Vacuum operated "blend" valve leaking

[roycet4]

My son's '96 Ranger, 4.0l has a vacuum operated valve that connects between the two heater hoses just after they connect to the heater core in the engine compartment. It appears to be leaking. Is this a dealer only part or can I get this from NAPA or Advanced Auto?? What is the purpose of this valve, to allow the truck to heat up quicker?? Sorry, did not take a picture..

Royce

 

[srteach]

If you are talking about a vac operated valve under the hood which is connected to both heater core hoses, it is called a heater bypass valve. It is on or off only, not blended, and is usually only found on AC equipped trucks. The purpose is to stop the heater and the Air Conditioning from fighting over control of the cabin temperature (coolant flow is short circuited around the heater core when you turn on the AC). The coolant is free flow through the heater core otherwise. Cabin temperature in Ranger trucks is controlled by blending cold air and hot, not by regulating the amount of coolant through the heater core.
That valve should be available from parts stores, I bought one from Carquest a while back. NAPA and Advanced should also have them.

 

[roycet4]

got it

Thanks very much, off to NAPA tomorrow

Royce

 

[whale]

^thread necro alert^

If you are talking about a vac operated valve under the hood which is connected to both heater core hoses, it is called a heater bypass valve. It is on or off only, not blended, and is usually only found on AC equipped trucks. The purpose is to stop the heater and the Air Conditioning from fighting over control of the cabin temperature (coolant flow is short circuited around the heater core when you turn on the AC). The coolant is free flow through the heater core otherwise. Cabin temperature in Ranger trucks is controlled by blending cold air and hot, not by regulating the amount of coolant through the heater core.<snip>

Is this true? Mine is also leaking from the control arm, however the arm seems vary position based on the hot / cold control in the cabin, not just "on / off"

Will

 

[RonD]

The two heater hoses coming from the engine must always pass coolant or engine will over heat, it is the way the system is designed.
This is different than systems that just had 1 valve on 1 heater hose, in these systems the heater core is not part of the cooling system and flow between the two hoses could be shut off.

The 4 hose by-pass/diverter can be an "on/off" or a variable flow, the important thing is the coolant is always flowing between the two engine hoses.
So the valve can send some or all of the coolant to the heater core, but return flow to the engine doesn't change.

If heater core ever gets clogged even partially then you would notice that engine temp would go up when heater was on, this is because return flow is reduce by clogged heater core.
This is counter intuitive since you would think heater being on would reduce engine temp, lol.
But with this type of set up turning off heater, opening by-pass, restores full flow between the two engine hoses.

On my '94 with 4.0l and A/C, there are no valves, just two hoses directly to the heater core, heater is turned on by opening the blend door inside the cab

 

[whale]

Alright, so the other post is inaccurate. The vaccum control has the ability to be off, full on, or a "blend" while the other circut is always open, allowing the water pump to circulate.