I've got a couple of bucks to do the plenum job correctly. The previous owner only replaced the gasket, he did not replace the plate. Since he worked on it, the engine makes a very prominent "sucking" noise under load. I've been all over the engine bay trying to track it down, thinking it might have been a vacuum issue. I can only pin point it somewhere at the rear of the engine up high. It is not the air filter housing. My vacuum-controlled accessories (ie, cruise, HVAC) all work as they should, but this sound is definitely not right. I don't want to burn a valve by running with a huge vacuum leak. My truck is using quite a bit of oil and is down on power as well, so I think the plenum kit from Hughes is the right thing to do. I just don't want to put this back together and still have a huge leak.

 

You only really need the plate and bolts..... which you can get cheaper on EBay, just source a good set of fel-pro gaskets locally.

Take off your air intake from the throttle body, I bet the sucking noise gets MUCH louder. Probably air passing thru IAC ports. It can be rather loud.

 

Too late. Already ordered the kit from Hughes. No difference in loudness with the air filter housing removed. Noise seems to be coming from lower.

 

If the plenum is blown, again.. take a look (if you can bend that way) at where the back of the manifold seals to the block. There is a rubber seal in there, and it is way easy to knock it out of place when installing the intake. Would be a collosal vacuum leak....

 

Also crankcase (valve cover) vac on drivers side that connects to air cleaner housing will make a huge sucking sound (like NAFTA).

 

Well, this past weekend I tackled the plenum issue, or my buddy did anyway. We still have a very loud sucking noise. I'm at my wit's end with it. We installed all new gaskets and seals (kit from Hughes) and the rubber gasket at the back of the block was still in place when we lifted the intake off. My buddy doesn't think it's coming from the intake seals, but something else. It's not the air box, as it still makes the noise with the airbox removed. Aside from the obnoxious noise, I'm afraid whatever this is is a bad vacuum leak that will ruin my engine.

 

Isn't just air turbulence at the throttle body is it? these engines suck a LOT of air thru a small hole at idle...... that can be rather loud.....

 

"Sucking sound indicitive of plenum issues?"

No; as gdstock pointed out, that's just the sound of U.S. jobs rushing to Mexico.

Here's my 2 cents; I love measuring things (well, not everything, if you know what I mean). How about doing a vacuum check on your intake to see if you really do have a vacuum leak. You just might not; my 318 is running great, but these engines just seem to generate quite a bit of noise when they breathe, kinda like my Uncle Herman. It might just be that after the PO did the plenum job, the increased sucking sound was an indication of a better-running engine; more air being sucked down through the intake, instead of up from the crankcase.

Also: I feel like a kid with a new toy with this TSB (09-05-00, dealing with testing for a blown plenum gasket);

http://dodgeram.info/tsb/2000/09-05-00.htm

It says that you can test for a bad gasket by measuring for vacuum in the crankcase; you could at least verify that your fix was good.

Lastly, you might want to check that the IAC "motor" is functioning correctly; maybe that could be contributing to the sucking sound.

[Oh Mr. Perot, where are you when me really need you?? Please come lift our nation's hood and take a look; she's runnin' real bad].

 

Thanks guys. Don't have a vacuum gauge, so I'll have to find someone who does. The noise is really only noticeable when the motor is under load. Don't really pick it up at idle.

 

I always thought the "Sucking Sound" was American jobs heading to Mexico.

I guess Ross Perot lied to us back in 1992.