Should I be using locktite on all the bolts??? - PeachParts Mercedes-Benz Forum

240diowa · #1 01-07-2006, 09:19 PM

I have a '74 240D which has a 220 motor. I have had alt. braket bolts come loose and break. I had some bolts on the front part of the motor come out and it was blowing oil out. I put in new bolts and now some of them have come loose and/or broken. The motor has great compression and runs great. Should I be putting locktite on all the bolts or is there something I should be looking for that is causing the vibration?

kip Foss · #2 01-07-2006, 10:37 PM

If you have bolts coming loose you definately need Loc Tite. Before you use it be sure to clean out the bolt holes and the bolt with carb cleaner. Use the tube to get into the hole and flush out the oil. Use a couple of drops on the bolt, a new lock washer, and tighten to spec. If you are having bolts break something else is wrong. You can go to a grade 5 or 8 bolt but no bolt in an engine should just break. Find out what is causing them to break.

t walgamuth · #3 01-07-2006, 10:41 PM

the red loktite.

tom w

Ken300D · #4 01-08-2006, 10:36 AM

You should probably be using either the blue or red loc-tite threadlocker.

Red holds stronger than blue, but it requires a bit of propane torch heat to get it to release. For example, I use the red loc-tite on the big starter bolts. They are easy to get torch heat on them to release. Not only is the started held tightly in place, but the loc-tite prevents the threads from corroding and making subsequent removal harder.

Ken300D

Brian Carlton · #5 01-08-2006, 10:50 AM

Quote:

Originally Posted by Ken300D

For example, I use the red loc-tite on the big starter bolts. They are easy to get torch heat on them to release. Not only is the started held tightly in place, but the loc-tite prevents the threads from corroding and making subsequent removal harder.

The starter may be in there for another 10 years before it needs replacement. Personally, I wouldn't want to be the new owner of that vehicle and find out that the reason I stripped the head on the starter bolts is that the PO used Loctite on them.

There is absolutely no reason to use Loctite on the starter bolts. They aren't going anywhere with 80 ft-lb. on them. Use anti-seize and make the new owner a happy camper..........unless you are keeping the vehicle forever..........then you can do what you want.

As a general statement regarding Loctite, I'd think long and hard before I used it. If the factory didn't require it, you've got to ask yourself a question? Why do I need this?

Need I point you in the direction of all the stories of members stripping out the heads of fasteners that failed to budge. Sometimes they face a monumental drilling and tapping operation that is well beyond their capabilities. How many of these fasteners had Loctite on the threads........added by the PO because he didn't want the fastener to fall out??

Loctite should be used as a last resort.

boneheaddoctor · #6 01-08-2006, 11:04 AM

I like to use Blue locktite on everything....but I would really think twice where I put locktite red.....you don't want to use that one on everything...trust me...I've seen horror stories trying to get something off that used that....even with a torch...with my own two eyes.

t walgamuth · #7 01-08-2006, 11:29 AM

mean to suggest that one should use locktite promiscuously.

i just mentioned that i use red cause i was afraid he might use the stuff that doesnt release (white?).

i only use it where the factory used it originally, like caliper bolts. and i usually dont use a lot.

tom w

240diowa · #8 01-08-2006, 11:38 AM

I guess what I'm hearing is to use locktite on all the fasteners when replacing them. Should I be looking for what is causing the vibration or is that just the nature of this engine?

t walgamuth · #9 01-08-2006, 12:36 PM

that is not the message.

first you should check to be sure that your motor mounts are good. if bad the vibration will knock your eye teeth loose.

second if that is ok, then i probably would use some locktite on the ones that seem to want to back out. probably not a good idea to use it on bolts that thread into aluminum, though.

but locktite is not an appropriate substitute for lock washers if those were installed at the factory. so i would try to verify which bolts had lock washers from the factory and try that first if some are missing. and those thin wavey washers are lock washers too, btw.

tom w

mikemover · #10 01-08-2006, 06:28 PM

PLEASE don't use the permanent lock-tite!!!!

I have had the displeasure of working on engines where people have done this, and it is NOT something you want to do. Believe me, if you do that, you'll be sorry in the future, next time you need to remove that bolt.

The MB engineers never used lock-tite on MB engines. On bolts that needed a little extra insurance, they used lock WASHERS... but never any type chemical thread-locking stuff that I'm aware of.

If they didn't use it at the factory, then you shouldn't need to use it now.

If you have vibrations that are so bad that nuts and bolts are coming loose, then either you're not torquing them properly, or you are installing them without the lock washers that they are supposed to have, or you have some mechanical problems or worn mounts that are causing excessive vibrations.

Mike

boneheaddoctor · #11 01-08-2006, 06:48 PM

Quote:

Originally Posted by t walgamuth

mean to suggest that one should use locktite promiscuously.

i just mentioned that i use red cause i was afraid he might use the stuff that doesnt release (white?).

i only use it where the factory used it originally, like caliper bolts. and i usually dont use a lot.

tom w

the red almost doesn't release in some cases....even with heat.

Some dummy did that on a 1947 Harley davidson knucklehead intake...which uses plumbers type fittings...(compression fittings, no rubber)

took 4 of us 7 hours with heat to get that apart.....and trashed the intake in the process....

Blue is fine on nearly everything...red should be used with caution........and I've never seen the white before much less used it...but from what you describe I would never need that one.

I keep the Blue in my toolbox....don't even own any of the red.

Brian Carlton · #12 01-08-2006, 08:03 PM

Quote:

Originally Posted by mikemover

The MB engineers never used lock-tite on MB engines. On bolts that needed a little extra insurance, they used lock WASHERS... but never any type chemical thread-locking stuff that I'm aware of.

If they didn't use it at the factory, then you shouldn't need to use it now.

If you have vibrations that are so bad that nuts and bolts are coming loose, then either you're not torquing them properly, or you are installing them without the lock washers that they are supposed to have, or you have some mechanical problems or worn mounts that are causing excessive vibrations.

This bears repeating again. I couldn't have said it better myself.

240diowa · #13 01-08-2006, 08:30 PM

I had taken the front pulley off to replace the oil seal. I torqued down the 8mm socket head screws to what I thought was tight enough without beaking the bolts. Within 100 miles they were all loose, they don't use lock washers. Could bad motor mounts cause this type of vibration?? I can see where the mounts would isolate the vibration from the engine to ther frame but would they rweduce engine vibration??

I'm not a fan of lock washers.
To me they really don't do anything. When tightening a fasterner you want to stretch it within its elastic limit. The lock washer is just a gap filler.

mikemover · #14 01-09-2006, 10:16 AM

Quote:

Originally Posted by 240diowa

I'm not a fan of lock washers.
To me they really don't do anything. When tightening a fasterner you want to stretch it within its elastic limit. The lock washer is just a gap filler.

Lock washers are not merely "gap fillers". They LOCK the nut or bolt in place. That is why the factory used them on certain bolts, and you should too, if they were there to begin with.

When tightening a fastener, you actually should tighten to the factory-specified torque specs... No more, no less. (ESPECIALLY on an engine/tranny/brakes... it is less critical elsewhere)

Mike

240diowa · #15 01-10-2006, 10:46 AM

Per the NASA Fastener Design Manual

"The lockwasher serves as a spring while the bolt is being tightened. However, the washer is normally flat by the time the bolt is fully torqued. At this time, it is equivalent to a solid flat washer, and its locking ability is nonexistent. In summary, a lockwasher of this type is useless for locking".

To me to only benefit the lock washer may provide is the edges of the washer where it is cross cut will dig into the mating surfaces and provide some resistance to anti rotation of the nut.

If the washer only serves to provide a spring load then just tighten the bolt a little tighter, does the same thing.