Stupid PCV question

[FORMONTOYA]

I've gone through 2 OEM PCV (read boost leak) valves in 1500 miles since the car came off jack stands December 05. I'm tired of buying and replacing them even though they are not that expensive. I was going to pull the nipple out of the intake and put a 1/8 BSPT plug in that location and use the nipple from the intake and replace the PCV valve, however, the nipple is a press-in fit so that's out of the question. I just capped off the nipple and used the PCV valve as my nipple to "T" into the vent line going to the intake before a G-2 gas filter (catch can).

My question is why do I have to hog out the PCV valve internals? There shouldn't be a differential pressure type of thing going on, therefore the PCV valve should remain open, shouldn't it?

Below is a half-a$$ drawing of what I propose and if someone can give me a legitimate reason why it should be hogged out, I'll just order a nipple for it.

 

[FORMONTOYA]

I'm thinking about using 1/2 your idea. I will use the oem style pcv valve to keep the metering of the vacuum the same & install the Mc Master Carr valve inline to combat boost blowing back into the crankcase, since the pcv valves are incompetent on that front.

I have an idea that it might work like that also. However, since I already have a few dollars wrapped up into this project, if you can give me until this weekend to confirm that it works before you spend any money.

No point in both of us pissing off money on just an idea.

 

[kenamond]

I guess in hindsight (i.e. after reading the outcome and subsequent posts), it makes sense that the filters are collapsing. If the check valve is letting the IM pull air in unabated, your filters could be seeing the same vaccuum as the IM which might be a bit much for them.

Since the Autozone PCV valves are cheap, just slap one in the valve cover and run your normal hose off of that rather than your fitting+elbow. That should provide the correct restriction and "snorkel" for modest additional $$ (unless those fittings cost as much as an Autozone PCV in which case, it could be cheaper). You could surely use the OEM one as well - even a bad one - I have 2 if you wanna stop by my garage . You'd probably never have to change it again. So if someone has a bad PCV, they can get all of the other parts and in-line them with the current, stock setup and be done with the problem.

EDIT: So yeah...if someone wants to do this mod, they just keep their PCV in place and hook up the hoses, filter, and check valve. Subtract the cost of the two fittings on the VC and what's your final cost?

 

[FORMONTOYA]

I guess in hindsight (i.e. after reading the outcome and subsequent posts), it makes sense that the filters are collapsing. If the check valve is letting the IM pull air in unabated, your filters could be seeing the same vaccuum as the IM which might be a bit much for them.

Yea, hindsight is a wonderful thing. Of course the filter is designed for pressure being applied to the inlet, and NOT vacuum applied at the outlet. Even though the inside of the filter housing is ribbed, it's just not enough to withstand the 22inHg.

Since the Autozone PCV valves are cheap, just slap one in the valve cover and run your normal hose off of that rather than your fitting+elbow. That should provide the correct restriction and "snorkel" for modest additional $$ (unless those fittings cost as much as an Autozone PCV in which case, it could be cheaper). You could surely use the OEM one as well - even a bad one - I have 2 if you wanna stop by my garage . You'd probably never have to change it again. So if someone has a bad PCV, they can get all of the other parts and in-line them with the current, stock setup and be done with the problem.

You're correct that even an OEM PCV valve is cheaper that the fittings that I bought. However, I did find a good source for the 1/8 BSPT to 1/8 NPT adapter which can also be used for an aftermarket oil pressure gauge with the sensor in the stock location.

Saturday (6-17-06) I'll have a chance to get back on the car to confirm if this works or not.

EDIT: So yeah...if someone wants to do this mod, they just keep their PCV in place and hook up the hoses, filter, and check valve. Subtract the cost of the two fittings on the VC and what's your final cost?

McMaster-Carr has several size check valves available. 1/8, 1/4, 3/8, and 1/2, I chose the 3/8 version because it was the smallest valve with the highest flow rating. The 3/8 check valve (~$20) plus the 2 end fittings (~2.50ea) would put it at $25-$30 dollars after tax or shipping.

 

[FORMONTOYA]

A couple of question I have for anyone....I know that the OEM PCV valve over time will lose its ability to hold back boost pressure.

1) Has anyone had a PCV valve that would NOT open up under vacuum?

2) Do you think that the flow rate through the PCV valve would change dramatically if the internals were removed?

 

[oldman]

1) Has anyone had a PCV valve that would NOT open up under vacuum?

I have not but I will still changed it as a maintenance item as if the other check valve isn't present. With that said, I wonder how long the check valve will last as well.

2) Do you think that the flow rate through the PCV valve would change dramatically if the internals were removed?

Yes, our pcv valve is a variable pcv valve, different vacuum = different flow rate.

 

[steve]

1) Has anyone had a PCV valve that would NOT open up under vacuum?

2) Do you think that the flow rate through the PCV valve would change dramatically if the internals were removed?

1 Yes, but only on valves that were long past their service life. Back when the DSM was under factory service the PCV was replaced every 30k. None of those were actually bad at that time but ithey didn't just replace it to be a money maker for the service and parts department.

2. Yes. The 1G Tech manual doesn't go into much detail. "The PCV valve has a metered orifice through which the mixture of fresh air and blow-by gases is drawn into the intake manifold in response to the intake manifold vacuum. The valve capacity is adequate for all normal driving conditions."

Steve

 

[FORMONTOYA]

With that said, I wonder how long the check valve will last as well.

I'm not sure either. I would have to ASSUME that it would last considerably longer especially with a "soft seat" as the seal mechanism for holding back boost. Hopefully it doesn't turn out to be a waste of time and money.

This little project is definitely something that will need some feedback on my part as to longevity verses cost.

 

[FORMONTOYA]

1 Yes, but only on valves that were long past their service life. Back when the DSM was under factory service the PCV was replaced every 30k. None of those were actually bad at that time but ithey didn't just replace it to be a money maker for the service and parts department.

2. Yes. The 1G Tech manual doesn't go into much detail. "The PCV valve has a metered orifice through which the mixture of fresh air and blow-by gases is drawn into the intake manifold in response to the intake manifold vacuum. The valve capacity is adequate for all normal driving conditions."

Steve

Thanks.

That's both good and bad news for me as I was hoping I could "gut" the PCV valve so it would become an item that did not require any maintenance. However, if it lasted 10K+ without having to be changed I would be happy.

Thanks again.

 

[FORMONTOYA]

It's been a while since the last post on the subject....but an update is in order after several PMs and remarks as to the progress of this project.


I did put the OEM PCV valve in place along with the check valve and was able to get the idle vacuum under control as anticipated. Although I wanted to get roughly 3K miles out of it before I gave an update, I only managed about 600 miles before another issue reared it head...
http://dsmtuners.com/forums/showthread.php?t=234518
Although the car is on jack stands now, I do start the car every weekend just to keep fluids circulating. The check valve/PCV setup does maintain the normal vacuum of 20inHg at idle. Of course there has been no actual "running" of the car on the streets since the above linked issue to check real world operation of this setup after the initial 600 miles. I hope to remedy this in the next 6-8 weeks and get the car back on the road to resume testing.

Thanks for your interest and I will update as warranted.

 

[gnomer]

I am so glad I found this thread. I am also very sorry to hear about your car; some people shouldn't be driving.

I am trying to figure out how to work a check valve into pcv system. The srt-4 community have use a similar setup with success.

I would really appreciated if you can filled me in on this puzzle.

I have figure out the following:
pcv-> 5/16 fuel line -> 5/16 barb 3/8 male fitting -> 3/8F inlet -> catch can -> 3/8F out -> 3/8 male check valve -> ? line size -> what size the nipple on the intake manifold? I think it's some BSPT size?

I try to figure it our from you part list but I was unable to.

1. What is the intake manifold pcv nipple size?
2. What size and type of line should I run?

Thanks
--
David

 

[FORMONTOYA]

The thread size of the hole in the valve cover where the PCV valve screws in is 1/8 BSPT.

On MY intake manifold the nipple that the PCV valve hose attached to appeared to be a "press fit" and not threaded. I didn't try to take it out, that's just how it "appeared".

I first tried it WITHOUT the PCV valve in place and afterward I was idling at 22-25inHg at around 900RPMs+. It didn't seem too bad above idle, but didn't really ever idle good.

Putting the PCV valve BACK IN PLACE brought everything back to normal.....18-20inHg at idle at 750RPM.

When I've done a boost leak test afterward with the check valve in-line with the PCV valve I didn't have a leak into the valve cover area when I normally would have with just the PCV valve alone.


The setup (rout)......


valve cover - OEM PCV valve - 5/16 hose (I used silicone...fuel line works) - check valve - 5/16 hose - intake mani.

Make sure you clamp or at least "zip-tie" the lines.

If I was going to incorporate a catch can I would put it between the check valve and PCV valve (a G2 gas filter will NOT work for this......I collapsed one while testing).

 

[gnomer]

Thank you for the quick respones. Check valve price went up a little. $22.93

Great find on the check valve:

crack pressure of 0.3 psi = 0.6108inHG(15.51mmHG greddy boost gauge read mmHG instead inHG go figure...) of vacumm to open the valve

http://www.wrh.noaa.gov/slc/projects/wxcalc/formulas/pressureConversion.pdf

psi = 0.491130 X inHG
inHG = 2.03602 X psi
mmhg= 25.4 X inHG
inHG= 0.0393 x mmhg

Thanks
--
David

 

[90 GSX]

I don't understand the need for a new ccv system? Doesn't the valve close under boost and open under vacuum? It should be simple. Plus I have run my stock PCV daily at 18 psi for much more than 1500 miles and it has never leaked. It got a little sticky but that was fixed by some brake cleaner. Even if there was some residual boost sneaking past the valve wouldn't that be releaved by the crank breather and the massive vacuum on the intake tube??

 

[gnomer]

I am no expert but the following are my reason for adding a check valve:

In theory the stock pcv valve should act like a check valve. Only allow vaccum and close under boost; but it also open progressively according to how much vaccum. One thing I learn when you try to do too many thing at once you often have to compromise. So by adding a check valve we take the function away from pcv and use a dedicated device; now all pcv have to do is open under various vaccum condition. Hopefully the pcv will live a long happy life just like in a NA engine.

We know the stock pcv leak under hight boost and we see dip stick pop out due to excessive crank case pressure. One of the possible reason is breather not able to pull enough pressure away from the crankcase.

Every one's setup is different if you are happy with your result then I am happy for you

It's the little tinkering that make me happy.

--
David Wang

 

[FORMONTOYA]

All I can say is that you're luckier with PCV valves than I am. I haven't had an OEM PCV valve last much longer than about 1000 miles, and forget about one from the local auto parts store, it doesn't hold pressure out of the box in a lot of cases around here.

Granted it doesn't take long to clean or replace one, but how long is it leaking before you find out about it? With it NOT holding back the boost PSI, it allows it into the valve cover area, where I don't want it, makes the turbo work harder because of the leak.

I just wanted something that I didn't have to work on so often that was affordable. It's not something that's a "must-have", but if you're tired of screwing around with it (PCV valve), this is a viable solution.

And yes you're correct....the only reason the PCV valve is in place (in my setup) is it is the "metered" orifice for the vacuum portion of the system.

 

[Dream On]

Sorry to bring this back, but if I wanted to run with an OEM pcv valve with an inline check valve straight to the intake manifold, which should I get? I think the dejon ones are way overpriced, and could probably find something at mcmaster, but I'm unsure of what to do. The one that you guys are talking about is threaded on both ends, I'd just like to put the vacuum line on each end, or screw on a fitting to each end that has a smooth end for the vacuum line on the other side. Thanks and sorry if this is a stupid question.

 

[gnomer]

the check valve come with 3/8" NPT male on both end. All you need is two 3/8" NPT female to barb.

go to mcmaster site and do search on

5346K54
Brass Hose Fitting Barb X Female Pipe for 5/16" Hose Id, 3/8" Pipe

The picture will make much more sense. the female npt connect to the check valve on both end and barb end allow you to run vaccum line to it.

HTH
--
David

 

[romeen]

Try usplastic.com. They have a large inventory of check valves, many with hose barb ends for easy install in your PCV hose. Different sizes, cracking pressures, etc. Most in $6-$7 range. I also got tired of leaking oem valves and am using check valve inline with PCV. Only about 1000 miles with this set up so far but no boost leak at PCV, 19mmHg vacuum at idle, car running great. Sorry I can't find the exact link.

 

[Dream On]

I found this one, not sure if it's what you're describing.
http://www.usplastic.com/catalog/va...ory_name=44&product_id=21096&variant_id=22297

or this one?
http://www.usplastic.com/catalog/va...ory_name=45&product_id=15641&variant_id=64175

 

[garrett21]

Ok, this is lightly off topic but if my car is at 15hg at idle is my pcv bad?/why is it off?

One thing that came into my head while reading all of this is what does a new evo have for pcv system. Has the problem been fixed for the evo? Could we swap an evo valve onto our cars?

 

[romeen]

I found this one, not sure if it's what you're describing.
http://www.usplastic.com/catalog/va...ory_name=44&product_id=21096&variant_id=22297

or this one?
http://www.usplastic.com/catalog/va...ory_name=45&product_id=15641&variant_id=64175

The less expensive one shown in second link is the one I'm using. Actually ordered a couple, one for me and one for a friend. Working quite well for both of us. The one in first link does seem to be of higher quality though.

 

[FORMONTOYA]

Ok, this is lightly off topic but if my car is at 15hg at idle is my pcv bad?/why is it off?

One thing that came into my head while reading all of this is what does a new evo have for pcv system. Has the problem been fixed for the evo? Could we swap an evo valve onto our cars?

The low vacuum at idle could be due to cracked lines, especially given the age of your car, that would be the first thing I would look at.

Don't know about the EVO PCV valve, but unless they went with a "soft seated" plug, it will have the same issue.

The problem is that PCV valves have a "hard seat". Over time having crud sucked through it, and jammed shut under boost, the seat gets coated with crap or buggered up and either doesn't open properly, or doesn't close properly. Usually the second scenario comes first and you're blowing boost pressure into the valve cover area which creates other problems as well.

 

[Dream On]

Alright, I ordered a couple of the cheap ones. I'll let you guys know how it goes.

 

[oldman]

Alright, I ordered a couple of the cheap ones. I'll let you guys know how it goes.

Adam, got an extra one?

 

[Dream On]

Bruce, clean out your dang pm box again. I tried to tell you that I got them in today and they're pretty solid. I blew as hard as I could and they don't leak. They crack open with only a little pressure on the other side also. Hopefully it'll work well.