Need expert advice: camshaft lubrication issues - PeachParts Mercedes-Benz Forum

joselu43 · #1 06-27-2006, 08:00 PM

A couple of weeks ago I had the valve stems seals replaced on the boss's 88 560SL. This monday morning the car would start and die making a pretty loud grinding noise. Pulled the driver's side cover and I found that the mechanic had improperly replaced the oil feeding tube and the 2nd & 3rd bearing were oil starved. Cleaned things up and attached two plastic tubes to the feeding holes and filled them with penetrating oil. The oil went down, and repeated the process several times. This morning I fed it regular oil, removed the spark plugs, oiled the cams and using the starter I rotated the cams. Repeted the whole thing several times. There is no noise and the cam rotates freely. I think the No. 2 tower is still pretty tight and the oil drains pretty slowly through it.
Here is where I need your advice:
Is there something I can do to improve things?
Should I replace the bearings? I am not worried about the cost as much as I am about the possibility of creating a larger problem when doing the job (As it happened with the seal replacement)

I will aprecciate your advice. Thanks.

Jl

Strife · #2 06-27-2006, 09:50 PM

Frankly, I would have marched down to the mechainc and gotten the dough to get the bearings replaced, somewhere else, FIRST before fooling around.

That being said, be aware that the bearing sets are line-bored, and have to be replaced as an entire set. There is a very specific procedure to installing them in the manual and it isn't a casual job. It is critical to determine that a chain-free, cam follower-free cam spin freely with no binding or tight spots in 360 degrees of turning.

Regardless of what you do, I would buy a new set of the plastic fittings for the oil tube, right now, and install them before driving it further. I don't think that they are designed to be removed and then reinstalled, period, never mind if they are old. When I did mine, it was a little tricky to get them to truly "click feel" in place (this is probably where he made the mistake, they were old and probably didn't click). It took more than finger pressure, but obviously a lot less than a hammer, to do this.

As to if the bearings are "OK", I can't really say, but it does seem like you might have gotten to them in time. OTOH, I personally would always worry a little in the back of my mind about unexpected cam-binding that would definitely be disasterous. I defer to expert mechanics on this issue.

joselu43 · #3 06-27-2006, 10:15 PM

Thank you Strife. I ordered the fittings yesterday and should get them Thursday or Friday. I plan to replace both sides.
Your comment on bearing installation is doubly appreciated, it makes me even more aprehensive of going that way. I guess I will do it if I have to.
The cam is spinning freely now, my concern is future lubrication. I am trying to figure out a way of checking it before the car goes on the road. I am assuming that if lubrication is OK when rotating with the starter, there is a good chance it will be OK with the engine on, is that reasonable?.
Does anybody know how big of a mess it is to run the engine with the covers off?

Jl

mbdoc · #4 06-28-2006, 08:10 AM

If the cam partially seized BOTH the cam & the bearing set should be replaced!!!

mercmad6.3 · #5 06-28-2006, 08:35 AM

...cam ,bearings and rocker arms all come as matched set($$$$$$$$). I Guarentee that the head bolts will strip in the block...you need to sue the Mechanic who fouled up first. The engine will run loud and tappety with ruined cam bearings so there nothing left to do but spealk to the lawyers.
PS the plastic oil pipe fittings are only about $5 per set so it's seriously false economy to reuse old hardened parts as you have just found out.

joselu43 · #6 06-28-2006, 10:19 AM

MB DOC, the cam was making grinding noises but it did not seize solid, is that what you mean by partially seized?

Jl

mbdoc · #7 06-28-2006, 10:23 AM

The camshaft is VERY hard & the cam bearings are SOFT...metal transfer! NOT good.

joselu43 · #8 06-28-2006, 10:33 AM

I am really afraid that mermad6.3 scenario migth be right.
What additional damage could it cause if I do not change cam and bearings?

Jl

Tomguy · #9 06-28-2006, 11:05 AM

Jl: Your cam and bearings might be able to take another 50k miles of abuse in this condition - especially if it's well-lubricated from here on out.

They may sieze up tomorrow - especially if starved for oil again.

It's hard to tell - and usually people like to play it safe. If it does sieze, two things can happen: 1) The entire engine stops (best case scenario). 2) The timing chain snaps and flops around inside with the engine running. Valves kiss pistons on one or both sides of the engine. Massive top-end and possibly bottom-end damage.

You CAN just replace the bearings if the cam is in good condition - but if it was starved for oil for any extensive period of time, the soft towers' metal shavings would probably have ground away at some of the journal. Best way to tell is removing the suspect cam and examining it and its towers for scoring. How does the engine sound while running?

If you do need to replace the cam as well as the bearings, you CAN leave the old rockers on, but you're best off getting new ones to prevent the old worn ones from wearing the new cam faster.

joselu43 · #10 06-28-2006, 11:44 AM

That is great info. Right now I am turning the engine with the starter and it does not make any noise out of the ordinary. The starving affected only two bearings (2nd & 3rd from front) and both accept oil. 50k miles would be great, this is my wife's car (even though it is my favorite and I and I bought it for her, best gift I ever made her) and she does not put that many miles on it. I plan on doing some testing before putting it on the road and then remove the cover and check for lubrication (A pain, of course, it is the driver's side cover). This should tell me how to go on next. I am also thinking about going to a lighter weight oil (been using 20W here in Florida). Does this make sense to you?
Thanks for the help.

Jl

Strife · #11 11-22-2006, 02:36 AM

I recently started working on a 380SL daily driver because I missed my 560SL in the winter, and I will not drive it in rain or snow. The car I got (at a good price with repair costs built-in) had very bad noises from the RH valve train. The oil tube actually just lifted off the cam bearings when I disassembled it; the followers actually had some concave spots; and the cam had a few eaten lobes. Anyway, I put in a new cam and followers (and oil tube fittings, naturally); it was very tricky to torque the cam bearings properly so that the cam would turn easily (slow and even multi-step torquing, combined with constant tapping of the bearings with a plastic mallet) helped a lot. I got the recommended torques without stripping anything (WHEW!!!). But I do worry that I do see some dullness in the cam's bearing journals, which I assume is aluminum from the cam bearings. Does anyone think this is a problem? Now? In 10,000 miles? in 50,000 miles? The cam didn't rattle in there, but let's face it, I can't hear 1/100000 of an inch...it does seem to turn REALLY easily...

ctaylor738 · #12 11-22-2006, 07:23 AM

If the cam turns easily, and all surfaces are smooth, and it is getting oil, then I wouldn't worry about it. You could "mic" the journals and the cam to be sure of the clearances.

I put one like yours back together with a used cam and rockers and it worked fine.

I know what you mean about the torquing process!