W211 E320CDI 2007 facelift front brake pads change: do I need to disable pumps/bleed, how to jack the car up

[pmcgsmurf]

I tried to undo that countersunk screw with some imperial hex key which seemed a good fit and after trying with quite a force it is no longer a good fit... T30 bit does not go in, T25 is too small, 4.5mm hex too big, 4mm hex too small. So removing that countersunk screw will be quite a challenge. I was hoping that perhaps that "magic" torsion spray will help - but the above suggests it will not.

I have no idea why you have decided to use "some imperial hex key".
Pretty sure from memory the bolt is a Torx 30, a good clean, spray of release fluid and a good tool are your friends.

Using the wrong tool will only make the job harder.

If you have rounded it now I would simply drill it out and get a new bolt.

 

[Petrol Pete]

I have no idea why you have decided to use "some imperial hex key".
Pretty sure from memory the bolt is a Torx 30, a good clean, spray of release fluid and a good tool are your friends.

Using the wrong tool will only make the job harder.

If you have rounded it now I would simply drill it out and get a new bolt.

I too thought that, my guess is the old bolt is not an original and the previous 'mechanic' that had a go at it damaged it. The original from MB will almost certainly be a Torx , but after that it could be a just a countersunk Allen head.

I say countersunk but some are of the 'step' design with a flared flush head in relation to the thread. I do not myself know which type will be on the OP's car.

 

[Trickythemerc]

This thread is beginning to worry me I think that when the OP is using imperial hex keys because he thinks they are a good fit in a torx screw Maybe time to leave it alone. Wrong tools and lack of technical skills when working with brakes will not end well.

 

[Stocho]

Hi.

Thanks for the replies. There is a huge amount of rust on the hub part of the disk. The screw in question is even pitted (though from rust but perhaps from previous removal). The screw did look more like T30 then hex but then hex key did go in and allowed me to apply quite a torque! T30 just does not go into it - probably due to rust. Will try again to get those screws removed. In the worst case scenario they can be drilled out - at least centering the drill bit will be no problem.

What I do still fear is that the disc even when fully unscrewed will not come off (memory from W210) but it looks like people here did not have this problem.

 

[pmcgsmurf]

Can you post us some pics please ?

 

[AMGeed]

WD-40 + a T30 torx bit. Failing that, drill a pilot hole in the screw and screw in an "Easy out" which should remove that little screw.
Try to remove as much rust from the hub as possible and use a lump hammer and piece of wood to drive the old disc off from the back face. Go round the circumference evenly to knock it off.

 

[Stocho]

Some Pictures. The disc is not warped - I filed down the lip in one place to take measurement and this makes it look warped.

 

[Stocho]

When posting the above pictures just noticed what looks like a crack in a back shield....

 

[pmcgsmurf]

That's a torx and looks original.
Still very dirty though, you need to get a wire brush into that and remove all the crud then spray some Plus Gas (or other release fluid) around the hub and the retaining bolt.

When the torx is clean knock the torx bit in and out a few times and blow the screw out to make sure the torx is all the way in making sure to push in at the same time as turning it.

 

[Stocho]

Success removing both screws!

1. Started with drivers's side [that I tried imperial hex (was able to apply a significant torque but no success) and T30 (which did not go in) before]. This time I used WD-40 and actually hammered T30 bit in. And it did move! Was able to unscrew it by about 2mm and then it was dead stuck, T30 lost grip. Hammering T30 in again, hammering in various other hex bits would not enable me to apply a sufficiently huge torque to remove it. At this point the car became undriveable as with that screw sticking by 2mm cant put the wheel on and then drive.
2. After much trying I decided to try the other side. Not least because I thought if I manage to get the screw on the other side out, seeing the devil and knowing it might help me defeat it. On the passenger side the screw did not look so corroded and I was using T30 from the start (by hammering it in). I was able to dislodge the screw. When it was about 2mm out it was going tougher and requiring much greater torque than dislodging it! However I managed to get it out in just one minute.
3. Them I returned to driver's sides. I was trying to drill with various drill bits and trying to hummer in various bits. Eventually I manged to hammer 5mm hex bit about 6mm in and it was very tight. This enabled me to finally fully undo that screw! I still have to separate the 5mm hex bit and the screw!


So with both screws out and wheels back on the cars is driveable. Tomorrow I will be ordering new brake pads, new discs and new disc-screws.

Parts wise genuine brake pads are quite well priced at £61.58 (Genuine Mercedes-Benz W211 E-Class FRONT Brake Pads and Sensor A0044208720 NEW! | eBay), not sure about the discs though at £119.26 (Genuine Mercedes-Benz W211 E-Class FRONT Brake Discs A2114210812 NEW | eBay) .

Are Mercedes discs better than ATE/PAGID?

I understand brake pads come with just two new screws rather than four. So I put the new ones on the bottom pins and reuse the old ones (with thread lock) for the top pin? What torque should be for these screws?

With regard to the caliper holder screws (the bigger screws that need to be undone to change the discs), do I need to order new ones or just reuse the old ones? What torque should be used for these?

 

[pmcgsmurf]

As I said with bolts like these you have to knock (hammer) the tool in.

I should have also said to loosen then spray plus gas and tighten back in. Keep doing this a bit at a time each time coming out further to clean the crud away and get the bolt out.

 

[Petrol Pete]

Don't forget to get a can of brake cleaner as well as some anti seize to put on the threads of your new disc bolts. Genuine brake parts direct from MB are sometimes quite cheap, try them first. MB Newcastle and MB Sunderland have an E bay presence.

 

[Petrol Pete]

Oops , I see you have already been to MB on E bay, thats the best you will do for original discs, I would buy them. Make sure they either come with new holding screw (the do not always) , If not make sure you order 2 (obv's).

 

[Stocho]

Hi,

Today received Discs, small screws, and brake pads:

Pardon our interruption...

I was planning to do it all from 6pm to 9pm - before it is dark.

But it was not a successful day:
1. I lost the locking wheel nut key.... But there are two W211 and luckily the key from the other car worked!
2. The caliper holder bolts are 18mm - unusual size. Most sets have 17mm and 19mm. Those bolts are extremely tough and without the correct tools I almost gave up ... but managed to get them off eventually using some imperial spanners that were almost a good fir and a 19mm socket. really what is needed for these is a 45cm breaker bar then the job would, surely, be easy.
3. Then I started trying to remove the disc. I was using a heavy sledge hummer (probably 2kg) and WD40. No amount of hammering would get off the disc. So, after trying for 30-60 minutes, I put it all back together....

How do mechanics remove discs (once all screws, caliper and caliper holding bracket are removed)? I can't imagine they are using even heavier a sledgehammer than I did... The discs are about 10kg - so local heat also would be a huge challenge giving the heat capacity of such a chunk of iron.... So how to get the old discs off?

 

[pmcgsmurf]

Didn't we mention having the right tools for the job?

Nothing odd about an 18mm Caliper Bolt.
What you really need to use for this is a 6 pointed socket and breaker bar as they can be tight.
Mechanic will have such things in his tool box.

Using an Imperial spanner on it means a big risk of rounding the bolt meaning bigger problems.

 

[Stocho]

Yes - having the right tools would help. However I managed to get to the point of removing the disc with the wrong tools which made a job, that would be easy with the right tools (proper jacks, 18mm spanners/sockets with long arms), quite challenging.... But then there is the final part - removing the discs. This is the point where I got stuck: caliper fully off, T30 screws off and yet after much sledgehammering I cant get the disc off.

Turning to the videos, in one the disc just comes off... literally with not trouble whatsoever - see 3:55 of

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In another video the mechanic does use a sledgehammer see 7:00 of

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His sledgehammer is about the same size as mine. It does not look like he was hitting the disc any harder than me but it still came off. One difference in technique that I notice is that the mechanic in the video was just hammering the disc towards the car. I was trying to hammer it way from the car by hitting the spot where caliper usually is in direction away from the car (hitting the internal side of the disc) and rotating the disc so that I hit all the various points. It would be a lot easier to sledgehammer the disk the way the mechanic dd in the video. But I was hammering for about 30 minutes and away from the car and to no avail.

I have a vague recollection of changing discs on W210 about 8 years ago - and back then again the most difficult part was not undoing any screws - it was actually removing the disc once everything else is unscrewed / removed/

 

[pmcgsmurf]

You are only trying to break the disc free from the hub.

Trying to knock it from inside to outside will limit the swing and force you can get with the hammer.

Just knock it on the outside and spin it as hard as you can, it will come off. Also spray some release into the holes too.

 

[Stocho]

You are only trying to break the disc free from the hub.

Trying to knock it from inside to outside will limit the swing and force you can get with the hammer.

Just knock it on the outside and spin it as hard as you can, it will come off. Also spray some release into the holes too.

I see what you mean about the technique, and this guy on the video also makes the same point about the technique.

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So I now know the correct technique - thanks a lot.

So, at this stage I am in the same position as a mechanic in a sense that mechanics do not have some proper tools for removing stuck discs that I do not have.

One question I have is: does the fact that only one side is lifted off the ground change the situation in a sense that hitting hard might result in steering systems being stressed/shocked while when both wheels are off the ground steering is not likely to get stressed nearly as much as it can just give in?

Also from watching the second video in post 36 it appears the correct torque for the caliper bracket is 115Nm. That is a huge torque which means to (more or less) properly finish the job I will need to get at least 45cm breaker bar. Given that it is tightened to 115Nm I am lucky that I was able to dislodge it with wrong spanner with arm no bigger than 25cm. To achieve a torque of 115Nm on a 25cm spanner would take a force equivalent to almost 50kg and to dislodge a screw even a bigger force....

 

[Stocho]

 

[Stocho]

Hi,

Today purchased 18mm socket, brake cleaner spray, and penetrating spray and tried again. This time, probably due to the combination of the correct hammering technique and proper penetrating spay the disc came off within about 5 minutes of hammering.

At this stage the question I have:
1. How safe is it to use use brake cleaner to clean the hub/caliper? My concern is whether it can travel to bearings / components that are supposed to be greased/oiled and was away the grease/oil.
2. I have two tubes of what I was told is better than copper grease (see last picture above). Which one should I use? Do I put it on:
a. the hub before putting the disc on the hub
b. the hub part of the disc (the part in contact with the wheel, nor brake pads)?
c. edges of the brake pads that are sliding?
d. back of braje pads?
e. is it ok to also put a bit on the wheel bolts?
3. I noticed some small cracks on the brake hose and also some corrosion on the brake pups - circled above. How serious is this?
4. Any other observations are welcome.

Thanks a lot to everyone for the help!