strange noise from engine

[fred_raven]

Car is running fine - goes well , doesnt use too much fuel , almost no oil , doesnt lose water. BUT has a strange noise from the engine - has been described as a warbble - or maybe more of a plob plob plob - on tickover - ( very difficult to describe a noise ) but it is quite loud, and not the same as other similar models. Any ideas ?

 

[MangoMan]

Induction noise???? Maybe.

 

[230K]

Hi

Try vibration damper first by holding it while engine running to see if it changes the noise.

Try the link below to thread on another site about purging, could be mucky injectors causing your strange noises.

http://www.mercedesshop.com/shopforum/showthread.php?t=113596&highlight=diesel+purge+606

230K

 

[GazCaff]

Is it not the vacuum pump?

 

[fred_raven]

Hi

Try vibration damper first by holding it while engine running to see if it changes the noise.

Try the link below to thread on another site about purging, could be mucky injectors causing your strange noises.

http://www.mercedesshop.com/shopforum/showthread.php?t=113596&highlight=diesel+purge+606

230K

tks for the suggestions 230K :

had the dampers changed 2 mths ago so def not that.

re the injectors - not so sure - watched the vid in the link - the biggest difference was a reduction in " slap " or "knock " noises - very noticable - mine has some but not as much as his originally before the "purge"

the noise i was referring to was there in his at the end - when his is running "quieter" there are 2 distinct sounds the rattlly sound - mine has this and a low freq thrum . this thrum is 4 - 8 times louder on mine. his rattly sounds are oblitterating the thrum . The thrum on mine is by far the loudest part of the noises.

Hope that makes it clear>

 

[Dieselman]

I think you mean it sounds like it's about to throw a rod. If so it's probably the MAF sensor.
Try disconnecting it and also get some readings from it. One test is to disconnect and block the EGR valve line. If the MAF doesn't see this within 5 mins then it's duff. If it sees it the engine will go into limp home and drop the turbo.

Also rev the engine up slightly and see if the sound goes on over-run but comes back on then the fuel switches back on.

 

[fred_raven]

tks for the reply dieselman - small query - whats the EGR valve line ?

As an avid reader of posts here i believed that if the MAF was faulty then there would be a noticable difference in engine power ! is this not the case?

 

[Dieselman]

tks for the reply dieselman - small query - whats the EGR valve line ?

As an avid reader of posts here i believed that if the MAF was faulty then there would be a noticable difference in engine power ! is this not the case?

The vacuum tube that feeds the EGR valve from the modulator. It's just near the ABS valve block.

On these cars the MAF won't show up unless it's really bad, you won't have noticed the reduced output as it often isn't too far off and is still smooth.

 

[fred_raven]

mmmm on sunday - after this noise was noticed - i was checking my duovalve again - no heat left side - seems to be just a bleeding issue . whilst i was at it thought i would use Parrot of Dooms other how to - clean the MAF . took it out cleaned it a little reassembled. Yesterday - lo and behold car seems quiter and more lively , but during the evening the noise returned for a while , but has now gone again. Sound like an intermittent MAF Dieselman?

Edit - just located the EGR ( i THink ) cylinder 1.25" dia 1.5 inch long approx - 1 elec conn. 3 vac pipes going to it . ?? blocked the pipe coming from the centre top - disconnected elec conn and within few hundred yds car still ran - but no turbo on kickdown - def reduction in go. reconnected and back to normal . Noise not so noticable this morning - but still there .