bluecar5556

Does anyone know where this plastic line goes to behind the engine? There isn't much room back there due to the bulkhead making it difficult to feel what is back there. It's a huge vacuum leak because I can hear it and the engine is barely idling.

I had to leave the work truck at the shop because I didn't want the engine to run lean from unmetered air bypassing the MAF and risk burning something up. Tomorrow, it will be round two trying to figure this out, without the vacuum diagram sticker on the radiator core support, in the morning so if anyone has an idea, please do share!

1999 F-150 5.4L

dcrawford

It appears that one end has a worn rubber elbow; that end should connect to your PCV valve. The bare plastic end should connect to a port on the back intake riser (it's the curved metal piece between the t-body and intake manifold). Also, there should be a rubber coupling to connect the plastic hose to the metal vacuum port. I've posted a video that may help.

http://www.youtube.com/user/ahubbard...72/7UL6yST1aUY

bluecar5556

Taking the TB off wasn't what I planned but thank you so much for the help, dcrawford!

dcrawford

You shouldn't need to remove the TB. I could be wrong... I have the 4.6L, so I am unaware of any differences in vacuum hose routing on the 5.4L. For me, it was tight to access the hose at the rear of the TB, but not impossible. The video was intented to show you the PCV line as a whole, brand new unit. I hope you were able to fix the problem.

dcrawford

Ah ha, I watched the video again. It helps if I know what I am talking about! I did not realize the differences in the 4.6L and 5.4L intakes. Make sure the rubber elbows have no holes. The one at the back of the intake is notorious for leaking. I think you can order the entire plastic PCV line inclusive of PCV valve and rubber elbows for around $30.

bluecar5556

Worked on my cousin's boat yesterday but had some time to take off the TB this morning and you won't believe how badly the rubber dealy is deteriorated, indicated by the red arrow. I'm surprised it didn't have a big vacuum leak, judging by the condition of the rubber dealy, but even if I managed to plug the hose back in w/o removing TB, there would have been a leak, most definitely.

Now my question is if the PCV valve already has intake manifold vacuum from the passenger side of intake, what use is the other one that is broke connecting to the rear of the intake?

You have been a huge help dcrawford, thanks again. Now it's time to give the stealership a visit tomorrow for the hose and assortments of proprietary rubber ford parts.

Carcrazygts2

On the PI 5.4 its more efficient according to ford. The revised pcv hose is just one coupling that goes to the rear of the manifold...

dcrawford

Are you talking about the other hose that connects to the driver side valve cover? If so, I think it's just a breather. You have two viable repair options: 1) Redneck engineer your plastic hoses back together with "patches" of EFI hose (and zebra stripe duct tape), or 2) Purchase both lines new from the dealership. I think both PCV lines are priced reasonably. I'll see if I can help locate part numbers.