4.7 bad valve seals?
Thread Starter
|
Registered User
Joined: Feb 2015
Posts: 2
Likes: 0
4.7 bad valve seals?
I was wondering if bad valve seals are common on high mileage 4.7. Mines been smoking for a while and im thinking it may be the valve seals.
It only smokes when it gets to operating temp and only when I blip the throttle. Its a huge cloud of light blue smoke. Spark plugs are clean, no signs of oil on them. Compression looks good.
Stops smoking when PCV and LDP hoses are disconnected from the intake leaving hose inlets unblocked. This I believe reduces intake manifold vacuum since its sucking in extra air from open inlets. Its got to have something to do with high vacuum in intake manifold since it only happens when I blip the throttle because high rpm with intake closed causes high intake manifold vacuum right?
I can rev up to any rpm and slowly decline without any smoke.
If I disconnect the same hoses and block off the hose inlets, which brings manifold vacuum back up, it starts smoking again. So I'm thinking its just when intake manifold vacuum is high it sucks oil passed the valve stem seals? Oh and I have already replaced PCV valve and made sure the hose is not clogged for that or the CCV breathers.
It only smokes when it gets to operating temp and only when I blip the throttle. Its a huge cloud of light blue smoke. Spark plugs are clean, no signs of oil on them. Compression looks good.
Stops smoking when PCV and LDP hoses are disconnected from the intake leaving hose inlets unblocked. This I believe reduces intake manifold vacuum since its sucking in extra air from open inlets. Its got to have something to do with high vacuum in intake manifold since it only happens when I blip the throttle because high rpm with intake closed causes high intake manifold vacuum right?
I can rev up to any rpm and slowly decline without any smoke.
If I disconnect the same hoses and block off the hose inlets, which brings manifold vacuum back up, it starts smoking again. So I'm thinking its just when intake manifold vacuum is high it sucks oil passed the valve stem seals? Oh and I have already replaced PCV valve and made sure the hose is not clogged for that or the CCV breathers.
Last edited by beeleco; Sep 19, 2020 at 11:26 AM.
Administrator
Joined: Apr 2010
Posts: 87,461
Likes: 4,219
From: Clayton MI
How many miles on it? Valve seals don't last forever, but, they usually show up as bad at first startup.... and you get a blue cloud. If you get your while on the throttle, I would be replacing the PCV valve, with a genuine mopar unit. They actually have the correct flow rate.
Champion
Joined: Oct 2013
Posts: 3,772
Likes: 449
From: Atlanta
Mine smoked occasionally when accelerating from a stop. By the time that started, I was well over 300K on the 4.7.
I replaced the stem seals back in the spring, along with the lifters and springs after a lifter failed and threw a rocker. No more smoke and absolutely no oil consumption. In fact, I cleaned out the tailpipe with a rag and it's still soot free today.
https://dodgeforum.com/forum/2nd-gen...tem-seals.html
https://dodgeforum.com/forum/2nd-gen...ine-issue.html
If you're going to replace the seals be sure to replace the lifters too.
I replaced the stem seals back in the spring, along with the lifters and springs after a lifter failed and threw a rocker. No more smoke and absolutely no oil consumption. In fact, I cleaned out the tailpipe with a rag and it's still soot free today.
https://dodgeforum.com/forum/2nd-gen...tem-seals.html
https://dodgeforum.com/forum/2nd-gen...ine-issue.html
If you're going to replace the seals be sure to replace the lifters too.
Last edited by Dodgevity; Sep 19, 2020 at 03:56 PM.
