What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

PCV clatter

TJ1978

TJ1978

I have MANY questions
 Premium
GMOTM Winner
Joined
Oct 27, 2019
Posts
5,816
Reaction score
7,377
Location
East Valley, Arizona
Please see second post as it contains more info:

Noticed this morning on cold start and after some investigation it seem the PCV is clattering at idle.

Even after the engine has reached temp of about 180-190 it continued. I thought lifters or something at first, but after putting my hand on you can feel the ball clattering away.

So.... bad valve or clogged breather (breather felt dry)? I didn’t remove the breather to check in hindsite I should have... Is the breather being clogged a possible reason?


I will add that today with his clatter, oil was dripping pretty good from the where the oil filter is, it was coming from high up also (not from valve cover that I could feel) . Also on the dust shield where the brakes are oil was coming from there as well. It was weird.

I’m reading a bad PCV will cause oil to start coming out off odd locations.

has less than 300miles on it and just started this morning.

Chevy 350

5320A317-3577-4ED4-9960-C5F8BD9A4025.jpeg
 
Last edited:
I will add that on the first start after replacing the fuel filter the RPM went way high like up to 2000+ rpm when I stomped the gas pedal it smoothed out. Idle was around 750-790. I tried increasing it to 850ish and PCV still rattled.

When I first started it this morning the fuel pressure was high like 9psi on th mechanical pump. I thought maybe some debris was causing a restriction after having run out of gas. I thought something came up from the tank..

I replaced the fuel filter arrow pointing towards the Carb and it stayed around 5-6psi after that crazy start with RPM going upto and past 2000rpm.

Everything sounds the same as it did before fuel filter change other than the rattling of PCV ball.


Could these issues stem from a new fuel cap?

26DD6A14-3076-4CC2-8C1D-5AF5B04713C3.jpeg
 
Last edited:
Ok I went out fired it up.
I removed the breather and and no smoke but PCV still rattled albeit not nearly what it did.

Pulled PCV and put my finger on it, noticeable rpm drop with and with out breather on.

On start up it fires right up and no crazy RPM spike like earlier.

I’ve read some aftermarket PCV valves can be finicky especially with GM engines.

I will orde a GM or acdelco brand and see what happens.

Im going to order this and see what happens.
https://www.amazon.com/ACDelco-CV774C-Original-Equipment-Ventilation/dp/B000C9QVD4
 
Last edited:
PCV and breather work together: something is wrong with one or both of them. Given that you know you oil soaked the filter, and the PCV is misbehaving, and they are both cheap easy parts, I would replace both and see what happens.
The RPM change with plugging the PCV inlet is just the vacuum change. That is what is supposed to happen.
Smoke/oil mist should only really be produced in small volumes inside the crankcase, and more noticeable at high RPM vs low. So that is normal for an idling engine.
 
Oil soaked filter? The breather you mean or?
The breather didn’t seem “soaked” but I will double check. I have a baffle there to prevent it from getting soaked with oil. But it’s a cheap replacement so I will do it. New PCV should be here Monday...

I’ve been reading on some other forums and it’s just mind numbing the hundreds of possible “it could be” “solutions”.

I’ll try PCV and breather first.
 
TJ1978 said:
Oil was dripping pretty good from right above where the filter is...
Click to expand...

Sorry, read that and thought you meant breather, not oil filter. Wouldnt touch the breather if you think its fine.

Oil on the block from "above the oil filter" can be a couple things:
A) Valve cover gasket
B) Back of the intake / oil pressure sender area
C) Rear main seal
If its A or B its relatively easy to deal with, at worst its just a intake re-seal.
If its the rear main, unless its pouring oil out, just live with it. At a minimum requires transmission removal to get to... not worth dealing with unless you have stuff apart for other reasons already.
 
Yeah,
Breather seems fine. Maybe I’ll get lucky and it’s just the PCV going bad or maybe even the grommet is too loose or something? It still rattles when disengaged so, who knows...

The oil leak, yes I’m not pulling all that off for rear main seal leak. I’ll just add oil. Valve cover seems good I’ll double oil pressure sender tomorrow.

All was fine, until I ran out of gas on thanksgiving then all this stuff came into existence. Weird...
 
Last edited:
Does the valve cover opening for the PCV need a baffle?
I had to make one for the breather and my PCV doesn’t have one....
 
Sometimes the PVC valve passages where the hose connects to the intake gets a build up of deposits and needs to be cleaned out --a coat hanger wire and carb cleaner will work for that..

If you got a cheap FRAM or department store brand PCV valve ,that may well be the issue..

I've seen a few SBC engines that had a PVC valve that "buzzed" like a bee,or clattered at idle,and it turned out there was a intake valve that wasn't closing all the way,a vacuum gauge showed the vacuum was unsteady,the needle was fluttering wildly ..on one engine the valves were adjusted too tight,another had a burnt spot on the intake valve face..a vaccum leak can cause that also,like a bad carb to intake base gasket..the lower vacuum makes the PVC valve spring flutter instead of keeping it fully open or closed..
 
diesel4me said:
Sometimes the PVC valve passages where the hose connects to the intake gets a build up of deposits and needs to be cleaned out --a coat hanger wire and carb cleaner will work for that..

If you got a cheap FRAM or department store brand PCV valve ,that may well be the issue..

I've seen a few SBC engines that had a PVC valve that "buzzed" like a bee,or clattered at idle,and it turned out there was a intake valve that wasn't closing all the way,a vacuum gauge showed the vacuum was unsteady,the needle was fluttering wildly ..on one engine the valves were adjusted too tight,another had a burnt spot on the intake valve face..a vaccum leak can cause that also,like a bad carb to intake base gasket..the lower vacuum makes the PVC valve spring flutter instead of keeping it fully open or closed..
Click to expand...

Where can I connect my vacuum gauge to see if a valve isn’t closing?

Where can I hook my vacuum gauge to see if it’s unsteady? The small port on driver side of th carb?

When my truck idles the rpm goes like, 750-780ish it doesn’t idle at consistant rpm. I figured that was just the cam or something. But it has always idled like this for the last 2 years.
 
You want a vacuum port that is fairly "large" like one with a 1/4" hose,that is right on the intake--using one on the carb or elsewhere can give false readings...
I usually use the vacuum modulator fitting on an older truck that has an automatic..newer ones with EFI,I haven't fooled much with,someone else can guide you better if that is what you have..
If you have EFI and an idle thats unsteady it might be the intake gasket ,that are common to fail and let some coolant get in the intake..

I'd first make sure the PCV hose isn't collapsing internally or full of crud,and clean out the port it hooks too..another thing to check is the EGR valve to make sure its fully closing at idle--if it hangs open slightly,the exhaust pulses in the intake can make the PCV valve do weird things and affect the idle quality too..
 
Stock valve covers have one--usually if there isn't one (on aftermarket valve covers) the PCV valve will suck up oil and cause it to smoke and maybe foul plugs,and can eventually lower the oil level enough to do harm..
Not having a baffle probably wouldn't cause the chattering though..
 
Got the new PCV Ac Delco GM part.
Hose looked good no debris or collapsing inside.

When I get off work I’ll fire it up and see.
Can I or should try to increase idle RPM to see if that gets rid of the rattle?
I’ve read idle RpM can cause the PCV to rattle as well.

Hopefully this works if not, what’s the next course for action?
@diesel4me
 
Idle speed may make a difference as the vacuum level will change if you increase it...

If it still chatters I'd get a vacuum gauge reading and see if the needle wavers rapidly,that usually indicates a valve isn't fully closing or maybe one is leaking and letting compression get in the intake..

And check the EGR for closing fully at idle,as I said earlier..it may appear to be closing fully,but may have some carbon stuck in the seat allowing some exhaust gases to sneak into the intake..an EFI engine will try to compensate for a vacuum leak there or elsewhere by increasing the fuel & air settings and that will make the idle vary ..
 
Yes,that is one way to test for a ruptured diaphragm on the EGR valve..
You can use a Mighty-Vac tool or even mouth suction to test for that too.or hook it up to another manifold vacuum hose and see it it retracts and stays retracted..

If the EGR valve is closed all the way and nothing is in the passage it blocks off ,then no exhaust gases should get into the intake,even if the EGR valve had a bad diaphragm ,because a spring forces it to close when no vacuum is there to open it..some engines have the vacuum to it controlled by a solenoid,that can fail and let it get vacuum when its not supposed too..
If your truck has a computer it should set a code for the EGR system if its bad or not closing off the passage completely..

I would try the new PVC valve first,then if it still clatters,see if raising the idle speed a tad by hand stops the rattling..it may be the engine just lacks good steady vacuum at a low idle speed for whatever reason..vacuum leaks,a valve not closing fully,etc..(a hydraulic lifter can "pump up" at times and hold a valve slightly open,this usually happens after a high rpm episode)..
A vacuum gauge helps to diagnose things like that..
 
Ok, new PCV fixed the rattle.... I sprayed carb cleaner around intake and carb and no increase in idle..

still not sure why on cold start my fuel psi is 8 then mellows to 5-7 once warmed up..mechanical fuel pump and no regulator...
 
Fuel is thicker when cold. At least that was always the case on my diesel. Would think it would be the same here.
 
You must log in or register to reply here.

Latest Posts

Top Bottom