1998 Ranger 4cyl. No heat. I just put on a new coolant valve with no change. After I had the old one on the bench and looked inside, it operates and appears to be fine. The coolant discharge to the radiator and one of the heater hoses at the valve are very hot to the touch. The other heater hose has quite a difference in temperature. It doesn't look like I'm getting vaccum to the diaphram on the coolant valve but when I apply vaccum to it, the diaphram on the conrtol valve it denfinitly cycles changing the temp of the cooler heater hose but there is no change in temp at the heater outlet. I have not had the heater apart, but from the outside the blend doors look like they are working fine, the air goes where it should. Its seems like there has been a quick change in efficiency, but it was not all of a sudden. It looks like to me there may be more then 1 problem, no vaccum to the coolant valve and something else?

Thanks Larry

 

If you bench tested the original and its functioning, replaced it, and by applying vacuum by hand and opening the new valve seems to work, you should be getting hot coolant on the heater core return hose. If its noticeably cooler to the touch on the return, it sounds like the core is restricted. Might try and remove the hoses and check for a blockage with a hose, then back flush and see if it will flow in the opposite direction. Whats the engine temp gauge read as far a temp?..

 

Engine temp is normal. I have used used my vaccum gun on the old and new valve both, the seem fine. I'm not getting vaccum to the diaphram so I looks to me that there is more than one issue. Back flushing the core sounds like a good idea. Thanks for the response.
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