So I've been discussing the Plenum problem and reading the TSB's on it for a bit now.. I know its a sooner or later problem; but I came to following test to check if a plenum is really seal is really good or not..

Tell me if you think this is a good test?

Checking at different temps; Cold temp; and Full operational temps:

1. Plug the PCV port on the valve cover.
2. Remove the Vent tube from intake hat
3. Plug with figure.
4. Wait about 4-5 seconds
5. Pay close attention if a "Sucking" Vacume feeling is present or not
6. Release

If tube expels air; there is no leak; as the inside of the crank case would naturally build up pressure from the gases that get by the rings by blocking the PCV and noting pulling positive ventilation; it would thus build up pressure and you would feel it after unplugging the vent very shortly as the built up pressure is released.

If plenum was bad and leaking; there would a vacuum with in the engine block thus not allowing for pressure to build as there would be a positive pull from the crank case. (varies depending on how bad the actual leak is if one is present)


Or I suppose you could hook up a gauge and see if its pulling vac or building pressure.. either way>

Let me know what you think about this test method...

 

Or shine a light down threw the throttle body and see if there is oil in there. I used my bosses snap on inspection camera. Works great for that!

 

Ugh double post!

 

Well that's the point of this test; you can look down there (I have a little mirror on a stick my paw gave me.. very old but works good.. but these trucks from what i can tell sucks a hella lot of oil through the PCV.. same goes for the air vent on the other side.. just nature of these engines.. my old FORD 5.0HO did the same thing.. Untill i removed the vent from the intake and simply put a filtered cap on it.

Just kinda throwing it out there to see what ppl though is all.

 

I just did a video of this, and some time in the next week I'll likely post it on Youtube. However it has left me a little confused since the result is normal and now I don't know whether I should go ahead and replace the pan gasket anyway or whether to believe the Dealer statements in the TSB that say to stop there. In my case I'm not losing oil or pinging, I just have a bit (?normal) of oil in the plenum and very bad gas mileage (9mpg).

Ultimately I'm looking for guidance as to whether this is a reliable test to exclude a leaking gasket. If air can't get through, then it certainly can't be severe. But I suppose I can imagine a situation where the gasket could leak from the outside, or a situation where the blowby gas production is high enough to overcome a pinhole leak. I wish more people here were familiar with doing that test since it would be nice to talk to somebody with experience regarding false negatives....

 

OK, I did post a Youtube video showing how that Chrysler recommend test is done, at least according to that TSB. It's here


Whether the test is reliable, I don't know.

 

Yes, the test is reliable. You may just have a lot of blowby going through the PCV valve.

 

Thank you, Tom. Right now I'm focusing on the thought I may have a slight vacuum leak, or perhaps the PCV valve is not constricting down as much as it would normally at idle -- notice that my vacuum was 17 at idle and 22 at about 2500 rpm. I think I"ll smoke it, and swap the PCV valve (although it does rattle). Any other ideas?

 

I haven't really used a vacuum gauge for a while but, just from memory, those numbers don't sound all that bad. Does the gauge stay steady at idle or bounce around?