Nailing or other (300D Turbo 82) - Page 2 - PeachParts Mercedes-Benz Forum

#16 10-11-2003, 04:05 AM

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

Judge · #17 10-13-2003, 11:22 AM

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.)

Wasuchi · #18 10-13-2003, 01:02 PM

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.

Judge · #19 10-13-2003, 01:28 PM

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?

Wasuchi · #20 10-13-2003, 01:32 PM

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

Judge · #21 10-13-2003, 02:48 PM

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>>

Judge · #22 10-13-2003, 06:08 PM

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.)

engatwork · #23 10-13-2003, 07:32 PM

Quote:

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

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?

Judge · #24 10-13-2003, 08:28 PM

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,

Quote:

Wouldn't worry too much about the tensioner. You leave it in place when rolling the new chain in. It is a simple matter to get to it later. To test it just remove it and pull the long shaft out and push it back into place from the backside. Then test it by applying pressure with your hands on the end. If it stays where it was set to it is fine. If it slides back, it is worn out. But you can get to the tensioner at any time. It is externally mounted.

The quoted language can be found in page two of a thread named
300td timing chain Available 300td timing chain

The tensioner is further described as.

Quote:

The tensioner will only go in one direction and has a spring clip around the shaft and groves in the body of the tensioner where the spring ?ratchets? into to prevent it from going the other way. The slide actually has a softer material than I expected.

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?

#25 10-14-2003, 02:58 AM

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!

Judge · #26 10-14-2003, 10:27 AM

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.

Judge · #27 10-15-2003, 01:12 AM

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.

#28 10-15-2003, 02:28 AM

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.

#29 10-15-2003, 02:32 AM

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

Judge · #30 10-16-2003, 12:42 AM

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.