Was suspected lifter noise, likely diesel knock, and what I am doing about it

[sams-vans]

Only had my T6 for about 9 months and recently, apparently suddenly, noticed what sounds like a lifter noise - tapping under load 2-3k rpm. No noise at idle. Van has 93k miles and otherwise runs perfectly. What follows is everything I am trying to avoid opening the engine to inspect lifters.

So I proceeded with a thorough oil change:

1. Add Liqui Moly engine flush
2. Drop original oil
3. Add new oil, warm up and drop that to flush the system
4. New filter and new oil
5. Add first bottle of Liqui Moly lifter noise fluid

So I know the oil system is as clean and fresh as it could be.

6. Drove van for about 50 miles. Held it back a gear or two to keep rpm between 2500-3000. Noise is a lot better, but still present.
7. A few days later I decide to add another bottle of Liqui Moly lifter noise fluid

First short drive to get the fluid circulating, a few more minutes at 2500-3000 and the noise is better again.

I am just sharing this in case someone else has a similar experience. Your mileage may vary. So far I can attest, as most do, that Liqui Moly products work and I am impressed how improved the noise is so far. I'll be delighted if it goes all the way to cleaning and quietening the troublesome lifter(s).

 

[Howzat]

Now you've done all that try giving the engine a good thrashing up to 3k revs through gears 2-4. I've found this can clear up a lot of issues like these.

 

[sams-vans]

Ahh I omitted that. I have been holding it down a gear or two and holding it 2500-3k. That really does seem to expedite the process.

 

[sams-vans]

So all this hasn’t worked. I still have a persistent lifter noise.

As a T6forum member do I have access to the service manual (the reason I became a member)? Because I can’t find it.

I’ve got an idea what’s involved to inspect the lifters and followers. But I’d like to check before I start this job - what’s involved and what, if any, special tools are needed.

 

[Dundee_Kev]

You sure it's a lifter noise? It may well be an injector making the noise

 

[sams-vans]

If it was an injector problem I’d expect other symptoms. Like rough idle, stumbling etc. Here’s what I have observed:

1. No sound at idle
2. Barely audible in neutral revving
3. Definitely audible when driving, engine under load
4, Sounds like someone is shaking a rattle paint can in the engine bay
5. The tick is rhythmic and constant, follows engine rpm
6. No other engine running or performance condition

If anything. After the oil service the engine is running so much better: smoother and better mpg.

 

[Dundee_Kev]

I'd get a 2nd pair of ears to have a listen to it. Injectors can cause a noise, but still run fine initially before giving up the ghost.

Just another thought, there isn't an exhaust leak in the engine bay? A slight leak at the manifold area can give a noise kinda like a noisy tappet

 

[The Flying Scotsman]

I have a very similar problem going on at the moment.
Do you have any black smoke above 3000rpm?
My T6 has exact same ticking and runs fine other black smoke above 3000rpm.
My mechanic has put VW injector cleaner into the fuel tank and told me to run that through on a full tank.
If it’s not any better he will test all the injectors and force a regen

 

[sams-vans]

I'd get a 2nd pair of ears to have a listen to it. Injectors can cause a noise, but still run fine initially before giving up the ghost.

Just another thought, there isn't an exhaust leak in the engine bay? A slight leak at the manifold area can give a noise kinda like a noisy tappet

I had a friendly mechanic (I have used before) join me for a road test listen today. He simply said he's heard it before and it was a simple fix for a VW tech. Of course that's anecdotal at best. He then said get VW to diagnose - they want 2 days and £170. Which might be where I end up (reluctantly).

No noticeable sign of an exhaust leak - smell, soot marks etc. Which doesn't mean one is not present.

 

[sams-vans]

I have a very similar problem going on at the moment.
Do you have any black smoke above 3000rpm?
My T6 has exact same ticking and runs fine other black smoke above 3000rpm.
My mechanic has put VW injector cleaner into the fuel tank and told me to run that through on a full tank.
If it’s not any better he will test all the injectors and force a regen

No black smoke at all. Engine purrs otherwise.

My injector deviations are:
Cylinder 1: 27
Cylinder 2: 27
Cylinder 3: 18
Cylinder 4: 37

If cylinder 4 is the eastern/right most cylinder, not the firing order. It might be interesting that I did have a failing glow plug in cylinder 4 - now replaced (as were the other 3 glow plugs). Perhaps there is some fouling on the nozzle. Perhaps another bottle of injector cleaner in the tank is due.

 

[sams-vans]

Maybe tick is not the best description of the sound. It's more of a clack. And it's louder (or more perceptible) with increased load. For example, opening the throttle from low rpm (<1500) it will clackety clack to 2000-2500 more prominently. With no load and light throttle (not coasting), there is no audible clack at all.

 

[Dundee_Kev]

Sounds like diesel knock I'd say. Probably due to an injector.

A very rough and ready way to check would be to pull one of the injector connectors off and road test to see if noise goes. Do that with each injector. You would then see which cylinder is the issue. You could then switch the injector from the offending cylinder and see if the noise moves with the injector.

 

[sams-vans]

Sounds like diesel knock I'd say. Probably due to an injector.

A very rough and ready way to check would be to pull one of the injector connectors off and road test to see if noise goes. Do that with each injector. You would then see which cylinder is the issue. You could then switch the injector from the offending cylinder and see if the noise moves with the injector.

I think you are right.

I need to go an have another look, but aren't the injectors under the charge cooler assembly, thus not easy to get at.

I have committed to running an injection system cleaning processes now. Quite a lot cheaper than 1-4 new injectors.

 

[Dundee_Kev]

but aren't the injectors under the charge cooler assembly, thus not easy to get at

They are indeed, it's all part of the fun. I think you can get to no. 1 injector to unplug it, but that's it.

 

[sams-vans]

I think we might be getting somewhere. I tried to run Liqui Moly diesel purge neat. But I couldn't get it to work. With hardly any fuel in the tank I decided to dump the product straight in and take the van for a 30 mile loop.

Now I have some new injection time deviation data. In particular, cylinder 4 will now drop to around +10us at times. Down from +38us consistently. Additionally, the clack noise is worse when cylinder 4's deviation is higher. When deviation drops to +10us or lower the clack is almost entirely gone.

I will give the purge product more time to work. But it might be too late to save injector 4.

 

[sams-vans]

Here's my injection time deviation data log.

I honestly don't know if I am interpreting the result correctly. Cylinder/injector 4 I am fairly certainly has an issue. 1, 2 and 3 I am just not sure about. Perhaps someone with familiarity with this data can shed some light on this.

I am inclined to get 1 new injector and replace cylinder 4. Then compare data. Perhaps get the original injector cleaned and tested to refit into cylinder 1... rinse repeat.

 

[sams-vans]

New injector is in cylinder 4. I’m struggling to code it in. I don’t have VCDS. Have an XTool D7 (I think). It has an area to gain secure access. But I can’t get it to accept a code. 27971 seems to be the consensus. It’s just not working.

But van starts, runs, idles. Cylinder 4 deviation is much better. After a few starts and a short drive it’s more or less the same as cylinders 2 and 3.

I’ll just feel better if I can get this injector coded in. Don’t really want to have to pay for VCDS at the point.

 

[Dundee_Kev]

Most garages should be able to program it in for you and will be cheaper than buying vcds.

 

[sams-vans]

2x VWs in the stable. One of which is a T6. Won't be long before VCDS pays for itself. So VCDS arrived this morning and away I went and got the new injector coded in.

Deviation apparently unchanged. Cylinder 1 and 4 still +20 microseconds. Cylinder 2 and 3 negative microseconds.

Oh dear - I hope this isn't pointing to a bigger problem? Think a compression test is next.

 

[sams-vans]

In case this assists anyone else in the future, I will continue to log what I am finding and doing to resolve the diesel knock. Which is seemingly getting worse.

My cylinder fuel time deviation is inconsistent. Sometimes Cylinder 1 is fine and Cylinder 2 is bad. Cylinder 3 always seems fine. Cylinder 4 is usually bad, but I have seen it fine for a few seconds. This inconsistency points to a fuel pressure issue.

I have logged the Fuel pressure control deviation and get -194 to 294 bar - which apparently is huge. It should be within +/- 10 bar. Over 50 bar is a problem. The actual deviation logged is erratic, all over the place.

Additionally, fuel pressure at the sensor was measured between 2.7 and 1850 bar. Both values are miles out of spec.

So I have ordered a replacement pressure sensor and N276 relief valve. And a new laptop battery so I can log live data with VCDS on the road.

Hoping it's not the High Pressure Fuel Pump at this point. But no bets are off.