Replacing my motor mounts in my '81 240D with auto trannsmission. if I understand the process I am supposed to remove the 8mm hex bolts from the bottom first. Those bolts are not easy to remove!

I have tried a fairly long handle socket wrench with a properly sized hex socket, but feel if I turn any harder, these heads will strip. That would be a bummer since the heads are recessed in there and would cost me a bunch more time to remove. I have tried to soak with lubricant, but it is pretty hard to get the fluid where it needs to go on that bolt since it is upside down and appears to be unreachable from the top side.

So what's the best way to remove it and minimize my chance of stripping the head? I am willing to buy another tool of some sort if it has a better chance of working (good excuse to invest in more tools).

-impact wrench?
-heat with torch?
-beat on it with hammer to loosen?
-other???
Any ideas are appreciated from those who have walked down this road.

Also, on a side note, the only leaky thing on my car is that steering box (or whatever that box is that the stering column is attached to) See pic, taken from underneath - it is just covered with fluid and grime - I need to power wash it and get it clean again to see where the leak is, but does anyone know where they usually leak? I even see fluid on the top of it looking down at it from the top in the engine bay.

As always, thanks in advance for any assistance.

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heat the aluminum arms that extend from the engine block with some kind of torch (not too hot.. abide by melting temp of Al)

let them cool

heat them again

when its fully cold again, heat it and try to twist the bolt.


lubricants / penetrants are often used incorrectly. This is one of those times.

all you are accomplishing is lubing the head of the bolt so that your socket will slip.

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I have used a very good quality hex key with a 3' pipe on it.
You could try hitting the center base of the hex recess with a center punch.
The hex bolt is screwed into the alloy arm off the motor, I dont know if it would help to heat that from above. Worth a try.

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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

Hey Treiberg,

I just replaced my motor mounts and shock on my 240D, auto.

Looking at your pictures you are going to need a longer lever. That ratchet will not crack the 8MM bolt. Need a three foot breaker bar. Try to use 1/2" tools.

Spry the bolt and head with a penetrant. Clean the allen socket. Insert the allen socket and tap it in with a small ball/peen hammer. You will feel it bottom out. And then have at it.

After those are backed out. Remove the shock (replace that bugger). Then remove the rear engine mount. Support the oil pan with a nice piece of wood and jack up engine. Depending on the deteriorated state of the mounts you may have to raise the engine more, seemingly more. After engine is raised the the 4x6mm Allen bolts are a POC. Then simply slide the old mounts out. Pay attention to the orientation of the metal rubber shields.

Respect those Al threads they are very fine. When installing make sure the frame and Al engine mount arm are perfectly lined up - perfectly. Lie under the car perpendicular to the opening. Look up. Make sure the frame bolt hole and arm are lined up. Thread the bolt by hand. If it is lined up it will thread quite number of turns by hand.

Good luck,
Zill.

Just need more lever, huh Zill? That sounds good as I do have a breaker bar. The reason I stopped and didn't push harder was not that I ran out of strength with my 1/2" socket, but that I noticed some deformation already happening...the socket was starting to get stuck in the head of the bolt and I needed to reverse direction on the wrench to get it back out.

Reading through the threads on the topic: some have suggested heat using a torch. I hesitate to use an open flame in an area where I have been spraying extremely flammable penetrant. I wonder if a heat gun (like they use for heat shrink tubing) would help. Some say heat the bolt, some say heat the arm. One thread the guy tightens it, then loosens it. That seems strange. Another one says lift the engine a bit to remove force. But actually the bolt is already in tension...lifting engine will only add tension to the bolt and make it tighter.

As previously stated:
No matter what you use to turn it Heat works wonders. Getting a punch that is slightly smaller than the inside of the Hex and giving it some good sharp raps with a Hammer is also helpful; more so due to the Aluminum arm.

Take a good look at the end of your Allen Socket. Some of them are rounded too much on the end. If you are worried about stripping the Allen Head you want the Allen part of the socket to be flat acrossed the end so that the Allen Head filles it top to bottom.

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84 300D, 82 Volvo 244Gl Diesel

Diesel911, what method would you use to apply heat? I am afraid of a torch around an area that has flammable penetrant. Could a guy use a heat gun?

Even if you set fire to the penetrant, a quick douse of water will end the fire. Then yoiu can carry on with the heat.

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I choose to be happy, even when the Mercedes is being awkward, lol

A Propane Torch is better. For this particular job one of those Butane Torches that you can fit in the Palm of your hand might work.
The Prpane Torch is over all more useful for the future.

A Heat Gun could still melt plastic stuff or Wire insulation and it heats a larger area more slowly.

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84 300D, 82 Volvo 244Gl Diesel

Use some valve grinding compound on the hex bit, it will help it bite into the bolt.
I use my breaker bar and a 6in extention all 1/2 in drive with the hex socket.
give it a quick pull, and it should snapp free. usually using steady pressure will make it slip. this has worked for me.

make sure the bolt head is cleaned out so the hex bottoms out in the head.

Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Where can I buy valve grinding compound?

Hey Treiberg,
Diesel 911 has some good points. Use a flat allen socket. Heat can't hurt. I'll bet Al will expand quicker than steel. Diesel is correct, heat the sucker and then smack it with a slightly undersized allen. Your idea about the heat gun may work but you will not generate the searing heat of propane. Have on hand a spray bottle filled with water.

If you are getting a good size breaker bar and still you feel it slipping either you have not fully inserted the allen (junk in the bolt head) or the allen itself is rounded or the socket is of poor quality (no dig intended). I noticed the same thing on the one of the 6mm allen bolts. It was slipping like you describe. I took a good look at the end of allen and noticed it was only inserted about half way. Gently tap in and have at it. It will break free.

If all else fails and you have access to a good indy shop take in and have them break the bolts. May cost you a couple of bagels.

Do you see allot of corrosion up in the bolt head area?

Good luck,
Zill.

I just removed my motor mount bolts today. I must say that you should be concerned about stripping the internal hex head. One of mine came out easily, but the other was stripped. I tried everything, torch- bad idea, set the rubber from the motor mount on fire. Large torx head driven with a hammer into cap, it just stripped some more. Some people on this site suggested just drilling the head of the cap screw. The problem with that was, how would I remove the remnants of the bolt from the arm in the confined space. Some said to pull the whole arm from the engine, that looked difficult, and had its own perils. After alot of searching i decided to use a type of modern easy out. It is double ended, one side a indexed drill bit, the other a spiral easyout. With this tool you use a reversable drill set on reverse, bore the hole, flip the easy out and screw the easy out into the bolt. Now the bolt is supposed to come right out with only the power from the drill. However most drills don't have enough tourqe, and mine didn't either. I had to remove the easy out from the drill and twist the bolt out with a socket wrench. It worked. This post may seem long however, the process of me removing my stripped motor mount bolt took almost 2 years. As long as the engine wasn't hitting the hood, I figured I could put off the repair. Do yourself a favor and try everything in your power to avoid stripping those bolts. My advice would be - square edged hex driver, valve lapping compound, Some heat on the arm- but don't burn up your car. I hope my saga will not discourage you, Good Luck, Dave

I have done this several times on several 240D's. I learned from another contributor here that it is imperative that you clean the socket head out completely. Don't be fooled by looking in and thinking you are seeing the bottom of the hex hole. There is often a hardened layer of mud, road debris and some corrosion at the bottom. In any case, clean it up thoroughly and then wet the Allen hex tool and dip it in an abrasive cleanser, like Ajax, Comet, Bon Ami, etc. and then insert it into the hex head bolt. This bit of advice was critical to my success. I typically tap in with a hammer to ensure it is at the bottom of the hex hole. The Ajax abrasive particles are fine and ensure you get a tight fit, with lots of extra friction to prevent the head from stripping.

I am sure lapping compound or another fine abrasive material work as well, it is just that Ajax/Comet/etc. are usually readily available.

I recommend you buy another, new bolt to replace the old one if the fit is beginning to loosen up. Take the old bolt to a decent hardware store and match it for thread, length and material grade.

Good luck,

Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

I had the same problems as you-stuck hex bolts on the motor mounts. As others have said 1)clean the hole in the hex out 2) gently tap the hex end into the bolt all the way so it is well seated 3) use lots of leverage to unscrew. It also helps to have an 18" extension on the socket wrench. Allows better leverage I believe. HTH, JEFF

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1981 240d aka "The rust bucket"