Hey folks I've got a serious problem. A couple days ago I had a heater hose bust and overheated some. Got the hose all fixed with little problems. Now its sucking gas like crazy. The idle is good and there doesn't seem to be any power loss. I'm thinking the plenum gasket blew out but just wanted a second opinion. Oh its a 99 with 5.2 2wd and about 155000. Also there are no engine codes or check engine light. Thanks in advance,Greg

 

If your at 155k and the plenum is original, I'm sure it has gone bad. I'm not sure if it's related to your heater hose issue though.

 

Yeah I don't think the two are related. And the plenum is original. Do ya think a bad plenum gasket would show up on a vacuum gauge?

 

Not sure. The recommended test on these forums is pulling the throttle body and taking a peek into the intake and look for excessive oil pooling.

 

I just looked and there is oil there just not pooling more like a thin coating.
Plus my vacuum gauge reading is steady as a rock no wobble or bounce at about 20 inches at idle.

 

Hmm. Maybe someone else can tell you about the vacuum test. I'm sure you have at least a small leak. I would change it, because on the off chance it hasn't blown etc, it will.

 

Thanks man. Better to be proactive and get it before completely goes.

 

Yea I agree. I changed mine on my ram at around 100k. I don't think I was completely shot, but was nice not to have to worry about it.

 

I just changed mine and it was blown in 3 places. Replaced it around 115,000. I barely even have to add oil when I check it anymore now.

 

Easy test for blown plenum.

Disabled, and cap off PCV system. (input side to manifold.)
Take off oil fill cap.
Start engine.
You should feel a bit of a breeze coming OUT of the oil fill. If there is vacuum there, plenum is blown.