Quote:
Originally Posted by artron9
Al Hook, thanks! The shop manual says there is a vacuum thermostat valve in the heater plenum as well as the heater control valve in the engine compartment. Merc Cruzer, my heater control valve is attached to the right inner fender. On the right head, there is a 45 degree elbow to which the 5/8 hose is connected.
This hose feeds to the heater control valve and from there to the heater core. Could this vac thermostat valve in the plenum be faulty? Could it affect the flow? Also, the blower does work but getting only cold air. Right now, thanks to you guys, the problem appears to be a plugged heater core. However, I'm still concerned about that vacuum thermostat valve in the plenum? But I think the consensus is that it should not have a bearing on the circulation?
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The heat control lever on the dash, just controls the amount of vacuum to the valve. Hence it can be fully open for max heat of partially open for less heat.
It would seem the easiest test would be to just disconnect the exit hose (the lower one) in the engine department and see if water is coming out of it. That will tell you if there is flow through the core. Since you have bypassed the valve, water should come out when the hose is removed.
As to the location of the valve, you can just take the 90 degree elbow out and replace it with the valve.
The valve could be faulty, sicne it is vacuum controlled. Try blowing through the valve. It should be closed, sicne the vacuum is used to open it.
You need to apply vacume to the valve to see if it opens. You should be able to put a small hose on it and see if you can open the valve when you suck on the hose. If it is hard to do then the valve is probably ok and you just need more vacuum.
So bottom line for now would be take the lower hose off and see if water come out.