87 420 SEL timing - Page 2 - PeachParts Mercedes-Benz Forum

lifeisabeach · #16 08-31-2006, 04:51 PM

I ordered the parts today right here on MercedesShop.com

E5004ME · #17 09-01-2006, 02:17 PM

Quote:

Originally Posted by lifeisabeach

I thought I found it here but I can't seem to locate it now.

I'm looking for a guide [w/ photos would be great] on the step by step procedure on replacing the timing chain, tensioner and guide rails on my 420SEL.

Thanks in advance

Check out this thread where Roncallo gave me thorough step by step instructions: 420SEL Timing Chain Guide Replacement

lifeisabeach · #18 09-02-2006, 08:06 AM

THANKS E5004ME for that link & Roncallo for his procedure.

It'll be about mid week before I start this repair but I can't wait

autozen · #19 09-04-2006, 04:14 PM

My advice before you get too heavy into the chain is to pull both covers, rotate the crank with a 27mm, and check the timing marks on the two cams. If they aren't right on, you've jumped timing. Also check for loose rockers on the left bank. If one is loose, just stop there.

lifeisabeach · #20 09-05-2006, 09:31 PM

Parts came today

I did get the air cleaner & cam covers off. The timing is right on but there is excessive slack in the chain due to what appears to be a bad tensioner and the inner left guide rail end broke off. The records indicate a new chain over 100k miles ago but no mention of chain rail guides or tensioner but for $727.30, in 1997 dollars I've got to assume they were all done even though they appear questionable, but.........??

I'm a bit worried that I didn't get new pins nor do I have the specific removal tool but I've successfully improvised in the past where specialty tools are
"required".

I dropped off the left cam cover today to be welded where it cracked so that it's done when I'm ready to reassemble.

It'll be a few days until I get back to it due to my schedule but maybe by the weekend.

lifeisabeach · #21 09-07-2006, 12:39 PM

I checked today when I had a few minutes and there are 2 loose rockers. The movement is very minimal but you can hear/feel movement. All the others are tight.

Remember, it started and seemed to run fine before disassembly, just a rattle w/ 200+k miles.

What do you think?

david s poole · #22 09-07-2006, 01:48 PM

minimal movement on two rockers shouldn't be a problem.when you have bent valves you can almost lift the rocker out of there.

Tomguy · #23 09-07-2006, 02:03 PM

You said it hasn't jumped time. The "Tapping" sound is likely the chain wailing off of the end of the broken rail(s) and/or the tensioner whacking the chain to keep it tight. If it hasn't jumped time, chances are 95% your valves will still be straight. Pop the new chain and rails in, for $200 and a few hours labor what do you have to lose? I'm sure if it's more severe someone will still be willing to purchase that 420 for more than you put into it.

lifeisabeach · #24 09-07-2006, 06:45 PM

The 2 rockers are just barely loose, probably just wear due to 200+ k miles and I may have to get in there at a later date. I'd like to get it running safely so I can check out more things before dumping more $ in it. I just got a bit concerned after AUTOZEN posted that "if there is a loose rocker, stop there" info, and I hadn't checked.

As from the beginning, since it runs so well I can't believe there are any bent valves [I don't know of any that even ran at all afterwards]. The tensioner is junk, no tension whatsoever. The left inner rail tip is broke off and the outer one broke as I turned the engine over by hand. They got pounded pretty good with that chain slapping around.

Yep, only $205 in parts and a few hours labor but I don't like wasting my time so I wanted to be sure the 2 rockers with a little looseness didn't mean bent valves. I was 99.9% sure the minimal looseness was only due to wear but I had to ask

I'll let you guys know the results after I get everything replaced and all buttoned back up this weekend.

autozen · #25 09-07-2006, 10:56 PM

Slightly bent valves is like being slightly pregnant. You have hydraulic lifters which means they are preloaded. You should not be able to move them at all. When you said the timing marks lined up, you were not specific that the crank was on TDC and the marks in the slots on BOTH cam washers lined up with the marks on the cam towers. With a broken inner rail and a distorted cam cover, you have to have bent valves. I'm not going to suggest a compression check at this point, because if you have escaped bent valves, rotating the engine at starter speed may finish the job, and I don't want to be responsible. If the marks all do line up, roll in a new chain and then do a compression check. You will need to remove the PS pump to change rails on the left bank. I believe you mentioned a failed tensioner. I guess that is possible, but that would be an anomoly on this engine. If you had an early 4.5 or 3.5 I'd say a failed tensioner is very possible. I changed many at the dealership in the early years. They would bleed down and cause the chain to really rattle during start up. I've never experienced a failure on a 3.8, 4.2, or 5.6.

lifeisabeach · #26 09-08-2006, 09:13 AM

I really appreciate your input AUTOZEN but why the doom and gloom?

I did exactly what I knew to do just as you previously outlined as far as checking timing and it's dead on. I didn't see the need to reconfirm the procedure, just the results. Could it have jumped around, yes, but I don't think so.

As others have suggested, it is very possible to have escaped valve damage.

This car would not run as well with bent valves, to any degree [and I've never seen/heard of anything other than severely crunched]. I don't know the history on this car as far as how it sounded or any noises other than my brief start up so maybe a couple of the lifters are showing their age allowing some play. I really have to grasp those rockers to get movement, it would have been easily overlooked by just touching them, definately not obvious.

The tensioner is a replacement Febi and has little to no tension.

I wouldn't do this any other way than to do all the upper rails, chain and tensioner before any tests.

I will post results, regardless.

autozen · #27 09-08-2006, 11:24 AM

I'm sorry. I don't mean to spread doom and gloom, and my real intention is to help you. I just have alot of experience with these engines. A couple of years ago a guy called me from Sacramento. He said he heard a noise and his 420SEL stopped. I told him he had bent valves which he did. I bought a 420SEL in San Francisco awhile ago. The guy was pulling away from a stop light when it quit. The valves were bent. I bought another 420SEL from a guy who said he was pullig out of his driveway when the car stalled. Tha valves were bent. I have a 380SEC sitting on my car trailer. The lady was hauling butt across a bridge when she lost power. When I pulled the head I discovered the valves were'nt bent. Because of the high speed the heads were snapped off of 4 valves. I can go on and on. My point is that if you didn't bend a valve, you are one of the luckiest SOBs on the planet. I think if you follow my steps in the earlier post, you will reduce the risk of bending a valve if they are all still good. Good luck and don't hesitate to ask for advice. I could explain exactly what goes wrong with these engines and why, but the topic has been well covered in earlier threads.

Tomguy · #28 09-08-2006, 12:00 PM

Quote:

Originally Posted by autozen

My point is that if you didn't bend a valve, you are one of the luckiest SOBs on the planet.

I definetly agree with this. No question whatsoever, you are VERY lucky. However, I also believe there is no question you DONT have bent valves. Your engine didn't stop at any point, it didn't lose power. It clacks loudly from where your chain is not riding right. Put the new chain and rails and tensioner on it, and drive it for years to come!