1985 380SL W-107 116.962 Sticking Hydraulic Compensator

[Cape Bob]

My question concerns hydraulic compensator noise. I tried changing the oil 3 times at 500 mile intervals and that did not work, nor did replacing Delvac with synthetic. Upon inspection for the 110k mile timing chain replacement the engine appears clean, there are no broken timing chain guides or oil tubes and the cam and rockers look to be in great shape. I think the noise is coming from #7 cylinder valve compensators. Rather than replace all the compensators on this side I was wondering if anyone had either cleaned the old ones or by inspection found which one was not functioning properly.

At 110,000 miles I am heavily into the front of the engine, after reading all I can from here I will replace timing chain, tensioner, guides, oil tube fittings, belts, hoses, water pump, thermostat, heater hoses, mono valve and those nasty allen head bolts that hold the alternator support on.

Thanks for any help.

[Cape Bob]

Well, upon further inspection from the purchase of the spring compressor. I found the real problem. Evidently oil was not getting to the cam and rockers on Cyl #3. As a result the cam has a flat spot on one lobe and a ridge on the other for the same cylinder. See Pic#1 The rockers are very worn also. Pic#2.

The plan is to replace the 2 rockers and leave the cam alone I checked a random rocker on a cylinder with no cam wear and it was perfect. I think I got to the oil tubes just in time, well almost. The engine was running perfectly even with the bad cylinder averaging just under 21 mpg tuned to European specs.

Will this cure the original valve noise problem?

Thanks

[ctaylor738]

A flat spot like that will begin chewing up the rocker, so there will be noise soon if not immediately. The bad news is you need a new cam. The good news is that you've done most of the work already.

[Cape Bob]

Chuck, thanks for your reply I was afraid the cam would need to be replaced. I have read other threads and they recommend replacing the bearing towers. I also read an old thread of yours where you installed a used cam did you need to replace the bearing towers as well or just swap the ones mated to the replacement cam?

How deep do I have to get into it besides the cam and 2 bad rockers? Do I need to replace the bearing towers and sprocket? How about the shims for the existing valve adjustment?

Thanks for the help.

[t walgamuth]

if installing a used cam i would try to get the towers with it if possible.

tom w

[ctaylor738]

The guy that I bought my cams from had the whole enchilahda for sale - cams, towers, rockers, and shims, all labeled nicely for installation. But a normal repair is a replacement cam and all of the rockers using the existing towers. This is what I would recommend unless you have scored bearings or other damage.

That said, you can probably get away with replacing just the bad rockers. But examine the undamaged ones carefully against the new ones for any sort of wear. On a good rocker you will see just a hint of a line at the apex of the curve where it meets the cam, and the curve will have the same profile as a new rocker.

Unless the sprockets have sharp pointed teeth or "egging", there is no reason to replace them.

The shims aka hockey pucks should be replaced as needed to get the proper pre-tensioning of the ball studs. The pucks come in six or seven thicknesses and there is a special tool to determine which thickness to use on a given cam lobe/rocker. It is important to do this right since if there is not enough pre-tension to keep the rocker tight against the cam lobe, you can get noise and "slap" and end up with more cam/rocker problems. There are several posts on how to make this adjustment. The place to start is to use your existing pucks and go up or down from there. BUT if any of them are worn where the rocker contacts them, they should be replaced with the same thickness.

[Cape Bob]

Thanks for the great information. I have a new cam and new rockers coming. I should be ready to disassemble this weekend.

A question I had is from what I can see the existing bearing towers look OK. Looks like I should have enough room to remove the sprocket and rockers and remove the cam without taking off the towers. Is this true or do I have to plan on removing the towers and torquing the head bolts?

I also have the go-no-go gauge coming to check the pucks. If the cam is equivalent to stock and the bad rockers caused the noise then I would think the pucks should be within tolerance. Is that a safe assumption?

I have to put the new water pump on first so I can set some good reference points for timing.

[ctaylor738]

If you can R/R the cam leaving the towers in place, go for it. The guidance is that the new cam needs to turn freely when installed.

I recommend bringing the engine to TDC on #1 before starting to dismantle and marking the sprocket and chain with a dab of paint.

Not sure of your reasoning on oil supply or bad rockers causing the problem. A flat spot comes from "slap" caused by a weak ball stud, which in turn can wear the rocker. You may wish to consider replacing those ball studs.

And you are of course going to install new plastic pieces on the oil tube.

Hate to see you have to go in again after all this work.

[Cape Bob]

Well, back to the phone for more parts. Removed the rockers and they looked ok for the most part, but the bearing towers are scored and I don't want to not replace them. The new camshaft would be soon scored to match the bearings

To answer my question on camshaft removal, if anyone is interested, after the front tower is removed (upper bolt was locked in tight make sure you have the right allen head socket and plenty of PB Blaster) the cam drops forward but it can't be removed. It appears that the rear tower is a larger diameter. So it will not pull through the 3 remaining forward towers.

More to follow I am sure.