changing a caliper- why can i see the bearings..? - PeachParts Mercedes-Benz Forum

wilburtual · #1 02-10-2011, 09:08 PM

i had a seized caliper on my 81 240d, rear right side- the rubber around the pistons were toast, so i decided to replace with a reman caliper- and a new rotor since the seized caliper destroyed the old rotor...
anyhow, it took some PB blaster and a rubber mallet to get the old rusty rotor off... but eventually it came off. after getting the new rotor on and the new caliper attached, i noticed that behind the wheel hub i could see some sort fo bearings... where the rubber boot part meets the wheel hub... the other rear wheel doesnt seem to look this way, and i can't see why a bearing would be exposed, so i assume this is a problem!!
sorta like the whole wheel hub assembly has pulled out exposing the bearings. i've attached a few photos so you see what i mean. i am not sure if it was like this before i took off the old rotor/caliper, or if I caused it to happen when banging the rusty old rotor off... i gave the hub a few taps with a rubber mallet to see if that would reseat/push it back, but it doesnt seem to budge...

79Mercy · #2 02-10-2011, 09:11 PM

looks like the axle isnt in place correctly. Is the bolt missing???

wilburtual · #3 02-10-2011, 09:13 PM

another photo pointing to what I am asking about

wilburtual · #4 02-10-2011, 09:16 PM

well.. you are talking about the bolt that is on the end of the wheel hub, in the center? yes, it is off, which is where i think i probably caused this.. was my first time taking a rotor off and thought i had to remove that bolt to get the rotor off -it was all rust colored, so i didnt know what was rotor and what was wheel hub...

probably my removing that bolt, let the axle slip off? thats how i noticed the issue - after i had rotor/caliper on and went to put that bolt back in place.. and it wasnt long enough!

79Mercy · #5 02-10-2011, 09:18 PM

thats your problem. Push the axle back into the hub and thread the bolt back in.

wilburtual · #6 02-10-2011, 09:19 PM

how do i go about getting it all to slide back on so i can re-attach the bolt? it doesnt seem to just push back on and a few taps of the rubber mallet didnt make it push back on either. but i didnt want to just start banging away at it.. should it just push back together?

wilburtual · #7 02-10-2011, 09:20 PM

hmmm, should i be pushing the axle out, rather than moving the wheel hub in... maybe thats what i am missing here...>?

Fredmburgess · #8 02-10-2011, 09:21 PM

You should be able to grab the axle and yank it out towards the hub (away from the differential at the center rear of the car). The splined part of the axle that is now exposed should slide further into the hub so that the bolt you removed will reach. Tighten the bolt and you're done!

79Mercy · #9 02-10-2011, 09:22 PM

Grab the axle and push it back into the hub.

The hub is fixed, you cant move that.

punkinfair · #10 02-10-2011, 09:25 PM

the splines can't be misaligned, they will be engaged until the axle is almost falling out of the hub. hit the outside of the hub carrier with the mallet while pushing on the axle, it should slide in. once you can see a few threads you can use the nut to draw the axle all the home.

you also need to get a new nut for the axle, they are single use. you might also want to get it torqued to spec by a shop, unless you have a really big torque wrench.

vstech · #11 02-10-2011, 09:50 PM

there is a LOT of stretch on the axle when the car is jacked up in the air. IF your car is SECURELY supported on jack stands, you can jack up the Lower Control Arm to bring the axle closer together.
if this does not work, you may have to drop the differential down to get the axle to move enough to reattach the bolt.
above the differential mount on the rear cover plate, are 4 13mm bolts holding the diff mount to the body of the car. place a floor jack under the differential, and support it. then remove the 4 bolts, and lower the differential. this will give you the clearance needed to reattach the axle retainer bolt.

wilburtual · #12 02-10-2011, 09:54 PM

aha! yup, makes a big difference pushing on a part that moves (axle) rather than the part that is fixed (wheel hub) @@

it slid back on with a little doing, and the bolt snugged it back all the way. thanks for all the super speedy replies!! you guys solved what i thought was a major problem in like 2 min after i posted the thread! i love this forum!!

i have a torque wrench that i have on loan to torque the caliper, but the axle bolt is pretty small (13mm?) and the torque wrench takes 1/2" sockets i think.. not sure if i have a 1/2" socket that small.. but i'll check. any idea what the torque spec is for that bolt? should i put the car in park to keep the axle from turning when I am tightening?

vstech · #13 02-10-2011, 10:02 PM

that long thin bolt is likely only going to need like 50INCH POUNDS... maybe 80INCH POUNDS... not sure what the actual spec is. use a 1/4" ratchet and make it snug. you don't want to break it! I seriously doubt a 1/2" torque wrench will adjust low enough to use on that thin long bolt!