M47 Diesel Engine Whine / Whistle On The Overun

[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 !

[Austingarages]

Originally Posted by ace1977lan

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 !

Very interesting, I guess in this country it never gets that hot!

But forgot to add, in all cases, this particular noise is nothing to worry about.

[cjmillsnun]

Originally Posted by Austingarages

Very interesting, I guess in this country it never gets that hot!

But forgot to add, in all cases, this particular noise is nothing to worry about.

Yep it's an annoyance more than anything else. But you get used to it. Or learn to turn the radio up one or two notches louder and then you can't hear it

[David3807]

Is this the same thing ??

http://www.the75andztclub.co.uk/foru...ad.php?t=19156

post 3 by Transam,

[Jules]

Not the same noise as that David.
I wonder if the PWM pusle width or frequency was changed in later ECU's

[grossebaby]

Just realised, my 04 model no longer does this! It used to but now no, I have had the fuel pump (the main one on the engine) re-realed and checked and come to think of it maybe that is when it stopped but I cannot be sure.

[Jules]

Can you dig out the bill and find out what they did?
We're all waiting with baited breath

[e668ecp]

Mine does this!!

[tonygardner]

so does mine and i have had the high pressure pump replaced

[Jules]

Had a member's car here last week with "the noise"
His broke the rules for this whine as it had the secondary fuel pump arrangement. (131)
Previously all the cases I've studied have been with the single intank pump arrangement
(but is was an 04 Reg MK1 body so many parts on it were on the cusp of the Facelift changeover)