vacuum leak/HVAC defaults to defroster

[mjtjnj]

Had this problem for a long time, now that I've been through the whole engine and put in new AC parts, maybe I'll figure it out. There is a pink vacuum line that, on my truck, comes out where the heater hoses and evaporator are (HVAC "box") and goes no where. Where does this connect on the 87 2.5L? I don't have a good vacuum line diagram.

There's also a blue vacuum line in the neighborhood that's got tape on it and traces back to the intake area, goes nowhere. Truck runs fine. ..I'm not convinced my defroster problem is from the vacuum "football."

 

Tom

[aemsee]

There should be a vacuum line going in to the truck with manifold vacuum, the one coming back out would be for the heater control valve on the heater hose. If the valve is gone, well, there you are. Cap off the line and see if your stuff starts to work.

[mjtjnj]

I forgot about that valve! My other trucks had it, and it used to stick. Maybe the PO took it off. I'll look when I get home -- thanks! For those that have the valve, what color are the lines going to/from it?

 

 

Tom

[HOrnbrod]

I forgot about that valve! My other trucks had it, and it used to stick. Maybe the PO took it off. I'll look when I get home -- thanks! For those that have the valve, what color are the lines going to/from it? Tom

 

Only one line going to the water control valve, and it's pink on mine. Just plug it off and bypass the H2O valve.

[aerocorey]

Also check on the vacuum lines that run over the right wheel well under the hood. I've had an MJ and an XJ with one of the lines in that spot cracked, and seen dozens of others in junkyards with the same line cracked. It'll cause your problem.

[Redramman]

My sons truck came with minor bumper dammage on pasenger side front ,and the vacuum reservoir ball located behind bumper/fender area was broke .I just conected the hoses together with an extra windshield washer hose T and caped off the third port, and the AC air came out of the dash vents .I am going to try to glue the vacuum ball back together with JB weld epoxy.

[aemsee]

My sons truck came with minor bumper dammage on pasenger side front ,and the vacuum reservoir ball located behind bumper/fender area was broke .I just conected the hoses together with an extra windshield washer hose T and caped off the third port, and the AC air came out of the dash vents .I am going to try to glue the vacuum ball back together with JB weld epoxy.

 

Just find another vacuum reservoir from a JY. Doesn't have to be from a Jeep. Any will do.

[Wildman]

My sons truck came with minor bumper dammage on pasenger side front ,and the vacuum reservoir ball located behind bumper/fender area was broke .I just conected the hoses together with an extra windshield washer hose T and caped off the third port, and the AC air came out of the dash vents .I am going to try to glue the vacuum ball back together with JB weld epoxy.

 

Just find another vacuum reservoir from a JY. Doesn't have to be from a Jeep. Any will do.

 

Or just ask in the classified if any one has an extra one :roll: