300D Timing Chain Replacement

[griffis]

Just changed the timing chain at 475,000km on my 300D. Wow what an improvement. Quieter, better pick up & hill climb performance. I will monitor fuel/oil consumption and report on any improvements in this area.

Before I made the decision to replace the chain, I checked the chain stretch, using a dial gauge indicator - came out at 20 plus degrees on crankshaft pulley - should be 13.5 degrees.

Changing the chain is really a three person job - one to crank engine, one to feed in new chain while maintaining tension and one to pull on old chain (to maintain tension). It is possible with two people, but the chance of the chain slipping on the sprockets is much increased and then you have to re time the system.

Chain tensioner & guides all looked okay, so left them as is.

Sean

[John Green]

Remove the rocker arms and glow plugs and it can be done on yoru own, as there is no compression and the rockers dont just due to the cam it turns over very easy.

[Ivanerrol]

That go for petrol engines as well John?

Remove rockers and spark plugs?

[Tony From West Oz]

Remove the rocker arms and glow plugs and it can be done on yoru own, as there is no compression and the rockers dont just due to the cam it turns over very easy.

Don't forger the IP which needs significant torque when coming up to an injection point and twists to pull the chain when past the injection point.
If not prepared for it, this can cause the chain to easily slip one sprocket tooth.

With care, it is a one person job, just watch for sudden loading of the chain as it is fed in.

I hope this helps,
Tony

[John Green]

That go for petrol engines as well John?

Each engine is slightly differant, but the basic principle remains the same. On the M116/117 V8's you can do it. On the M102/103 you can't remove all the rockers as they also hold down the cam, what I do with them is remove all except the No.1 rocker carrier and then wind in the chain. Aparts from stopping the engine from jumping it is a good way of checking the condition of the cam and rocker arms.

Don't forger the IP which needs significant torque when coming up to an injection point

Good point, but i/we did one only two weeks ago and can remember the pull of the pump as we wouldn int he chain but it was very minimal. Don't forget that there is that special bolt int he block to the L/H side of the engine that stops the chain from jumping on the IP sprocket.

[griffis]

All makes for interesting reading/opinions.

I did remove my glow plugs. I never even thought to remove my cam followers. I still think that having three people made the job that much easier, safer(less chance of the chain jumping a tooth) & probably quicker.

One interesting observation - the new duplex chain has significantly thinner link joining pins, compared to the old original chain - any comments?

Sean

[John Green]

the new duplex chain has significantly thinner link joining pins, compared to the old original chain - any comments?

Umm, I have bad news for you. You have a sub standard non genuine chain.... The OE chain has the thicker pins to cope with the extra strain of the diesel and the unbalance of the 5 cylinders. It also has to be joined with a special tool that peens over the ends of a special link to make 100% sure it does not come undone. I bet your chain had a circlip style joiner?

There are quite a few products that I will only sell certain brands on timing chains is one of them, radiators and ignition leads are a few others. The associated risk of using parts like this is not worth the money saved.

[griffis]

Hi John,

I was afraid you might say something like this.

As an ex bike rider I have no real issues with the clip joiner for chains. I have always found this method of chain joining to be reliable as long as the clip has the closed end pointing in the direction of chain travel.

The thinner joining pins are a worry. I will contact you for a price on an original specification chain.

Regards

Sean

[John Green]

The problem with the clip is the vibration of the diesel shakes them off sometimes.

[griffis]

Hi again John,

There should be no side thrust on the chain joiner link and the vibration from a reasonably well tuned 5 cylinder could not compare with the stress/harsh environment of a bike drive chain.

Sean

[John Green]

My knowledge of bike chains is zero, but do know of multiple cases of OM series engines that have had a chain link come apart when the circlip version was used. Maybe it is the strain caused by the smaller pin, who knows.

[griffis]

My knowledge of bike chains is zero, but do know of multiple cases of OM series engines that have had a chain link come apart when the circlip version was used. Maybe it is the strain caused by the smaller pin, who knows.

At the end of the day its practical experience/knowledge that counts - I bow to your superior grasp of both.

Regards

Sean

[lockiedog]

Hi

I am about to do my timing chain and I am just asking what tool do you use to press the new clip on with, can you use any standard timing chain tool the fits the chain.

And also how hard is it to replace all the slides and rails?. Do you need the pullers to get them off like the say in the manual. ( because i just did a timing belt in a hilux and in the manual it said you need a puller but I got them off without)

And do you know any good mercedes benz machanics in brisbane that would do the job. (And a rough prices).

Thanks Alot

Alex

[mathuisella]

Thinking about doing the timing chain myself after i take a look at it tomorrow morning. How did you go with it Lockie ?

[Tony From West Oz]

IIRC, the chain guides can be removed by screwing a suitable thread (bolt) into the retaining pins and removing the pins (interference fit) and the guides can then be removed.
I used 3 hammers to peen over the link pin ends to secure the 'link side plate' in place when I replaced the timing chain on my OM617 952 engine.