[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.