Hi, the PCV valve and I think the diaphragm part specifically has failed for the third time on my 2022 Superb with 14,000 miles, it's a 1.5TSI 150PS. The PCV unit has been replaced twice already under warranty and now the dealer is saying they don't know what the problem is or how to fix it!

 

The symptoms are;

- A reduction in engine driveability with a slight surging behaviour at part throttle most noticeable when accelerating gently to moderately in lower gears

- A reduction in full throttle performance, most noticeable in low and mid range engine speeds where boost would be highest, the very top end doesn't feel much different

- A humming noise coming from the PCV valve on top of the valve cover which changes in character when the dip stick or oil cap are removed, or a finger is placed over the tiny vent holes above the diaphragm housing

- When shutting off the engine the humming noise fades away just after the engine stops rotating as I guess the vacuum in the inlet manifold reduces

- The engine speed races when dip stick or oil cap removed when engine at idle

- There is potentially excessive vacuum in valve cover as oil cap and dipstick require more effort than expected to remove when engine at idle

- On overrun having blipped the throttle in neutral there is a turbo 'chatter' type sound which I don't think I would normally expect to be present

- On cold start I have smelt exhaust gas in the engine bay

 

No fault codes or warning lamps present

 

Quick video attached

 

 

The slight tappy knocky noise in the video seems to be something to do with the EVAP valve mounted to the inlet manifold as I can feel it vibrate at the same time as it makes the noise, this has only started recently, I'm not sure if this related in anyway to the PCV problem or not.

 

 

I wondered if anyone else has experienced the same problem and maybe knows the root cause as I'd really appreciate understanding this problem properly.

 

Thanks

 

 

Is it using any oil?

 

Good point thanks, forgot to mention that, no increase in oil consumption observed.

 

Oil consumption has always been pretty low, less than 1 litre over 10k miles. 

When you block the vent on the PCV I guess you feel suction on your fingertip?

 

 

At idle when the engine is hot there is I think a general overall continuous suction but its slightly pulsing. 

 

 

Yet, that fits with the diaphragm having failed again.

I guess keep asking for warranty replacements until they find out why they are failing? 

Thanks yeah, it's another 4 week wait to get a workshop booking for warranty, the first time it was a 5 week wait plus the car was at the dealer for 8 days at the most recent visit so the whole thing has been running for months already! 

 

 

Frustrating, for sure. Are there any other dealerships near enough to be worth calling to see if they can fit you in sooner? It doesn't look like a time-consuming replacement job.

 

Or you could just order the part and DIY fit at your convenience, in the UK it appears to be £63.55 + VAT which includes the seal, for the 05E103495AH shown in your video, which appears to be the latest revision (formerly 05E103495T until 1st April 2022).

I called another dealer but that was a 6 week wait for a workshop booking!

 

I agree it's a quick and easy job, but the part fails so quickly I don't think it's worth changing again without determining the root cause.

 

Some full throttle accelerations with maybe some high rpm overrun has so far always resulted in the failure.

So possible to fail the part within minutes of it being fitted.

1 minute ago, Superb_Owner_1 said:

the part fails so quickly I don't think it's worth changing again without determining the root cause

I'd feel the same.

There must be something else wrong. Not sure I've seen mention of it failing though, for the 1.5 engines.

Hello @Superb_Owner_1

 

I have the exact same problem in my 2020 Skoda Octavia 1.5L engine 150hp.

Same suction in ths oil cap and oil measurement as well as hissing noise coming out of the pcv and stops as soon as I put my finger on it.

 

Did you manage to fix this issue?

Hi,

 

Quite a lot has happened since my last post. The engine in my car continued to worsen in terms of driveabilty, it also started to whistle loudly when hot from around the intake pipe area just before the turbo compressor, and it developed a significant vibration. As well as continue to exhibit all the previously symptoms I posted about.

 

The vibration was traced to a failed flywheel, and failed thrust washers on the crank. The latter resulted in significant amount or metal in the sump and metal particals in the oil.

 

The engine has just been replaced under warranty including the turbo.

 

With all the diagnostic work and learning over the past few months I'm pretty sure that the pcv diaphram had never actually failed, by that I mean perforated. For some reason it's made to oscillate causing the humming sound.

 

Even with the new engine the pcv valve still has the same humming sound which stops when you put your fingers over the holes, and you can hear the sound decay when the engine is turned off as the inlet manifold pressure increases.

 

Despite the new engine in mine I'm still not convinced it's running quite right as it feels down on power but it's still running in so I'm holding back on testing it at this point. The steady state torque control instability and whistling sound have gone, as well as there being a significant reduction in nvh from the engine.

 

My thoughts are on the pcv valve humming is that there is a small air leak somewhere in the evap or crankcase ventilation piping but nothing has been found to date (and there has never been any fault codes relating to it). And this may also explain why the engine feels a bit down on power.

 

I'd love to know if anyone else has experienced this humming sound from the pcv valve and if the cause was found, I'm sure it wasn't as loud as it is now when the car was new.

I did find a video on YouTube for a symptom I have observed on my car which is a knocking sound coming from the evap purge valve.

 

The video shows the evap pipe from purge valve to carbon canister is split, I checked the pipe on mine in the same area but could not see any visible failures.

 

https://youtu.be/EAz9wVGhEv4?feature=shared

Thank You for the detailed response.

I'm sorry about the engine, I hope that from now on everything will be as good as new and better.

 

As you mentioned, you currently still have noise coming out from the pcv holes? Do you still have suction from the oil cap and the oil measurement stick?

Just want to make sure.

My engine feels good overall but I don't want to make it worse over time by not finding the problem.

I have the same noise on Canister Evap pipe. I replaced it since you can hear it through the cabin.

After replacing it with the original part, same noise. The mechanic told me it's a normal sound for those engines and it's not an engine knock or something like that. It related to the fuel lines and it will be the same noise even if you replace it over and over.

This was the whistling noise on the car's original engine 

Yes there is still quite a lot of vacuum in the valve cover, I think some is normal, and the pcv valve still hums.

 

 

One question I have is whether anyone with this engine notices there never being any vacuum in the fuel tank?

 

I thought it  was usual for there to be some vacuum on petrol cars as the vapours are pulled into the intake.

 

When removing the fuel filler cap on my car after short or long journeys three is never any air in rush into the tank.

About the fuel tank I really don't know.

 

Do you still feel suction in the oil cap with new engine and PCV?

4 hours ago, Skoda_Owner89 said:

About the fuel tank I really don't know.

 

Do you still feel suction in the oil cap with new engine and PCV?

 

Yes, there is a fair amount of suction at the oil filler cap when the engine is idling, and some at the dip stick too. Removing either when the engine is running results in increased idle speed.

 

I think this is normal, however what is considered to excessive vacuum in the valve cover I don't know. The vacuum level has never been measured on my car and I don't have a reference valie for what the normal range is.

 

What I can say though is that after the engine has been operating for a while, say several long journeys, the dip stick is really hard to remove, for instance to check the oil level (engine off obviously). I'm not sure if this is just a design issue or whether there is excessive vacuum which is pulling a small amount of air past the dipstick seals and drying them of oil.

Thank You for the information!

I'll keep you updated if I find anything about this issue.

They changed 3 pcv's and still same noise.

 

My brother has the exact same engine and his pcv is very quiet, no air vacuum from the pcv holes.

But, the suction in the oil cap and the dip stick is still there.

 

I don't have any idea why mine making the exact noise as yours in your very first video.

1 hour ago, Skoda_Owner89 said:

Thank You for the information!

I'll keep you updated if I find anything about this issue.

They changed 3 pcv's and still same noise.

 

My brother has the exact same engine and his pcv is very quiet, no air vacuum from the pcv holes.

But, the suction in the oil cap and the dip stick is still there.

 

I don't have any idea why mine making the exact noise as yours in your very first video.

I'll post any updates too.

 

I'm sure the humming from the pcv wasn't present when the car was new until around 10k miles or so which is when all the issues started, they were subtle at first getting progressively worse over time.

 

One thing to note is I think there is an earlier and later version of this engine, mine I believe is the later where the evap is routed to just upstream of the compressor, I think in the earlier version it is routed to the pcv valve on the valve cover. 

 

The pcv on mine has a blanking plug where the evap pipe would have connected.

 

Whether this is relevant to the behaviours observed I've no idea.

Do you still feel suction on each of the two holes of the PCV head and have a "vacuum cleaner sound"?