timing chain tensioner - Aus 450SE

[s class]

BTW, the old tensioner was very soft.  A new euro-type unit is on order. 

[WGB]

Replacing the tensioner should be a given - they are the major failure point in the M116/7 engine and why M-B didn't spend a few dollars extra and use a ratcheting design beggars belief.

The tensioner slipper liners are available here because I fitted one to my 450.

I think the risk is in trying to replace the liner wihout removing the whole backing assembly from the motor.

In an M117 motor as opposed to the M100 the bottom pivot point can be removed without removing the water pump so making the whole process a lot simpler and ensuring that the liner is properly clipped into position and not liable to slipping off the backing.

Bill

[TJ 450]

I found removal of the tensioner slipper quite straightforward. From memory, I think the sprocket needs to be removed and held off to the side, to allow sufficient clearance. All that needs to be removed is the alternator, air pump and associated fittings if still fitted.

I purchased a lining from the local MB franchise. I have travelled 20,000km since the chain renewal and there is very little wear evident overall.

It is also worth noting that a worn tensioner equates to extreme wear of the timing chain and sprockets when the chain is loose. Just about everything about a worn tensioner means impending doom. Except maybe the act of throwing it in the bin, or dissecting it for R&D.

I did notice actually, that there was some wear evident on the rollers of that chain in Pompy's car, so that chain may have been replaced some time ago. Anyway, measuring the degree of stretch will give a definitive answer as to the state of it.

It is again also worth noting that MB went even further backwards with the light alloy versions in the '80s. The replacement circa 1996 Febi tensioner removed from my 380SE can be pushed right in with hardly any pressure at all. This circa 1996 replacement occurred after the valves were bent on the LH head of course, to add even more information.

The moral of the story is that peace of mind can be obtained by replacing these relatively inexpensive consumable parts when required and inspecting the timing chain stretch at regular intervals, but I think we all live by this premise anyway.

Tim

[s class]

TJ, I agree with you completely.  Pompy was told by the seller that the chain had been replaced not long before the car was laid up, however I'm not so sure.  Stretch was 12.5 degrees. 

[s class]

[WGB]

Very Nice - you can see the removable liner on the slipper.

Bill

[s class]

Yep, new parts are always nice. 

I'm still waiting on the new tensioner and sprockets. 

[s class]

The chain guides are in :





The rest of the new bits and pieces have arrived :

[s class]

I was delayed in completing the timing apparatus, as I found the left camshaft thrust washer had previously been chiselled and butchered.  New ones are not expensive from the dealer, but it meant a 10 day wait for ex-supplier stock.  It arrived this week :



Valve covers refitted, everything cleaned up :



Re-mounting the power steering pump :

[KenM]

Not hijacking this thread completely, from what I have been able to find out I think the changeover from D-jet to K-jet must have occurred in September '75. I have recently looked at 2 450se's here, one a June '75 D-jet and one a Dec '75 K-jet, which (sort of) backs this up. Are there any advantages/disadvantages of one system over the other, performance or reliability wise that is?
Cheers,
Ken

[s class]

In a well sorted car, D-jet is technically superior and should give marginally better performance.  In practice, k-jet is possibly simpler, and repairs are usually less expensive.  I don't think its a huge issue one way or the other though. 

[pompy]

K jet V8's also have hydraulically adjusted tappets which D jet V8's don't have - a big bonus, I think.

[WGB]

Sometime in 1978 production the power was restored in a Euro 450 so a late 1978 and 1979 model has the same power as the D jet.

What was your timing like after fitting all the new gear.

I ended up about 2 degrees ATDC with my 450 motor which I considered was due to the wear in the unchanged crankshaft cog.

Bill

[s class]

WGB, its about 1 to 1.5 degrees retarded on both sides.  Too small to worry about offset keys. 

[WGB]

That sounds about as good as you can get with an M117 withoiut a new crankshaft sprocket.

Bill