Timing Chain.
Morning all,
Just a cursory thought, I know the GD 300 460 has a timing chain and not a belt, but does this ever need changing or is it a lifetime part, if it does need changing what are the intervals between changes and is it a big job? Thanks
TBH not really.. say 250,000 miles between chains? .. or more. It is a pain as you have split the chain so need a tool to do that. Go google "OM617 timing chain" .. as that is your engine (460 300GD not a 463) .. sure there must be info on it. There are a few of these engines with a million miles on them.. and I suspect no one did the timing chain; seem to remember you can measure the stretch of the chain by looking at the timing of the camshaft if you really have a spare few weekends.
It is not a well known fact but Mercedes schedules do claim timing chains to be checked/ renewed some; every 100,000 miles intervals.
This is due to the chain stretching and cogs wearing. However, it is not a practice, largely due to costs of renewal involved.
Before you embark on renewal, there are tests that can be done to check if the chain has stretched. The test checks for valve timing in relation to the TDC mark. If these are excessive, the injection or firing timing will be expected to be out hence, generally suffer a loss of power and increased fuel consumption.
With the chain and cogs to be renewed the chain slides are renewed as well. The job can be done with the engine in situ save for the front end disassembled to allow room to do the work. I would go further in evaluating a renewal job and that is to consider the engine oil pressure, if the oil pressure is at its bottom end of tolerance reading this is an indication of a worn engine in such a which case, instead of wasting money in renewing the chain, you ought to be investing in an engine reconditioning.
It is not a well known fact but Mercedes schedules do claim timing chains to be checked/ renewed some; every 100,000 miles intervals.
This is due to the chain stretching and cogs wearing. However, it is not a practice, largely due to costs of renewal involved.
Before you embark on renewal, there are tests that can be done to check if the chain has stretched. The test checks for valve timing in relation to the TDC mark. If these are excessive, the injection or firing timing will be expected to be out hence, generally suffer a loss of power and increased fuel consumption.
With the chain and cogs to be renewed the chain slides are renewed as well. The job can be done with the engine in situ save for the front end disassembled to allow room to do the work. I would go further in evaluating a renewal job and that is to consider the engine oil pressure, if the oil pressure is at its bottom end of tolerance reading this is an indication of a worn engine in such a which case, instead of wasting money in renewing the chain, you ought to be investing in an engine reconditioning.
As ever, very helpful, thanks Rakesh. I feel I'll shortly be able to sit my "O" level in G things!!!!
Hi
I will second Rakesh's comments...
All MB chains listed as 100,000 intervals....
However never in 27 years seen one changed at that just because of the interval
Usually 125,000 - 150,000 on the petrol's and 250,000+ on the diesel's
Exceptions with poorly maintained M102 engines and early/mid 90's OM601/602 engines
M102 liked to eat chain gears and chains if not looked after 100% from 75,000 onwards
OM601/602 had a batch of poor chains that liked to stretch and screw the engine but most if not all of these will have been rectified by now....supplied hundreds of chains and dozens of engine for these in the day..
Gav
Be thankful that we have a chain in our engines. I heard a story many years ago about a Landcruiser which broke a timing belt in one of the multivalve engines at 60 mph. Piston hit the valves and a huge repair bill for the owner.
Alas, the same is true for timing chains; if these break it does the engine damage. 
Having said the above, there are some engines with timing belts that are, "xxxxxx safe" - MENTAL BLOCK preventing me to remember the term but the engine does not damage.
I am sure Steve Kirk will help me out here.
Some engines are " Non Contact" ie if the belt or timing chain fail the valves do not impinge on the piston crown...Toyota AGE engines are one example. I have done a few merc timing chains in my time...early M102 engines where awful i have known them start to rattle at 12,000 miles , the early M102 's had a simplex chain , this changed to a duplex around 83 i think . All merc timing chains used to be a doddle to change , as it was the practice at the time to use split link chains , so all you had to do was remove the tensioner...split the chain....join the new chain to the old one ....slowly wind the engine over ...then join the new chain with a split link. refit the tensioner....check you timing marks ...job done.I don't think the split link chains are still available .
SK
Have seen thousands of OM6## series engines in west africa with 20+ years daily use....still running with hardly any teeth profile left on sprockets
Perhaps one failure of single row oil pump chain
This is one of the worlds great longlife engines - might want shells seals and rings after 500,000 miles , will then do another 250,000
You are right about the Landcruiser..t.belt is the achilles heel , although the rockers are meant to break to prevent Major damage
Landcruiser with 606 ? now that would be an overlander !
Lambretta Li series scooters had duplex drive chains enclosed in an oil bath, utterly indestructible too
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Thanks for all your answers, my engine has done 138700 with full history, so what I'm reading is there should be nothing to worry about too much.
Thanks again.