Fathers Truck, stuck on defrost

[Klitch]

How many things can cause the diesel trucks to be stuck on defrosters?

[inki]

Mine did the same thing back when I owned it. It turned out to be a vacuum leak in the hub because it only did it when I switched to 4 wheel drive.


Sent from my Autoguide iPad app

[Zaairman]

He either has a vacuum leak at the reservoir, bad line, or a bad vacuum pump. If the pump is good, you will hear it running with the engine off and key on.

[Klitch]

Ha howdy zaairman

I'll have to have a listen, I do remember hearing vacuum pump before. I think he has no 4x4 or any climate control. Sounds like vac leak, prob at the reservoir. Where's that at?

[Zaairman]

Passenger side of the engine compartment.

[ttyR2]

It's common for the vac lines that go to the front axle hubs to crack and leak.

[Klitch]

Appears that the solenoid on the passenger fender for 4x4 auto-hubs does not seal, allows vacuum to atmosphere. Though I'm confused, switching to 4x4 does eventually slowly pull (probably slow because I keep breaking the circuit, making the pump run constantly) to 14" of vacuum then it dumps to 0.

[Klitch]

Originally Posted by ttyR2

It's common for the vac lines that go to the front axle hubs to crack and leak.

Those rubber lines are shot, will be replaced asap