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Discussion Starter #1
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I'm asking this here, because I think there are more "nuts+bolts" familiar wrenches here than there are on the 107 board - but the following is a problem common to both types of cars.

When I purchased my 380SL at 95K miles, it made a terrible valvetrain noise and I purchased the car with repairing this priced in. As I thought, the rearmost lobe on the RH side was eaten, and the cam follower was severely grooved. This might have had something to do with the oiling tube so loose as to be easy to actually lift off of the cam towers.

I replaced the cam with a new aftermarket cam, and all new rockers. The oiling tubes were cleaned to surgical standards and fitted with new plastic fittings. Naturally, I used break-in lube. To be on the safe side I also replaced the hydraulic compensator for that valve with a new one. The shim looked a bit "polished", but still OK.

Before I owned it, this was obviously not an example of a "well-maintained" engine. When I change the oil every 3K miles (religiously), the oil looks old and the car may burn 1 quart every 1-1.5K miles, not great, but not unreasonable at 130K miles. There is some blow-by. My 560SL leaks, not burns, and at 3K oil changes (on a 108K engine), the oil looks almost as good as when it went in.

Anyway, all seemed well on the 380SL.for 25K miles, although there were a few surprises along the way - but nothing from the RH head. Until now. I took the RH side apart, and basically, the same thing happened again, although I obviously caught it much sooner. The cam looks only a little "gouged" on the lobe tip, and the follower is not nearly as bad (but still completely unacceptable) as the last time I did this.

I really don't want to replace the cam again. I actually would be willing to do it if I found a good used one cheap(if possible) but I would worry about pushing my luck with the cam tower bolts, which are of course really head bolts. Even if I had limitless time and money, you can do this only so many times.

I have, however, cleaned the oil tube (I do NOT think it is plugged), put new fittings on, and replaced the cam follower and put in a good used hydraulic compensator (all assembly lubed). I have the "normal" old shim (which measures OK) and next biggest shim size shims that I can install. I've installed the "normal" one and I don't hear any undue noise...uhhh...yet.

Questions:

1. Why does this always seem to happen on the 116? On the RH, and on the last cam lobe???
2. What are the ramifications of putting on the thicker shim? (4.75 to 5.1mm). Any guesses on how long this will last? 10 miles? 100? 1000? 10000? 100000? (ha ha).

Thanks
 

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1982 380SE AMG euro(parted out),1983 300SD "Good Girl", 1984 500SEL AMG euro "Bad Girl"
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3,256 Posts
It does seem to be te right side cams that take the brunt on these engines, both m116/m117. Have you tried to see what the run out is on that valve stem? Take the springs off and put a wire tie on the stem, relieve pressure on the cylinder and give it a twist with a dial gauge there to see what it tells you.
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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I would rather install a good used OEM cam (with all the towers and lifters in the same positions), than a new after market. But that's perhaps just me.

The right cam on the NA cars going bad seems to be more frequent.
Could it have to do with NA cars not having separate down pipes for each Cyl bank?
I know it's the case in the NA M117 500 / 560 cars, where the pass side header goes into a pipe to curve behind the engine, to join with the drivers side manifold into one single down pipe.

That can't be good for the R bank breathing.
 

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1985 380SE; 1984 500SEC
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The right cam on the NA cars going bad seems to be more frequent.
Could it have to do with NA cars not having separate down pipes for each Cyl bank?
I know it's the case in the NA M117 500 / 560 cars, where the pass side header goes into a pipe to curve behind the engine, to join with the drivers side manifold into one single down pipe.

That can't be good for the R bank breathing.
Er, shouldn't that be the other way around? It is the left (driver's) side header that makes the 90-degree bend into the cross-pipe. The right (passenger) side exhaust should be the freer-flowing of the two. So I'm not sure we can run with that hypothesis.

I remember Jonathan posting a long time ago that the right side is prone to oil starvation during (hard) cornering. It is critical to maintain the correct oil level. If the engine is burning oil (most likely attributable largely to valve stem seals at that mileage) and the level is not periodically topped-off between changes, there might be a greater risk of starvation. But knowing how thorough you are with your cars, strife2, I doubt that's the issue.
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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Er, shouldn't that be the other way around? It is the left (driver's) side header that makes the 90-degree bend into the cross-pipe. The right (passenger) side exhaust should be the freer-flowing of the two. So I'm not sure we can run with that hypothesis.

I remember Jonathan posting a long time ago that the right side is prone to oil starvation during (hard) cornering. It is critical to maintain the correct oil level. If the engine is burning oil (most likely attributable largely to valve stem seals at that mileage) and the level is not periodically topped-off between changes, there might be a greater risk of starvation. But knowing how thorough you are with your cars, strife2, I doubt that's the issue.
I definitely don't have Jonathans expertise when it comes to our cars.
Not sure about the SL, but on my NA SEC I had this weird header / exhaust routing before installing Euro logs with down pipes on both sides of the engine.
Cheers
 

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1985 380SE; 1984 500SEC
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Teutone:

I should have put my brain in gear before replying as above. While what I said about manifold routing does apply to 126 cars, I keep forgetting that strife2 is talking about his SL. According to the exhaust schematics on timevalve's website, there are two separate downpipes for the 380SL, one from each bank. That suggests there is no cross-pipe and, therefore, reasonably good flow from each side. Perhaps strife2 can confirm. Sorry for the misunderstanding.
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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The heat here is turning my brain to mush.
Could be a contributing factor? After a timing chain / OEM tensioner / all front guides + new distributor worm gear with sprocket install, Jerry (R.I.P.) also did the bottom oil pump chain + guides, + rebuild pump.
After dropping the upper oil pan, we were surprised about the amount of debris around the screen for the oil pump intake.
It might be a good idea to clean that area, but the upper pan gasket should be replaced with new.
Cheers
 

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Discussion Starter #9
The heat here is turning my brain to mush.
Could be a contributing factor? After a timing chain / OEM tensioner / all front guides + new distributor worm gear with sprocket install, Jerry (R.I.P.) also did the bottom oil pump chain + guides, + rebuild pump.
After dropping the upper oil pan, we were surprised about the amount of debris around the screen for the oil pump intake.
It might be a good idea to clean that area, but the upper pan gasket should be replaced with new.
Cheers
This is a worry - I had a broken guide in this car and did not recover all the pieces - but on my car, "dropping the oil pan" involves subframe off or engine out. Maybe I can cut a "window" in the pan with a jigsaw and put a plate over it afterwards...:) yeah, riiight...

The oil pressure looks good - but is that really indicative of the volume?
 

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Discussion Starter #10 (Edited)
Well, as an update, the replacement of the cam follower resulted in the beginnings of another gouged-out cam follower in about 100 miles. Obviously, the (gouged) cam tip won't allow a decent oil film to form, so the cam is toast (as is another follower). So, the lesson to be learned is a _gouged_, worn lobe tip mean the cam simply has to be replaced.

I'm debating what to do, although it may be worth a shot to put in a good used cam. I'm getting very good at this part. Beyond that, I'm thinking about parking it for now.

AzimuthAviation: your mailbox is full, but if you read this,
is the cam/etc a RH cam for US 116 82-85 engines? What would you want for it? If you read my sad story, the new cam follower was flattened and gouged within 100 miles by the flattened, gouged cam tip. Obviously, the cam tip didn't allow an oil film to form. And I used assembly lube, and "broke it in", too. :( But I knew that this was a $20 gamble. Please PM me.
 

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CH4S Admin , Outstanding Contributor
1985 500SEC, 1991 190E 2.6.
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In another cam discussion here an expert pointed out that a re grind doesn't really work, as the lobes have a thin layer of treated / hardened surface.
As you well know, once that's gone, the lobes wear down quickly.

I forgot which cams were the same, the 450 to the 500, 380/420, and the 500/560?
Should be easy to find out with google, or the MBUSA EPC.
Any wrecking yards in your area?
A good 8 mm allen socket and breaker bar should do it.
 

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Discussion Starter #12
Well, most of the "junk cars" around here are, in fact, junk, and not too many are MB's. I might have a lead one one from a member here, and I'm looking at another one on eBay, but it looks amazingly rusty at that price (how can something get so rusty in CA). From what I've read, anything beyond the tiniest amount of surface rust on a cam will be the beginnings of failure, because on a microscopic level, the case hardening surface has been compromised. OTOH, others just scour it off with a pad, or just let the engine do the work, and then put another 200K miles on the engine. So, who knows.

I've also discovered that not all of my shims are the same. Some are 5.1mm, and the one on the bad lobe was 4.7mm. If I replace the cam, I think I'd better figure out how to re-shim it. I've got the go/no-go tool but never really applied it because the conditions for proper adjustment looked tricky, and I didn't HEAR anything particularly bad until recently. Maybe a too-thick/thin shim contributed to this problem.

The thinking is (hopefully this is true), you might need thinner shims over time, as the valve pockets recede. It sounds like my gums.
 

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1982 380SE AMG euro(parted out),1983 300SD "Good Girl", 1984 500SEL AMG euro "Bad Girl"
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In another cam discussion here an expert pointed out that a re grind doesn't really work, as the lobes have a thin layer of treated / hardened surface.
As you well know, once that's gone, the lobes wear down quickly.

I forgot which cams were the same, the 450 to the 500, 380/420, and the 500/560?
Should be easy to find out with google, or the MBUSA EPC.
Any wrecking yards in your area?
A good 8 mm allen socket and breaker bar should do it.
Like anything else, there are good jobs and bad ones. A good cam builder can put together a stick that'll live long beyond the first run it had.
 

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1982 380SE AMG euro(parted out),1983 300SD "Good Girl", 1984 500SEL AMG euro "Bad Girl"
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3,256 Posts
Well, most of the "junk cars" around here are, in fact, junk, and not too many are MB's. I might have a lead one one from a member here, and I'm looking at another one on eBay, but it looks amazingly rusty at that price (how can something get so rusty in CA). From what I've read, anything beyond the tiniest amount of surface rust on a cam will be the beginnings of failure, because on a microscopic level, the case hardening surface has been compromised. OTOH, others just scour it off with a pad, or just let the engine do the work, and then put another 200K miles on the engine. So, who knows.

I've also discovered that not all of my shims are the same. Some are 5.1mm, and the one on the bad lobe was 4.7mm. If I replace the cam, I think I'd better figure out how to re-shim it. I've got the go/no-go tool but never really applied it because the conditions for proper adjustment looked tricky, and I didn't HEAR anything particularly bad until recently. Maybe a too-thick/thin shim contributed to this problem.

The thinking is (hopefully this is true), you might need thinner shims over time, as the valve pockets recede. It sounds like my gums.
It might be a wash. The thrust pieces wear too. I've looked plenty over and they seem to get a slight double groove showing on either end of the rocker tip path.
 

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1995 E280 Wagon w124, 1995 C280 w202
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1982 500 SEC (Euro)
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I'm asking this here, because I think there are more "nuts+bolts" familiar wrenches here than there are on the 107 board - but the following is a problem common to both types of cars.

When I purchased my 380SL at 95K miles, it made a terrible valvetrain noise and I purchased the car with repairing this priced in. As I thought, the rearmost lobe on the RH side was eaten
What oil did the previous owner regularly use?

A monograde oil or an oil with a too high cold viscosity,
an oil with low ZDDP content (such as the latest API SM specs)
a poor quality/obsolete grade oil (previous than SL spec)
and/or the car being used less than 30 mins every time,
and/or revving the car when it has not warmed up properly

... will grind the cams way faster than normal.
 

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1982 500 SEC (Euro)
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I've also discovered that not all of my shims are the same. Some are 5.1mm, and the one on the bad lobe was 4.7mm. If I replace the cam, I think I'd better figure out how to re-shim it.
It is detailed in the service manual. The shims are sold in different thicknesses, and the right thickness is verified using a special measuring tool that is placed on the hydraulic ball stud.
 

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Discussion Starter #18 (Edited)
It is detailed in the service manual. The shims are sold in different thicknesses, and the right thickness is verified using a special measuring tool that is placed on the hydraulic ball stud.
Well, it SEEMS simple, but it's a tricky business to keep the hydraulic compensators pumped up and pretensioned properly in order to get a correct reading, particularly on a car where removing/installing the valve cover is not trivial and without it (unlike a small block Chevy, with it's ridge at the edge of the head), there's oil all over the place. I've been very seriously thinking about taking a few 116/117 cam covers I have and cutting the tops off of them, and maybe even putting in a plexiglass door so I can see what the heck is going on in there while the car is running, without wearing a raincoat and/or creating another Exxon Valdiz incident.

Jeez- you'd think something called a "go/no-go" gauge would be simple to use...
 

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Well, it SEEMS simple, but it's a tricky business to keep the hydraulic compensators pumped up and pretensioned properly in order to get a correct reading
Good point, but the service manual (sheet 05-213) only say "crank engine with starter motor for 30 seconds prior to checking." So this should be enough, i think. Unless the hydraulic ball studs are failing.

So i guess it would be (1) put on the valve covers (maybe without screwing them), (2) crank engine, (3) take out valve covers, (4) check with the gauge.

Still of course is über time consuming, for all 16 valves!

Sorry for the off topic.
 

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MBZ '87 300SDL, MBZ '85 380SL, RR '77 Silver Shadow II, MBZ '98 E300TD
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464 Posts
--------------------------------------------------------------------------------
I'm asking this here, because I think there are more "nuts+bolts" familiar wrenches here than there are on the 107 board - but the following is a problem common to both types of cars.

When I purchased my 380SL at 95K miles, it made a terrible valvetrain noise and I purchased the car with repairing this priced in. As I thought, the rearmost lobe on the RH side was eaten, and the cam follower was severely grooved. This might have had something to do with the oiling tube so loose as to be easy to actually lift off of the cam towers.

I replaced the cam with a new aftermarket cam, and all new rockers. The oiling tubes were cleaned to surgical standards and fitted with new plastic fittings. Naturally, I used break-in lube. To be on the safe side I also replaced the hydraulic compensator for that valve with a new one. The shim looked a bit "polished", but still OK.

Before I owned it, this was obviously not an example of a "well-maintained" engine. When I change the oil every 3K miles (religiously), the oil looks old and the car may burn 1 quart every 1-1.5K miles, not great, but not unreasonable at 130K miles. There is some blow-by. My 560SL leaks, not burns, and at 3K oil changes (on a 108K engine), the oil looks almost as good as when it went in.

Anyway, all seemed well on the 380SL.for 25K miles, although there were a few surprises along the way - but nothing from the RH head. Until now. I took the RH side apart, and basically, the same thing happened again, although I obviously caught it much sooner. The cam looks only a little "gouged" on the lobe tip, and the follower is not nearly as bad (but still completely unacceptable) as the last time I did this.

I really don't want to replace the cam again. I actually would be willing to do it if I found a good used one cheap(if possible) but I would worry about pushing my luck with the cam tower bolts, which are of course really head bolts. Even if I had limitless time and money, you can do this only so many times.

I have, however, cleaned the oil tube (I do NOT think it is plugged), put new fittings on, and replaced the cam follower and put in a good used hydraulic compensator (all assembly lubed). I have the "normal" old shim (which measures OK) and next biggest shim size shims that I can install. I've installed the "normal" one and I don't hear any undue noise...uhhh...yet.

Questions:

1. Why does this always seem to happen on the 116? On the RH, and on the last cam lobe???
2. What are the ramifications of putting on the thicker shim? (4.75 to 5.1mm). Any guesses on how long this will last? 10 miles? 100? 1000? 10000? 100000? (ha ha).

Thanks
I have yet to hear another explanation on RH cam wear other than the loading being somewhat higher. In your specific case though, I suspect oil starvation from the oiler tube. I've owned several 3.8L M116 cars with more than 200K miles on them with only slight cam wear and on the RH side no less. Frequent oil changes and replacement of the oil tubes and retaining clips at 100K miles probably contributed to the long life. There is no reason the top end of the M116, camshafts and followers included, can't get to 300K before needing a freshening up, save for periods of neglect or abuse by previous owner(s).

As for the shims, it is tricky to use the go-no-go gauge and the shop manuals isn't terribly helpful with that. It's essential to getting everything dialed in. There is a fair degree of room for error, which is why you don't necessarily hear any clacking, but it's best to be within the permissible limit so you don't use up all of your adjustment from the hydraulic compensating elements.
 
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