Author Topic: How do I test if PCV is faulty?  (Read 4063 times)

Offline Charliemk6

  • Not said much yet
  • **
  • Posts: 27
How do I test if PCV is faulty?
« on: 23 May 2019, 12:08 »
Hi all, still troubleshooting rough idle.

I've heard there is a test to see if pcv is faulty by blowing in to it?
I e tried it with the top pipe and cannot blow through it, only suck?

Does this mean it's ok?

Any help appreciated!


Offline david25

  • I live here
  • *****
  • Posts: 504
Re: How do I test if PCV is faulty?
« Reply #1 on: 24 May 2019, 14:33 »
Now = 2011 MK6 GTI - Reflex Silver
Past = 2006 MK5 GTI - Tornado Red and Solid Black

Offline DUBbleChin

  • Not said much yet
  • **
  • Posts: 19
Re: How do I test if PCV is faulty?
« Reply #2 on: 27 September 2019, 15:42 »
I'd read somewhere that while the engine is running, remove dipstick. If it stutters, pcv is OK.
Nov '11 Candy White GTI, 5dr, heated leather, Rns510, DCC, Revo stg. 1, Sachs clutch, MST cai, Jetex 3" cat back, H&R springs, 19" TSW

Offline Snoopy

  • Moderator
  • Serious forum addict
  • *****
  • Posts: 7,732
  • A.K.A. Geoff.
Re: How do I test if PCV is faulty?
« Reply #3 on: 29 September 2019, 11:41 »
Not sure how test off the car but if you remove the dipstick the car should stutter very slightly then return to normal. If it keeps stuttering or stutters alot its faulty. See video in below quote for a working one.
 
Something else that needs checking with the pcv fails is the rear main seal as if the pcv valve has failed for a period of time then the presure normally turns the rear main seal inside out or unseats it.
Check for an oil leak under the car between the gearbox and engine. It normally leaks out the hole on the bottom of the gearbox bell casing. Then runs along the sump and engine bottom bracing. If the seal is even leaking slightly it can cause a rough idle.
Kept forgetting to do this so sorry for delay but here's mine for comparison:



« Last Edit: 29 September 2019, 11:53 by Snoopy »
Mk6 GTI  &  Mk1 GTI 
34 years of GTI ownership.

Offline Charliemk6

  • Not said much yet
  • **
  • Posts: 27
Re: How do I test if PCV is faulty?
« Reply #4 on: 02 October 2019, 09:12 »
Not sure how test off the car but if you remove the dipstick the car should stutter very slightly then return to normal. If it keeps stuttering or stutters alot its faulty. See video in below quote for a working one.
 
Something else that needs checking with the pcv fails is the rear main seal as if the pcv valve has failed for a period of time then the presure normally turns the rear main seal inside out or unseats it.
Check for an oil leak under the car between the gearbox and engine. It normally leaks out the hole on the bottom of the gearbox bell casing. Then runs along the sump and engine bottom bracing. If the seal is even leaking slightly it can cause a rough idle.
Kept forgetting to do this so sorry for delay but here's mine for comparison:



Hi Snoopy, this is in fact what happened - the PCV failure caused the rear main oil seal to fail, so even when I replaced the PCV the issue continued.  Spotted the oil leak and realized the issue.

This was costly and very frustrating, because of this PCV failure it has cost me over £600 to repair as the whole Gearbox has to be dropped.  I ended up changing the clutch at the same time and replacing the rear main oil seal with a much stronger revised version.

Seems that this version of the Golf was designed with lots of weak parts prone to failure...

Anyways its all done now after several months of aggro!

Thanks for you reply Snoopy - hopefully this thread will help someone in future.

Offline Snoopy

  • Moderator
  • Serious forum addict
  • *****
  • Posts: 7,732
  • A.K.A. Geoff.
Re: How do I test if PCV is faulty?
« Reply #5 on: 03 October 2019, 20:56 »
for reference the uprated oem seal is much better but is a pain to fit as needs a special tool due to its design. If you dont use the tool it may not seal correctly and leak again resulting in it needs changing again.
 
The other option is to use this.  :smiley:

https://www.ecstuning.com/b-iabed-industries-parts/billet-aluminum-rear-main-seal-upgrade/462-103-171f~iab/#tabProductDetails




Imo every modern car has the possibilities of issues due to design tolerances v cost its not just VWs or this particular model. im from a family of car enthusiasts most of them work in the trade so I get to hear most the stories. As an example we did the crank seal on my cousins BMW 3 series about 6 month ago because it did more or less what happened to your GTI.
« Last Edit: 03 October 2019, 21:24 by Snoopy »
Mk6 GTI  &  Mk1 GTI 
34 years of GTI ownership.