, the valve is closed. But if the valve is closed, the hot water can't run through the hose. so it should be the opposite. But the Valve seems to be OK.
I heard that there are exisiting valves from G.M. that look totally eqaul, but one Valve is open without underpressure and the other one is closed.
Is that right? That might be my Problem, doesn't it? It's just strange. thans for your help.
Engine Code Y, Oldsmobile 307, Model 1990

have a look at the picture, thats how my valve looks:

http://www.mtgparts.com/merchant2/graphics/00000001/p13cfull.jpg

regards

OK. Some possibilities : Could be the valve is the wrong valve.
Have you tested it? You could take it out of the car, apply vacuum (underpressure) to it with a vacuum gun, pour water into one end and see if it runs through. Also pour from the other end to see if there is a "backflow preventer" setup which only allows flow in one direction.

Does the new valve look just like the old one? Did you hook it up in the same way? It might only flow in one direction.

Or you could test it when it is still in the car, with vacuum from the engine, but block off the heater hose of course.

Of course even with no vacuum, you could just pour water through to see if it flows then.

Any chance the heater core is plugged up? Did you use any radiator "stopleak"? That stuff can clog up a heater core.

The guys at the parts store might be able to look it up in the database to verify that it is the right one (opening when vacuum/ no vacuum, etc) for your car.

Another remote possiblility is that the heat blend doors are malfunctioning.

I checked the valve outside of the car. If there is no vacuum (in my caprice than the heater lever is dialed on hot), the valve is closed, it is almost closed, just a little bit of water can run through (so no hot water can run through, also it should now).
The valve looks exactly the same, as the old broken one.
I built it in correctly, you can check it, by looking at a screw wich is fixed up on the valve. The one in the picture doens't has that screw.
If vacuum pulls the membran, the valve will open, and hot water can run through it.
You can see how it works if you have a look at the pic.
There is a spring inside the valve, connected to the membran. The spring pushes a little round piece of metal in the valve, to the point where the valve canal is getting smaller. so if there is no vacuum, the valve is closed.
Where can i switch the vacuum? any suggestions.

I checked the valve outside of the car. If there is no vacuum (in my caprice than the heater lever is dialed on hot), the valve is closed, it is almost closed, just a little bit of water can run through (so no hot water can run through, also it should now).
The valve looks exactly the same, as the old broken one.
I built it in correctly, you can check it, by looking at a screw wich is fixed up on the valve. The one in the picture doens't has that screw.
If vacuum pulls the membran, the valve will open, and hot water can run through it.
You can see how it works if you have a look at the pic.
There is a spring inside the valve, connected to the membran. The spring pushes a little round piece of metal in the valve, to the point where the valve canal is getting smaller. so if there is no vacuum, the valve is closed.
Where can i switch the vacuum? any suggestions.

I don't know how you can switch the vacuum.

It sounds like they gave you the opposite valve for your car. Maybe they can give you the "right" one that opens with vacuum, and you can exchange the wrong one for it.

ANd there is always the option of just removing the valve and replacing it with a straight piece of plastic connector pipe. That's what I did with my Caprice.

@ragepage
you were right, they gave me thr wrong valve, i checked that right after the winter was over.
I don't know why GM produced the exactly identicly looking valve, with opposite functions? i am glad the heater works again, without any problems at all.

regards