Nailing or other (300D Turbo 82) - Page 3 - PeachParts Mercedes-Benz Forum

Judge · #31 10-16-2003, 12:56 AM

Hi Cummingsnut,

Needed to vent a bit. My hope of buying a beautiful classic cheap and driving in style has turned into a headache.

As answers to your questions, no, I haven't yet tried the idea of listening with compressed air to determine the bent valve. Sounds like a good test.

I just tossed the oil filter, so I won't be able to check for metal. But I'm sure there is some metal in there For what must have been thousands of miles before I bought the car, the air filter container was hammering against the valve cover. ( Two out of the three arms of the T bracket used to hold up the air filter cover had broken off.) That hammering of the air cover against the valve cover was destroying the sleeve that one of the front bolts passes through. Small pieces of the inside of the valve cover were breaking off into the engine..

Judge · #32 10-31-2003, 06:04 PM

Thanks everyone for all for the help and advice.

To update, I haven't fixed the problem, and now don't think that I will be able to. Its still making noise.

One mechanic advised that it was a bent valve, but his behavior has been flakey, so I'm not following his advice.

With the second mechanic, I saw what he did, plus I know and trust him more. He also cracked open each injector one by one, and accross all cylinders the engine slowed and became rough. He pulled off the valve cover and examined the lobs, finding them to be okay. He examined timing and timing chain, again it wasn't the cause. He reviewed my work on adjusting the valves, and did a better job than I did, and quicker.

At the end he said that to find the problem he'd have to take off the head. We also talked about putting a different engine in it. For right now, I decided the price is too high, because the cost will be about as much as the car is worth. Additionally, it doesn't seem to worth it because except for for the "nailing" sound, the engine runs well.

So I think that I'll drive the car "as is" for about a year and then sell it, all the while, looking if I find another answer. In the mean time, if anyone wants to buy it for about $900, its got 220 k miles, new coolant hoses, filters and belts, changed fluids, new bulbs, cleaned engine, and some other small fixes.

lietuviai · #33 10-31-2003, 07:59 PM

I think that I may have the same problem you do. I have been trying to find the source of the problem by following the replies to your thread. I am sort at the same point that you are, except that I'm going to drive the beast until it just goes to pieces. I don't care anymore. It runs, it gets me from point A to point B. Its a car I don't have to worry about if I left it parked someplace. When it gives up, I'll just junk it. I didn't pay that much for it. I bought it just for the heck of it in the first place.

Judge · #34 11-17-2003, 11:50 AM

One of the guy's mechanic friends came by and after listening a matter of seconds says that the knocking problem is a spun bearing, probably on #3.

He speaks real confidently.

I looked around on the web a little to try to understand just what a spun bearing means, and came up with these references.

Movie called Rod knock from under the engine with oil pan removed

Find the proper movie file below

The second reference is for a rabbit and talks of fixing a spun bearing by dropping the oil pan, but not pulling the head.

Drop pan to fix bearing and low oil pressure

Generic Shop Advice

lietuviai · #35 11-17-2003, 10:34 PM

A spun bearing is a real bad thing in most cases as it usually not only causes damage to the crank but to the bearing journal as well. I'm sure I don't have this problem since there is a mention of low oil pressure as is usually the case with spun bearings and I have normal oil pressure. Also you will probably find metal in your oil when you drain it. How is your oil and oil pressure?

Judge · #36 11-18-2003, 05:51 PM

I've got decent oil pressure. It pegs at 3.0 whenever I'm driving. After warming up, it falls to between 1 and 2 during idle after the engine is fully warmed up.

I've only had the car about 6 weeks and changed the oil just once. It seemed particularly dirty and somewhat sluggy. I don't know if it was dirty and sluggy from lack of maintance, or because the seller had filled it with a heavy weight oil to mute the noise. I had some feedback that diesel oil always comes out black looking.

I did not check the filter or the oil for metal flakes. I'll plan to when I do the next change.

Seems like my logical question is, what would I be able to tell about the condition of the motor by dropping the oil pan. I've never messed around with rods, cranks, pistons, bearings, and I would need a good reference to read up on before hand.

lietuviai · #37 11-18-2003, 06:25 PM

It would be quite a job since it has a two piece oil pan. The small bottom one is easy but the large upper one requires partial removal of the engine from the car to get it out not to mention all the other things that have to be pulled off before even pulling up the engine. I looked it up on my CD shop manual and there are 10 pages explaining the procedure.

psfred · #38 11-18-2003, 09:39 PM

You don't have a spun bearing. A spun main will give a deep clunk like a large brass hammer pounding on the crankshaft, the higher the load, the louder it is. Will go "clank clank clank" on takeoff, and fade away to almost nothing at speed.

It will weld the bearing to the crank journal, starve that bearing and the crankpin bearing it lubes of oil, scratch the crank, and eventually the crank will go. I know, my brother's 300D did exactly this. Will last a couple months, no more.

It does NOT sound like a bad injector. It is definitely deep in the engine and is almost impossible to hear at speed.

A snap snap snap noise is much more likely to be a bad wrist pin bushing than a spun main.

Kebowers · #39 03-24-2004, 11:02 PM

Lots of things can make a 'nailing' sound in a diesel. Starting with a bad fuel injector, faulty injector pump check valve, low compression, carbon deposits (piston hits them), pre-chamber a little too deep (see above)

Run a compression check on the engine to see if rings, pistons, and valves are good and tight. Then have the injectors checked for spray pattern. Then run a couple of bottles of TECHRON through the engine to remove excess carbon deposits.

My bet is on a bad fuel injector.

coachgeo · #40 03-24-2004, 11:42 PM

my .02 for what it is worth is eliminate the best you can the most common reason for knocking.

1. buy some lubramolly Diesel purge and follow the directions on the can (will clean injectors)

ORRR

2. Pull injectors, pull them apart (IN SEPERATE CONTAINTERS) soak them in carberator "chemical" dip. Soak over night and reassemble the injectors. DO NOT MIX PARTS. Reinstall with new overflow hose between each injector.

Start car! My bet is your nailing will be gone but hey... Im just a hack with lots to learn.

#41 03-25-2004, 08:59 AM

Not that this helps, but I think it's BABBIT not RABBIT. It's a special alloy named for the inventor, used for bearing metal.

Judge · #42 04-05-2004, 11:41 PM

Been a while, but I'll update.

Looks like I got ripped off. I found what seemed like the perfect mechanic. I verified with a friend who used to paint at the local Mercedes dealer that the mechanic had worked there for years, and knew what he was doing. This was the mechanic that said a spun bearing on number two

I paid him partially in advance, supposedly for parts, and then he ended up getting sick and going into the hospital with a recurrence of cancer. That part of the story is also verified.

He's out of the hospital and not going to the chemo that they scheduled him for. He doesn't return any of my calls, and is no longer at his usual place.

I've driven the car some, but I don't trust it, and would not use it cross the bay bridge with it for example.

'm looking for the easier thing to do to try to elimate the problem. Two estimates were for more than I paid, and more than the car would be worth fixed up.

Cleaned the injectors didn't change the nailing.

I'm looking next at seeing if a bit of a glow plug could be stuck inside, as was discussed in this
thread.

I'm also reading up to figure out how to access the prechambers. I'm guessing they are the part that the injectors thread into, and they themselves are threaded into the engine.

Finally, I'm guessing that the glow plugs are located just under and to the side of each injector, and all have an electrical wire going to each.

psfred · #43 04-06-2004, 08:48 PM

Correct on all counts.

You will need the tool to extract the pre-chamber, it won't just slide out anymore. It's held in by a ring that screws down, you must also have the tool to get that out (if you use a chisel or punch, the usually "cheap mechanic" way, they won't screw back down correctly). Shop made tools will work -- they have been described in this forum before.

I'd just pull the glow plug and crank the engine -- if there is a chunk of something in there, it should blow out the hole where the plug fits.

Peter

Judge · #44 04-15-2004, 09:26 PM

Turning the engine with glow plugs removed also didn't work. I needed to ask if turning the engine with the injector pipes off would create a mess, and did so in the small thread below. A rag over the ends was sufficient.

turn engine w/g-plug & injector pipe removed

Judge · #45 05-13-2004, 11:58 AM

I'm now thinking this noise isn't a detonation issue. That is because when I add centane additive boost, there is no change, and I've cleaned injectors, and swapped injectors position.

If its mechanical "interference" than the car keeps on running so I'm either lucky or it is not a a main bearing, or rod problem.

There is a tendency that the sound is louder for the first two seconds if the car has sat over night, and on the occasional 90 degree day, when the engine temperature is high. When the engine is running it is hard to locate the sound with a long screwdriver pressed to the ear, or borrowed mechanical stethoscope.

So, what type of "mechanic interference" issues would give a sound like baddly adjusted valves, and be worse for the first two seconds after sitting overnight, and/or when the temperature of on the engine guage is pushing 100c?