Removing a hex bolt that is in tight

[JHZR2]

It’s the belt tensioner on my new 91 350SD. Probably original. I had noticed early on that it was in bad shape.

I have a new Mercedes tensioner, it’s the same as the one on there. They are installed with some sort of thread locking sealant.

I’ve been using a quality 12mm SK hex socket on a 18” or so SO ratchet. I can put a decent amount of torque on it and it’s going nowhere. I can flex the ratchet a good bit.

My concern is rounding the stupid hex bolt out. Then I’m really screwed. The tensioner is functional now, but I wouldn’t trust it. I’m concerned if I mangle the bolt, then the whole front end needs to come out. Lots more work.

I don’t think I can get penetrant on there. I probably can run the car to get it hot and then try again. I’ll go at it next time (carefully) with a 1/2” breaker bar and hex.

Installation torque is 100nm with onmifit 10, which seems like a theeadlocker. I’m inclined to use 243 since that’s what I have on hand, with a primer. I do have 271 but I’ll cross that bridge when we get there.

Any recommendations to do this without messing anything up?

All the other bolts on the front end are very clean and came out of the engine easily. The fan clutch bolt showed zero corrosion on the threads. So I don’t think this is a corrosion issue fwiw…

Thanks!

 

[RooflessVW]

I'd put my right angle impact on it.

Barring that, get it hot as hell and quench it with some penetrating oil.

 

[97K15004WD]

Hit it with the blue wrench and get it hot, then try removal. If doesn't budge the threadlocker didn't get hot enough to liquefy.

 

[JHZR2]

I'd put my right angle impact on it.

Barring that, get it hot as hell and quench it with some penetrating oil.

Is there an issue with using an impact to remove a loctited bolt? For example with residues in the female threads?

Hit it with the blue wrench and get it hot, then try removal. If doesn't budge the threadlocker didn't get hot enough to liquefy.

I’m not sure how that would work. The tensioner looks like this:

If I hit the bolt with heat, it would expand faster than the block that it’s threaded into. Wouldn’t that make it ultimately harder to remove and more chance to damage the threads? I would think at minimum if I use heat, I need to get the engine up to temperature so there isn’t a huge disparity.

 

[Creekside]

Is there an issue with using an impact to remove a loctited bolt? For example with residues in the female threads?


I’m not sure how that would work. The tensioner looks like this:

View attachment 120581

If I hit the bolt with heat, it would expand faster than the block that it’s threaded into. Wouldn’t that make it ultimately harder to remove and more chance to damage the threads? I would think at minimum if I use heat, I need to get the engine up to temperature so there isn’t a huge disparity.

You want the bolt to expand and then contract to help break some of the corrosion that’s preventing it from moving. Also I don’t know anything about SK hex sockets but my money would be on Bondhus.

 

[RooflessVW]

The bolt will expand less than the hole.

I'd have no issues using an impact. There may be some residue (dust) on the threads but you can chase them.

 

[JHZR2]

The bolt will expand less than the hole.

I'd have no issues using an impact. There may be some residue (dust) on the threads but you can chase them.

Look at the tensioner. I can’t really hear the hole/block unless I run the engine. Too much thermal mass and tight area. I could notionally heat the bolt.

I’m not sure that there is corrosion based upon removal of all the other bolts on the front of the engine, which have all been clean. Loctite perhaps.

I don’t have a chaser for whatever that is, nor will I by tomorrow. The female hole may go through the block.

 

[spasm3]

IF you know there is some locking sealant, absolutely heat! Heat then impact. If you can't get impact on it, 6 point, or box end wrench and tap it with a hammer in both directions. If it loosens at all, then the breaker bar.

 

[JHZR2]

IF you know there is some locking sealant, absolutely heat! Heat then impact. If you can't get impact on it, 6 point, or box end wrench and tap it with a hammer in both directions. If it loosens at all, then the breaker bar.

It’s a female hex.

Ok might as well run the car and then heat the bolt direct after.

 

[ms21043]

I'd try the 1/2 drive breaker bar

 

[CleanSump]

That bolt is coated with red loctite and torqued to 75 ft lbs. Had this issue with my old 92. Propane torch and a longer breaker bar was the solution.

 

[spasm3]

It’s a female hex.

Ok might as well run the car and then heat the bolt direct after.

Sorry the pic made me think it was an external hex. Still heat it good and hot with a torch.

Its surprising how easy some bolts come out with a lot of heat, once the locktite lets go from the heat.

 

[Mazomopar]

Any reason it could possibly be left handed thread?

 

[spasm3]

This is from the locktite website. Need to get the bolt to 500 F.

"Loctite Threadlocker Red 271 is designed to lock and seal threaded fasteners permanently and prevent loosening from vibration. Ideal for fasteners up to 1” (25mm), this unique formula is great for engines, machinery, and vehicles for valve covers, water pumps, and alternators. Loctite Threadlocker Red 271 is moisture resistant and protects threads from leaks, rusting, and corrosion while eliminating the need to stock up on expensive lock nuts and washers. Fast and easy to use, this heavy duty, high-strength threadlocker sets in just 10 minutes and fully cures in 24 hours. Loctite Threadlocker Red 271 is a permanent solution for locking and sealing threaded fasteners and is only removable once cured by heating up parts to 500°F (260°C)."

 

[eljefino]

Your concern should be side-loading the bolt and shearing its head off. More possible, IMO, than rounding it off.

Use the heat as suggested.

 

[JHZR2]

You want the bolt to expand and then contract to help break some of the corrosion that’s preventing it from moving. Also I don’t know anything about SK hex sockets but my money would be on Bondhus.

A hex socket is easier. My bondhus set only goes to 10mm.

 

[Hall]

If it loosens at all, then the breaker bar.

...and the longest one you can get too. I thought HF had a 30-36" one in 1/2" drive but I only see a 3/4" that long (36"). For $20-25, even if it was only used for this bolt, it would be worth it.

 

[JHZR2]

This is from the locktite website. Need to get the bolt to 500 F.

"Loctite Threadlocker Red 271 is designed to lock and seal threaded fasteners permanently and prevent loosening from vibration. Ideal for fasteners up to 1” (25mm), this unique formula is great for engines, machinery, and vehicles for valve covers, water pumps, and alternators. Loctite Threadlocker Red 271 is moisture resistant and protects threads from leaks, rusting, and corrosion while eliminating the need to stock up on expensive lock nuts and washers. Fast and easy to use, this heavy duty, high-strength threadlocker sets in just 10 minutes and fully cures in 24 hours. Loctite Threadlocker Red 271 is a permanent solution for locking and sealing threaded fasteners and is only removable once cured by heating up parts to 500°F (260°C)."

The FSM specified Omnifit 100M:

OMNIFIT® 100M is a red, all-purpose, fast-curing threadlocker adhesive of medium viscosity. The product is used to secure threaded fasteners that can be disassembled again using normal tools. It cures in the absence of air (anaerobically) by metal catalysis. This medium-strength threadlocker prevents screw-fasteners from coming loose and causing leaks as a result of impact and vibration.

• All-purpose
• Fast-curing
• Used where disassembly may be required using normal tools

Actually looking at literature online, it is intended for hand tool disassembly, not requiring heat.

See here for 100M vs 220M::

 

[GSCJR]

I don't think you need heat there, a breaker bar should do the trick or an impact wrench, if there's room. Good luck!

 

[JHZR2]

I don't think you need heat there, a breaker bar should do the trick or an impact wrench, if there's room. Good luck!

I have a right angle air impact but no 3/8 impact hex. Might need to just buy a cheapie to ruin.