Mercedes-Benz Forum banner

1 - 20 of 75 Posts

·
Outstanding Contributor
450slc5.0cab 280sl5sp 280se4.5 500se+500slAMG +250seStkW108 350sl4spdX3 500secEuro
Joined
·
22,562 Posts
Discussion Starter #1 (Edited)
I have seen pictures of failing timing chain guides, but I think mostly the straight ones, and most often a little broken bit here or there. I have also seen pictures of heads ground through by the timing chain with a weak tensioner, and even a valve cover that the timing chain busted through. Based on all this, I have started to believe that the biggest risk of broken tensioners are:
- bits of the tensioner clogging the oil sump
- bits of the tensioner causin some type of interference
- the resulting smaller tensioner allowing greater slack in the timing chain

I know these are very important, but posts like this one seem like they are just intended to instill fear in anyone looking to buy a plastic guide 107.

So let's have a real discussion with maybe some real world examples.

Thanks!
 

·
Registered
1974 450sl, 1986 190e, 97 sl320 40th sold
Joined
·
506 Posts
I know i wished i had of researched before i just bought my 107. All the threads on it have scared me into doing it and I wish i hadn't bought it now lol mines got 115k on the clock and im gonna do the timing job but it looks like a pain in the arse, not to mention costly. I know with my luck i'll have a b!tch of a time getting those guide pins out too. I plan on doing it the half @ss way (top gears, guides, chain) and to do it right you need to pull the motor.. wtf ! I can only imagine what this job would cost to do at a shop !
 

·
Premium Member
1983 380SL, 2000 S430, 1991 420SEL (retired) - RHD
Joined
·
5,520 Posts
I've had both cars "blow" without any warning clatter. The 107 (3.8)at 65,000 miles -14yo and the 126 (4.2) at about 120,000m -12yo. I don't know what actually caused them to go but in both cases a valve went through the valve cover cover- front cylinder on the left (US driver) side. In each case 2 valves were bent.
In the 126 I had been asking my mechanic about changing everything but he said "no clatter no worries" yeah right! I also changed my mechanic.
All I can say is don't wait for warnings- replace them at age and/or mileage.
 

·
Registered
1974 450sl, 1986 190e, 97 sl320 40th sold
Joined
·
506 Posts
Not trying to hijack your thread but i just looked up prices, $189 including shipping for 2 new cam gears, new chain, three guides and the tensioner guide. Sounds fair right ? also do you recommend replacing the tensioner as well ? thanks
 

·
Outstanding Contributor
450slc5.0cab 280sl5sp 280se4.5 500se+500slAMG +250seStkW108 350sl4spdX3 500secEuro
Joined
·
22,562 Posts
Discussion Starter #5 (Edited)
In my opinion the tensioner is the most important of all. I am more asking about the guides than anything else.

I guess if the guides are gone, then the tensioner is more likely to max-out and become ineffective. Is that the logic? Or might we assume that a broken guide bit will quite often fall between the chain and one of the chain sprockets taking it off the gear?

I don't dispute that we need to replace these guides. I just wonder what is the most likely thing to happen when they do break.

I still maintain my position that you replace the tensioner quite frequently. Tensioner springs get weak, and dirty oil (looks to me like it) can easily clog a tensioner. In my opinion, it is the most complicated and sensitive component that is replaced in a timing chain job, and I can't help but wonder why it isn't recommended to be replaced more frequently than the other components that are much more difficult to replace. Seriously, the tensioner is just two bolts on the side I the engine. Also, if the chain is slack, it is more likely to slap around and cause a guide to break. Don't you think?
 

·
R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
Joined
·
32,345 Posts

·
Premium Member
1983 380SL, 2000 S430, 1991 420SEL (retired) - RHD
Joined
·
5,520 Posts
No tension equals chain slap. I just replaced the tensioner , chain and guides but it was the new tensioner that made the big difference to the looseness of the chain. Replacing the tensioner is easy.
 

·
R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
Joined
·
32,345 Posts
No tension equals chain slap. I just replaced the tensioner , chain and guides but it was the new tensioner that made the big difference to the looseness of the chain. Replacing the tensioner is easy.
I agree. It was most likely the cause of the chain slapping the head in both my '72 and '73 4.5. When I rebuilt the '73 the new tensioner was noticeably stiffer than both the '72 and '73 used ones.
 

·
Registered
1984 380 SL
Joined
·
246 Posts
In my opinion the tensioner is the most important of all. I am more asking about the guides than anything else.
.....
I still maintain my position that you replace the tensioner quite frequently. Tensioner springs get weak, and dirty oil (looks to me like it) can easily clog a tensioner. In my opinion, it is the most complicated and sensitive component that is replaced in a timing chain job, and I can't help but wonder why it isn't recommended to be replaced more frequently than the other components that are much more difficult to replace. Seriously, the tensioner is just two bolts on the side I the engine. Also, if the chain is slack, it is more likely to slap around and cause a guide to break. Don't you think?
I am so completely not car familiar but these posts have made me nervous. Since the odo in my car has been replaced at least 3 times (me doing the 3rd) I'm guessing my miles to be up in the danger zone. Can someone please post a pic of the tensioner so that I can locate it and what? pull on it to see if it's really loose? I would like to appear somewhat knowledgeable if I pull this into a garage for repair so that I don't get hustled for more work than necessary. I think I have an honest repair shop, but....
 

·
Registered
1984 380SL
Joined
·
2,328 Posts
Fonzi, you re working yourself toward the position taken by a very experienced Mercedes mechanic I know, Jacobs Automotive, East Syracuse NY 13057.

He said if your guides are good you're fine. A little looseness at startup will be held in check if the guides are good, and then you can work on the tensioner -- the easy part. Obviously the uppers are critical.
 

·
Registered
1988 560SL (California Model)
Joined
·
5,104 Posts
I still maintain my position that you replace the tensioner quite frequently.
Aftermarket probably...OEM I would disagree. General opinion is to change all in the 90,000 to 100,000 mile range. Why not buy quality once and be done with it. The vast majority of us (guessing here) do not use our cars as a daily driver. I changed my original (OEM) tensioner at 100,000 miles. I drive it on average 4-5 thousand miles a year. Do the math. I am sure that in 25 years I will be more concerned about changing my "Depends" than the tensioner.
 

·
It Is What It Is, Dude
Joined
·
22,841 Posts
I am so completely not car familiar but these posts have made me nervous. Since the odo in my car has been replaced at least 3 times (me doing the 3rd) I'm guessing my miles to be up in the danger zone. Can someone please post a pic of the tensioner so that I can locate it and what? pull on it to see if it's really loose? I would like to appear somewhat knowledgeable if I pull this into a garage for repair so that I don't get hustled for more work than necessary. I think I have an honest repair shop, but....

Do the chain stretch check as outlined in section 5 of the EGv107. If the chain is stretched tensioner condition becomes more critical.

The dreaded start up rattle IMO is more related to some amount of chain stretch compounded by tensioner leak down that can lead to a guide rail breakage.

Damage such as what Dig experienced with the broken out cam cover is indicative of a broken guide rail getting grabbed by the TOP side of the chain and hitting the cover. Had that bit of guide rail been under the chain, and then traveled between the chain and sprocket a more catastrophic failure more on the order of what Aussiemerc desribes would likely have occurred. As it was Dig had no progressive damage.



 

·
Registered
1981 380SL
Joined
·
256 Posts
This is one of those "German Engineering" items that just gets my goat. What's the point of a SOHC V-8 as compared to a pushrod V-8? Why, less valvetrain mass to enable more RPM and therefore more power, right?

If so, why is the redline on my 380SL so much lower than the redline on my 1966 Plymouth Sport Fury with 383? Which one makes more power (a LOT more)? Which one runs smoother? Which one is more reliable? Which engine has smaller exterior dimensions?

So, given how plain lousy the Mercedes V-8 is, why did they do it? Personally, I think it was marketing. When competing in the price range that the car lived in, you had to be able to say that you had exotic overhead camshafts. And now we all get to live with them.

Rant off.
 

·
R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
Joined
·
32,345 Posts
This is the most redundant thread ever posted IMO. The subject has been covered.

The question has been answered over and over and over and over,,,,ad nauseum
 

·
One of the BW Old Guard/R129, W204 Moderator
1997 SL500- 40th Anniversary
Joined
·
7,166 Posts
This is the most redundant thread ever posted IMO. The subject has been covered.

The question has been answered over and over and over and over,,,,ad nauseum
AMEN!
What happens is simple... your wallet gets thinner by several thousand dollars!
 

·
Outstanding Contributor
450slc5.0cab 280sl5sp 280se4.5 500se+500slAMG +250seStkW108 350sl4spdX3 500secEuro
Joined
·
22,562 Posts
Discussion Starter #16
This is the most redundant thread ever posted IMO. The subject has been covered.

The question has been answered over and over and over and over,,,,ad nauseum
Oops. :) Sorry there. It's still fun for the dummies. I'm sure that you know I don't go digging very often. The explanation on DigMeNow's valve cover was new information to me. Thanks Dave! I was thinking the chain was way off the sprocket, but Dave's explanation make much more sense.... I think.
 

·
R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
Joined
·
32,345 Posts
no problemo. always good to bring it to the top for noobs
 

·
Registered
560SL
Joined
·
66 Posts
Hi - with all due respect, even if we all ultimately agree on this issue, I think this is an important topic to discuss. On this forum, there's a consensus that timing guides, chain, tensioner etc. should be changed every 8-10 years due to the guides in particular getting old and brittle. I find that convincing.

Offline, my experience has been that there's no such consensus. I've spoken to experienced mechanics who've told me that, on the double-chained SLs, you shouldn't worry about it unless there's unusual noises. I've had another Mercedes mechanic tell me to get the rest of my 160K mile car in mechanically good condition before dealing with timing chain. These are guys who make their living working with their cars and in whose economic interest it would be to recommend getting this work done, so it feels weird to dismiss their perspective.

It's hard to argue that at a minimum the timing chain stretch and condition of guides should be at least evaluated, and if you can afford it, you should get the work done.

Still I have some questions. Has anyone had experience of the 560SL having timing guides break? What mileage did it occur? Were there any symptoms?

Also, does an old set of timing chain guides, tensioner etc. impact engine performance? Does the car drive different in any way? Or is the only real symptom the slap and/or engine failure?
 

·
It Is What It Is, Dude
Joined
·
22,841 Posts
Still I have some questions. Has anyone had experience of the 560SL having timing guides break? What mileage did it occur? Were there any symptoms?

Also, does an old set of timing chain guides, tensioner etc. impact engine performance? Does the car drive different in any way? Or is the only real symptom the slap and/or engine failure?


The only difference between the timing components in an '89 560SL and a '74 450SL is twenty five years. They both use the same exact parts.

The timing chain stretch and cam sprocket tooth wear result in each camshafts' timing being retarded in relation to the crankshaft's top dead center. The right side will be more retarded than the left. This does cause a loss of performance, but as it occurs slowly over time it likely would not be noticed.

As you mentioned, periodic inspections are the best insurance against catastrophic failure.
 
1 - 20 of 75 Posts
Top