My 300SEL has 132000 miles and I think I am overdue on a chain replacement but my mechanic tells me it is OK. How can I be sure??

You can check to see if there has been any elongation of the timing chain by setting your crank to TDC for #1 cylinder and then see if the timing marks on camshaft sprocket and on the cam tower line up while at TDC. Look for scoring or other wear marks on the chain. These double-roller timing chains built with high-quality German steel and machine work, in my opinion, do not have a so many miles and replace tagged to them. If the oil has been changed regularly there is really no reason to change them until they show signs of trouble (e.g. noisy, hard to start (because of chain)), etc. I'd go with your mechanic's advice. Save the dollar's of installing a new one and shorten your oil change interval. My bias is towards full synthetic lubricants.

Yours is a single row timing chain, not double. But it is nevertheless a very sound chain, not known for problems. A 103 motor has a very short path - only two sprockets because it is a single overhead cam engine. I agree with the mechanic - no need to worry about it. I once had one changed at 280k and it was fine.

In Australia we change the chain at 100000k Because of failures to the tensioners.When either of these go they get tangled in the chain and the
result is the same as when the chain lets go.Not good.
What are your tensioners made of? Mine were a white plastic.Not good.


83 380SEL `125k from new.

Sorry Paul i dont know what these two guys are trying to sell you,maybe they own shops and want your 2 grand buisness when the chain breaks.all 102 ,103,116,117 and diesels need there timing chain replaced at 200,000km.if you have a 24 valve 104 6 cyl engine than you would be fine ,but you have the 103 engine and the chains need to be replace at 200k.So i would advise you not to listen to these 2 (well i wont say what i wanted to say) guys and get the chain replaced.We would charge about $400 canadian here in vancouver.I dont know where you are ,but it should be arount there.And that 400 is a lot nicer than 2 grand..Ok it is 2-1 against me but i have been a mechanic and working on MB for 14 years,i like to see what the other 2 work on.So paul probaly other people will relpy,but i would advise you to replace it .Good luck Harald

meangrean,
I replied in good faith. In retrospect, I should not have replied. I shouldn't have assumed the chain was double roller. I am aware of the consequences of a failed chain. My chain tensioner failed and am just replacing the tension rail and chain guides, so was very fortunate I didn't lose the chain. I replied before you did and I am not against you and certainly not disrespectful of your years as a MB mechanic.
ralph

I have had two very good, trusted mechanics, both former lead mechanics at dealerships, tell me, completely indenpendently, do not touch a working unmolested factory chain on a 103 motor. They do not fail. Both said the same thing, the replacement would not be as sound as the original factory work. If it's not making noise on start up - don't touch it. Nothing wrong with replacing the tensioner - it's about a $30 item and quite easy to get to. Anyone who says there is a replacement interval is making it up - it doesn't come from Mercedes.

The chain on a M103 engine will last forever. Don't change it unless there's a problem, as others have said here. Due to the relatively smooth direction of travel (SOHC) it is not subject to a lot of wear. Just change your oil regularly and you should have nothing to worry about.

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

I can't answer the question until you tell me if your car has a 3.5 , a 4.5 . a 2.8 , or a 3.0 liter engine.

__________________
Auto Zentral Ltd.

Re: Autozen, Sorry about that, the car is a 300SEL,(1988) with a 6 cyl 103 engine with 132000 miles.

My '87 300E (gas engine) still runs on the OEM chain. It has a little more than 300k on the clock.

__________________
95 R129
04 Infiniti G35.5 BS
10 X204

Pardon my ignorance, but was there a 300SEL that actually used anything other than the 3.0 liter M103?

Thanks in advance for the enlightenment...

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Well in the 126 body style it only the 6 banger,but from 65-73 there was
the 109 body style ,the 300sel had a 3.5,4.5 and a 6.3 litre engines in them.
And Elau i wish you luck on your next repair bill

You left out the original 109 300SEL motor - the 3.0 liter, obviously not a 103 motor. There was probably a 140 body 300SEL in Europe in the early 90s with a 104 motor.

Naw, the car will be in the junk yard if the chain goes.

__________________
95 R129
04 Infiniti G35.5 BS
10 X204