MK5 Golf GTI

All Things Mk5 => Mk5 General Area => Topic started by: lloydy123 on August 25, 2020, 04:28:38 pm

Title: Excessive vacuum in valve cover - **RESOLVED**
Post by: lloydy123 on August 25, 2020, 04:28:38 pm
Hi folks,
 
I have excessive engine vacuum in my 2008 2.0 TFSI with 190,000 miles (Ive had it since 3 years old). I have read hours of forums on this one!
I first became aware of an issue when it threw up the CEL, code P0171 - lean burn bank 1.  The car drives perfectly, pulls very well etc, idles normally, no blue smoke or excess oil consumption.
I checked for vacuum leaks and found a split hose at the brake vacuum pump which I have now sorted. There are no leaks remaining.
Problem is that there remains to be HUGE vacuum on the engine. It is impossible to remove the oil filler cap while the engine is running. To be able to remove it I have to break the vacuum by removing the dipstick and then struggle with 2 hands to remove the filler cap. Also  since repairing the vacuum leak when I switch the engine off I can hear oil gurgling from within the engine which occurs until the vacuum is dissipated. I replaced the PCV valve in the hope of resolving the vacuum issue, even though the existing valve appeared to be working normally.
 
Does anybody know why i could have such a huge vacuum? I'm concerned that oil may be vacuuming to where it should not be and hence the gurgling!
 
Many thanks


Update- problem resolved, see page 3
Title: Re: Excessive vacuum in valve cover
Post by: GVK on August 25, 2020, 05:34:42 pm
Have read about internal failure of the valve cover causing similar issues but thats all I know.
Title: Re: Excessive vacuum in valve cover
Post by: ROH ECHT on August 26, 2020, 06:15:14 pm
The N80 may not be opening. If stuck closed, engine vacuum could be higher and it would run leaner because it counts on the fuel vapors when running.

It could be a throttle or runner flap issue. If those are closed when they should not be can raise vacuum. Are you attempting to loosen the filler cap when you cold start it when runner flaps may be closed? Is it different when warmed?

Also, the PCV diaphragm may not be opening or routing vapors properly to the intake manifold when in vacuum. If you decide to try replacing the PCV...use the same type or last revision for the type you have. There are two different designs and revisions for those two.
Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on August 26, 2020, 07:10:30 pm
Have read about internal failure of the valve cover causing similar issues but thats all I know.

Interesting, I've had a read about that just now, seems to be more related to oil consumption problems than vacuum problems, seems a v bad design!
Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on August 26, 2020, 07:18:22 pm
The N80 may not be opening. If stuck closed, engine vacuum could be higher and it would run leaner because it counts on the fuel vapors when running.

It could be a throttle or runner flap issue. If those are closed when they should not be can raise vacuum. Are you attempting to loosen the filler cap when you cold start it when runner flaps may be closed? Is it different when warmed?

Also, the PCV diaphragm may not be opening or routing vapors properly to the intake manifold when in vacuum. If you decide to try replacing the PCV...use the same type or last revision for the type you have. There are two different designs and revisions for those two.

I know that the N80 was closed when I checked it with the engine running while warm.

The filler cap is almost impossible to open when the engine is both cold and warm.

I replaced the original PCV, which had a torn diaphragm, about 2 years ago, unfortunately I disposed the original one. The replacement was a random aftermarket one, then I replaced that again last week with a febi bilstein one. From what I had read the PCV changed in late 2006 where the non return valve for the rear brother was moved from the PCV to the rear breather pipe.

I've ordered a vacuum tester and if that shows a high value then I will order up a genuine PCV valve as it must be that which is causing the excess vacuum. If that doesn't work then I'll change the N80 valve. I really hope it isn't a runner flap issue as the car isn't worth much at such high miles, but i'll keep you updated
Title: Re: Excessive vacuum in valve cover
Post by: ROH ECHT on August 27, 2020, 07:37:11 pm
But did you electrically test the N80 (supply power) to be sure it opens?

Alright, so with the PCV...there is one for a valved rear breather tube and one for an open rear breather tube. So you should disconnect the short hose between the rocker cover and rear tube to discover which you have so you match it properly with the correct PCV.

If you see a check valve where circled as in the pic...rear tube should be open and the correct PCV pn is 06F 129 101 R:
(https://live.staticflickr.com/65535/49585988672_6406376445_c.jpg) (https://flic.kr/p/2ixK9Tb)

This is the open or non-valved rear tube:
(https://live.staticflickr.com/65535/49585742626_8a73d1776b_z.jpg) (https://flic.kr/p/2ixHTK1)

If you see no valve where circled...the rear tube should be valved and the correct PCV pn is 06F 129 101 P:
(https://live.staticflickr.com/4664/28219935189_ea3f4b6d01.jpg) (https://flic.kr/p/JZGxyH)

This is the valved rear tube:
(https://live.staticflickr.com/65535/49585979007_605af5912a_z.jpg) (https://flic.kr/p/2ixK71x)


Title: Re: Excessive vacuum in valve cover
Post by: pudding on August 28, 2020, 01:44:31 pm
I thought 06F 129 101 R can work with both the open and valved rear pipes?

I remember fitting revision P along with the valved rear pipe (otherwise you get a high rpm pulsing idle) which was fine, but have since fitted a revision R and not seen a change in engine behaviour.   So do I need to switch back to P?

Bloody confusing all this PCV nonsense  :grin:

Title: Re: Excessive vacuum in valve cover
Post by: ROH ECHT on August 28, 2020, 11:20:05 pm
I thought 06F 129 101 R can work with both the open and valved rear pipes?

I remember fitting revision P along with the valved rear pipe (otherwise you get a high rpm pulsing idle) which was fine, but have since fitted a revision R and not seen a change in engine behaviour.   So do I need to switch back to P?

Bloody confusing all this PCV nonsense  :grin:
Yes...Revision R will work with both rear tubes. You just have two recycle valves to be concerned with. It is more important which rear breather tube is installed and that a Revision P isn't used with the open rear tube.
Title: Re: Excessive vacuum in valve cover
Post by: pudding on August 29, 2020, 12:12:24 pm
Gotcha, thanks Ron  :happy2:
Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on August 31, 2020, 05:38:15 pm
But did you electrically test the N80 (supply power) to be sure it opens?

Alright, so with the PCV...there is one for a valved rear breather tube and one for an open rear breather tube. So you should disconnect the short hose between the rocker cover and rear tube to discover which you have so you match it properly with the correct PCV.

If you see a check valve where circled as in the pic...rear tube should be open and the correct PCV pn is 06F 129 101 R:
(https://live.staticflickr.com/65535/49585988672_6406376445_c.jpg) (https://flic.kr/p/2ixK9Tb)

This is the open or non-valved rear tube:
(https://live.staticflickr.com/65535/49585742626_8a73d1776b_z.jpg) (https://flic.kr/p/2ixHTK1)

If you see no valve where circled...the rear tube should be valved and the correct PCV pn is 06F 129 101 P:
(https://live.staticflickr.com/4664/28219935189_ea3f4b6d01.jpg) (https://flic.kr/p/JZGxyH)

This is the valved rear tube:
(https://live.staticflickr.com/65535/49585979007_605af5912a_z.jpg) (https://flic.kr/p/2ixK71x)


Thanks for this. I've checked and my rear breather tube is open and my PCV has a valve, so this should be the correct setup.

My vacuum gauge finally came and it reads  a vacuum of 16 inches Hg and very steady, at idle when cold. Is this correct?
Title: Re: Excessive vacuum in valve cover
Post by: ROH ECHT on September 01, 2020, 02:19:03 am
Yep, sounds like the vent-tube and PCV pairing is correct.

Did you test intake manifold vacuum?

My intake shows vacuum to usually be at 18 to 20 inHg when it first starts and it is throttled by the TB and flaps...but shortly thereafter it goes to 21 to 22 inHg. From what I have seen, most see the same numbers on a boost gauge. So your gauge is actually showing less vacuum than mine does on the boost gauge.

Can you do something for me? I am suspicious of the PCV not opening at idle into the intake manifold. With it not running, disconnect the "corrugated PCV to intake manifold tube" from the intake manifold. Wipe the oil from it and (pardon me) suck on it to see if it is open or if it feels plugged. It should be open and then closed when you blow into it.

Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on September 01, 2020, 10:11:30 am
Sorry I should have said that was measured at the dipstick port
Title: Re: Excessive vacuum in valve cover
Post by: ROH ECHT on September 01, 2020, 05:03:27 pm
Right, good. Thanks for confirming this. The reason why I asked is because I know what is normal in the manifold and if the PCV is open, then the engine should reflect the same and this might point to the PCV not being fully open to the manifold via the PCV.

It might be worth it to try another PCV...but you can do the test I asked for before. I am just not sure if you applying suction on the disconnected tube can reproduce the vacuum needed to test the PCV valves and diaphragm. So a trial replacement may be needed. If a new PCV doesn't fix the issue...you can swap them around again and hold on to the new PCV for when needed.

I will continue researching this...I wish another had more insight on this topic. I am trying to find out more about something I saw that was pointing a finger at the oil level and oil pump. Can you make sure there is max oil on the Dip's x-hatched marking? How long has it been since the oil filter was replaced?

Just didn't want to drop that concern on you without seeing if the PCV is the problem or not. So let's get the PCV sorted first.
Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on September 02, 2020, 12:46:07 am
Thanks for your help. I have found a split in the the end of my brake booster vacuum line just before the one way valve, this is likely lowering the vacuum. Taping it worked temporarily but now it is getting worse.

I have to confess that my car is an Octavia VRS but I use this forum as there is a great knowledge base of the 2.0 TFSI engine! Apparently the part for this is no longer available from skoda and the aftermarket part from Vaico is not available either. Is anybody able to direct me to the right hose that I can cut to length? All vacuum hoses that I can see online specifically say not to be used for the brake booster line!

(https://live.staticflickr.com/65535/50296160022_684b0aa717_c.jpg) (https://flic.kr/p/2jCuY5N)IMG_0640 (https://flic.kr/p/2jCuY5N) by L Pat (https://www.flickr.com/photos/186923893@N06/), on Flickr

(https://live.staticflickr.com/65535/50295323808_550266c7d2_c.jpg) (https://flic.kr/p/2jCqFvj)IMG_0856 (https://flic.kr/p/2jCqFvj) by L Pat (https://www.flickr.com/photos/186923893@N06/), on Flickr

I still have to perform your check of the PCV diaphragm although I replaced the PCV and both operated in the same manner.

I changed the oil and filter a few weeks ago, always changed at 10k intervals. It sits at the max line and burns oil slowly, about 1.5 litres between services.
Title: Re: Excessive vacuum in valve cover
Post by: mjmallia on September 02, 2020, 08:12:46 am
Buy a new one way valve that the hose is connected to from TPS or dealer, and that is attached to it with the new one

You will also need a sealing cap, due to the new valves having an additional nipple that is not used......mine was green from TPS

1K0612041GM

(https://lh3.googleusercontent.com/proxy/RGysgq7e0nkES8Z98JcW3VaXBWT3bgWS9Tvr7obrZrA0NWgp35ndV__CoiVoQV4DFXRMP8kCOoFA7AE3iNknHOgIYmrdE8P7rEH4)
Title: Re: Excessive vacuum in valve cover
Post by: ROH ECHT on September 02, 2020, 04:03:41 pm
Right...the hose comes connected to an assembly: https://www.ecstuning.com/b-kayser-parts/brake-booster-hose/1k0612041gm~kay/?gclid=Cj0KCQjwhb36BRCfARIsAKcXh6GjJdZjQezAgWLUL6IGuo0syaFZviswWrY2f6g53bsx_JovU8T_PFgaAsWeEALw_wcB
Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on September 02, 2020, 04:14:34 pm
Thanks, I was hoping to get a small length of that pipe or equivalent as opposed to having to buy the whole unit! But it may be my only option
Title: Re: Excessive vacuum in valve cover
Post by: titchy on September 02, 2020, 04:23:03 pm
I tried a repair then it split in a different place a few days latter bite the bullet renew it all
Title: Re: Excessive vacuum in valve cover
Post by: ROH ECHT on September 02, 2020, 04:28:44 pm
LOL, this ↓ always throws me off when I see it.
"There are no leaks remaining."
Sometimes I suggest checking it again...but I didn't. :doh:
Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on September 02, 2020, 04:48:26 pm
LOL, this ↓ always throws me off when I see it.
"There are no leaks remaining."
Sometimes I suggest checking it again...but I didn't. :doh:

LOL! Sorry! It was leak free, but just for a heat cycle or two! I’m surprised I can’t find any loose hose to the correct vacuum standard, I’ll have to go to the stealer!
Title: Re: Excessive vacuum in valve cover
Post by: LC5F on September 02, 2020, 05:04:07 pm
All vacuum hoses that I can see online specifically say not to be used for the brake booster line!

They are covering themselves in case their part fails and you end up with no brakes
Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on September 02, 2020, 05:23:31 pm
All vacuum hoses that I can see online specifically say not to be used for the brake booster line!

They are covering themselves in case their part fails and you end up with no brakes

Understood! So would any 8mm vacuum hose with good wall thickness do the trick? I think some folks use fuel line too
Title: Re: Excessive vacuum in valve cover
Post by: Deano45 on September 02, 2020, 05:24:20 pm
The brake vacuum pipe or pipes come as one unit ...I had to buy one myself last month the good news it’s only £29 complete from vw.
Title: Re: Excessive vacuum in valve cover
Post by: ROH ECHT on September 02, 2020, 05:58:13 pm
Understood! So would any 8mm vacuum hose with good wall thickness do the trick? I think some folks use fuel line too
It has to be a non-collapsable tube. It will still have brakes, but it will take a heavy foot for them to work. And they fear this will catch someone off guard as we are used to the help of the brake booster.
Title: Re: Excessive vacuum in valve cover
Post by: LC5F on September 03, 2020, 04:33:27 pm
If one part of the hose has split, it is pretty certain the adjacent parts won't be far away from failure.

If it's a "get you home, road side repair" - yes chuck something in that wont crush under vacuum- as ROH ECHT said - and ideally resistant to heat and oil.

But for a permanent fix, that you don't need to worry about, replace the whole assembly...
Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on September 03, 2020, 09:56:59 pm
You’ll be relived to hear I ordered the part from the stealer. £38!
Title: Re: Excessive vacuum in valve cover
Post by: pudding on September 05, 2020, 01:21:35 pm
Looks like your vacuum pump could do with a reseal judging by all the oil residue on it.  You can get an O ring kit from ebay to do that.  Simple job.
Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on September 07, 2020, 03:28:15 pm
Looks like your vacuum pump could do with a reseal judging by all the oil residue on it.  You can get an O ring kit from ebay to do that.  Simple job.

I presume I just unscrew the end plate and apply the new seal?
Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on September 10, 2020, 03:01:22 pm
Understood! So would any 8mm vacuum hose with good wall thickness do the trick? I think some folks use fuel line too
It has to be a non-collapsable tube. It will still have brakes, but it will take a heavy foot for them to work. And they fear this will catch someone off guard as we are used to the help of the brake booster.

I have replaced the brake booster hose with the official part from skoda and blocked off the extra vacuum port from the check valve. The vacuum is reading 13inHG from the dipstick which seems high. I understand that intake manifold vacuum should be 18-22inHG but should the crankcase vacuum not be much lower?


(https://live.staticflickr.com/65535/50327042612_6ca3b6ffc9_c.jpg) (https://flic.kr/p/2jFefpf)IMG_0945 (https://flic.kr/p/2jFefpf) by L Pat (https://www.flickr.com/photos/186923893@N06/), on Flickr
Title: Re: Excessive vacuum in valve cover
Post by: ROH ECHT on September 10, 2020, 04:17:17 pm
My guess is there is a small crankcase leak somewhere. This could be a leaking seal where anything is connected to the head or block. I have seen a leaky rocker cover seal cause less vacuum at the dipstick. Could be a leaky oil filter housing seal.

Can you replace the dip-stick, remove the IAT sensor, and test intake manifold vacuum?

If the vacuum is more...then it likely has a small leak with something attached to the crankcase (high or low).
 
If you see the same vacuum...then you may need to disconnect the PCV tube from the intake manifold and plug both openings with the gauge toward the manifold. If vacuum stays where it was at the dipstick...then it may be a leak in the manifold itself or in something attached to it.
Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on September 10, 2020, 04:38:38 pm
My guess is there is a small crankcase leak somewhere. This could be a leaking seal where anything is connected to the head or block. I have seen a leaky rocker cover seal cause less vacuum at the dipstick. Could be a leaky oil filter housing seal.

Can you replace the dip-stick, remove the IAT sensor, and test intake manifold vacuum?

If the vacuum is more...then it likely has a small leak with something attached to the crankcase (high or low).
 
If you see the same vacuum...then you may need to disconnect the PCV tube from the intake manifold and plug both openings with the gauge toward the manifold. If vacuum stays where it was at the dipstick...then it may be a leak in the manifold itself or in something attached to it.

So the intake manifold pressure is 22inHg when warm which is normal. My understanding is that the crankcase vacuum should only be 1-2inHg if even, is this right? When the car is switched off the dipstick vacuum gradually returns to atmospheric pressure over about 45 seconds which shows that there must not be a big leak anyway.

I checked the n80 and it is clicking well when a power source is applied.
Title: Re: Excessive vacuum in valve cover
Post by: ROH ECHT on September 10, 2020, 08:39:08 pm

So the intake manifold pressure is 22inHg when warm which is normal. My understanding is that the crankcase vacuum should only be 1-2inHg if even, is this right? When the car is switched off the dipstick vacuum gradually returns to atmospheric pressure over about 45 seconds which shows that there must not be a big leak anyway.

I checked the n80 and it is clicking well when a power source is applied.
To my understanding, yes. If there is less vacuum in the crankcase than you see in the manifold...then something which is connected to the crankcase's containment bits will have a bit of a leak. Could be rocker cover, oil filter housing, oil pan, vacuum pump, etc..
Title: Re: Excessive vacuum in valve cover
Post by: lloydy123 on September 15, 2020, 12:12:03 pm
RESOLVED!!

I replaced the PCV valve with one from the dealer and the vacuum has dropped to from 13inHg to 2inHg, just where it should be. Interestingly the 2 aftermarket PCV valves which I had tried both gave different vacuum readings but both were far too high. So do not buy a D2P autoparts or a Febi aftermarket PCV as despite appearing identical to the original and suck/blow testing in an identical way to the original they result in far too high a vacuum!

Thanks to the help of all the folks who contributed.
Title: Re: Excessive vacuum in valve cover - **RESOLVED**
Post by: ROH ECHT on September 15, 2020, 04:05:51 pm
Glad this was finally solved. I myself do not trust the quality of aftermarket PCVs...but one day they are all that will be available. Unless, VW sees a good reason not to eliminate them from their stock. Because then this problem would be widespread for their service dept's. I've already seen a number of poor quality PCVs causing leaks of boost when new.
Title: Re: Excessive vacuum in valve cover - **RESOLVED**
Post by: lloydy123 on September 16, 2020, 12:09:01 am
Glad this was finally solved. I myself do not trust the quality of aftermarket PCVs...but one day they are all that will be available. Unless, VW sees a good reason not to eliminate them from their stock. Because then this problem would be widespread for their service dept's. I've already seen a number of poor quality PCVs causing leaks of boost when new.

Lesson learned!!
Title: Re: Excessive vacuum in valve cover - **RESOLVED**
Post by: ILO on February 22, 2021, 10:22:40 am
I have a mk5 gti with the same problem as you, i have change pcv 2 times and still i have not fixed the vacum. Do you think a pcv delete will fix my problem? Does anyone what are cons of a pcv delete?