Vacuum Leak somewhere on Auto 4x4 - How to test Vacuum Solenoid???

[Metalhead]

I've got a new intermittent vacuum leak somewhere on the auto hubs system. I say intermittent, because on some days the system works perfectly on demand. On others, the AC system switches over to blowing through the defrost vents after 10-15 seconds, and I verified the hubs were not engaged by spinning the u-joints by hand.

I've already replaced a hub seal at the right front that I verified as bad. After that repair, the system worked perfectly for about 2 months until now.

It doesn't seem that I have another bad hub seal, since the system still engages perfectly on demand on some days, but maybe you all might have some thoughts on that...

How about the vacuum solenoid at the dash? Is there a way that I can test it? Maybe it's bad, letting a big leak happen on some days, not on others.

Thanks in advance...

BTW, I see the other thread going on this right now that's similar, I'm keeping a watch on that for this problem as well...

 

[Dogman]

The EZ way to test is go to the vac. pump, pull the line and cover it with your finger if the pump stops working then move to the next point in the line and keep testing. Also pull the vac. lines at the frame for the hubs and cap them. This will get-rid of test the hubs first. A spot I found that was leaking was a rub spot on the main little feed line into the truck. It run by the blower fan and the fender. Check the vac. line going to the heater core hot water shut off. If you find out the control switch is bad let me know. I have the part # for just the switchs. The dealer will try to only sell the hole control unit for a few hundred. Switchs I think less then 20 bucks.

 

[Roland_Jenkins]

About the air blowing through the defroster. Check on the passengers side, just under the dash and towards the right. A hose may have came loose.

 

[Metalhead]

About the air blowing through the defroster. Check on the passengers side, just under the dash and towards the right. A hose may have came loose.

I will check that Roland. Only thing I wonder though, wouldn't I be having the air through the defrost all the time if it were this hose? Not just when I'm in 4x4?

 

[Roland_Jenkins]

I would think so. There must be a vacuum manifold for the 4x4. Wonder if a hose is off or sucking air?

Stuff like this makes me glad I have manual hubs.

 

[mantis]

I would think so. There must be a vacuum manifold for the 4x4. Wonder if a hose is off or sucking air?

Stuff like this makes me glad I have manual hubs.

Tell me about it ,I don't like this system at all.I know that alot of times they leak by the pumkin.

 

[dpantazis]

the solenoid is on the pass side fender under the hood.

check the plastic barbed elbows on the bracket at each wheel. look for the brake hoses. vac hose its the littler one. look at the elbow trapped between the sheet metal and the hose.