1979 450sl cam noise - PeachParts Mercedes-Benz Forum

benzportland · #1 06-30-2009, 08:21 PM

Hello - I am looking at a 1979 450sl to purchase, and there is a ticking or clicking noise coming from under the left (driver side) cam cover. I have found bits and pieces here and there about the lobes, camshaft, oilers, etc but nothing really comprehensive on examining and/or servicing them. I assume from the noise and importance of the part it really needs to be serviced ASAP, but I am wondering if this is a DIY for someone who is not a mechanic. Any advice, tips, points, would be greatly appreciated.

mbboy · #2 07-01-2009, 06:18 AM

Quote:

Originally Posted by benzportland

Hello - I am looking at a 1979 450sl to purchase, and there is a ticking or clicking noise coming from under the left (driver side) cam cover. I have found bits and pieces here and there about the lobes, camshaft, oilers, etc but nothing really comprehensive on examining and/or servicing them. I assume from the noise and importance of the part it really needs to be serviced ASAP, but I am wondering if this is a DIY for someone who is not a mechanic. Any advice, tips, points, would be greatly appreciated.

Probably one or more worn rockers. You'll also have to get a valve spring compressor for an overhead cam engine to remove and examine them, a gauge to check their height after you've done that, and some shims to adjust their heights.

KD Tool has a compressor for around 50, or you can get the MB version for around 100.Not very hard or expensive to replace, as there are some reasonably priced after-market rockers for around 20@ vs 60@ for MB OEM's.

If it;s caused by worn cams, the rockers and cams should be replaced together. Cams are not too hard to remove and can be remanned for under 100 each.

While you;re at it you should check to see if the timing chain is stretched and.or the guides are worn. They need to be replaced every 100k miles or so, to prevent major engine damage. There are many posts on checking and replacing chains and guides in the archives.

Good luck!

benzportland · #3 07-01-2009, 02:38 PM

Thanks so much! Do you happen to know also if there are any pictures, diagrams, or etc available here for assistance as well?

PanzerSD · #4 07-01-2009, 08:02 PM

Perhaps this is the same noise that I hear from my 4.5 in the SEL?? I DO see some scoring on the most visible part of the cam with the oil cap off. and a ticking that I could swear was an exhaust leak, but can't pinpoint it yet.

PanzerSD · #5 07-01-2009, 08:02 PM

is it cheaper and easier to just replace tat whole cylinder head if one had the parts?

mbboy · #6 07-02-2009, 08:15 AM

Quote:

Originally Posted by PanzerSD

is it cheaper and easier to just replace tat whole cylinder head if one had the parts?

Don't even think about that unless the car needs a valve job and/or head gaskets, because it's burning oil and/or coolant. In that case, you're looking at 25-30 hours worth of work, and hundreds of dollars in parts and machine shop costs.

benzportland · #7 07-20-2009, 06:12 PM

Still looking for a diagram or picture, if anyone has one available. The "tapping" noise is loud enough to her it pretty well when driving with top off, and of course it taps faster as I accelerate. I am wondering also if it is a good idea to continue driving it for now, or fix it first?

GaryF · #8 07-21-2009, 10:26 AM

Quote:

Originally Posted by benzportland

Still looking for a diagram or picture, if anyone has one available. The "tapping" noise is loud enough to her it pretty well when driving with top off, and of course it taps faster as I accelerate. I am wondering also if it is a good idea to continue driving it for now, or fix it first?

Undo the 4 bolts and take a look under the cam cover.

benzportland · #9 07-21-2009, 01:56 PM

I plan to do that but I am not sure what I should be looking for under there.

sublettd · #10 07-21-2009, 10:01 PM

When you pull the cover off, drag your fingernail across the cam lobes to see how much wear is discernible. Also inspect visually for grooves int he cam lobes.

My engine rebuild on the SL has been extended. With just 3,000 miles on it, one of the cam lobes is shedding metal pieces and am now in the process of replacing the cam and all of the rocker arms on that side of the engine.

If you wind up replacing the cams, it can be done (just barely) by pulling the radiator, loosening the motor mounts and raising the engine. However, if you pull the heads, you're much better off to go ahead and pull the engine/transmission. You'll save time and probably money by going this route.

Also, if you pull the heads on the aluminum block, resign yourself to heli-coiling the head bolt holes and putting in timeserts. Kicker here is that you need a plate ($600.00) for proper alignment to drill/tap the holes.

Too, if you wind up having to remove the cam towers, you're also most likely going to pull a thread, which will also require the hole to be heli-coiled. The MB manual says if you heli-coil one hole on a side (bank) then you need to do the entire side.

Been there. Done that. Good luck.

sublettd · #11 07-21-2009, 10:05 PM

Just noticed you are working on a 450SL. Steel engine. That's good.

benzportland · #12 07-22-2009, 01:40 AM

Thanks that gives me a better idea. I think the cams in mine are pretty accessible without having to do all the removal.

sublettd · #13 07-22-2009, 10:15 PM

Well, we thought the cam shafts could be removed by raising the engine. As it turns out, you have to remove the cam towers and along with them comes the cam. There is a collar on the front lobe that won't allow the other lobes to clear through it.

The whole drill was to keep from having to remove the top row of bolts securing the lobes to the head...for fear that one or more threads will pull when retorquing the bolts. Those bolt holes were the only ones not heli-coiled. We'll see.

Interestingly, two of the cam lobes were being eaten away and EVERY rocker arm on the passenger side was rubbed almost flat. Also, one of the rocker arms had a big chip out of the side of it. This was with only 3,000 miles on the rebuilt engine.

What's really puzzling was that we figured when we pulled the other valve cover we'd see the same thing occurring on that side. Pulled the cover and everything on that side was beautifully pristine. Maybe the rocker arms we put on the passenger side had not been hardened. They were certainly being lubricated. If anyone has any theories, I'd be interested in hearing them. Thanks.

benzportland · #14 07-23-2009, 02:06 AM

This would all apply to your 500sl, correct?

Strife · #15 07-23-2009, 02:40 AM

I am in the middle of something similar. I have a 380 that I bought with a flat lobe on the RH side at the rear. I replaced the cam with an aftermarket cam and all new rockers. I think that I did a darned good job and this lasted about 30K miles (if I would have done a bad job, professional mechanics told me that I would find out very, very quickly). Now, I've had the same problem come up. Same side, same lobe. I'm replacing it again, this time with a used MB cam and one new rocker (all the others looked good). This is the LAST time I'm doing this on this engine. I replace my oil and filter every 3K without fail.

Needless to say, I, too, worry about retorquing. I don't know how many times I can get lucky.

I think that the oil tube is very tricky to reinstall. You MUST use new oil tube fittings every time you remove them. They are NOT reinstallable. Also, they need to fit down ALL THE WAY. You have to really tap pretty hard with a rubber mallet to make that happen. I cleaned the oil tube to the point where it appeared surgically spotless the first time but this time I'm not taking any chances and I'm replacing it with a new one. Under a magnifying glass, I can see that someone (the PO) may have screwed with the holes and enlarged at least one.

I'm worried about ZDDP additives being removed from oil. After I do this, I'm using Diesel oil, which still has it (google ZDDP). I may also think about having the oil pan dropped and cleaned out. This is a pretty expensive job. I worry about junk clogging the screen and possibly starving oil at highway speeds. I KNOW that I have at least some pieces of a plastic chain guide down there.