[pcmaher]

I'm looking for some "easy" ways to check timing chain stretch on my 95 S600 (140,000 miles). I do not know if the timing chain was changed on the car, and have no way of finding out. I was having trouble with my beater, a 1987 Olds wagon with a 307 V8. I suspected timing chain problems. So I removed the distributor cap, and hand-turned the crank the opposite direction while watching the distributor rotor. The rotor should rotate almost immediately if the timing chain is in good shape. On the beater, it didn't. There had to be at least 20 degrees of crank rotation before the rotor began turning. Disassembly confirmed an incredibly stretched chain and worn cam sprocket. Can this method be used on the V12? Are there any other methods I can use? I'm trying to avoid as much disassembly as possible. I'd sure appreciate a good tech's advice / opinions.

 

[JNLeChevet]

Approved MB method is by electronic diagnostic tool which detects difference between camshaft and crankshaft position. Can also be checked mechanically by removing valve covers and using two pieces of 4mm drill stock to rough check or with a dial indicator for more precision. My rough rule for the V-8 engines has been 5 degrees on the crank which I imagine would be appropriate for the V-12.

Caution: If the camshaft timing has been previously adjusted to compensate for chain wear, you will get a false (optomistic) reading.

Be safe - if the history is unknown, replace at 125K or so.

 

[Merc600sec]

Do not rotate the crank in the oposite direction on a V12, Big problems if you do...I have seen a posting dealing with that situation and the effects..Not at all pleasant..

And the V8 engine is an entierly different beast...

There is a way to do it with a twin beam scope using the flywheel sensor and the cam sensor.. and looking at the trace... however I am sure that the engine adaptive system will have compensated for any stretch you might have..So possibly the best way would be to get MBstealer to get you the printout and have a look..

 

[pcmaher]

Thanks for the responses people. I've also had the good fortune of communicating with other experts as well. Just an FYI, there aren't many people familiar with the magnificent V12. Anyway, I'm learning that it's not so much the chain one needs to worry about, but the guides and tensioner. These are the items that can go bad on you. I've been thinking about getting my hands on a borescope, and see if I can do a visual inspect down there. I don't think there's a way to gain access though. Oh well, I may just mentally prepare myself for this project over the summer. I just hate to think that this hardware might have been changed by the previous owner. I don't have any records from him, so I don't know what was done (or wasn't). I'll be sure to take lots of pics and post them if I do this.

 

[Merc600sec]

If you can find a friendly MBstealer.. he will be able to tell you if that chassis number ever had chain parts assigned to it.. here in the UK I understand that MB keep records of all the replacement parts fitted to our cars..That way they have a complete history of manufacture..That is why a MBdealership will always ask you for your vin number when ordering parts..

 

[pcmaher]

I went through a lengthy posting on another forum about my inability to obtain service records for my car. This one response pretty much sums up the situation here in the States...

I'd like to try and clear up a few myth's concerning the workings of MB dealerships. The dealer who serviced the vehicle in question is the only one who can provide the COMPLETE service history. MB dealerships are not linked by computer when it comes to service records unless it's a warranty/recall item. The printed record of all warranty/recall work performed is known as a VMI. Customer pay items don't show up on VMI's. Any dealer can pull up a VMI on an a particular vehicle regardless of where the work was done. To get a complete service history will usually require obtaining the actual service file which includes all repair orders and associated paperwork. If the vehicle was serviced at more than one dealer you'll have to visit all of them. At my dealer, if a vehicle doesn't come in for eighteen months the service history is automatcally deleted from the computer system. This system is internal to my dealer and can't be accessed by other dealers. The Privacy Act is indeed the reason for the denial of the service history. All paperwork associated with vehicle service is loaded with personal information about the client. Addresses, phone numbers, credit card information, signatures, etc, are all plain to see. You'll need written permission from the owner of record to obtain the service file. Several people posted that they've been provided with this information in the past. The Privacy Act is a relatively new thing, so what was true in '86 doesn't apply today. Another result of the privacy Act at my dealer is restricted access to the warranty department. This is where the service files are stored. I hope this clears up any misconceptions. I don't think the dealers are stonewalling anyone, they're just following the rules.