I have a 09 f150 with 160,000 on it. For the last couple months I was hearing an occasional buzzing sound from the engine compartment. Couldn't duplicate it while not driving. The buzzing sound has changed somewhat but it's follow by a grinding sound that seems like the hubs are trying to lock while in 2 wheel drive. I think the buzzing is coming from either the IWE solenoid or the vacuum check valve. My question is this. If I pull the vacuum line off the the solenoid and plug the line will the hubs remain locked till I can dig into this a little deeper. I was thinking that they would stay locked. I should still be able to shift in and out of 4 wheel drive correct? Any help on this would be great.
Thanks

 

Where is the solenoid located ?

 

IIRC, The solenoid is on the firewall, but I could be wrong....

Yes, if you unhook the vacuum lines from the hubs and plug them, the hubs will stay engaged, making it safe to drive.... Assuming that there isn't a problem with the IWE, but either way you will where the problem is.

 

I unplugged the vacuum lines to the hubs and the grinding stopped. Its been at the dealer for 2 days now and they cant figure it out. It holds good vacuum while in the shop and the hubs stay disengaged. While driving they try to lock.

 

Sounds like the check valve. The check valve is there to hold vacuum to the IWE when manifold vacuum drops.

I'd check the vacuum at the end of the line while driving, it should stay fairly constant as the manifold vacuum drops.
Serving ideas.
I could be wrong.

 

Thanks for the reply. I'll have them check that.

 

The dealer said they won't replace the hubs because if it doesn't fix the problem they will loose money. They can't find any vacuum problems. So I guess they are not interested in fixing it. I took the check valve off and I can blow air thru it in both directions. I didn't thin that would be possible if it were good. The grinding is when I accelerate. Maybe the vacuum is dropping and the check valve isn't holding vacuum in the hubs.Both hubs are making the noise so I don't think its the hubs. Both wouldn't go bad at the same time.

 

If you already have the check valve out, id just throw another one in there.

Unless it is really expensive .....

I agree, it sounds like these guys aren't being particularly helpfu...