Nailing or other (300D Turbo 82)
 

I recently bought a 300D Turbo that had a nailing sound. When I bought it I thought that the sound was misadjusted valves, and that I'd be buying a car that I could fix cheaply.

I've done the valves and that got me more power, but no change in the nailing sound. I also changed filters all around.

That led me to research and this board. There is a lot of information in this board on "Nailing" generally describing it like the sound of a hammer nailing.
hammer nailing nails

In trying to find the problem, I then cracked open each of the injectors in turn, and that hardly or did not change the nailing sound, each time engine speed dropped, and idle became rough, but almost no change in the nailing sound.

I borrowed a mechanic's stethoscope, and found that the nailing sound seems to come from low down near the front of the block, right near the oil pan and the pulley the fan belt rides on.

I also notice that from underneath, the fan belt to some extent is wobblying in time with the nailing sound.

I'd like to hear some opinions on what to do next, and Is this likely to be the type of problem that destroys the engine if I keep driving it as is?

Someone just recently had the lower pulley come loose. Might check to see that it's tight and look for the thread too, it was in the last two weeks I believe.

http://www.peachparts.com/shopforum/diesel-discussion/75706-sos-need-help.html


This is it!

A bad belt can make a noise astonishing like a bad rod -- it will go away when the belt is changed or the glazes section sanded.

However, a clank near the front of the engine can be a bad bearing, at worst actually spinning in the block. This would be bad news -- is it worse on acceleration or the same all the time? Same all the time would be more likely to be a bad balancer or pulley....

Peter

The nailing sound is a little worse under acceleration.

I'll go ahead and run the car for a couple of seconds with all the belts removed and then report back what I hear.

Well, I took all the belts off, and started the car up. No change in the nailing sound.

I had also listened a little more with the stethoscope, and I become less sure that I am able to localize just where the sound is coming from. But generally lower down.

I'm waiting for a diesel specialist, but non-mercedes specialist to take a look see.

Anyone want to give their thoughts on what is wrong, or what to try next??

Chain slap or rod knock.

Peter

If there is any evidence that an oil cooler line was replaced before you bought it, I'll second the view that it is a bearing problem.

Cracked piston, piston contacting the precombustion chamber, or (Dare I say) cracked crankshaft?

Well, I've certainly got a range of opinion on what the problem could be.

The diesel mechanic came by to take a look, but unfortantely I couldn't see with my own eyes how he made his diagosis.

The mechanic says that the problem is a bent intake valve on #3 piston.

I expect I will go with the mechanic, but am open to any board wisdom. Like I said, I couldn't hear the problem with a stethoscope on the valve cover, but heard the problem lower down and when I crack open the injector for # 3, the engine slows and idles rougher.

And if the diesel but non-mercedes mechanic fixes the bent valve problem, is there anything that I should be particularly aware of.

Count me as a skeptic on the bent intake valve on #3.

Skeptic #2 right here.

I would think you would be getting a lot of smoke with a bent valve. Maybe a chugging sound too. I've had a bent exhaust lifter and it made a chugging sound and a nice blue cloud that smelled like oil and diesel. The mechanics I went to diagnosed it as a bad IP and one said burned piston... it was much cheaper and easier to fix than either of those. Something else would have to be pretty messed up to have a bent valve too. Keep us posted, guess you either need to go with that guy or try to get someone else to check it out. Good luck.

Where are you located? Maybe someone could point you to a good indy in your area.

Thanks for the advice. I added my location to my profile: San Francisco Bay Area. One local independent thought it would cost more than the car is worth to do a valve job.

At this point I'll try to arrange with the diesel mechanic who said it is a bent valve, and tell him that I will pay when the problem is fixed, rather than pay him to fix a bent valve. That way he stands by his diagnosis or doesn't.

Somehow I doubt that it is a bent valve, but then I'm not experienced enough. Here is one mone more piece of information.

When I last had the valve cover off, I noticed that where the front left valve cover bolt rises into the valve cover, the metal had been destroyed. That is, the air cleaner bracket had broken, and the air cleaner had become a small hammer vibrating against the valve cover. Eventually a small piece of the interior part of the valve cover had come loose and was missing. Maybe, that small piece of metal could have caused a bent valve?


I don't have a complete history of the car, on when the timing chain was replaced, and if anything causing damage had occured.

Thanks Board for the company in diagnosising this.

Cheap ways to look for a bent valve: Look under the valve cover, or take off the intake/exhaust manifolds and look in the ports. Compare it to the other valves and take it from there.

Sounds more like a dead chain tensioner and a badly stretched chain - they will run on the vavle cover if the oil gets low enough (don't ask how I know, but if anyone EVER claims "they didn't hear anything" when the car ran out of oil and locked up, they are lying!).

Peter

Hey Judge, I have an 85 300D that was making a hell of a knock also. I am a diesel technician employed by Cummins West. I started doing some investigating into this noise, you know usual things like possible spun bearings, cracked piston, dropped valve etc. I pulled the head and decided to just rebuild the entire engine and be done with it. From reading your postings I would be very doubtfull if you have a bent intake valve. Did you remove the air cleaner and listen, a bent intake will pop very noticably through the intake manifold. The quickest way to check for sure is what we call a cylinder air test. Remove your valve cover so you can see the valve positions, remove your injection lines and #3 injector. Nect, bar the engine over with a racthet on the alternator until both valves at #3 are fully closed. You need an air compressor and a rubber tipped blowing nozzle. Take the nozzle and stick it in the injector bore sealing the opening with the rubber tip. Now blow air into cylinder, its normal for the piston to be pushed down during this, if a valve is bent you will hear the rush of air either in the intake or exhaust. This is the quickest most reliable short cut for this I know without getting to deep into this engine. I live in Weston Ranch at the south end of Stockton which is not to far from San Francisco. I just got done doing a valve job on my cylinder head. I groung the seats and valves and replaced the guides and seals. If you are interested bring that head to me and we can discuss a deal to rebuild your head, definately cheaper than a machine shop quote. If the valves are good and dont require excessive grinding and the head is not cracked or warped then the parts would probably run about $100.00

cummingsnut,
I'll get back to you. I take a misguided pride in trying to be self-reliant in fixing my cars. Sometimes that pride has done me wrong, and I've spent much more time trying to fix something, than it would have cost to bring it to a mechanic. But I like the grease, the learning, and the "you can do it yourself feeling." I'm also following your report on the other thread, keep reporting.



I want to do all of the tests to determine the "nailing or other clanking sound, " without removing the head. I'm afraid that if I take off the head, I'll have a vehicle taking up the garage for months, before I get it back together.

Next step, I'm going to take psfred's advice and check today for chain slap caused by an elongated chain, and broken tensioner.

Though it must be somewhere in the archives, I'm not sure how I tell if the tensioner is broken. Maybe its an obvious test, as in you know the tensioning function, and you can see that the tensioner has become stationary, therefore the tensioner must be broken

(Search tension even in titles bring up soo much information, that I'd be too many hours trying to read it all.)

If the chain tensioner is bad I think the chain will/should be loose. You should be able to tell once the valve cover is off. I'm sure someone will correct me if I'm wrong.

I've got the valve cover off, and i'm having a harder time of aligning up the marks to check for chain stretch than I thought. Perhaps two people are needed to be efficient because each time I move, get up, see that I went to far, do again ....

Following up on Wasuchi's post, would loose pratically mean, doing the old fashion test on fan belts, of pressing it and seeing if there is a certain amount deflection?

Yeah, that's pretty much what I meant. You shouldn't be able to get much deflection at all if everything if working right.

Using the non-dial gauge method of lining up the marks, I find that the chain stretch is 2 to 3 degrees.

The postings here was most helpful in understanding how to check the marks for stretch of timing chain.

I'm now following the instructions in a pdf file on this

http://www.meimann.com/docs/mercedes/ web page about removing the tensioner.

And this thread asks how taut is taut, and then provides a description of the operation and possible adjustment of the tensioner.

This board is great. I hope by documenting what I'm doing, it will be helpful when someone is trying to fix a similar problem>>

Tensioner is out.

It is straight forward to remove it, just follow the directions on tensioner.pdf file found on the following web page. http://www.meimann.com/docs/mercedes/

My first impression findings are
both the spring and the work end of the tension show obvious signs of wear.

The spring is ground "shiny" on several sides in the middle. (does that make sense, or is a photo necessary.)

The work end of the tensioner is also ground shiny off-center.

I'm finished working for today on the car. but I'll call to see what the dealer will charge for the part, to compare with mail order. (Edit. Dealer says that have to order it and it runs more than $300. hemm. the dealers don't want do it your selfer business.)

Just about everyone I have ever opened up that had been in there awhile had some of this. You should be able to get a tensioner assembly for alot less than what the dealer quoted. Don't forget to pick up a new gasket when you get the tensioner too. How does the rail look?

I'm figuring out from reading these forums how I would know if I should or should not replace the tensioner. And I'm trying to not spend money on something that won't fix my ultimate purpose of the nailing sound.

For the tensioner, I found this good information posted just about a year ago by Old Deis,

The quoted language can be found in page two of a thread named
300td timing chain Available http://www.peachparts.com/shopforum/diesel-discussion/49322-300td-timing-chain.html?perpage=15&highlight=tensioner%20AND%20bad

The tensioner is further described as. by the starter of the same thread at page 5.


engatwork

I understand that the rail is the curved thing, well curved rail that some were calling the banana slide in the thread that I linked to.

The chain will ride on the rail and it is tensioned by the tensioner that I just removed. After I removed the tensioner, there is a lot of chain slack by the rail.

I notice some deep sratches about an inch down on the rail. How do I know if I should replace the rail?

Hey Judge I respect the fact that you like to complete a job on your own. I am the same way, working for a Cummins Distributor I know how things run internally in a shop environment. I will not take anything I own to a shop unless it is warranty. Even on my Camry, I went and bought all the tooling and an OBDII scanner just because I know one day it will pay for itself. Anyways, I was just offering if you needed it. Feel free to post any cylinder head questions if needed. I am going to replace the timing chain and the oil pump chain when going back together. But after reading your post about the tensioner I think I better take a better look. Are there two different types of tensioners? I think mine has a piston with a small spring that pushes against the rail with oil pressure. But I am not positive, its an 85 300D if that means anything.

Also, Judge is absolutely correct. This forum is great!

This is a please correct me if I'm wrong post, but in one of the threades I linked to, Larry Bible realized that there were two types of tensioners.

My tensioner is acting like a piston or shock absorber, which I understand makes it broken, because it should be acting like a rachet.

If I got this right, there are in effect two springs. One the traditional spring, and the second that looks like a cross between a circlip and an o-ring. The second circlip spring catchs on the ridges inside the housing.

Fustration. I put a different tensioner in, and I'm still hearing the knocking, nailing, or whatever sound.

The diesel mechanic has been flacking out , but maybe he has an excuse.

Still a couple lessons learned.

1) To rotate the engine inorder to line up the marks (or adjust valves) use the jumper box that is on the sidewall between the battery, overflow radiator tank, and the air cleaner housing. A pair of point nose plyers works well to jump accross the terminals. Then once you are close, you might be able to turn the engine the last bit using either the bolt at the alternator or the power steering. (It ain't easy doing it the official 27 mm bolt way.)

2) lift the hood up completely, to the completely verticle, rocket ship in takeoff position. (pull the latch out on the drivers side.)

3) be carefull when working around the radiator plastic pieces, such as the small piece that connects a hose to the expansion tank.

Hey Judge, just curious if you attempted that air test I worte about. Its nice to have the piece of mind knowing its not a bent valve. Another thing to check for would be metal in the oil. Remove your oi filter and lay on a bench covered with rags. Now take a hack saw and cut open the filter and spread the fiter media apart. Making sure that you a looking at the inlet side of the media take a little brakleen and lightly spray some of the oil off. If there is metal it usually shows up when doing this.

Do a search on pre combustion chambers, some very good threads on how they can cause a knock.

I'm starting to hate this car, but I shouldn't, I should blame the mechanic; myself.

Even that I live in the Cty, the Mercedes dealer didn't have the tensioner or gasket in stock, and wanted over three hundred for the tensioner. I didn't want to wait for mail-order, and thought that I give a try at the junk yard. Found a beautiful 300D Turbo in great shape in Hayward. I picked up a good looking tensioner from the junk yard, carefully scraped off and cleaned the old gasket, and installed the new tensioner. I thought I was doing great!! Should have known.

After starting the car up, it still had the "nailing/knock" but worse in now also leaked oil at the tensioner.

Any good mechanic would have taken the tensioner out, and redone the gasket. But I hadn't hired a good mechanic. Instead, I checked if I had tighened the 13 mm bolts. They weren't tight, so I tightened, and a couple twists later one broke off. Argahhhh.

Came back a three hours later, and the car had a $35.00 residential parking ticket. Double Ughh.

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..

Update
 

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.

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.

Update, new mechanic says spun bearing, possible #3
 

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

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?

Oil Pressure and Metal in Oil
 

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.

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.

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.

knock knock what's there
 

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.

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.

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.

Update, next look for glow plug bit in pre-chamber
 

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.

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

turning engine with glow plugs removed
 

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.

http://www.peachparts.com/shopforum/diesel-discussion/91857-turn-engine-w-g-plug-injector-pipe-removed.html

Now thinking Mechanic rather than Detonation
 

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?

I've read in a few replies including a couple to my own posts is that it could be the vacuum pump making the noise. I still have my "tick" after putting in an other set of injectors. The car does seem to run much better now and has more power, idles smoother and doesn't stall soon after starting it cold if I let my foot off the pedal.
Additonally I've gone through and readjusted my valves and even checked my chain for stretch the guides and tensioner for wear. Too my pleasant surprise I found virtually no chain stretch on the car with over 225K miles on it.
I think I'm probably overeacting to my problem.

So, how many miles have you driven this since you first noticed the noise?

Have you done the compression check?

Metal in oil?

Although I can't hear the engine, it is starting to sound like a possible rod bearing problem. It knocks until the oil pressure pumps up in the morning and it knocks when the engine is hot. If this is the problem it may not be too late yet to repair with new bearings.

Also, I would want to rule out the vacuum pump as the cause before I jumped into the bottom end.

Good luck.