Valve Stem Seal Replacement OH NO - PeachParts Mercedes-Benz Forum

wallacewalrus · #1 07-12-2015, 09:33 PM

Greetings,

Today, while replacing valve stem seals on my 1982 300D-T, a nut fell into an abyss. The nut in question is the 14mm bottom valve retaining nut. The abyss is located behind the cylinder #3 valves, right under the rearmost camshaft tower. It appears to be an oil passageway going back down to the block... I 'm not sure. I 've never had the head off or done any major engine work. It 's very difficult to get a good view inside. Also very difficult to capture photographically, but I 'll post a picture. Hoping someone who has had the head off can provide some insight.

1. Do I need to remove the cylinder head in order to access this cavity and retrieve the nut ?

2. Is it safe to turn the engine over in this state ? Hoping it might just fall back down (& forward) to the oil pan. Seems like wishful thinking.

Any help very much appreciated.

Correction: cylinder #5.

WallaceWalrus

Wodnek · #2 07-12-2015, 09:56 PM

Is it somewhere you can get a magnet down to? I would think turning it by hand would be ok, but I have no idea if it can go further or not. Being that it is an oil passage, it doesn't seem like there is anyway it can get in the combustion chamber, but i don't know that it wouldn't get stuck in an oil passage somewhere. It would be a gravity feed passage down though, so if the passage ways are large enough, it should eventually make it to the pan.

wallacewalrus · #3 07-12-2015, 10:22 PM

Thanks for the reply. I believe it is a cavity with a small circular oil passageway draining from the bottom. I 'm able to probe with a long skinny screw driver, and I think the nut is accessible if I can put together the right setup with a magnet on a wire. Alternative is removing the camshaft which would greatly improve access to the cavity.

I 'm not sure whether the nut can move through the oil passage or not. Not familiar with the size of those passages. It has a long path back to the pan.

moon161 · #4 07-12-2015, 10:23 PM

I'm not familiar with the passage. In most cases, the choice for getting things out from where they're not supposed to be is out the way they came. You might try a magnet on a stick sort of probe.

The factory manual might have a diagram of where those passages go, and you might be able to determine how safe it is to push or flush it down.

Buying or making a strong magnet on a stick, or perhaps a dipstick sounds easier that dropping the lower pan. If it's on #3, that is not, i think over the lower pan either.

wallacewalrus · #5 07-12-2015, 10:46 PM

Thanks for your thoughts.

The access underneath that camshaft tower (or bearing mount, as the manual calls it) is very narrow. I will keep trying to get a magnet in there though.

Does anyone know whether I can remove the camshaft bearing mount without fiddling with any of the rest of the camshaft or timing chain ? If so, I could just slide that off and it would expose the cavity enough so I could get a number of tools in there, maybe my hand.

ollo · #6 07-12-2015, 11:01 PM

There are several magnetic pick up tools available. I have the cheap one from lisle, as well as a flexible "grabber" from a local auto parts store. They have saved me many times. Don
Sorry, I copied an inappropriate link Look Here for Magnetic Pickup tools: Pelican Parts - European Automotive Parts and Accessories - Porsche • BMW • Mercedes • Volkswagen • Audi • Saab • Volvo • MINI
Don

ROLLGUY · #7 07-12-2015, 11:16 PM

Quote:

Originally Posted by wallacewalrus

Thanks for your thoughts.

The access underneath that camshaft tower (or bearing mount, as the manual calls it) is very narrow. I will keep trying to get a magnet in there though.

Does anyone know whether I can remove the camshaft bearing mount without fiddling with any of the rest of the camshaft or timing chain ? If so, I could just slide that off and it would expose the cavity enough so I could get a number of tools in there, maybe my hand.

If you put it at TDC and remove the gear, you can just remove the entire camshaft and towers. It is not that hard, and won't affect the timing as long as the crank remains at TDC. It would be easier to replace the seals with the cam and rockers out of the way in the first place....Rich

EDIT: corrected- you would not be able to put each piston at the top, so the cam and gear needs to stay for replacing the seals.

wallacewalrus · #8 07-12-2015, 11:50 PM

Thanks Rich. Anyone know the size on those torx bolts ? There are two of them on each camshaft tower. I will need to buy a socket, or a set.

ROLLGUY · #9 07-12-2015, 11:58 PM

Quote:

Originally Posted by wallacewalrus

Thanks Rich. Anyone know the size on those torx bolts ? There are two of them on each camshaft tower. I will need to buy a socket, or a set.

They are actually head bolts, so they need to be torqued to the proper spec. The tool is available here (Pelican Parts). I believe it to be a 12 point 12mm. Part # TOL-M0105-SIR

wallacewalrus · #10 07-13-2015, 12:16 AM

Quote:

Originally Posted by ROLLGUY

They are actually head bolts, so they need to be torqued to the proper spec. The tool is available here (Pelican Parts). I believe it to be a 12 point 12mm. Part # TOL-M0105-SIR

Would I need to loosen the other head bolts and re-torque everything ? No experience torquing head bolts, but I know it is a critical operation.

I 'm thinking of trying to remove just the rear tower. I have a broken old 617 I can try it out on first.

ROLLGUY · #11 07-13-2015, 12:24 AM

Quote:

Originally Posted by wallacewalrus

Would I need to loosen the other head bolts and re-torque everything ? No experience torquing head bolts, but I know it is a critical operation.

I 'm thinking of trying to remove just the rear tower. I have a broken old 617 I can try it out on first.

All the towers need to be loosened in order to remove any of them (locating pins). I don't think it would be the end of the world if you just removed the tower head bolts and re-torqued them.

Left Coast · #12 07-13-2015, 12:50 AM

I think it's the #5 cyl, not #3. At least that's what your pic is showing. Fish it out with a hook on the end of a piece of stiff wire. Be patient and you'll get it. I think it's too big to fall through into the block.

cooljjay · #13 07-13-2015, 01:07 AM

I can't tell where that is...but here is a head...I see two areas where this nut can fall....behind the 5th cyl....and in front of the 1st(timing) chain....

wallacewalrus · #14 07-13-2015, 09:32 AM

Quote:

Originally Posted by Left Coast

I think it's the #5 cyl, not #3.

Yes, thank you.

Thank you Jay for posting the head picture. The nut is in that kind of cleaver shaped cavity that is very clearly shown. Can you tell me what is at the bottom of that cavity, and would a 14mm nut have a chance of falling through ?

WallaceWalrus

wallacewalrus · #15 07-13-2015, 09:53 AM

Very excellent news-- nut retrieved using wire hook as suggested by Left Coast. Really did not take long. Thanks very much. Come to Ukiah, California, for free beer.

Future valve stem seal replacers-- beware the abyss at the rear. It is little talked about.

Onward.

WallaceWalrus