2 questions on the M116 4.2-liter V8
 

1. Can anybody give me a link to a thread on DIY timing chain and guide replacement?

2. Why does the service manual for the 420SEL tell you to pull the engine and transmission as a unit? Is it too difficult to pull the engine alone for some reason? Maybe the bell housing bolts are too hard to get to or something?

Thanks again for all your help.

retro (Bill Crowell)

Why would you pull the motor?

I have the equipment to pull the engine and I would pull both the engine and trans as a unit because in the long run, it is easier. Most people wouldn't pull the engine to do a timing chain but after seeing a lot of problems in the front of these engines, I would pull the engine and replace ALL the guides including the oil pump chain and its tensioner. But, that is just me. I have a tendency to over repair my own cars. I look at it as "do it once, and do it right."
Paul

Stevebfl, I failed to mention that, in addition to a timing chain that is overdue for replacement, I also seem to have a leak from the transmission front seal. I was just wondering if it wouldn't be easier to pull the engine alone to fix this, leaving the transmission in place.

You obviously have no point of reference for the usefullness you seek to achieve. Doing $4000 worth of work to accomplish $500 worth of value is OK if you just need a hobby. But when real value is observed you would know that what you want to do to your engine is waste and what you seek to do to your trans is insignificant. The trans will benefit little with a bandage, whereas the engine is realistically repaired from the top unless you have 350,000 miles on it.

You should take the trans apart and replace all the seals and leave the engine in the car and replace the upper rails and chain, simple job. The end result would be a much more desirable auto

stevebfl, you are right: I'm a noob who just got his first M-B about a month ago. I'm a halfway-decent mechanic, but my primary experience is with American cars, although I've done my own work on the Porsche and the Jaguar that I owned. The reason I was asking about the possible M-B engine pull is that that's how you'd fix an American car with a bad transmission front seal. You'd pull the engine and leave the tranny in place. So what is it about the 420SEL that makes it easier to pull the transmission than the engine?

Thanks.

retro

I don't know of any car that is easier to pull the engine than the trans and I have probably done just about all of them. Maybe a front wheel drive Volvo would be easier.

Thanks for the advice, stevebfl (but then again, I'm a masochist). Sorry you were having a bad hair day yesterday.

I'm strictly a home mechanic. I don't have a lift. I'm working on the floor of my garage, with the car up on jack stands, using a creeper. One of my least favorite things is pulling a transmission like that. I guess it's a lot easier if you have a lift. That's no doubt why I prefer to pull an engine rather than transmission.

My hair is bad every day as I ain't got none.

It's easy to replace the upper chain rails with the engine in place. Then you can determine just how much chain wear, or stretch, you have.

Please check my repair thread:

http://www.peachparts.com/shopforum/tech-help/185820-chain-guides-replaced.html

Thanks for the link, Warren! I'll definitely check it out. (Later edit: That's a really great thread, Warren! I really liked it. I am sure I will find it very helpful.)

I know it is advisable to do the timing chain with the engine in the car, and the only reason I was thinking of pulling it was due to the transmission leak. I was just wondering why there seems to be a general opinion that it is fairly difficult to pull the engine. Come to think of it, evacuating the A/C system is a pretty big PITA.

I am just used to working on old American cars, where it is just about as easy to pull the engine as the transmission.

I did also eventually find a link for M116 timing chain replacement on the competitor M-B site, by a different author. I will be comparing your techniques with interest. (Later edit: Both threads are good, but I like yours better, Warren, especially the pictures.)

retro (Bill Crowell)