Timing chain opinions

[Liam7755]

Hey guys,

What’s your opinions on timing chain/guide and acceptable noises?

I’m hearing such conflicting opinions on it .. some are saying on a cold start a slight rattle can be fine for 2-3 seconds and almost a normal feature of Mercedes diesel engine … others are saying no, get the chain tensioner replaced and then some are even saying you can’t replace the tensioner without doing the chain as well???

Engine I have is the OM651 925

 

[markjay]

I am not sure about your engine specifically, but most MB engines have hydraulic chain tensioner, meaning that the chain will rattle until oil pressure builds up inside the hydraulic tensioner.

The issue is when the hydraulic tensioner starts leaking. What you'll get theb is a rattle at almost every engine start, i.e. not just on a cold start.

Also, keep in mind that the hydraulic tappets will also rattle on cold starts, again it takes a few seconds for the oil pressure to build up and for the hydraulic tappets to fill up with oil (which would have drained into the sump overnight). So listen carefully to hear if the rattle comes from the top end (tapets) or from the edge of the engine block (chain).

 

[Liam7755]

I am not sure about your engine specifically, but most MB engines have hydraulic chain tensioner, meaning that the chain will rattle until oil pressure builds up inside the hydraulic tensioner.

The issue is when the hydraulic tensioner starts leaking. What you'll get theb is a rattle at almost every engine start, i.e. not just on a cold start.

Also, keep in mind that the hydraulic tappets will also rattle on cold starts, again it takes a few seconds for the oil pressure to build up and for the hydraulic tappets to fill up with oil (which would have drained into the sump overnight). So listen carefully to hear if the rattle comes from the top end (tapets) or from the edge of the engine block (chain).

Thanks for your time to reply dude! It’s just that, working out where it’s coming from. It is there, but I’m unsure as it sounds like it’s coming from the right side of my engine (drivers side UK) .. what makes it worse is the om651 usually always sits longitude .. in my jeep it’s not! Its width ways .. so my timing chain is actually aimed at the gearbox

 

[JHS]

Thanks for your time to reply dude! It’s just that, working out where it’s coming from. It is there, but I’m unsure as it sounds like it’s coming from the right side of my engine (drivers side UK) .. what makes it worse is the om651 usually always sits longitude .. in my jeep it’s not! Its width ways .. so my timing chain is actually aimed at the gearbox

So is mine in the S205 (longitudinal)