some questions. first time i did the brakes on this car (W126 300sd) everything was so easy to take off. like the caliper bolts and such. should this be giving me trouble? (or am i just that good) should i put loctite on these items when i re assemble.

also u know the part that has the 10mm hux nut that holds the rotor in, not sure what it is called but you knock the dust cap off and it is there. how tight should i tighten that? as hard as i can or what? thanks

__________________
198? 300D ???K - Future DD
1989 300TE 285K - traded in '12
1984 300SD 186K - Sold in 08
1978 300SD 330K - Died in 05

The caliphers have 2-19mm bolts and are not to difficult to remove if you use a cheater pipe. They are also easy to remove if you use a impact wrench(air operated). Most of the bolts have locktite on them. Many mechanics will tighten the bearing nut fairly tight and then back it off 1/8 of a turn. Check the bearing play by putting the wheel on. Then pulling on the wheel at the 12 and 6 o'clock position. You are trying to rock the wheel and feel how much play is in the bearing fit....Jim

__________________
James A. Harris

The caliper bolts are specially made with an anti rotation material on the threads. They are made to be used only once. However, I frequently reuse the old ones and put a dab of Loctite on them. Just make sure you use a torque wrench and tighten them to 80 ft.-lb. Since 80 ft.-lb. is nothing for these large screws, I usually take the old screws to 90 ft.lb. just to be extra safe.

Peter explained this above. The torque on that clamp is 20 ft.lb. It's not a big screw and you don't need a lot of torque to prevent the clamp from rotating. I usually tighten it without a torque wrench.

thanks guys. i did use a cheater pipe and i am a pretty big guy so i suppose 80 lb-ft wouldn't be too hard for me. i was just worried since it seemed like the PO didn't do such a good job on the up keep of it.

can u believe the inner pistons on the calipers didn't even have a boot/seal on them? resulting in a warped/scored rotor. and stuck piston on both sides. i just got around to redoing everything.

so is it correct that need to tighten the locking nut so there is no "play" but not so tight that the wheel can not turn? i don't have a torque wrench and it is usually "as hard as i can tighten" on the big bolts and ""reasonable" on the smaller ones. i know i need to invest on a good set of torque wrench.

__________________
198? 300D ???K - Future DD
1989 300TE 285K - traded in '12
1984 300SD 186K - Sold in 08
1978 300SD 330K - Died in 05

No, this is definitely not correct. You must have about .001 axial play in the rotor. Anything less than this and you risk "pinching" the bearings. This will cause them to generate a ton of heat and they won't be around very long. Tighten the locking nut until you can just sense the very slightest amount of play. Then tighen the screw on the clamp and make absolutely sure that the clamp does not rotate when you do it.

As far as a torque wrench is concerned, I urge you to get one before tackling this job. You cannot depend on "as hard as I can tighten" when dealing with the caliper bolts. Depending on the length of the extension bar, you could easily overtighten them. Or, you can easily tighten one quite a bit more than the others.

Furthermore, you definitely need a torque wrench for the five lugs that hold the wheel to the rotor. If you tighten these "as hard as I can tighten", I can assure you that you will likely warp the rotor. They need to be tightened to 80 ft.-lb. and not more. You will think that 80 ft.-lb. is not enough torque when you do it for the first time.

This thread and the stuff in the DIY certainly answered all of my questions!!! Tomorrow is going to be the big day, I'm gonna go to the dealer to grab the seals and a couple tubes of grease.....then some loctite....from somewhere....I assume most homedepoty stores would have that. Then its to work. Our goal is front rotors/bearings/pads on the front of the '83, and the rear pads/rotors on mine (the '82).....We went to sears tonight and got the heavy duty tools, 15" breaker bar with adapter bit, 1/2" ratchet, and a set of sockets 9mm-19mm, and a 10mm hex bit for the wrench....ah, the smell of new tools. Yes we are slowly collecting the tools for this stuff, as we haven't done much of these types of jobs before ourselves. Hopefully we will be successful tomorrow, I think we will be.

*edit: I think we will need a torque wrench too........and possibly a dial gauge

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Loctite comes in two styles. One is removable strength and one is permanent. You want the "removable strength". Also, you don't need a lot of Loctite. Just a dab on two or three threads is more than sufficient. You won't be happy next time if you coat all the threads with it.

Stop at Poop Boys and get the little packets of "brake slide lubricant". They sell them right at the cashier. Again, after thoroughly cleaning the slides in the caliper, add just a very little bit to the slides. Eight surfaces in each caliper. Do this before putting the caliper back onto the rotor. You won't be able to get your finger to the far surfaces with the rotor in the way.

Be very careful not to use too much otherwise the grease will get onto the pads and the rotor and you will definitely be


Definitely and possibly.

Ok now we have everything we need toolwise, I was just wondering how one uses the dial gauge, like where do you put it in order to take an accurate measurement? This is pretty much the only thing I don't understand, I just need to know how to use the thing.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

The dial gauge needs to be setup on a suitable stand so that you can indicate the hub of the rotor. When setup properly, you can push the rotor in toward the vehicle and then pull it out and you will see the movement on the gauge. Rotate the clamp until the movement of the rotor is about .001 inches. At this point, you will probably not feel the movement any more. It is very small.

I've never used the gauge due to the difficulties of setting up a suitable, and rigid, stand.