1987 560SL, running rough/tapping - PeachParts Mercedes-Benz Forum

briandownunda · #1 01-01-2008, 10:10 PM

Hi, I am a new member of this forum. I have just purchased a 1987 560SL with 94k well documented miles on it. The timing chain, rail, tensioner, and tensioner rail were replaced at 85k miles, about 2 years ago. I bought the vehicle knowing that it has a mechanical problem. It runs very rough & has a fairly loud tapping sound. The seller chose not to have the vehicle repaired.

I did a compression check and cylinder #4 has a very black, apparently fouled spark plug, and the compression seems low. All other cylinders check out OK & spark plugs look OK.

Any recommendations on how I should proceed ? Could this be a bad rocker, or, perhaps a worn cam lobe ?

thanks in advance for your help/suggestions !

Brian

jhodg5ck · #2 01-01-2008, 11:37 PM

Bad rockers/worn cam lobes won't give you poor compression. A bent valve however will.

I'd remove the valve cover to see if the valve is closing fully.

Jonathan

briandownunda · #3 01-02-2008, 07:00 AM

Hi Johnathon,

Thanks for the reply. When I said that the compression "seems low", that may have been an incorrect statement. When I tested the compression, I the max value it went up to was the same as the other cylinders, however, my wife said (she was my assistant) that the needle on the guage was bouncing up and down quite a bit.... a lot more than with the other cylinders.....when I attempted to remove it, the hose spun around and the bolt at the end did not....I ended up having to remove the guage using a long pair of needle nose pliers. I then recrimped the hose after that test, which was the first test. I am thinking that I need to retest that one as, possibly, the guage was giving a bad reading because of the loose hose.

The spark plug did look bad though, it had a bunch of black deposits on it while the others looked clean.

Assuming that the valve is not bent (I will verify this at my next opportunity) what would a spark plug look like for a cylinder with a bad cam lobe or rocker ?

Thanks,

Brian

ctaylor738 · #4 01-02-2008, 11:22 AM

I would replace the plug on principle. The miss may be caused by a badly fouled plug, or a bad plug wire or possibly a cam or rocker worn so badly that the valve is not opening, or all of the above.

The best way to test this IMO is to attach a inductive timing light to the wire, start the engine, and see if it flashes. I would est all the cylinders this way.

As noted, the noise could be a bad ball stud, or worn cam lobe/rocker arm. Use a 2 foot piece of hose or an engine stethescope to see if you can isolate it to a cylinder, then pull the cam cover on that side and have a look at the valve gear. Do a search on "ball stud" and you will find a lot of information on how to check them.

John1 · #5 01-03-2008, 02:54 PM

What is a "Valve Gear"??

John

ctaylor738 · #6 01-03-2008, 08:28 PM

It's not a physical gear.

I used the term as a quick way to refer to the cam lobes, rocker arms, and ball studs - everything that gets touched to open the valves and allow them to close.

560 SEL · #7 01-09-2008, 11:28 PM

[quote=briandownunda;1720311]Hi, I am a new member of this forum. I have just purchased a 1987 560SL with 94k well documented miles on it. The timing chain, rail, tensioner, and tensioner rail were replaced at 85k miles, about 2 years ago. I bought the vehicle knowing that it has a mechanical problem. It runs very rough & has a fairly loud tapping sound. The seller chose not to have the vehicle repaired.

When you first start the car is there any blue smoke, your problem sounds like bad valve seal leaking oil into cylinder... As far as tapping sound that might be a valve that is hanging up do to deposits. the 5.6 engines do this I have found out with my 560 if I run shell v power or Bp it cleared up my valve tapping.. I would start there with mileage on the engine an the work that was done what I have mentioned sounds more like the problem.. these engines are strong especially the bottom end.. I just replace valve seals at 135k that stopped one spark plug from fouling.. my oil consumption prior the job was a quart about 1k miles I have 8k on the valve seal job an no oil consumption try these first see if that solves your problem
Bob

560 SEL · #8 01-09-2008, 11:46 PM

Brian
Your problem sounds like leaking valve seal how is oil consumption, any blue smoke at start up. as far as the valve tapping if you take a hammer handle and push down on the lifter if it is bad it will compress but I believe you will find that is not the case.. what kind of fuel are you running on my 560 if I use off brand of 93 I find my valves start to tap I run shell v power or BP that solved my valve tap problem.. Also there is noise from the chain the engine sounds like sowing machine that is normal. The missing problem could be caused by ingintion wires, cap , rotor. If they have been changed its injectors. If they are orginal they will need to be replaced, but before try cleaning with techroline injection cleaner.. its process of illumination... let me know i have been all through this engine ..

briandownunda · #9 01-10-2008, 09:42 AM

Thanks for your reply !

Yes, I do have some blue smoke when it starts as well as a couple of fouled spark plugs. I am beginning to think that I have the same problem you did.

I would like to go ahead & replace the valve seals. Can someone tell me the list of special tools that I really need to do the job ?

e.g. spring compressor, air compressor fitting for spark plug hole, something to slide the new seals onto the valves ? something to hold the camshaft in place ?

Also, the list of parts I think I need is the following (did I miss something ?)

cam oiler kit A6350-15447 2 $ 6.79 $ 13.58
left valve cover gasket A8030-25375 1 $ 11.39 $ 11.39
right valve cover gasket A8030-25376 1 $ 11.39 $ 11.39
valve cover seal washer A8033-83101 8 $ 0.96 $ 7.68
valve stem seal kit A8069-26467 2 $ 16.79 $ 33.58
Thanks in advance !

Brian