I know my truck has a vacuum problem. When HVAC is set to face it blows defrost. With the vehicle off and key in run, I don't hear any pump running. What I haven't been able to figure out is where the hell my pump is at. I'm starting to get the feeling it doesn't have one/missing one? From what I've found I think it suppose to be on the passenger side fender, but I can't find any missing hoses or electrical connectors. Online videos mostly are for the 6.0L and it looks like a different setup. In the attached photos you can see the vacuum reservoir, blower motor, and the controller for the 4x4 hubs. I did use a bleeder to test the hoses last night. I have a holding vacuum on 2 of the 2 lines I tested. One should have been the front hubs, the other the HVAC or engine side. I'm hoping another member has a picture or can take one of the same engine and point it out. My Hanes doesn't even cover that part which is another annoyance.

 

You don't have a vacuum pump the engine creates vacuum when running. Diesels don't make vacuum that's why they have a pump.

 

I did not know that...

Basically, I need to do more vacuum testing and figure out where I'm leaking at.... I don't suppose anyone has a diagram of the vacuum hose routing on the 5.4L engine do they? Also should mention there are not CEL's on.

I found this one on AutoZones repair guide site.
http://repairguide.autozone.com/znet...52801e54d9.gif

 

Would a leaking head gasket cause a vacuum leak?

 

No it wouldn't, you have a broken vacuum line somewhere. The default on the HVAC system is to go to defrost, The most common area is the lines running to the lock out hubs..

 

Well that's a slight relief.

I tested the vacuum line going to those and it was holding vacuum. Same with the black line going towards the firewall. I'll have to try some of the others and see if they hold vacuum as well.

Got one of these last week: Mityvac Vacuum Pump - Save on Mityvac Pumps at Harbor Freight!

Sometimes I get ahead of myself and need to slow down when troubleshooting...

Is there any sort of vacuum lines running to the rear axle? I have this T block on my axle which is the brake lines splitting, but I'm not sure what the additional hose is.... It's draped over my pumpkin right now. The smooth one I'm referring to, I know the one with ridges is the supply for the brakes.

 

It's a vent hose for the rear diff

 

FYI, I ended figuring out what the issue was probably about a month or two after starting this thread. The leak was coming from my 4x4 actuator. In the first and second pictures its the yellowish looking box on the fender on the left side of each picture. The bottom of that part was cracked open. Slight pain getting it off the fender, but all in all not bad to fix.

Now at some point I need to rebuild the locking hubs as they don't seem to be fully engaging even when manually locked.

 

Did the 4x4 locking hub rebuild with parts from DieselOrings Works great now.



In need of service since last owner did not take care of them.



Tear down, simpler than what it looks like.