PCV rattle 98 JGC 5.2

I noticed a strange rattle under the hood today, the PCV was vibrating a million miles an hour. It still runs good but sounds a bit different (other than the rattle). I just replace the PCV a week or so ago. Any ideas? Thanks in advance, JK

Reply to
JRK58
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Reply to
L.W.( ßill ) Hughes III

Hello Bill, I'm not real sure how close to intake port it is. I just replaced it and it's not doing it anymore. Pretty weird, I've never seen anything like it.

Take care, JK

Reply to
JRK58

The factory likely forgot to put in the spring or the wrong spring or something like that. Things 'do' come broken right out of the box.....

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

There are actually two different PCV valve designs for the Mopar SB, one with and one without a spring. I've also found that they may carry the same part number because I suspect they peform almost identically once in service. The one without the spring, however, is quite noisy as you have discovered.

I've also come to believe that there is very little that breaks on a PCV valve that might require its replacement, short of a broken spring. What does happen is that they clog up and could use a good cleaning from time to time. A little blast of WD-40 followed by brake cleaner and they're good as new.

Oh, and you can tell the ones without the spring before you buy them by shaking the package. The weight moves freely if there is no spring.

My 2 cents.

Reply to
RCSnyder

Reply to
L.W.( ßill ) Hughes III

Bill,

I must beg to differ.

I have purchased two very different replacement SB PCV valves wearing the same Fram part number and the difference between them was one had a spring and the other did not. The one without the spring rattles like a baby's toy at idle while the one with the spring is hardly noticable. I tossed the baby rattle for the same reason as did JRK58.

Fram apparently does not consider the presence of the spring as required for proper operation of the PCV circuit in a Mopar SB, nor do based on my understanding of the valve's operation.

For those who are unfamiliar with the related airflow process, I pulled this from

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"The theory behind PCV operation is this, A hose from the intake manifold goes to the PCV valve. The PCV valve usually sits in the top of the valve cover. Then another hose comes from the air filter housing, either from the inside of the air filter or through a breather filter, and to the crankcase. Now when the engine is running air is drawn from the air filter housing into the crankcase, through the PCV and into the intake. So there is a vacuum inside the crankcase."

It would appear that the rather upright orientation of the valve when installed in a SB valve cover allows the valve weight to provide enough closing pressure keep the air flowing the proper direction while maintain the required amount of manifold vacuum. Contrary to your statement, the spring's purpose is not to open the valve at low throttle but to keep it closed until vacuum pulls it open so that a certain amount of manifold vacuum is maintained at all times.

Think about the importance of maintaining manifold vacuum. Power brakes would be without assist, vacuum spark advance curcuits would be neutered along with many emission control systems. Fortunately PCV valves gum up more often than stick open making their failure less noticable. Poor fuel mileage and a black exhaust pipe would be good things to watch for in a more modern engine.

Hope this helps.

Bob

Reply to
RCSnyder

Reply to
L.W.( ßill ) Hughes III

L.W. ("ßill") Hughes III did pass the time by typing:

In all my dealings with those doodads I've come to the realization that those without springs are simply rejects that made it though. And that 99% of the time a spray or three of carb cleaner will make the old one just like new again. It's that cracked O-thingy they fit into that needs to be checked and replaced every now and then too.

Reply to
DougW

Reply to
L.W.( ßill ) Hughes III

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