APN UIM PVC Cap - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 07-05-2007, 02:18 AM   #1
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Default APN UIM PVC Cap

APN UIM supplied PCV cap has exposed hole in top.
My previous GM UIM has a sealed cap. I transfered
older cap to new APN UIM...assuming that APN cap
for other engine variations....?

Having a problem using both older(2) o-rings and seating/locking PCV cap.
I don't want to break the [email protected] UIM trying to fit both. Seems like problem with
lower PCV o-ring. Left it out and used old o-ring on cap top. I know about problems
this can cause with idle.

Any APN UIM installers ran into this problem?

btw..UP and Running...
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Old 07-05-2007, 08:58 AM   #2
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Glad to hear it'* up and running. The kit you got was for a 96+ engine and your engine is the 95. That hole is for a MAP sensor that your year did not have.

My suggestion would be to contact APN and mention the mix up, they will probably send you a regular cap quickly.
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Old 07-05-2007, 08:59 AM   #3
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The 96 and newer L36'* have a MAP sensor attached to the PCV cap. 95 doesn't. So you did the right thing by moving the cap over, unless they're different in some way.

Make sure you don't have two o-rings down there, or try a smaller one. It must be sealed.
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Old 07-05-2007, 04:34 PM   #4
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Buddy, if I understand you to say that you installed the PCV valve without an O-ring on the bottom, that would be a problem. You don't want to try to install the PCV valve with two O-rings on the bottom, but it will need one or you will produce an unwanted and harmful vacuum in your crankcase. This will mess up the idle, and often results in a whistling sound as the air from the crankcase is pulled around the outside of the PCV valve at idle by the high vacuum in the intake manifold. High crankcase vacuum can also pull in the lip seals on the crankshaft wearing them in an abnormal way causing early failure. The bottom o-ring is about 5/8"-3/4" OD and the one for the cap on top of the PCV valve is about 1.5" OD. You need them both but no others for the PCV.

Your PCV valve is oriented as shown in this image, right?

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Old 07-06-2007, 05:12 AM   #5
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Quote:
Originally Posted by bill buttermore
Buddy, if I understand you to say that you installed the PCV valve without an O-ring on the bottom, that would be a problem. You don't want to try to install the PCV valve with two O-rings on the bottom, but it will need one or you will produce an unwanted and harmful vacuum in your crankcase. This will mess up the idle, and often results in a whistling sound as the air from the crankcase is pulled around the outside of the PCV valve at idle by the high vacuum in the intake manifold. High crankcase vacuum can also pull in the lip seals on the crankshaft wearing them in an abnormal way causing early failure. The bottom o-ring is about 5/8"-3/4" OD and the one for the cap on top of the PCV valve is about 1.5" OD. You need them both but no others for the PCV.

Your PCV valve is oriented as shown in this image, right?

Yes billbuttermore....identical....
Will short term running of engine cause any damage until until i get
new cap from APN?

I need to triple check/measure cap variations between installed older
GM UIM cap and supplied APN cap.....awaiting reply back from
APN techie..

Thanks willren...and billboostman for replies....we are all thinking alike...
Outstanding support from all you guys!!


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Old 07-06-2007, 12:12 PM   #6
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Check for the presence and severity of a vacuum leak into the crankcase by removing the oil filler cap at idle. Does the idle change? Place the palm of your hand over the oil fill opening. Can you feel a vacuum? If there is no change in the idle and no discernible vacuum, then if you have a leak around the pcv, it must be small.

Some options if you have a leak: If the APN cap fits with both a lower and upper O-ring, and you can easily seal the hole in the cap, (rtv silicone, JB kwik weld, etc) you might want to try that rather than running with a vacuum in the crankcase.

Also, you could try a thinner lower O-ring to see if you can get the old cap to seal. I have to push down pretty hard on my cap to compress both O-rings sufficiently to get the cap to rotate into the lock position. A little oil on the O-rings will help, too.
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Old 07-06-2007, 02:00 PM   #7
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Quote:
Originally Posted by Buddy

I need to triple check/measure cap variations between installed older
GM UIM cap and supplied APN cap.....awaiting reply back from
APN techie..

i just got an APN UIM for our 95 Bonneville. The PCV cap is identical to the one pictured below right, on their web page and has two branches on top, one covered with a yellow cap and one with a red cap. Do they intend for owners of 95 models to leave the yellow and red caps on to seal the top of the PCV?



In addition to the parts pictured above, included was a bag of 16 blue O-rings (.288"ID, .590"OD, .108"thick) and 6 short (.185" high) black sleeves slightly smaller in diameter than the O-rings. Are the O-rings for the injectors, what are the sleeves for?

-sp4149
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Old 07-06-2007, 03:16 PM   #8
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The piece pictured bottom right is the vacuum fitting for the power brake booster (yellow) and the vacuum reservoir (red) is it not? Fits on the firewall side of the UIM. The piece on the left is presumably the cap for the pcv chamber for models with a MAP sensor. Perhaps they expect you to re-use your old pcv cap if you have the '95 without the MAP sensor. If Buddy is right and the old cap does not fit on the APN UIM, then they will need to alter their kit to accommodate owners of the earlier L36s. Otherwise, sealing the APN MAP cap is another option. I would guess that the 6 seals are indeed for the injectors. But sixteen blue o-rings???
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