616 timing chain R&R ... new ideas? - PeachParts Mercedes-Benz Forum

samboyellowsub · #1 02-09-2010, 11:47 PM

I read removing GPs will ease the process of timing chain replacement because you're eliminating compression. What about taking out the rocker arm assemblies also? It seems that taking the load off the cam shaft would make turning the crank super easy. especially since it might be my GF giving me a hand to keep tension on the chain(s) while I roll in the new one. I'm just worried that one of the valve springs could pop the shaft backward and the chain would jump teeth

.

One other thought I had was to make a guide like some have made. I have access to all the .80" aluminum I want at work. Would this be strong enough if it was riveted on the seamed side, or should I just take off the rocker arms for better chances?

I've also read about cranking the engine over slowly before starting so the new chain can soak in some oil first. Out of curiosity, has anyone tried soaking it the night before installing new one?
Thanks.

jt20 · #2 02-09-2010, 11:50 PM

Taking the rockers off will help... but taking the vacuum pump off is even more critical

...that is, IF you are concerned about jumping teeth / unexpected forces

jt20 · #3 02-09-2010, 11:52 PM

I would not soak the chain... it is going to 'break in' to 2 degrees regardless.

All it will do is make it very difficult to hold during installation.

samboyellowsub · #4 02-09-2010, 11:57 PM

Quote:

Originally Posted by jt20

All it will do is make it very difficult to hold during installation.

thats exactly why i wasn't going to do that regardless of whatever anyone said, I was just curious

oh and thanks for the vacuum pump tip. that slipped my mind!

layback40 · #5 02-09-2010, 11:59 PM

X2 with jt20 !!
Vac pump out is a good idea. I once opened the old chain, attached the new one to it, turned the motor over so the new chain followed the old one around, when the new chain was all the way around, disconnected it from the old one & joint it together, then checked the timing, all was good. Made it very easy.

You better have something special for your GF if she is helping you!!!!

samboyellowsub · #6 02-10-2010, 12:03 AM

sounds good. easy is what I want when I'm trying to maintain the timing! even if it takes longer to get to that step.
whats a good link or tutorial on checking the timing by the way? is the method of measuring the stretch kind of a good way to do it (make sure its 1-2 degrees from zero?)
thanks

layback40 · #7 02-10-2010, 12:06 AM

in a word, yes!! you probably will have 0 degrees of stretch or even - .5 degrees.
Good luck!!!
Best to be prepared for the possibility of the IP getting out of time if you mess up.

samboyellowsub · #8 02-10-2010, 12:18 AM

oh yes, that thing. With the vac pump off, the GPs out, and the rockers off, thats another thing that could add some stress. is there a particular way to hold the chain to make sure that the IP pump drive gear's teeth stay firmly on the chain. that is the last thing i need to go out of time. I'm going to read up on it. know of any good tutorials (maybe with pictures)?

Edit: also, how would I know if an offset woodruff has been installed? and would it be a problem leaving it in there if it was only a 1 or 2 degree one? (my assumption is no)

jt20 · #9 02-10-2010, 12:31 AM

keen foresight.

The IP will not pose a resistance worth your concern at this speed and level of control.

If there is an offset key, you will know by lining up the timing markers on the camshaft and crankshaft (as you mentioned). If it is about 2* or less you can leave the key in there.

Ken300D · #10 02-10-2010, 12:34 AM

I did a timing chain replacement by myself using plastic tie straps. You go through a lot of tie straps, but both sides of the chain (new going in and old coming out) are firmly strapped to the cam gear at all times. Going slow is part of the equation when using this method.

Ken300D

samboyellowsub · #11 02-10-2010, 12:42 AM

Ah, one more thing I was going to do... change the oil before I replace the chain! It'll be bout time anyway. best not subject it to dirty oil on the chain's first day on the job! I'm sure a lot of you do that anyway but maybe this could be a fresh idea for one or two people and if so, its not a wasted post!

thanks for all the tips

barry123400 · #12 02-10-2010, 10:17 AM

Have you verified the current stretch on the old chain indicates the need? Many of the cars we buy have already had at least one chain change. We have no way usually of knowing that without records. Other than correctly checking the existing stretch.

If you are going to change the chain make sure you do not use one certain brand as it is inferior to others. You can research for the name ofthat brand or a member might post the name of the poor replacement chain from memory.

If by some chance you do pull the rockers on the valvetrain. Make sure you number them. They must all go back to the exact same place they were removed from. You probably knew that but just in case. Each rocker developes it's own individual wear profile with time.

Also important that you check the condition of the chain slider. Many times a new chain is rolled in with without it done. This slider can become the cause of a chain failure if in bad condition down the road.

leathermang · #13 02-10-2010, 11:44 AM

Since I actually own most of the paper manuals for the things being discussed... in this case the 615, 616,617 NA manual.... I am going to go look at it... with regards to the vacuum pump removal.

My initial impression is that there is no way I would take the valve train apart...what advantage is that supposed to provide ?

What really counts is KEEPING TENSION ON THE CHAIN DURING THE CHANGE OVER.
There is also a special tool which clamps above the cam sprocket to KEEP THE CHAIN in CONTACT with it during this procedure... the combination of those two things should make for good results...

I highly recommend reading the 616 manual due to the warnings which are presented no where else... even the Haynes manual does not present all the needed warnings which are in the FSM.

It is important in our engines with regards to chains to replace all the things IN CONTACT with the chains... rails, and that sort of things

jt20 · #14 02-10-2010, 11:51 AM

G,

There is no mention of removing any parts for installing a new chain. (maybe the tensioner spring)

It is, of course, unnecessary to remove any parts from the engine... however, in the OP's situation, without the recommended tools, and without having done the procedure before.... it is quite valid to facilitate the process by removing components that posit an obstacle to the smooth, consistent turning of the crank in unison with the camshaft.

samboyellowsub · #15 02-10-2010, 02:10 PM

Quote:

Originally Posted by barry123400

Have you verified the current stretch on the old chain indicates the need? Many of the cars we buy have already had at least one chain change. We have no way usually of knowing that without records. Other than correctly checking the existing stretch.

and by the same token, I don't know how many times the stretch has been corrected. I am going to measure it out of curiosity but I'm definitely going to replace it with the Iwis brand chain which is the good brand that you were thinking of. The bad brands are just about every other brand!

Quote:

Originally Posted by barry123400

If by some chance you do pull the rockers on the valvecrain. Make sure you number them. They must all go back to the exact same place they were removed from. You probably knew that but just in case. Each rocker develops it's own individual wear profile with time.

I have to replace the valve stem seals anyway, so I was thinking I'd pull the rockers anyway. I'm going to make sure I'm prepared with an empty egg carton to keep everything in its right place. Good point, thanks.

Quote:

Originally Posted by barry123400

Also important that you check the condition of the chain slider. Many times a new chain is rolled in with without it done. This slider can become the cause of a chain failure if in bad condition down the road.

What am I looking for on the slider? Scratch marks? What wear is normal. I haven't gotten ahold of the FSM so I'm a little in the dark about some things.