ticking/Rattle

[chrisbrad66]

hello all, just got back from a run to cardiff today, i've noticed a strange constant tick/rattle that seems to come from the engine/gearbox, i just had a major service done so it's not old oil or the like, i was wondering if their has been issues with camchain tensioners or guides on these engines? by the way it's a s320 cdi with 107000 on the clock, it sounds like camchain to me but could be something else, it only does it when warmed up.Funnily enough it's not there when you give it a lot of throttle, omly on light loading and when moving forwards i think
Thanks all for looking

 

[chrisbrad66]

just been for another ride/listen, it's definately a ticking, which is only audible when moving forward and doesn't increase with speed, just a constant tick

 

[Ian B Walker]

Wonders if it is an injector problem. Dieselman, over to you or the Fabled Oliver (BlackC55)

 

[fredfloggle]

just been for another ride/listen, it's definately a ticking, which is only audible when moving forward and doesn't increase with speed, just a constant tick

Not the brake modualtor is it?

 

[chrisbrad66]

dont think it's the modulator, it's definately engine related and it's audible just, when you rev it in neutral but more pronounced when gently accelerating, it does sound like the tensioner not doing it's job properly and allowing the chain to slap a little, sound familiar anyone?

 

[BlackC55]

It is a normal noise discussed alot.

I had one in when I worked at a dealer and it was deemed normal by the MB technical dept.

Some do it alot some not at all. I have also heard of injector cleaner improving it.

 

[BlackC55]

It is coming from your injectors BTW

 

[fredfloggle]

just been for another ride/listen, it's definately a ticking, which is only audible when moving forward and doesn't increase with speed, just a constant tick

Well if it was injector related I would (perhaps wrongly) expect it to follow engine speed .

 

[chrisbrad66]

i would have thought it would follow the rise and fall of the engine too but thats why i asked on here to get the experts opinion thanks BlackC55 and fred floggle, still concerned though as i have read elsewhere on here of tensioner and tensioner guides failing at 100000 to 120000, and also read of it in a used car review for the 320 cdi engine, they reckoned about 200 quid ish to replace tensioner and guides plus parts, does this sound right and if so any offers to do it just to put my mind at rest

 

[recycled]

that tickle is nothing to do with the tensioner or chains.
the tensioner is very pronounced especially at start up and it is not faint at all.
not sure about what you read but i think someone on here has a cdi with 400k miles on it with the original chain and tensions

 

[stevesey]

just been for another ride/listen, it's definately a ticking, which is only audible when moving forward and doesn't increase with speed, just a constant tick

Purge control valve? (does an s320cdi have one?) - mine's only audible at idle/very low speed (and has vanished since I fiddled with the valve). On a 202 the valve doesn't operate below 70oC engine temp and for the first two minites after a start, which fits you comments about only occuring when warm.

 

[recycled]

what does this valve do.? irritates me so much

 

[stevesey]

what does this valve do.? irritates me so much

Vents petrol fumes from the tank, via a charcol filter into the inlet manifold. Emission legislation meands you are not allowed to vent any fuel vapour from the tank to the atmosphere, hence you suck it into the inlet manifold when throttle is open. Normally you don't vent at idle because it can upset the idle mixture, but mercs seem to pulse the value (hence the ticking) to achieve a little venting at idle.

P.S. Mine was transmitting a nasty rattle into the cabin, so I lifted it off the rubber mount and left it an at and angle of 30 degrees, just supported by the pipes. Pretty sure noise didn't go straight away, but after a couple of days it had gone. Put back on mount and noise hasn't returned. Valve can still be heard ticking it you are close to it, think I must have disturbed some dirt in the valve.