Update (what a board!)
 

Sitting for 30minutes, tapping back on start up. Isolated to upper (draped cord of stethescope over #3 wire) and tapping consistent with spark noise in headphones.
Now noise disappears completely after 1min 46sec. and does not come back on start up until 30 minutes without starting.

Have ordered headgasket.
Tom

I would cancel the order of a head gasket. It is completely useless to remove the head if you don’t know where the problem is.

From your description I would suspect a hydraulic valve adjuster, easy to diagnose without taking the engine apart. Those adjusters have a small sealing ball in it to retain pressure. If this does not work properly it will give the symptoms you described.

Just remove the valve cover and feel all the rocker arms, you will have to turn the engine, the clearance can only be measured if the cams are opposite of the rocker arms. Disable the ignition if you use the starter engine to turn the engine, if the engine start the oil will spray out (a lot of it).

It takes only a very small debris to let the adjuster malfunction. If you can move the rocker arm the adjuster is defective. They are easy to replace and not very expensive.

Noise from a bent rod or damaged bearing will not go away and the tapping (mostly more violent than that) will be at twice the speed of the ignition and change under load.

Tapping from a adjuster will be at the speed of the ignition and will not change under load. If the sealing ball still works somewhat pressure will build up after some time and the tapping will go away.

Well, as I suspected, the insurance company paid for a complete engine. I took the pan off the water damaged engine and here's what I found. :bigcry:
Attachment 36930 Attachment 36931

BTW, the owner said the "puddle" was only two inches deep.

This post got me thinking. Tha last of the water damaged vehicles at my dealership finally got OK's from the insurance company to start repair work. It's a 2002 E320 with about 35K on the clock. When it came in several weeks ago (on a flat-bed) it didn't run, but it cranked over OK. We found the air filters and MAF sensor soaked. A compression test revealed cylinder #4 to be a little low, about 145 PSI vs. 175 PSI for the rest. The insurance company authorized removal of both cylinder heads to inspect for internal damage. The piston-to-deck height @ TDC was checked and found to be uniform across the board, however, the #4 piston appeared to be turned slightly clockwise when looking closely, straight down at it. I don't know if the compression was low before the water event, but I doubt it. We're going to recommend replacing all the rods and the #4 piston, but with insurance companies you never know. They may only want to replace the #4 rod or they may pay for a shortblock.:confused:

Is the bearing soft enough to save the crank on that engine? Not that it matters, since you can replace it. I'm just curious.

i am told that if the rod bends it always twists as well. so a little bend might not show up very easily on a deck to piston measurement but the twist, it appears, does show.

let us know what you ended up doing.

tom w

Out of curiosity, what do you do with these engines? It might be fun to have a complete 500 that just needs rods and maybe bearings...

i just looked at the two pics of the bent rods.

OH MY!

the story about 2" of water doesnt seem to "hold water" does it...sorry couldnt resist.

tom w

On this particular engine I'd be more worried about unseen damage to the crankshaft. Apparently the insurance company agrees, which is why they authorized replacement of the complete engine. Having it checked for fractures and straightness probably isn't worth the time or money. BTW, if any Forum members ever wind up in a situation like this, push your insurance company for a complete engine. It includes a new intake manifold, alternator, P/S pump, A/C compressor, wiring harness, etc.


It all depends on the insurance company. If they authorize replacement of the complete engine, the damaged engine belongs to the client. FWIW, I've never had a client ask for their old engine. As a result, I have three M272's, two M112's, and two M113's (one's an AMG), sitting on pallets in our storage building. All of these were damaged as a result of some severe weather/flash flooding earlier this year. If the insurance company opts for a re-built engine, the old one must be returned to MB or a core charge will apply.

i would think the cranks would be fine. they are forged, right?

tom w

Hmmm, you have an M113 you're not doing anything with? :D

Well, after going back and forth with the insurance company, we're finally done. We replaced all six connecting rods as well all the bearings. We figured we might as well replace the rings while we're there, so we did those too. I took the suspect rod in and hung it on a wrist pin, along with one of the new rods. This is a good way to check for even the slightest bend. They matched up perfectly, so there goes the bent rod theory. I did notice however, that the wrist pin was binding slightly on the rod in question, as compared with all the others. Apparently, the wrist pin bore was compressed/deformed when the engine locked up. I can't explain the low compression in that cylinder though. Maybe it was low before the "water event" but it seems like an awfully strange coincidence. I would've run another compression test, but with new rings why bother. Anyway, the car runs fine, and the owner is happy.

Since my last post, another "puddle" victim has arrived at my shop. It's an SLK 350 (M272). It was sitting at a local independant shop for a few weeks before the proprietor got fed up with the insurance company and told the owner to get it out of there. We replaced the engine with a re-built unit (the insurance adjuster wouldn't pay for a complete engine). As soon as we started it up the alternator was screaming, so we replaced that too. The owner asked me to drive the car for a few days, just in case something else goes wrong.

That brings the total number of "puddle" victims to five. All of them were damaged by a few days of rainy weather in early September. Three of them had the engines replaced, while we repaired the other two. I wound up with another M272 in the collection. I'm sure we'll have a nor'easter or two before next spring. When that happens, the guys in the shop will be working some serious overtime!!!

thanks for the update. very very interesting stuff. the binding wrist pin is interesting. it was binding in the top of the rod? or was it the piston?

obviously something going on there too subtle for the eye to catch!

tom w

It was binding in the rod. There was no problem with any wrist pins or pistons. I haven't seen anything like this before, but the longer I stay in the MB business, the more I realize how much I don't know!!!:book:

yep, that is how life is.

thanks for sharing.

tom w