I've noticed for a past couple of weeks I get a healthy clunk in my rear left wheel well. I've narrowed it down to a lose caliper that has a bit of up and down play in it.

However, when I replaced my pads over christmas the two 19mm bolts that hold the caliper in place went in without a problem. I even used blue threadlocker which is still holding the bolts because I couldn't get them to budge.

How in the world is it possible for two bolts to remain stationary yet somehow they moved or possibly got smaller?!

I'm lost.

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-Typos courtesy of my mobile phone.

is it possible you left the tie rod mount bolts loose? or the wrong bolts got put in? are you certain the caliper is moving? not just the pads?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
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My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

That's pretty improbable, in as much as the problem is on the rear of the vehicle.

I would suggest that you try retorquing those bolts to spec.

I would do this too ... even with the threadlocker it's possible maybe they weren't quite tight enough and backed out a bit. Are they OE bolts?

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

Remove the bolts, clean the threads and the holes, re-apply a small amount of loctite and re-torque.

If the threads weren't clean the first time they may have "bound up" on the old thread locker and not snugged all the way down.

x2 on the OE bolts question. Any chance you got them mixed up and put the wrong bolts back in?

I would pull it off and take a look.

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84 300D, 82 Volvo 244Gl Diesel

They're the correct bolts. When I work on a wheel I work one at a time on each axle before moving to the next.

The bolts are the original bolts as well. I did torque them to spec when I did the change.
I'll jack it up and take a look.

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-Typos courtesy of my mobile phone.

My son had this problem on his Lexus after a brake shop did a brake job. They had stripped the threads on one of the bolts. They are replacing the caliper mounting bracket at their expense - it's a special order item.

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Charles
1983 300D, bought new, 215k+ miles, donated to Purple Hearts veterans charity but I have parts for sale: http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/296386-fs-1-owner-83-mb-300d-turbo-rebuild-parts.html

I have always reused my Brake Caliper Retaining Bolts but the FSM tells you to replace them each time; they have some sort of nylon thread locking stuff on them built into the Bolts.
So I a curious to see if a cause can be found.

Could it be secondary to Vibration?
Also if you rebuilt the Calipers yourself the Caliper Pistons have to be properly oriented.
Too much Wheel Bearing End Play?
Warped Brake Rotor?
Torque Wrench Calibration off?
If the Calipers were a rebuilt set maybe the Holes were previously elongated and the rebuilder did not notice?

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84 300D, 82 Volvo 244Gl Diesel

If you put your hand onto the caliper it is quiet obvious what the problem is. I wish I could show you because the problem I described is 100% spot on.

Let me buy new bolts and try again. I bet that the threadlocker is holding the bolts in but didn't snug itself in all of the way.

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-Typos courtesy of my mobile phone.

You said what was wrong.
If you torqued the Bolts and they were not loose to begin with there has to be a reason for them to be loose now. Loctite is very dependable unless it gets too hot.
So I gave a list of stuff I was speculating could cause the problem.

You reminded me of something else.
If the Brake Caliper Flange that the Bolts go through is too thin the Bolts would go all the way up to the unthreaded portion and would Torque up properly but would not tighten up on the Flange of the Brake Caliper.

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84 300D, 82 Volvo 244Gl Diesel