Hello all, my friend owns a 1997 ranger i believe a 4cly.
I think she has a vacuum problem, anyway here are the signs and symptoms.

1. She doesn't get any heat until she starts doing 55 down the highway.

2. At the valve type assembly (where the 2 hoses start from and go thru the firewall) there is a small leak, but it seems like it is a leak under pressure, it bubbles then drips. (I think thats the input tube to the heater core and the valve is not operating correctly.)

Is that valve vacuum operated just like on my 78?

3. After going 55 down the highway, she puts in the clutch and coasts to a stop the engine still holds a high rpm, like she was still at 55. She can only get the engine to drop to idle without shutting it on and off is by turning the defrost/floor/heat/AC **** to off.

4. Plus I noticed that on her valve cover gasket just aft of the oil filler cap there is a vacuum port that sticks up about 1/4 inch. It is not capped nor is there any hose laying around that should be attached to it. It does provide a good pull at idle.

Should this port be capped or should there be a hose going to it?

I am thinking that she has a vacuum problem somewhere with the prime culprit being the obvious port. But since I don't have a schematic diagram of her vehicle I don't want to tear into it yet.

Any input would be greatly appreciated. Thanks

 

Try a vacuum guage. They are cheap and will tell you almost any problems you have.

 

You said that this mystery port has good pull at idle. So, you've tested it with a guage? Put a cap on it & road test the truck.

 

Yeah I would use a gauge if available but I have that problem solved.
The engine temperature will not stay hot at idle. When you increase rpm engine temp goes up and heater blows hot air, go to idle and engine temp drops to cold and no hot air....seems like a bad thermostat to me.