I need to change the belt tensioner on my 87 300E 103 motor, and the 8mm bolt that mounts the fan clutch to puylley is stripped!?

Anyone know how to get that bolt out without removing radiator and condensor?

Thanks

Isn't it an allen bolt?

I'm sorry. I wasn't very clear. I had a mechanic rebuild my head but he stripped the 8mm hex bolt so now I cannot remove my fan clutch the way I should be able to. I know the procedure well. I am just wondering if there is any type of extractor that I can use without having to remove radiator and condensor, to drill and use e-z out.

I had this problem and found that the only way I could get the bolt out (drilling wouldn't work without removing the a/c condenser as well as the radiator) was to remove the fan bearing bracket, with fan attached (which was enormously difficult, I recall having to cut one or two of the bolts with a hacksaw blade because they were too long to remove with the fan still on) and then putting the fan bearing bracket in a vise (gently) and using a small cold chisel to loosen the bolt. NIGHTMARE!

Only done it once though, there may be an easier way. Oh, and I replaced the bolt with a high tensile one which makes it a lot more resiliant to stripping.

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Andrew
300e 294,000mi
380sel 185,998mi
380se 309,980mi

Man, that sucks.

Unfortunately (particularly since the bolt is recessed in the hub) you will need to clear stuff from the front of it.

You might get away with just the radiator, if you're lucky.

Then try to:
* weld something to it, if you have a MIG welder and can get access (not sure if this will work).
* Bash a hex plug into the bolt (what's left of it) with a lump hammer and then undo it.

Good luck!

Does anyone know if there any extractors that are specific to internal hex head?

Special tools
http://www.irwin.com/irwin/consumer/jhtml/browse.jhtml?catId=IrwinCat100310

I would take the easy route = weld something to it, if you have a MIG welder and can get access, this is cheap and will work.





Have a great day.

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1985 300SD
1983 300D
2003 Volvo V70

https://www.boldegoist.com/

I also recommend the mig welding route, I've used this trick several times to get broken studs out, and it's worked every time. (works really well on broken off studs in aluminum heads!) Part of it's success is that when you weld the bolt it heats up, which helps to loosen it. I don't know of any specific easy-out type extractors for the Allen bolts. You could check the size charts for metric/SAE allen wrenches, maybe you could find a very slightly oversized wrench you could pound in after filing a bit.

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Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C

I think most of us have run into this one before.

I recall using an 8mm closed-end where you can get it over the bolt head will help. An open-end simply doesn't have enough grip.

Haasman

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'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)

Is the threaded portion of the bolt stripped or is the 8mm allen head rounded off?

The latter has VERY soft metal and rounds off easily.

If this is the case, S-K tools makes a "pipe plug socket" that's good for removing rounded allen heads.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

It is a simple procedure, but it requires shop air and a right angle air grinder. You will also need a drum shaped grinding bit that has a grinding surface on the end. it is hard to describe but the bit is steel, looks like the shape of a new pencil eraser, and needs to be about 10mm in diameter. Stick it in the end of the bolt and continue inward until the bolt head falls off. Then remove the bolt with your fingers. Hope this is clear.

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Auto Zentral Ltd.

You may want to try a torx of about th 8mm size. It has a better gripping capacity than the allen-head. Not a pro, but my 2-cents.

Sorry to hear about your current plight. I will share with the forum a few techniques that I developed to avoid rounding off allen head bolts (AKA: Cheese Heads) as well as contending with one when it is rounded off.

The Loosening/Removing technique:

1. Feel for the grip of the allen bit, it should be fully seated in the bolt head (clear debris as needed)
2. Begin by applying slow, steady pressure to the tool you are loosening the bolt with.
3. Feel the bolt and the allen drive, if you sense the allen drive is just rotating STOP
4. Reverse direction and tighten it until you hear the bolt CREAK
5. Again with slow steady pressure try loosening the bolt, if the tool begins to rotate without hearing the bolt creak STOP.
6. FOR STUCK FAN BOLTS:
7. A block of wood (oak flooring material has been my choice) placed on the radiator surface will give you sufficient area to pry against without damaging the radiator.
8. Place a bent end pry bar against the wood then pry against the allen drive socket end in order to create more inward force
9. Again with slow steady pressure try loosening the bolt, if the tool begins to rotate without hearing the bolt break free it is “ALTERNATIVE METHOD TIME”

The Alternative Method:
Requires the use if a 90 degree high speed device (Die Grinder with Rounded end Bits)

1. R&R Radiator
2. Place a ½ rounded end bit (small flute) into the to die grinder
3. With care and caution (avoid tool chatter) begin to grind the center of the head
4. Once you have established the pattern for the bit continue grinding
5. Grind deep enough so the fan just falls off OR
6. Grind deep enough and then pry the fan off

The Avoidance technique:

1. The bolt securing the fan spins on it center axis
2. It does not require excess pressure to hold the fan in place
3. Once the bolt is seated, give it a little more torque (1/8 of a turn-MAX)

When accessible allen bolts develop problems:

• For 5mm allen bolts hammer a 10mm 10 point socket onto the bolt head
• For 6mm allen bolts hammer a 12mm 12 point socket onto the bolt head

FWIW:

• Some Intake bolts will simply break due to electrolysis, break them and move on
• A ¼ drive allen drive socket works best for the Air injection pumps on 116/117
• A Micro-torch and Zepreserve work well on stubborn distributor bolts
• When attacking broken wheel studs, cobalt drill bits cut well at 75 to125 RPM’s
• Metal curly cues are your visual evidence that a drill bit is working properly

You can get JB Weld at Home Depot. Supposed to be kick-ass stuff. Just read the back of the bottle. Goes on as a liquid, dries rock hard.

Thanks for all the help guys. I'm waiting for the parts to arrive and I will try a few things suggested before I take it to the shop. I know a good mechanic who has an air grinder and anything else he may need to remove it, so I might just pay him to take care of it for me.

The Mig welder idea is the Great! Now I just need to buy a welder

Happy 4th