M47 Diesel Engine Whine / Whistle On The Overun

[Jules]

M47 DIESEL ENGINE WHINE / WHISTLE ON THE OVERUN REVISITED

I am re-kindling this problem as its really niggling with some M47 Diesels out there! Some owners can't hear it but when I point it out to them, they are sorry I did!!!

Always on the face lift 75 or ZT's and affects about 2 in 10 cars I've had.
I agree with various findings of others on this subject

ie High pressure Fuel line resonance in the form of a 1Kz tone between approx 1500 RPM & 3000

Put the engine under load and whine disappears so we can rule out belts, bearings, turbos etc. Also mileage is not a factor either as we've had Brand new stock with this noise !

Electronic fuel regulation is from the ECU and is a PWM waveform and guess what it's I believe from memory a 1Khz waveform!! But why would it only seem to effect later diesels? a mystery to me for the last 3 years.

Here are some old threads on the subject from the other side

Hi everyone, about six weeks ago I bought a 135 diesel ZT-T (registered Aug 2004 ). The car developed an annoying whinning sound that is present on engine overun and can be heard everytime the cluth is depressed to change gear and the engine revs drop. I thought it sounded like an air leak.
I took the car into the local Rover dealer in Basingsoke after work for them to have a listen. A mechanic came out and promptly ran the car into the workshop for further investigation. A hour later I was still sat in their reception area and they were now putting the car back together. I was informend that noise was being transmitted from the high pressure fuel line under the inlet manifold but they could not trace what was causing it. They suggested I book the car in for a full days investigation.

Before I was due to take the car in the Service Manager contacted me to say that he had been in contact with Rover Technical and that it was a known problem but at the present moment it was being investigated and there was no fix. I could not get a time scale for the fix but he assured me it was being given a high priority.
Not being able to do anything else I waited unaware of the impending doom faceing MG-Rover.
I recently have been in contact with the Sevice Manager and the news is not good. He has been working for Rover for 18 years and he has built up a lot of contacts but has been unable to contact anyone - he said basically he knows as much as what people read in the paper - we're all in the dark.
Now faced with no warranty and no technical support I am left with a great car but a very annoying noise.
Does anyone have any ideas on a fix? Cheers Nick


Thanks for the input.
I managed to get a copy of the original work sheet from my Rover dealer that was completed for their investigation. It refers to a "resonance narrowed down to the low pressure/high pressure joint pipe under the inlet manifold". It also mentions that BMW are looking into the problem - maybe I'll try speaking to them.
Somebody else said to me other manufacturers have run into these problems, especially on common rail diesels running very high fuel pressures. Noises from the fuel lines/pumps which have been cured by the fitting of a relief valve - I think they may have metioned Ford.
Cheers Nick.


The specs are for the Rover 75 2.0 CDT classic....

Again the scan is not so hot, but here goes:-Well actually the scan failed, but as it is a public document that anyone
can check on the diesel car site, I'll type the relevant bits....

"One of the best things BMW left behind when it fled Longbridge was its superb 2.0litre M47R for the 75. It is unique to Rover: The 320d uses the
same block, but with high pressure rotary pump instead of common-rail to achieve more power." The facts reveal 116bhp, 192ft/lbs of torque.

[Roverron]

If it is a resonance you should be able to affect it by damping the pipe.

Try few hose clips clamped around the pipe to add mass in case it is just the pipe length and method of attachment that is the cause.
Or try some rubber strips under the mounting bracket.
Or cable tie some lead strips to it (lead roof flashing)

It is plausible that the modulation of hp regulator is the root cause but is should be possible to locate exactly where the noise is being produced and damp it.

Ron

[Jules]

Thanks Ron I was thinking along those "lines" !
It may even be a pipe that needs slightly bending a different way so the tension is different.

It's got to be an assembly issue as it only affects approx 2 in 10 cars

I would like to spray that expanding foam around but that would be an awful mess!

Last year I took a CDTi up to Frank Massey in Preston who specialises in diagnostics & PWM's etc. He even runs Diagnostic courses for garage techs.
He thought it was regulation but we ran out of time to look further.

I would like to swap a high pressure pump assembly from an CDT that doesn't have the Whine to a CDTi ??
Any differences as far as you know. Rail pressure's same as its just a remap?

I'm going to do a visual now on a CDT & CDTi to see if I spot any differences.

[Roverron]

Originally Posted by julesbass

Thanks Ron I was thinking along those "lines" !
It may even be a pipe that needs slightly bending a different way so the tension is different.

It's got to be an assembly issue as it only affects approx 2 in 10 cars

I would like to spray that expanding foam around but that would be an awful mess!

Last year I took a CDTi up to Frank Massey in Preston who specialises in diagnostics & PWM's etc. He even runs Diagnostic courses for garage techs.
He thought it was regulation but we ran out of time to look further.

I would like to swap a high pressure pump assembly from an CDT that doesn't have the Whine to a CDTi ??
Any differences as far as you know. Rail pressure's same as its just a remap?

I'm going to do a visual now on a CDT & CDTi to see if I spot any differences.

If it only affects 20% of facelfited models, maybe its because this 20% are using new parts (different supplier?), whereas the others are assembled from the parts used on the prefacelift cars. Or maybe only 20% of facelfited models have only one low pressure pump and the associated piping.

Ron

[Jules]

Think your right again Ron....
Bit like the duff batch of squealing clutch plates on 04 plates.
Have you seen any of those? many were replaced under warranty.

[MGOracle]

Its almost certainly to do with the use of one pump on the later models.

[johnbillard]

This sounds familiar - I have an engine buzz at about 1800 rpm that occurs only when car has warmed up (2006 registered CDTi Tourer, 29k miles). It is also intermittent and varies in intensity. While I'd love to fix it I'd really like to be assured that it is not a serious problem that might be ignored, at least for now?

Kind regards to all

[razorriggott]

I have an 2004 CDTi with 39k that displays this noise. My previous 1999 CDT with 90k was fine. It is really annoying, someone please help!

[Austingarages]

This is a very interesting thread!

Working on these cars day in day out, as far as I'm concerned, all late model diesels have this noise - but some are quieter than others. In fact a friend of mine has just bought a Rover 75 Contempory SE CDTi Manual which has the noise, he was not aware of it until I pointed it out to him!

The problem lies with our old friend Project Drive, they did some plumbing to remove the secondary low presure fuel pump next to the battery, revised fuel pipes, revised conections to fuel cooler, etc. Ever since they did that, this noise is present. As far as I can detect where its coming from, it is caused by the PWM signal to the high pressure fuel regulator in the high pressure pump - this sets up a vibration down the fuel lines (you can best hear it with a stethoscope on the return pipe from the regulator. The alterations they made to the plumbing must have somehow taken out the damping effect within the fuel lines to set up this noise. I have swapped the Regulator from a good known early car and it does reduce the noise for a short period of time and then its back again....

So the 2004 facelift of Rover 75 / MG ZT started from VIN 321638, however, the fuel pump delete was from VIN 5D332301, so there are a few lucky facelift owners out there that "should" not have this problem!

The only solution I can think of (unless someone comes up with a fuel pipe damper - rather like the 75 diesel clutch pipe damper maybe!) is to fit the older type fuel system!

One thing I have learned from here reading all of this, is that MGR were aware of the problem and were in the course of dealing with it...

As for BMWs not have this problem, I wonder if thier engineers have a Project "FAHRT"!

[ace1977lan]

Originally Posted by Austingarages

This is a very interesting thread!

Working on these cars day in day out, as far as I'm concerned, all late model diesels have this noise - but some are quieter than others. In fact a friend of mine has just bought a Rover 75 Contempory SE CDTi Manual which has the noise, he was not aware of it until I pointed it out to him!

The problem lies with our old friend Project Drive, they did some plumbing to remove the secondary low presure fuel pump next to the battery, revised fuel pipes, revised conections to fuel cooler, etc. Ever since they did that, this noise is present. As far as I can detect where its coming from, it is caused by the PWM signal to the high pressure fuel regulator in the high pressure pump - this sets up a vibration down the fuel lines (you can best hear it with a stethoscope on the return pipe from the regulator. The alterations they made to the plumbing must have somehow taken out the damping effect within the fuel lines to set up this noise. I have swapped the Regulator from a good known early car and it does reduce the noise for a short period of time and then its back again....

So the 2004 facelift of Rover 75 / MG ZT started from VIN 321638, however, the fuel pump delete was from VIN 5D332301, so there are a few lucky facelift owners out there that "should" not have this problem!

The only solution I can think of (unless someone comes up with a fuel pipe damper - rather like the 75 diesel clutch pipe damper maybe!) is to fit the older type fuel system!

One thing I have learned from here reading all of this, is that MGR were aware of the problem and were in the course of dealing with it...

As for BMWs not have this problem, I wonder if thier engineers have a Project "FAHRT"!

My car started doing this recently I thought it was the turbo at first, it only seems to do it at when the engine gets warmed up and the outside temp is around about 15 degrees and above. I recently drove to the South of France & Spain with outside temps of up to 32 degrees and the noise wasn't there at all. Get back home and it re-appears !