116 Engine Serious Valvetrain Oiling Problem - PeachParts Mercedes-Benz Forum

Strife · #1 05-07-2008, 12:35 PM

(85 380SL)

I got to work with serious valvetrain noise, both sides. Looked under the oil cap and only drops were coming out of the oil tube hole visible to me. On my 560 and on this car I know I should see a stream. The car was running normal oil pressure and the oil was slightly below the halfway mark between the red on the dipstick.I put in more to get it near the top of the "upper" red guide. No change. Mileage is now 111K. Cam lobe I can see is not scored or damaged(yet).

Any ideas would be appreciated. I brought it home, parked it, and can't take it apart now because its hot. I will after work, though.

-MAYBE an oil tube popped off (again)? Both sides??? See below.
-Blockage in engine (unlikely that plastic guide chunks are a problem, see below)
-cam oiler tubes blocked with sludge (both?) Unlikely, the engine is very clean and the oiler tubes were cleaned when the fittings were replaced. It was very clean and unblocked before cleaning, but I did it anyway.

History of engine:

Bought at 95K with serious knock/banging on RH side
Upon purchase, replaced timing chain, upper guides/, tensioner, tensioner arm. I don't think this had ever been previously done. The old guides were not chipped or broken.
Knock was due to popped-off oil tube fitting on RH side, unmaintained for several months of driving, leading to multiple RH cam lobe wipeout; all cam followers as well as RH cam were replaced properly with break-in lube, etc.
Oiler tube fittings were replaced with new and installed properly all the way in seats, and were never re-inserted (which would wear the barbs out).
Oil changed while in my posession at 3K intervals. The oil is clean and the filters look pretty good when replaced.
Oil pressure is 2 bar idle, 3+ bar off-idle.

Needless to say, I'm worried. I thought that this problem was put to bed.

Strife · #2 05-07-2008, 11:01 PM

Follow-up: OK, I found...uhhh...the problem:

On the RH side, the rearmost fitting was a bit loose but I'm pretty sure it was still performing OK. The cam, bearings, and followers look good. The cam and followers were replaced 15K miles ago.

But....

1. The LH oiler fittings were melted except for the one at the front.
2. The oiler tube was partially plugged at the fittings by melted plastic.
3. The cam is blackened and the rearmost lobe is eaten; the rest don't look too good.
4. Many followers are worn.
5. The cam bearings are blackened.

Other than that, no problemo

Well, it's obvious what needs to be replaced, but I am worried about what went wrong first, and if I replace these parts, will it happen again?

Basically, what the heck happened? I am absolutely, positively sure beyond any doubt that the fittings were installed properly and entirely in their seats, touching. If they weren't, I think I would have known a year ago. I had replaced the fittings of both sides when I did the major work 15K miles ago. The only thing that I can think of is that this engine was obviously not maintained very well (considering how I bought it) and maybe I should have replaced the LH valvetrain stuff when I replaced the RH parts.

I'm going to TRY to boneyard this stuff, but if I can't get a good price, I'm going to have to think about other options. This is very, very depressing.

t walgamuth · #3 05-08-2008, 06:29 AM

Very sorry to hear of the trouble. Obviously you will have to replace the melted parts. You'll just have to make sure all the oil passages are clean and verify flow once its all in place. The bottom end on these cars is so robust that you should be just fine at that point.

Good luck.

Tom W

donbryce · #4 05-08-2008, 08:41 AM

I feel for you. I re-read your posts, but could not determine if you replaced the LH oiler tube fittings? If not, then the meltdown must be the result of age, although the few 116 and the 1 117 engine I've dealt with all had old and brittle fittings. Hard to imagine them melting.
On the other hand, if the LH fittings were new, done when you repaired the RH side, then I'd ask where they came from? I installed, this past winter, an aftermarket set of these on both sides of my SL 117 engine, but the car has yet to see the road this season. Now I'm worried that they might melt down like yours!
It really SUCKS that Mercedes would put such a weak link in an otherwise bullitproof engine, including those nylon chain guides, which are the equivalent to me of the modern day engine timing belt. Really, how much more engineering would've gone into tapping those stupid barbed holes in the cam towers and using threaded fittings for the oil rail?

Strife · #5 05-09-2008, 12:16 AM

Well, I got these fittings (both sides were done) from ********, but I'm not going to consider them as a source of the problem. An additional and very disturbing find: the oil tubes contained a few small pieces of what looks like hi-temp silicone/RTV. I assure you, I don't even have this in my house, much less would I have used any in this car. Also, when I reinstalled the tubes when I did the timing chain I cleaned them and they were absolutely spotless.

Here's how I see it - one of these things happened:

1. The engine had been abused, when I replaced the RH camshaft no doubt the LH bearings/journals were on their way out anyway (the LH cam in fact had a little wear on ther rear lobe then, and it's worse now). The rear bearing oil film failed, that fitting melted, this stopped the flow to the others. Of note, the hydraulic compensators all seem to have a good supply of oil and there was plenty near the drain hole and to hit the exhaust manifold when I removed the valve covers.

2. The tube popped off (this time on the LH side). I have to think that this is extremely unlikely.

3. REALLY SCARY: Where did these bits of RTV come from? Just suppose that the PO or his/her mechanic had used it on the oil pan or valve covers (I see no evidence of this). Even if this were true, _how_ did it get past the oil filters, which have been replaced and looked very clean, as did the canister? It is worrisome that the RH side oil flow was reduced (but not down to zero, the front oil tube hole was dripping at idle, and everything looks OK. Maybe there was a lack of pressure and everything was gushing out of the melted fitting area). How do I know that if I repair this, that it won't happen again? Certainly, I can check for good oil flow at start-up. But what about any more RTV? In 100 miles? 1000? On a long trip where I might not notice noise until the one final loud bang?

Anyway, I'm hoping for #1, but #3 has me worried. I will know more when I take the cam bearings off of the LH side. IN the meantime, I have a line on some used parts that will probably run $200; to replace all this new, even at a discount, will be over $700, and I'm not sure that I'm willing to gamble that much on this. Should I reassemble it and find no oil flow, I'm going to have to consider some other options - which is a darned shame, because I just put a good bit of time and money in this car.

donbryce · #6 05-09-2008, 07:46 AM

I read your post #2 again, and caught where you did both sides at 15K. My bad. I'm inclined to go with the heat from the rearmost bearing failure melting the fitting and blocking the flow. Sounds reasonable.
When I had the oil pan off my 560, I found 2 large pieces of RTV in the oil pump screen, along with a small piece of plastic chain guide, and a larger piece of guide on the floor of the pan.
There was a big chunk of guide lodged on each side of the engine chain passageways too, each just big enough to not go down to the pan. I crazy glued all the pieces together to ensure that I had found all of them. I figure I dodged several major bullits.
You weren't so fortunate with the RTV. However, if not already done, I'd drop the pan and do a thorough investigation for additional pieces of flotsam and jettsom before they migrate up to the oilers. Just my amateur thoughts.

Strife · #7 05-23-2008, 12:09 AM

Well, I got the engine back together and running after an extremely helpful MB mechanic in KY got me a LH cam, bearings, and rockers at a good price, and, shockingly, all these parts were in excellent condition after 115K, even the rear lobe of the cam (the donor engine itself jumped the chain and bent valves). He marked all of the parts in order for me. I was worried about the cam being bent but it went on with no problems and spun freely after torquing.

I went crazy cleaning the cam oiler tubes, even to the point of making a 1500 grit "sandpaper reamer" and I got the insides mirror-smooth and flushed the heck out of them - after I was done, they were surgical theater clean. Then I blew them out with pressurized brake cleaner fluid and rechecked. The manual says "replace if plugged" but I'm confident that I got them totally spotless.

As to the original problem...well...I probably will never know. I know that the PO had allowed the engine to be abused to a degree, and it's possible that the rear LH bearing got progressively worse (the rear cam lobe was not good when I bought the car, but I decided to live with it), which blew the oil film, heated the bearing up, melted the fitting, then the other bearings got bad also, then all of the other fittings melted and the lobe/follower surfaces were damaged.

Some observations:

1. If you don't have a solid stream of oil at idle hitting the RH front cam lobe (visible through the oil filler) at idle with the car cold, something is really wrong. I think the lack of back pressure on the LH side made the RH side pressure lower, making more of a "drip" than a stream. Enough to keep everything lubricated, but still, not right.

2. DO NOT EVER IGNORE a "new" noise. I'd guess that I was 10 miles from diasater. I couldn't turn the old cam in the old bearings by hand. I'm sure I wasn't far from a broken chain, cam, or plastic guide, and failing at speed this would be an automatic engine replacement. There was a lot of aluminum transferred to the surface of the cam journals.

3. I did notice that when this problem started, the oil pressure seemed to take 1/2 a second to come up entirely when the engine was cold started. Usually, this is was absolutely immediate on this car.

3. One of my personal victories that came with maturity was becoming patient and methodical. I am not a mechanic by trade, and doing this work is not second nature to me (yet). To protect myself from accident (and a boo-boo in this area would become very expensive very quickly), I do things by the book. This includes:

1. Cleaning the bolt threads and oiling them
2. Cleaning the head/bearing mating surfaces
3. Liberal use of assembly lube
4. Stepped torquing in the order as shown in the manual, SLOWLY

Basically, one stripped thread in this area would run about 2K - the cam bearing bolts are head bolts.

ctaylor738 · #8 05-23-2008, 10:51 AM

... but what if RTV was used to seal the head gasket, and some got around the oil feed to the cam bearings? It worked its way into the oil passage, and plugged it, and some got pushed up into the oil tubes, where it could not escape, and thus never made it back to the oil filter.

I know this sounds a bit far-fetched, but can't think of anything else that would explain what you describe.

Note added. I just looked at the flow diagram. The RTV could also have gotten into the main passage from the timing chain area. Was the front cover ever off? Pretty common to use RTV to seal it.