Hello, fellow MB enthusiasts....How do you change the oil pump chain on the m116 4.2L aluminum engine? Specifically, the 1988 420 sel. Does the front cover (timing chain cover ) have to come off? Do the heads have to come off to get that timing chain front cover off? Thanks.

 

There is a way to replace the chain without removal of the timing cover, but you will only be able to change the top rails/guides for the chain. You would remove the valve covers, exposing the cams and the chain.

 

BENZITCH...he is asking about the oil pump chain, not the timing chain.

Do D Do ... Remove oil pan. Remove oil pump and sprocket.

Lift chain off top sprocket, install new chain and pump, reassemble.

Its pretty easy. If you can properly change spark plugs, you can do it.

 

Excellent info...thank you so much...Good to know this is an easy job and I am glad that I don't have to pull the heads... I would have had to get many more parts and at that point it gets expensive... Benzitch, I will use your method soon for we will be doing the upper timing guide rails and timing chain at the same time so it would have been a good excuse to change the lower t/c guides but I am not ready to do the cylinder heads yet.....and I would rather not get into the fiasco of all that rubber on the intake manifold that is likely brittle. I think the heads do have to come off to get the timing cover off the front of the engine
So as far as the oil pump chain goes, all I should need for that job is the oil pump chain and a lower sump pan gasket? Is there anything else that I could do as prev. maintenance while I have that oil pan off? Thanks again.

 

What caused you to be looking at replacement the oil pump chain?

 

I think I read about doing the oil pump chain on another forum. I have noticed since driving this one... the oil pressure guage does some funny things, including staying on zero. It has done it twice to me. The first time it did it was 2 days following when the used replacement motor was put into it. I shut it down as soon as I noticed...waited a few minutes and restarted it and it was fine. It just did it again last week, and I thumped the dash and it came back. I am thinking it is an electrical issue with the guages now.... but I had already purchased the oil pump chain by the time I figured the electrical. It was cheap $16.00 and I need to remove the oil pan to pound out some dents and give it a coat of paint. I think I read that someone had a dented oil pan and found the pickup rubber to be broken so I would like to check that out, I have another used oil pump from an engine that had the timing chain skip. I have also observed the guage to go as low as 1.5 bar on the guage when hot, but it also fluctuates bit ....which also could be electrical.

I will post what I find in the oil pan.

I will do this at the same time I do the timing chain and 3 top guides and tensioner + new metal guide rail (bigger one ).
I got a metal guide rail with a neoprene lining from Swag for resting against the tensioner itself and 3 smaller whiteish plastic guides for the top of the cylinder heads (Swag). Are there metal guides availible for the top of the cylinder heads (3 smaller whitish ones) or was it just the metal variation for against the tensioner (the bigger one)??

Is there anything else I would need for the timing chain job or should I start a new thread to ask. Can the retaining pins for the guides be re-used? How can you get those out....there is not much room on the front for a slide hammer. I should have done this when the engine was out but did not know how the engine and tranny would be. I believe the engine has about 250,000kms so it is probably overdue for a timing chain before it skips.

I had two other cars identical... one with a cracked left valve cover.... and the other which I got this motor from... for the car we are driving now. The body and interior for the one we are driving is minty, but would like to freshen the motor before something bad happens. The engine this running one replaces also had the timing chain skip.

So in total I have 3 of these with 1 good motor..now in the nicest body
The one car had the timing chain skip at 210,000kms and the other at 285,000kms. The good one already has 250,00kms on it... right in the middle, so I feel like we are driving on borrowed time everyday it leaves. Not a nice feeling considering the time it took to put this motor/tranny in.

Thanks for the help.

 

It sounds like you have the correct parts. The tensioner rail is aluminum and has a plastic guide attached to it. The other guides you will be replacing are plastic. Metal guides are used in the older engine, I forget the engine# but its the 450. You do not have to pull the manifold or heads to do this job or timing case removal for lower guides, which I am finishing up now on mine. I pulled my timing case and the lower guides were awful at 85,000 miles/29 years.

You will need a pin puller. Do not use a slide hammer. Make one or buy one. Mercedes source daught calm has them. Replace the oiler clips and clean out the tubes that oil the cams. Get valve cover gaskets and new washers. Might as well get a new tensioner also.

If I were you I would start a new thread. There are guys here like BENZITCH and many others who can help better than myself. I hope it goes well for you and way to go for getting in there and giving it a shot.