I was reading that every 15,000 miles that Valve Clearances on Diesels in the W123 Chassis need to be checked and adjusted if necessary. Is this complicated?

It is not complicated. I would recommend getting a manual like Haynes or the MB manual on CD to get the correct clearance specifications for the intake and exhaust valves. I would also recommend getting the special wrenches specific to adjusting valves and a good set of feeler guages. The procedure is to do one valve at a time at a certain sequence because you want to check the clearances when the cam lobes are at their lowest position where you can take a reading with feeler guages. The procedure is very easy. I did mine for the first time when I bought my car last August.

Joe,

You didn't indicate what model car you have. If you have a four cylinder it is much quicker and easier. The stretched five cylinder has a valve at the back that is difficult because of it's proximity with the firewall.

But, overall, the job is not that difficult, or complex. Although you can accomplish this without the special wrenches, the wrench set would probably cut the time needed, in half.

If you are driving mostly road miles, I think you'll find that 15,000 miles is not necessary.

Good luck,

I do mine twice yearly, regardless of mileage. For winter, I set both the exhaust and intake valves an additional 5: intake from 10 to 15; exhaust from 30 to 35. Return to book for summer Helps compensate for the gradual wear on my engine with 170k miles. Be sure your timing chain and tensioner are in good condition. How may miles on your engine since they were last replaced? Doug.

Douglas,

You did not mention what engine you have, but as I recall, the non-turbo engines are .003" and .012".

Have a nice weekend,

Miles on Engine
 

Douglas,

My engine has exactly 155,000 miles and is a 5 cylinder turbo-diesel. The valves may have been adjusted by the dealer when the car was taken in for scheduled maintenance, however, I am not positive. I thought I better do just to make sure. I doubt the timing chain has ever been replaced. What mileage should the timing chain be changed?

Joe

Joe,

If the car has had frequent oil changes there may very well be no wear on the timing chain. There is a procedure for checking the chain for stretch. You will need the MB procedure and a dial indicator to perform the operation. If the chain has not stretched, you will probably be okay.

If, however, you are one for wearing a belt AND suspenders, you can roll in a new chain without too much trouble. You will need the crimping tool for this operation.

Good luck,

According to MB factory manual valve clearance is as follows:
Turbo diesels;intake; 0.10mm Exhaust;0.35mm
Non-Turbo diesels;Intake; 0.10mm Exhaust;0.30mm
Valves are adjusted with the engine cold.
To convert metric dimensions to inches, divide metric dimension by 25.4 Hope this helps.
Bill Lewallen Lexington,Ky.

When I rerplaced the timing chain and tensioner, I was amazed how much better the motor sounded. The effects of chain stretch are gradual and insidious on diesels, so one doesn't notice them. Also, when a chain breaks in a diesel, the results are generally catastrophic--read, expensive. If you haven't had the car since new, you have no clue as to how frequently the oil has been changed. Frequent oil changes are the best defense agains chain stretch and wear. Therefore, I suggest you change the chain and tensioner. But, as others have pointed out, you must have access to rent or borrow the special crimping tool. Don't rry the job without the tool; when you use the tool, you will comprehend why I say this. My parts supplier has one that she loans to DYI people like me.

IMHO Douglas is being correct in being cautious, however, if you check the chain for stretch and there is none, you will be no better off by replacing the chain.

Replacing the chain would cause no harm, but replacing the tensioner itself unless there is a problem with it, will probably gain nothing.

Good luck,