Rattle on cold start up.

[Pitsmoor Col]

I have noticed a rattle on cold start up, but it's not doing it every time. Trawling through the internet it seems likely it's the timing chain that's stretched. But if the chain is stretched would it not rattle every cold start up ? sometimes it goes on for about 15-20 seconds or more right till I get to the end of my road. Some times it's just a couple of seconds, and sometimes it's not there at all. Has any one else had this problem ?

 

[Pitsmoor Col]

Car is 2014 C Class Diesel bluetec Automatic W205, with 137.000. on the clock.

 

[Jim2]

I have noticed a rattle on cold start up, but it's not doing it every time. Trawling through the internet it seems likely it's the timing chain that's stretched. But if the chain is stretched would it not rattle every cold start up ? sometimes it goes on for about 15-20 seconds or more right till I get to the end of my road. Some times it's just a couple of seconds, and sometimes it's not there at all. Has any one else had this problem ?

I'd be inclined to get it checked out anyway......I think that the wear in the chain and tensioners can be measured while in situ. And it has 137'000 Miles on it....what kind of service history does it have?

 

[ajlsl600]

Think oil drainin from tensioner at times, o, ring leaking, sometimes it hold up sometimes not and then you get rattle till oil gets there. Try changing it. Not an expensive diy. Disable stop start at every first start up. Will save yr chain timing gears.

 

[Pitsmoor Col]

I'd be inclined to get it checked out anyway......I think that the wear in the chain and tensioners can be measured while in situ. And it has 137'000 Miles on it....what kind of service history does it have?

It has loads of history, but to me it's only on paper I never trust history records. It's been a rental until I got it

 

[CowleyStJames]

Could be timing chain tensioner which can be changed in situ.
Chain can also be changed I situ by connecting new chain to old and pulling thru.
Trouble is, the three sprockets can also be worn and only the cam sprockets can be changed in situ.
Engine out for lower sprocket

 

[umblecumbuz]

651 engine. Noted for their timing chain rattle. Could be mild and will go on for years without getting worse, but well worth investigating, because they are known for jumping teeth when this symptom is present - with obvious results.
Not wishing to alarm, but caution is better than bravado.
Wasn't aware that chain could be changed 'in situ'. I would definitely query that. My info is that it is an engine out job, as the chain is at the rear of the engine.

 

[M80]

I'm no expert on the 651, but expect to become more knowledgeable as I'm expecting to pick up a Viano with one on Thursday.
This might suggest the chain can be pulled through.
Timing Chain Kit Febi Bilstein (44973) | eBay
I anticipate some tension being required on the split original chain during the process to avoid skipping a tooth down below though.

But I wonder of the intelligence of changing the 2 accessible top gears and leaving the crankshaft gear unchanged.
I'm researching in anticipation of the job being a when rather than if.

 

[Jim2]

It has loads of history, but to me it's only on paper I never trust history records. It's been a rental until I got it

Being an ex rental is not exactly encouraging, but even so, it will have have come from new with its MB guarantee, and the rental companies generally get things fixed if they go wrong during this time. Does it say any where that it had work done on the chain?

 

[M80]

Om 651 ??? | Mercedes-Benz Owners' Forums
A recent thread, post 5 gives some cause for increased confidence, to my mind check for chain wear and hopefully that'll mean just the tensioner needs replacing.

 

[Pitsmoor Col]

I think I will make further enquires as to the cost and whether it needs doing, via an independent MB approved gang, then take it from there. But I think it will need doing sooner or later.

 

[ajlsl600]

If rental, likely stop start in use, that being the case chain sprocket investigation a good idea. I would still be trying tensioner 1st.might get lucky and it shuts up.....

 

[M80]

I would imagine that a good tensioner could still quieten a worn chain (and gears).
Even so the good tensioner should eliminate the jumping of teeth scenario.
How weakened would a stretched chain be?
Would valve timing be out be any amount that would matter?

 

[ajlsl600]

A good tensioner will not fix a fd chain.but if oil is passing the plunger at shutdown and overnight a new one may well resolve that. And therefore in my view worth a try,if it does nothing yr still at chin,maybe gears and will need tensioner.so nothin to loose and maybe a lot to gain,less hassle,expense.?

 

[Dean Fletcher]

651 engines seem to get a bad rap. There all not bad.

 

[ajlsl600]

As posted.there are many in commercial use doing astounding miles.itsjust NOT a short journey engine and dealers never tell customers.

 

[gianton]

Had the same issue, changed the chain tensioner at 188k miles and rattle gone. Now at 214k miles and car drives like new.

That was the sound on a cold start.

 

[bembo449]

id only ever have the actual chain replaced if the car started to mis-behave , if it performs well then get the tensioner changed and see if that cures the rattle , keep us posted

 

[Dean Fletcher]

Had the same issue, changed the chain tensioner at 188k miles and rattle gone. Now at 214k miles and car drives like new.

That was the sound on a cold start.

Ouccchhhh

 

[Pitsmoor Col]

It's going in on Mon, 21 Sep. for investigation. No doubt they will say it needs timing chain, gearbox, back Axle, a couple of Ashtrays, Boot lid, radio, Front Carpets, and Fluffy Dice replacing. The bill will of course be a suicidal inducing equivalent to the national debt. Oh well happy days.