Vacuum pump runs constantly

Spastik monkey · Apr 5, 2012

I've recently noticed my vacuum pump runs constantly with the key on. The AC defaults to defront but will switch to whatever setting after a few seconds once the engine starts running. Any idea what would cause this?

BigAlsPSD · Apr 5, 2012

Vacuum leak, haha. Sorry just had to. Maybe a cracked reservoir? Or a split in a hose somewhere, check connections under the glovebox.

Mwilbur516 · Apr 5, 2012

Check your hub seals. The seals get dried out, crack and leak causing the pump to run constantly.

Spastik monkey · Apr 5, 2012

Mwilbur516 said:
Check your hub seals. The seals get dried out, crack and leak causing the pump to run constantly.

Even with the 4x4 disengaged? Where is this seal located?

MorganY · Apr 9, 2012

Fixed an issue like you described today. A/C at defrost and vacuum pump running constantly key on. This one happened to be the rubber connector at the vacuum pump. FUBAR'd

Spastik monkey · Apr 10, 2012

Well I tested it. It all holds vacuum until I plug in ESOF the solenoid. I'm thinking the solenoid is shot.

HOOV3R · Apr 10, 2012

Went through the same thing with my truck. Swapped solenoids with my dads truck and it worked perfect. I think it was about $70 at the dealership.

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Spindrift · Apr 13, 2012

Younger1993 said:
Fixed an issue like you described today. A/C at defrost and vacuum pump running constantly key on. This one happened to be the rubber connector at the vacuum pump. FUBAR'd

That damage looks exactly like what squirrels and mice do up in this neck of the woods during the winter months. Couple of years ago, I lost an entire engine when the buggers chewed through my engine harness.

jngreen · Apr 13, 2012

Spastik monkey said:
Well I tested it. It all holds vacuum until I plug in ESOF the solenoid. I'm thinking the solenoid is shot.

Yep, my solenoid is shot as well. I just plugged mine at the vacuum reservoir since my 4x4 is also disabled.

Zmann · Apr 13, 2012

got mine from the ford dealer on this site 25% off and free ship

and to clarify a bad hub seal won' cause the pump to run and run unless the solenoid sticks open

Spastik monkey · Jun 25, 2012

Replaced the solenoid. It still runs constantly, but after about 2 min the air will siwtch over to AC. I changed out the lines that go to the hub as well. I'm stumped

FX4 F2-Fifty · Jun 25, 2012

After the truck sits for a while, is there still a vacuum?

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Spastik monkey · Jun 25, 2012

Nopef

Zmann · Jul 2, 2012

cracked canister ?

Mdub707 · Jul 3, 2012

I'm in the same boat right now, just replaced all of the lines going down to the hubs. Both hubs have been replaced before under warranty, so they're not that old...

Where's this solenoid located?

HOOV3R · Jul 3, 2012

Pass. side fender between the canister and the battery.

Mdub707 · Jul 3, 2012

Ok I'll have to check that out. Any way to test if it's bad or not?

My HVAC system will ONLY blow out the defroster now, no other settings at all. auto 4x4 still not working either... hopefully that solenoid fixes it.

spastik monkey, you have a spare solenoid you want to sell? Sounds like you just bought one and it didn't fix your issues, so your old one is probably still good right?

svilla · Jul 3, 2012

Have you checked the gray vacuum line that plugs in the valve inline with the heater hose on top of the passenger side of the engine? When mine had the same problem, that is what it was.

Mdub707 · Jul 3, 2012

Checked it as far as what, making sure it's plugged in? I remember finding it unplugged a couple years ago when Ford took the cab off one of the times, and plugged it back in, still nothing. I even moved the valve last night by hand to make sure it wasn't "sticking" or anything. What exactly does that do there?