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PCV Valves

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Pushr0d

Well-known member
Joined
Mar 25, 2019
Messages
114
I finally took the time to see if I could get the rear valve out of the head without rotating the engine. I had a pretty significant amount of oil getting past the grommet, and have had the new grommet for quite a while. Turns out, with a bit of force, the valve just squeaks by the frame. It doesn't look like the front will come out without dropping the front of the engine.

My question is, how is the valve supposed to act? When I blew in either end, I didn't get a lot of resistance, and nothing moved inside with vigorous shaking. I'm assuming it is a one-way valve - from the head to the airbox - but I can't find anything on the Web that verifies that. I'd just buy a new one, but they're crazy expensive - at least $32 each!

I ended up putting the valve in a US bath with mineral spirits for a while, then re-installed it with the (much tighter) new grommet.
 
Pushr0d said:
I finally took the time to see if I could get the rear valve out of the head without rotating the engine. I had a pretty significant amount of oil getting past the grommet, and have had the new grommet for quite a while. Turns out, with a bit of force, the valve just squeaks by the frame. It doesn't look like the front will come out without dropping the front of the engine.

My question is, how is the valve supposed to act? When I blew in either end, I didn't get a lot of resistance, and nothing moved inside with vigorous shaking. I'm assuming it is a one-way valve - from the head to the airbox - but I can't find anything on the Web that verifies that. I'd just buy a new one, but they're crazy expensive - at least $32 each!

I ended up putting the valve in a US bath with mineral spirits for a while, then re-installed it with the (much tighter) new grommet.
Click to expand...


If you look on here I think I copied TPEHAK's pictures of one that was cut apart. I think its just a small umbrella valve and a small filter.
 
Steve: It's a one-way petal valve. Pretty common style of valve on many emissions/breather systems. When functioning properly, air should only flow from the cover side thru the valve and out the hose side....not in opposite direction. Single flow direction keeps atmospheric contaminants out of the engine internals and theoretically generates more crankcase vacuum freeing up HP....so I'm told.
 
Barrett - thanks for that! So it is actually a PCV, and not just a 'breather'.

Well, I have at least one bad one. You'd think they'd last more than 13 years!

I'll put a watch on eBay for a couple that aren't stupid expensive. It's not the cost - it's the principle. That's Mercedes/BMW pricing!
 
Yes sir Steve, you could call it that. Over time, what shortens their lifespans is the intensely hot environment they reside in and the stress/pressure of the hose bend placed upon them. Used might pop up on Ebay.
 
Small note. An umbrella valve like in that passive PCV system won't perfectly seal with a 'breath test' like that, and frankly doesn't need too. It's meant to survive millions of pressure waves in a hot and oily environment and needs to be effective, not perfect.:eagerness:
 
Cooter, there's almost no difference which end you blow in - very little resistance.

What little there is might probably be the foam 'oil trap'.
 
FFS people. It’s like Facebook around here.

759750.jpg
 
I think I've seen that pattern on a video game!


Yeah - there's no way the valve I've got is working properly. The 'umbrella' looks like it seals against flow 'downward'. Mine has little restriction both directions.

I checked at the local HD dealer - the part is 'obsolete', but listed. Last price was $35 and change.
 
Plus shipping.

That umbrella type PCV system is common on motorcycles, you just need it to fit in the tight space you have, or put a hose on a 90% fitting in the cover and remote mount one.
 
Pushr0d said:
Cooter, there's almost no difference which end you blow in - very little resistance.

What little there is might probably be the foam 'oil trap'.
Click to expand...

There is a noticeable difference when blowing in the valve from one side to the other. Blowing from the engine side, air flows pretty freely through the valve. If you blow in from the hose side, there is a definite blockage. On the older Sportster motors this umbrella valve is replaceable. Luckily there are plenty in stock at VPI and probably St Paul.
 
Those umbrella valves come in the rocker box seal kit from Harley for the old tube frame Buells.
 
3419,

I only responded as I did because the cost in Europe is freakin' incredible!

At StPHD, they're -only- $37 each. Plus shipping.

I'm going to see if I can find a suitable 'replacement' - like Cooter says - if I can find one that fits in the limited space. I'm thinking there might be room in the airbox. Leave the 'oilscrubber/breather' in place, and put the umbrella valve downstream.
 
Cheap Alternate Part

Okay - an update. Still outraged by the cost of a 'genuine' replacement part (StPHD - $34 plus $5.66 shipping), I decided to look for a suitable alternate.

I found an umbrella/mushroom style valve at Advance Auto Parts. It's a Carquest #PCA 1026. The callout says it's for a 2000 VW Passat 2.8L. $4.49, plus tax. It has a small valve body, and a hose barb at 90 degrees.

I replaced the section of hose that ran from the 'original' PCV in the rocker box cover into the airbox, and left it about 5 inches longer. I heated the end of the hose, and forced the new PCV into it. Then I tucked it under the velocity stack, with the outlet pointing down to drain any oil that collects in the valve.

Resized_20211106_153043_01.jpeg

I 'breath tested' it, and I get a seal going into the motor, and free flow coming out. I couldn't tell any difference in operation when I rode the bike to work this morning.

I also tested the front 'original' valve. It sealed when I blew into it, and flowed freely coming out, so I didn't bother adding a valve to it.

Another plus - this approach negates the need to rotate the motor, as the stock valves remain in place, where even when the valve part fails, they act as a breather/mist scrubber.
 

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