: Whistling pressure relief on N* Intake Manifold???



gdmarques
06-09-08, 09:49 PM
Anybody ever seen this valve on the end of the intake manifold on a N*? After going nuts for a week trying to isolate the source of a strange whistling noise from my engine (which sounded like a bad bearing, and my mechanic was sure was my AC compressor) I found this spring loaded flap valve at the end of the intake manifold. After reading all the posts here about this type of noise coming from the manifold gaskets themselves I replaced them, but it made no difference. Using my auto stethoscope with the probe removed I found this valvew which sits behind the power steering pump reservior. I was shocked to find this since it seems odd to have such a huge opening which could allow unfiltered ait directly into the engine. I assume its a backfire relief or some other over pressure relief valve. After cleaning the gasket (which is molded into the flapper) and the seat, and reinstalling the manifold again the noise was gone. Anyone ever seen this and/or know what its purpose is?
:eek:

Ranger
06-09-08, 10:08 PM
It is called an over pressurization relief valve. In the event of an over pressurization (backfire), the valve is forced open to relieve pressure rather than having the manifold explode.

gdmarques
06-09-08, 10:19 PM
Thanks for the quick response. Ever heard of one of these whistling or causing a vacuum leak before? I doesn't look like a replaceable gasket on the valve. Is the assembly replaceable or come as part of the manifold itself?

Ranger
06-09-08, 10:51 PM
It is not common, but I have heard of one or two leaking, causing a wistle and/or a high idle. Not sure if it is replaceable separately or not.

Submariner409
06-10-08, 09:33 AM
There have been 1 or 2 "whistlers" in here a year or so back. My 02 FSM shows the valve removed in a couple of line drawings, so I assume it's replaceable. Sort of a screw-on collar retainer. I think there are a couple of different valves, depending on year.

ahamay115
07-22-10, 12:34 AM
Sorry to bring up an old thread, but this is exactly what I have been searching for all night! I have a 1997 Deville, and for months now I have been having oil fill up very slowly in the valley under the intake manifold, but only on the left side (passengers side - the valley has a separator in the middle). I have replaced the intake manifold gaskets, and they are definitely not leaking. But this pressure relief valve (as pictured above) seems to have oil around it, mainly at the bottom as though it is leaking oil... I'm confused because as far as I can figure, the intake should not have any oil in it, correct me if I'm wrong. Can anyone help me out with this issue? It has been going on for a while now, and the "fix" has been to remove the intake manifold every six months or so and clean up about a cup or so of oil. I cannot see any sign of seepage or any cracks of any kind. The only thing I can see is the oily residue around this pressure relief valve.

Any help would be greatly appreciated!

Thanks!
-Chris

Ranger
07-22-10, 12:34 PM
The intake does have "oil" in it. It is from the crankcase gases sucked into the manifold via the PCV and then settle out ofter shutdown. It should not have enough to leak out of the over pressurization valve I wouldn't think unless you are over filling your crankcase. You're not keeping the oil level at MAX are you?

tateos
07-22-10, 02:08 PM
Ranger is correct - it is normal to have a slight coating of crankcase vapors on the inside of the intake manifold, but for it to be leaking out of that valve would seem to require a huge amount of oil and also frequent backfires. The Northstar is somewhat prone to occasional backfiring when starting - that valve prevents blowing the manifold up, or off the heads.

A couple thoughts:

Are you sure the oil is not coming form the PS pump or hoses, or from the valve covers or from around the PCV valve?

Also, there were some posts awhile back about improperly installed or caulked PCV valve baffles on the inside of the right valve cover causing excessive oil pooling inside the valve cover

ahamay115
07-23-10, 12:18 AM
Its strange because even though this oil issue keeps coming back, the car has been running great. The gas mileage is up, no backfiring that I can think of, it just drops a quart of oil every couple thousand miles, maybe less, but it has always seemed to use oil since we got it with 27k miles on it. It now has almost 90k miles on it, but I'm not sure how long it has been accumulating. The first time we pulled the intake off there was a ton of oil in the valley, which had started to overflow and was all over everything! But since we first cleaned it, it has only had a small leak that slowly over time accumulates. Maybe it is just the oil slowly accumulating from what comes out of that pressure valve at startup...? It doesn't appear that anything else is leaking, I'm not low on PS fluid or anything else, just oil every so often. I don't think I've ever seen the car on the max line on the dipstick. I change my own oil around the 3k mile mark and add the 7.5 quarts and where the level appears on the dipstick is where I try to maintain it at.

Any other thoughts or ideas?

Thanks!
-Chris

Submariner409
07-23-10, 10:57 AM
Make sure that the PCV valve is the correct part number (large parts store lookup) and that the vacuum hose from the valve to the intake manifold is not broken or cracked - on your 1997, if the PCV grommet in the rear cam cover, passenger end, is loose, the engine will tend to blow oil out of that grommet. If it does, the oil runs down the face of the cam cover and onto the intake manifold flange area. It may make its way into the valley from there........

subscribe your car to www.alldatadiy.com for a year or so.....

Eninety2
06-27-11, 11:03 AM
im having the same leak out of that little flapper behind the PS pump. giving me rough starts, hesitation, and surging.

i work at a shop, and both ALLDATA and the local dealership confirm that it CANNOT be replaced. you have to replace the entire intake manifold.

Honestly, its seems spring loaded and i guess over time the spring loses it tension. i tried sealing it up with silicone, but it failed miserably.

RippyPartsDept
06-27-11, 12:07 PM
My parts catalog shows the valve as #3546341 and that is is available separately from the intake manifold

http://img818.imageshack.us/img818/16/blowoffvalve.jpg

Eninety2
06-27-11, 12:16 PM
thanks!

What catalog are you using?

RippyPartsDept
06-27-11, 01:05 PM
the GM EPC ...

you can get basically the same illustrations from compnine's catalog

Eninety2
06-27-11, 05:14 PM
ok, i got it ordered. $25 my cost which isnt bad. only thing, does anyone have any input on changing it out?

RippyPartsDept
06-27-11, 06:07 PM
yeah that's a good deal... basically the same price I can offer (before shipping)

Submariner409
06-27-11, 07:00 PM
ok, i got it ordered. $25 my cost which isnt bad. only thing, does anyone have any input on changing it out?

Remove the intake manifold. Literally hundreds of posts and threads with pictures and diagrams on the process in here, Seville, and Discussions: Cadillac Tech Tips. For some more manifold pictures and diagrams, click on Community in the black bar ^^^, click on Albums, open my two - the red Seville.

bob67cam
08-23-11, 03:06 PM
im in the process of changing 1 now, mine was loose, but im trying to find a new o ring for it, both valves i have, have o-rings that are hard as a rock
however mine does not have a vaccuum line running off of it, what does that line normally goto?...mines a 95 aurora, but theres no hole in the barbed area on mine...just curious
im going a different way on mine, i need to replace the serpentine belt aanyways kinda, so i pulled the fuel rail and the motor mount off the front of the engine and u gotta pull the power steering pulley off, then pull the lile power steering bracket off to be able to get to it, there are different mounts for the engine from olds to caddy but the rest is the same

Ranger
08-23-11, 03:47 PM
There is no vacuum line involved with the manifold overpressure relieve valve.

bob67cam
08-23-11, 04:53 PM
yea i know it doesnt actually do anything, however i was curious, guessing maybe a map sensor or something, however it tells me that mine which is non-existant and discoed however theres another which i would just have to cap off, so far finding the o-ring is coming up with notta, im guessing the o-ring will come with this thing

Ranger
08-23-11, 09:59 PM
I don't even think you have a vacuum line going in that end of the manifold if I remember correctly.

I would suspect that the O ring comes with the valve.

bob67cam
08-24-11, 12:01 PM
ok got the o-ring, i forgot to get the part number but its a balkamp, its in the balkamp book, just not something the stores usually carry, so it will need to be ordered