T4 TDi suddenly very noisy

[farmsyncro]

Hi,

(started in transporter page) Our T4 TDi has suddenly developed a really bad diesel rattle one cold start up. It was parked running OK but the next morning it rattles really badly & vibration felt through gearstick. The rattle doesn't sound like one cylinder, it is general, it doesn't sound like a bearing, it is like normal diesel rattle X3. If you have your head under the bonnet you should really wear ear muffs!
Fuel was filled 300km before problem started. It drove & sounded normal when parked.

I have checked:
Timing on VAG COM. This was showing "too far advanced to measure". I have corrected this but this has barely changed the noise. If this was to slip I would expect it to slip retarded NOT advanced.
Fault code 17656 was logged on VAG COM this was cleared and has not reappeared.
N108 resistance measures 16 Ohm.
N108 is clicking with 12 V applied.
N108 was removed and checked to find it completely clean & replaced. I can see the pintle moving when 12V is applied.
Wiring to N 108 traced back to firewall & ECU & appears OK.
Fuel drained at filter and is clean, no petrol smell & looks & smells like diesel.
Harmonic balancer appears OK and has not slipped (I marked it on previous cam belt change).
I ran it with serpentine belt removed and the noise does not change at all.
I checked the DMFlywheel and get about 5mm movement on the outside diameter.
I have disconnected MAF while running - no change.
Oil pressure is 70 psi cold. Oil is about 3000km old.
I have removed and inspected and replaced every fuse.
I have removed and inspected and replaced the ECU connectors - these are clean & dry.
The latest:
Disconnect the 4 pin coolant temperature sensor when warm. This should force the ECU to use a generic value rather than the sensor value. - No change but error recorded on VAG COM.
Disconnect the #5 "needle lift" sensor on the injector. No change but error recorded on VAG COM.

None of the above has changed the noise. VWWatercooled member "Jets" has heard this & I expect he will correct my description of the noise if I am wrong. (How bad is the noise?: When I revved the engine to 1500, Jets took a step back & his eyebrows went up!)

Why would the timing change to advanced? This was correct at last cam belt change about 10,000km prior.

Where do I go from here?


Thanks,

Farmsyncro

[doc_777]

My suggestion is don’t run the fcuker until you manually check the timing! Cam belts can and do slip. Unusual, but it happens. Best to spend the time and check it I reckon.

[gldgti]

Hi,

(started in transporter page) Our T4 TDi has suddenly developed a really bad diesel rattle one cold start up. It was parked running OK but the next morning it rattles really badly & vibration felt through gearstick. The rattle doesn't sound like one cylinder, it is general, it doesn't sound like a bearing, it is like normal diesel rattle X3. If you have your head under the bonnet you should really wear ear muffs!
Fuel was filled 300km before problem started. It drove & sounded normal when parked.

I have checked:
Timing on VAG COM. This was showing "too far advanced to measure". I have corrected this but this has barely changed the noise.

What do you mean you have corrected this? And also, was this not part of the normal timing belt adjustment procedure that you referred to having happened ~10kkm previously?

Aside from that, I would proably suspect the advance piston in the injector pump. It may be stuck in the bore, although if that was the case it would probably seem more normal at high rpm and really loud at idle. Is this the case?

[farmsyncro]

My suggestion is don’t run the fcuker until you manually check the timing! Cam belts can and do slip. Unusual, but it happens. Best to spend the time and check it I reckon.

Timing has been checked. It was advanced. It was corrected with no significant change to the noise.

[farmsyncro]

What do you mean you have corrected this? And also, was this not part of the normal timing belt adjustment procedure that you referred to having happened ~10kkm previously?

Aside from that, I would proably suspect the advance piston in the injector pump. It may be stuck in the bore, although if that was the case it would probably seem more normal at high rpm and really loud at idle. Is this the case?

The cam belt and injection pump belt, water pump and rollers were changed about 10,000km prior. The cam timing and injection timing was set at this time.
After this noise started I checked the injection timing again (ie having driven about 10,000km) and found it was "too advanced to measure" in VAGCOM. In other words, it had moved and it had moved advanced!

I have corrected this by releasing the drive pulley from the end of the cam and turning this relative to the cam, re torquing etc etc (ie the normal way). The injection timing now is within the guide lines in the "TDiTiming" chart on VAG COM.


Re the: "advance piston". Is it possible to access this when the pump is fitted to the engine?

It is hard to know if it is normal at high revs because it makes such a racket at lower speeds I am reluctant to rev it. The power appears normal as far as I can tell.

When performing the "Output tests" in VAG COM, what effect should be noticed when the "Commencement of Injection valve N108" is cycled?
On this engine there is nil effect. (this would support the above diagnosis of advance piston stuck)

Thanks for your input.

Farmsyncro

[gldgti]

When performing the "Output tests" in VAG COM, what effect should be noticed when the "Commencement of Injection valve N108" is cycled?
On this engine there is nil effect. (this would support the above diagnosis of advance piston stuck)

Thanks for your input.

Farmsyncro

You should hear an obvious change in the "diesel" rattle. If I rememeber correctly (its been a while since I did one of these) it should be "normal, then loud (adnvanced) then quiet (retarded).

If you are hearing no difference then the timing adjustment may not be working correctly (stuck piston).

The timing piston is in the base of the pump and runs transversly to the axis of the pump The piston acts to move a bearing roller ring that the pump cam plate rides inside of. This means as the advance piston moves the bearing rollers (relative to the pump housing) the injection pressure is built up relatively advanced or retarded to the zero point setting (when there is no fuel pressure (i.e static timing setting). On TDI pumps, it is somewhat complicated by some solenoids which are used to adjust the fine tuning of the timing as per the VCDS checks - these solenoids regulating pressure bleeds to one or either side of the advance piston - but essentially, the piston in the bottom of the pump moves against a spring to advance the timing. Fuel pressure pushes on the piston to increase the timing as fuel pressure (rpm) increases. Access will depend on the exact pump fitted to your engine.

What engine code are we talking about?

[farmsyncro]

You should hear an obvious change in the "diesel" rattle. If I rememeber correctly (its been a while since I did one of these) it should be "normal, then loud (adnvanced) then quiet (retarded).

If you are hearing no difference then the timing adjustment may not be working correctly (stuck piston).

The timing piston is in the base of the pump and runs transversly to the axis of the pump The piston acts to move a bearing roller ring that the pump cam plate rides inside of. This means as the advance piston moves the bearing rollers (relative to the pump housing) the injection pressure is built up relatively advanced or retarded to the zero point setting (when there is no fuel pressure (i.e static timing setting). On TDI pumps, it is somewhat complicated by some solenoids which are used to adjust the fine tuning of the timing as per the VCDS checks - these solenoids regulating pressure bleeds to one or either side of the advance piston - but essentially, the piston in the bottom of the pump moves against a spring to advance the timing. Fuel pressure pushes on the piston to increase the timing as fuel pressure (rpm) increases. Access will depend on the exact pump fitted to your engine.

What engine code are we talking about?

Hi,

It is an ACV engine, 2003.

This would make sense that it is stuck in full advance. There is definately no effect when the N108 is cycled. I might try this on another vehicle. (Jets, I'm heading your way)
I think I can get some access while it is still mounted to the engine, I will have a look this afternoon.

Thanks for your input.

[gldgti]

See attached image of the ACV engine, I have annotated the position of the cover over the timing piston bore.

If you decide to remove the cover and take a look inside, know these things:
1) Fuel will come out and you may lose prime.
2) I am not directly familiar with the 5 cylinder pump ( I have pulled apart, rebuilt and modified plenty of 4 cylinder pumps, but never a 5) and I cant tell you if there might be a spring under that cover or not... so be careful! There may also be shims under the cap if there is a spring there. If you reassemble incorrectly, it will change the timing advance curve. This should be avoided!
3) Do not attempt to remove the piston from the bore completely - I am not even sure if you can physically do it with the rest of the pump still together, but dont try - if you can, you might not be able to reassemble without completely dismantling the pump. You should be able to remove that cover and see if the piston will move without much risk. I anticipate the spring will be under the back side cover and this end will be where the fuel pressure is acting. Either way proceed with caution.
4) KNow that the housing and bores are aluminium, so take care not to score the bore with sharp tools etc. The piston will be steel.

[farmsyncro]

[ATTACH=CONFIG]33359[/ATTACH]
See attached image of the ACV engine, I have annotated the position of the cover over the timing piston bore.

If you decide to remove the cover and take a look inside, know these things:
1) Fuel will come out and you may lose prime.
2) I am not directly familiar with the 5 cylinder pump ( I have pulled apart, rebuilt and modified plenty of 4 cylinder pumps, but never a 5) and I cant tell you if there might be a spring under that cover or not... so be careful! There may also be shims under the cap if there is a spring there. If you reassemble incorrectly, it will change the timing advance curve. This should be avoided!
3) Do not attempt to remove the piston from the bore completely - I am not even sure if you can physically do it with the rest of the pump still together, but dont try - if you can, you might not be able to reassemble without completely dismantling the pump. You should be able to remove that cover and see if the piston will move without much risk. I anticipate the spring will be under the back side cover and this end will be where the fuel pressure is acting. Either way proceed with caution.
4) KNow that the housing and bores are aluminium, so take care not to score the bore with sharp tools etc. The piston will be steel.

Cheers

[farmsyncro]

Update:

I could only access the cover of the Injection pump timing control piston (as indicated in the above picture), This reveals a spring and the back end of the piston which I could not move. So I removed the Injection pump so I could access both ends of this timing control piston. It was stuck in the bore & I could only move it by gentle tapping. Once I had moved the piston the spring was not able to return it.
There were odd polish marks in the bore where the piston has been rubbing so I polished these off & was able to free up the piston a bit so I could at least move it with my fingers and its return spring.

This is now refitted, retimed but still noisy (I think) and again cycling N108 in VAG COM does not change the engine noise at all (as it did in another engine tested). I believe the timing control actuator piston or possibly the ring that this moves inside the pump must be stuck. I will source another pump or open this one up to find out what is going on.

So now some questions:
If the noise I have is caused by the timing actuator stuck why, when I measure the timing on VAGCOM TDi Timing graph, can I NOT make it quiet?
Is the timing value in TDi timing a REAL raw timing figure?
How can I get a raw timing value and what should this be set to to get quitet operation at idle? (I understand this will not be suitable for any other engine load or speed, I just need to find if the engine will run quietly)

Thanks,

FarmSyncro

[gldgti]

The timing signal read in VCDS comes from the 5th injector, which has a needle lift sensor. This is what supplies the timing data to the ECU.

If the timing control piston is/was seized, this is the likely cause of your problem. The little valve with the wire coming off it to the right of frame on your first photo is (i think) what the ECU uses to modulate the fine control over the timing. I think that valve bleeds pressure from the pressure side of the piston in order to retard the timing from the basic setting. However in my experience (and according to theory) the extent of control afforded by this valve is not significant, perhaps 2-3 degrees of timing (enough to change the diesel rattle, and affect emissions though).

The timing ring in the pump should not seize in my opinion, based on the design of the pump.

When you set the basic timing, how are you doing that? are you just aligning timing marks or are you measuring cam plate lift at TDC using a dial gauge in the back of the pump?

*** Edit***
Another thought I just had - if the fuel pressure in the pump is too high, this may be causing or adding to the problem. It seems unlikely that this would be the case, as the design of the fuel pressure regulator is robust and should not fail upwards (if that makes sense). However, if the return flow from the pump is restricted (like the return barb has been crimped or bent) enough, this would result in too much pressure and too much advance. Just something worth checking.

If you want to call me to discuss I have PM's you my phone number.

[farmsyncro]

Update:

Following gldgti's comments I have disconnected the N108 solenoid to disable any function, good bad or otherwise. I have then tried to find a timing point where the engine will operate quietly (as normal).

I adjusted the timing several times by releasing the Injection Pump (IP) drive sprocket on the camshaft and rotating the IP very slightly before re tightening the cam sprocket. Each adjustment I monitored with VAGCOM.

I have had the timing set from 1 ATDC to 19 BTDC on measure blocks "actual injection timing".

At no point was the engine its normal quiet self! At 1 ATDC it was hard to start as you would expect which indicates to me that the "measurement" is probably correct.

Now I think there must be a IP problem. I am not familiar with these so I can't see the sense in disassembling it as I do not know what I would be looking for. The quotes I have been given to recondition the IP are from $2k up and I never got a straight answer if they can fully test the N108 function.

Yes, I am still convinced it is "diesel rattle" and not some other mechanical noise.

I have a s/h pump in transit from a very kind VWWatercooled member and a "plan C" s/h pump at a wrecker on standby.

The fact that cycling N108 in VAGCOM has no effect still bugs me. The fact that this started one morning on cold start still bugs me.



Does anyone have any other thoughts or suggestions on what could cause this?

Farmsyncro

[gldgti]

Can you take a video of it running and post it on youtube for me?

[farmsyncro]

Can you take a video of it running and post it on youtube for me?

That will test my capabilities but Yes, I'll try.

[gldgti]

Leaking injector is about the only other thing I can think of that might cause a similar issue. You could test that by loosening injector unions one by one as its running and listening for any change in the sound as each one drops out.