Have you had a timing chain break!? - Page 5 - PeachParts Mercedes-Benz Forum

#61 09-17-2001, 06:35 PM

Michael, do not use, and do not let anyone else use, an abrasive wheel to clean the gasket material off the head and block surfaces. The grit is difficult to remove and will chew up the cylinders. You need to take your time to scrape the residue off. To protect the inside of your cylinders (should you decide to leave the bottom end alone), I found it useful to get a drafting compass to draw and cut out circles of manila folders to put over the top of the bores. You can tape the paper to the outside of the cylinders by using a corresponding circle of masking tape just a little larger. Then get a nylon bore brush (gun cleaning), do not use a metal brush and do not chase the threads with a tap, the nylon will clean the threads just fine. Blow out the bolt holes with air. When putting the head bolts in, be sure to liberally apply oil to the bolts. These are just some tips you may find helpful. Let me know if you should have anymore questions.

engatwork · #62 09-17-2001, 08:18 PM

SS - why do you recommend NOT tapping the threads out?

#63 09-17-2001, 10:39 PM

Engatwork, the last time I tried to clean up the threads in aluminum using a tap it ate up all kinds of aluminum filings. I found no trouble in cleaning up the head bolt holes on my 380 as described above. I did not have to use inserts. The bolts torqued up really nicely. However, it was necessary to tap the hole for the insert for my oil pump bolt that had stripped out of the hole. Anyone else with experience on this subject?

mplafleur · #64 09-17-2001, 11:29 PM

I looked closer at the cylinder walls. There is absolutely no ridge whatsoever. In fact, all the cross-hatching is clearly visible. I'm thinking so far that there is nothing I need to do to the pistons and cylinders.

The head parts will take a few days to get here. I have to find a shop in the area that can work on it.

I'll start taking the rest of the engine out. At minimum, I will get a new oil pump. I will take a closer look at the crank, bearings and journals.

Thanks much for the info on preparing and renewing the head and block surfaces.

#65 09-18-2001, 06:43 AM

Southern Son offers good advice. That is not the first time I've heard of the woes of those air operated gasket surface cleaning products. I have a simple scraper that uses a single edge razor blade. It's a little time consuming but does a very good job without introducing grit into the engine.

I'm not surprised about your cylinder walls. That's a good sign. My biggest worry now continues to be your oil pressure. This brings up further thoughts. When you fished out the timing chain pieces were they very dry? With low or near zero oil pressure, this could be related to the chain failure. As others have advised, analyze everything until you find the source of your oil pressure loss. It's common for everyone to replace the oil pump when pressure is low, but it sounds like you already know that the problem is most likely elsewhere.

Thanks for the minute by minute reports and good luck,

mplafleur · #66 09-18-2001, 07:45 AM

The cam and head were well oiled and the timing chain had oil on it. It had been allowed to dip dry for a few days and with much wiping with a shop towel, it is still a bit oily to handle. Since the timing chain does not travel through the pan, where does it get its oil from?

#67 09-18-2001, 07:53 AM

The timing chain gets its oil from the front main bearing, plus on some MB engines, any oil from the oil pressure relief valve is deposited on the chain, I don't think it got much from there in your case. With low oil pressure, if the front main has excessive clearance, you would expect that the timing chain got plenty of oil.

With the cylinders in good shape it just doesn't sound like an engine that was abused in any way. But, if it was ever allowed to run low of oil the majority of such damage would be to bearing surfaces.

Keep on inspectin'.

Good luck,

mplafleur · #68 09-18-2001, 10:13 PM

Head parts on the way. Found a shop today. Will get the head to the shop tomorrow for disassembly and cleanup.

Drained the oil pan tonight. I only found some pieces of the chain rail, but I have yet to remove the pan. I've removed almost everything on the topside, except for the A/C. I'm trying to remove that without losing my charge. I have a 20lb can of R-12, but I don't want to use any if I don't have to.

BTW:

The engine has never been low on oil that I know of.

It has been VERY hot however, when I had some cooling problems a year or so ago. I've had to replace the radiator 4 years ago. Water pump 3 years ago, the heater core, circulation pump, and some vacuum operated valve last year. Everything on this car leaked. Now I've a vacuum leak inside.

(I get hot air ALL the time)

I'm considering picking up a high milage late model M-class next year. What's the record on that one?

#69 09-19-2001, 07:03 AM

Michael,

I wonder if your oil pressure sender is okay. You keep giving us more information that indicates that the bottom of the engine is in good shape, the cylinders looked good, the engine has been kept in good repair with frequent oil changes and has never run low of oil. All this is just making me wonder about the sender. There was a poster a few weeks ago that was getting totally scared to death over low oil pressure only to find that replacing the sender did the trick.

It's too bad you could not have put a mechanical guage on the motor while it was still running to check this. Then you would know whether or not you should dig deeper at this point.

I think that your discovery of the guide rail pieces in the pan is the first real clue we've seen about what led to the failure of the chain. Given what the chain looked like, it just HAD to be broken by something locking up and yanking the chain apart. A broken guide rail would sure do that.

At this point in your investigation, it is beginning to look as if replacing the timing chain and ALL associated components along with the fresh head might be the thing to do. It's really hard to imagine the bottom end being bad. But if you could prop up the engine enough to slip off the oil pan it would let you pull down a few bearings and take a look. It wouldn't hurt to slip a mic over a few journals while you're there.

BTW, I totally understand your desire to not lose any of the gaseous gold R12. You should be able to swing the a/c compressor out of the way and hang it somewhere with coat hanger wire to keep from straining the hoses. I have only a little R12 left in my 35 pound can myself, and I'm taking every step I can to preserve it.

Hang in there and good luck,

mplafleur · #70 09-19-2001, 05:12 PM

I have taken out my oil pressure sending unit. It there a way I can test it?

#71 09-20-2001, 06:32 AM

The only way I would know would be to use an ohmmeter on a known good one and compare the two. If you knew someone with the same model, it would be worth putting it in their car temporarily to see if it is the culprit. If it is indeed bad, I believe it would be a good indication that rebuilding the timing chain system and top end of your motor will get everything back in good shape.

Is there anyone in Michaels area with the same model 190?

Good luck and God bless America,

mplafleur · #72 09-21-2001, 09:42 PM

Things are progressing, albiet slowly. It turns out that all valves, but two intake valves were bent. Here is the worst exhaust valve.

Head is in the shop. It's all clean now and pressure tested fine. Amazing that all the guides are ok. So are all the pistons I hope. I will inspect them closer this weekend when I take the lower end out. I can then look for wear on the rod and main bearings.

I got a box of parts today. Chain, guides, head rebuild kit, head bolts, but no valves and only one set of seals.

I will have to call about that tomorrow. I was hoping to give the shop all the parts on Monday.

Well, the family is here with a movie and popcorn and I just got home from work. Popcorn for dinner is fine with me.

God Bless America!

mplafleur · #73 09-21-2001, 09:45 PM

Sorry, here is the picture:

#74 09-21-2001, 10:04 PM

Michael, the good news is..once you have it all back together, it should remain in good shape if you monitor the condition of the chain. As I suspected under another thread heading on your engine, it appears to me that the chain did get loose, jumped a few teeth and experienced interference resulting in chain separation.

That engine should be good for another couple of hundred thousand miles upon completion (maybe a great deal more!).

mplafleur · #75 09-25-2001, 12:51 AM

Well, I just got the block out. I took the pan off. I found a couple more small guide rail pieces, but I also found half a chain roller and a small part that came from I don't know where.

I'll take a picture and post it on a new thread and see if anybody can identify it.

I also took off one rod bearing and one main bearing. I'll describe those tomorrow after I get some sleep.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Just how often should a timing chain be replaced?	Greg in Oz	Tech Help	16	07-25-2005 05:02 PM
Info on how to replace timing chain tensioner & upper chain guide	bodyart27	Diesel Discussion	11	10-15-2003 04:53 PM
OM603 timing chain installation report	gsxr	Diesel Discussion	3	08-15-2003 11:00 AM
W126 Timing chain help	BenzMatic	Tech Help	5	08-03-2003 05:14 AM