I've been at rebuilding my 240D awhile, so I'm not sure I'll be able to stand the smell of gasoline long enough to do this, but I'm about to change the timing chain, rails and tensioner in my 300E, for peace of mind reasons.

I assume that the masterlink on this chain is bradded in place with the special tool just like the 240D. If so, is it the same tool as the 240D? Also, it appears that by pulling the top front of the timing chain housing, the rails etc. will be exposed. Will removing the top part of the cover allow me to change everything? Should I change the tensioner at the same time?

According to the records, the chain, and apparently only the chain, was changed on this car before. After reading some of the comments regarding rails breaking, I've decided to replace rails and chain, so I can enjoy myself while driving the car, rather than worrying about it.

Tbanks for any help anyone may offer.


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Larry Bible
'84 Euro 240D, 516K miles
'88 300E 5 Speed
Over 800,000 miles in
Mercedes automobiles

The chain can be removed after removing the top cover only, but to remove the tensioner rails, the lower front cover must also be removed. Items to be removed:

fan shroud, fan and clutch, coolant, bypass tube, plug wires, dist cap, rotor, air cleaner, valve cover, pulleys on water pump, tandem pump, crank pulley, belt, alternator, 3 bolts on tandem pump, harmonic balancer and hub (required puller rented from auto parts store), bolt on crank (really hard to remove, you can either try to fix the crank by jamming a screwdriver handle into the opening on the front of the flywheel housing into the flex plate or buy a tool from technitool, or put a big breaker bar on, brace it against the ground and hit the starter, not sure how safe the last suggestion is to you or your car, but it worked for me) tensioner (big allen head drivers- 14 and 17mm, I think), lower front cover. Make sure that you have the crank lined up to TDC before removing the damper. Another caution- don't turn the engine backwards after the tensioner is loosened, maybe not at all, because the chain will bind up at the lower guide rail and crack it.
Good luck, a manual is recommended.

How many miles Larry?

The chain is rolled in from the top, with just the top cover removed. It is crimped with the same tool but with an added fixture for the single roller chain.

Unless you know the rail to be badly worn or if you are over 200k I wouldn't worry about the lower rails The only time I've seen problems here is when someone lets the chain loose on the slack side and the rathcheting chain tentioner comes out. If this happens the tentioner must be removed, disassembled and reinstalled to its spring loaded extent. If the tentioner gets out it can make the chain so tight that the cam can break.

Does anybody know if image files can be loaded to this site? A picture is (as they say) worth a thousand words even if it takes a books worth of server space.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

We can load any files, webmaster wiill see this I am sure.

I have never had to replace the timing chain on a 103 engine. They just don't wear out. They are short and well lubtricated. Why are you doing a chain????????

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Whoa, no timing chain replacement?! I'm no tech, and this is the first time I'm hearing that this replacement is not recommended. Wow, how about some more details, Benzmac? I was planning on having mine replaced in the next little while (89 300TE, 250km) - but this changes everything. I think. Thanks, as always, for the advice everyone.

The timing chain on the 103 engine just breaks in at 200K miles...I dont think it should be a problem..we're not talking about a Acura/Honda timing belt now...

Agron
1989 300E

I had the timingchain changed on my '86 300E just for the peace of mind. I asked the mechanic for the old one to compare it with the new one. The difference was about 1/2 inch in length. The milage is about 250K on the car. It cost me $300.00 canadian including the tennsioner (aftermarket), chain and the drivebelt (both original Merc.). It may not have been necessary but I sleep better now, what can I tell you.

Alex

The advice I've had, is replace the chain if you have everything apart, as its cheap insurance...

However, dont worry about it as they dont go. And anyway, at the sort of mileage your car will have if it does go, you'll probably need a valve job anyway!!

Bri

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Brian Drought
1991 300CE
http://www.users.globalnet.co.uk/~drought/
ICQ: 2180069

Sorry Folks,

Thanks for all the great replies. Benzmac, to answer your question, I thought that I had seen a post where it was highly recommended to replace one of these chains indicating that they were bad about breaking. Maybe the message I saw pertained to a later, two cam 300E.

I won't argue, there's more than one of you telling me this chain is as rugged as an anvil.

As always, thanks for the great information. Looks like I will reclaim a Saturday that I was going to give to the car. Maybe there's a big Black Bass in my Pond that needs catching.........

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Larry Bible
'84 Euro 240D, 516K miles
'88 300E 5 Speed
Over 800,000 miles in
Mercedes automobiles

Jason,

The serpentine drivebelt system is a very maintainance free system. The inspection methods given by a number of manufacturers give a criteria of number of cracks per inch. I have never seen one of these belts brake from age (I have seen many burned-up over frozen bearings though). We have replaced belts with many segments missing from the groves. These belts will eventually trigger the A/C engine/belt speed comparitor and they usually get replaced in Florida.

The problem with the tentioner is that its efforts are dampened by a rubber hub that works on the same concept as a suspension control arm bushing. The center of the bushing is turned by the adjustment and the tentioning arm is loaded by the tention transmitted through the rubber hub. There is no need to replace unless the hub is sheared or obviously failing. Experience can detect a weak hub.

By guide rails I'm not sure what you mean. The belt is guided by the pulleys and the grooves. Another common failure point in this system is the bearing bracket. This is what the fan rides on (not the water pump as in most motors). The single bearing doesn't handle the load of the fan/fan clutch and belt system as well as the other bearings (water pump, P/S, A/C clutch, Alternator).

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by stevebfl (edited 03-17-2000).]

One bit of advice, if someone does have to replace the timing chain and rails on any Mercedes engine, only use factory parts. No aftermarket parts will do here. If one of these 'cost saving parts' fails, it will cost 5 thousand to repair. I have heard horror stories about aftermarket tensioners, and I have seen the aftermarket rails break in less than 20K miles!!!!

The v8's did break chains often, the 6's, all of them, were bullet proof...

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Jason,
The tensioner rattle/ tensioner shock that the dealer is referring to is just part the serpentine belt tensioner system, not that of the timing belt. It is an easy and cheap repair/replacement - just had it done myself.
Besides that, I too am anxious to hear the replies to your question re the rails etc., having a 300E and 300TE in the stable, and accumulating lots of kms!
Regards,
Nick