Intermittent Groaning from front of E300D engine

[johngreen11]

This is really causing me headaches. The groaning noise is evident at start up at tick over, taking the revs above 1000 it goes completely. Putting any pressure on the steering wheel also makes it go.

Loosing and retensioning the large front drive belt also seems to effect the frequency it occurs. I've checked for smooth running of the alternator, power steering, water pump and ac compressor pulleys and all run smooth with no resistance or rough spots. I've also check the tensioer pulley and the pivot arm bearing. The shock absorber seems ok but vibrates slightly at the bottom end at tickover. Nothing is loose.

After a journey of about 30 miles the noise is present at tickover but sometimes if the engine is switched off then left for 10 minutes on restarting the noise has gone.

The belt was changed about 4000 miles ago using a Bosch item not Mb one.

I have also listened around the engine using a stick of wood to try and locate the source of the noise but with no success.

Anyone got any ideas what it can be. It sounds a bit like a bearing as it seems in time with the belts movement. A dealer suggested the pivot arm bearing on the belt tensioner but when I checked it it was free and smooth with no side play.

Can anyone help please?

 

[JB direct ( wigan )]

re

im having a similar problem to this at the moment on a sprinter 311 cdi
it also seems in tune with the belts movement
can anyone help solve this

 

[jberks]

It may be that the pulleys run smooth when not under pressure. 2 thoughts come to mind. Firstly, don't know a lot about power steering pumps but presumably they have some sort of pressure release valve. Could it be the that as you put pressure on the pump or increase the pressure by increasing revs, this opens or closes the valve properly and the noise goes away?

What happens when you load the alternator? Put all the electrical stuff you can on, when groaning. This should have a similar effect on the belt to the pressure on the wheel. If it doesn't stop it, it points to the pump., If it does, it rules out the pump.

How about going round each ancilliary in turn with a shot of WD40? Helped me identify a noisy alternator against the water pump once.

 

[JB direct ( wigan )]

re

if you look at the belt when its ticking over you can see play in the belt as though its slack but turn the engine off and put pressure on the belt and its tight plus if you put the indicaters or wipers on when ticking over you can here the engine go higher and lower in tune with the indicaters ... this gets me thinking its the alternater but there is no diference with the headlights on they stay the same brightness whether its ticking over or reving ... its going in for service this weekend so will see what they say .... have asked them before but 1 says its the alternater ... another says its the pump and others have said different again ... if it was up to them you would have rebuilt the engine before you get to the problem