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2007 E220CDI, 1990 300E-24V, 1987 W124 3.6 AMG build 1993 E500 W124, 94 320CE, 1997 W140 S280
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Discussion Starter #1
I have seen this before on a friends AMG w220 with these exact calipers. There are stainless plates held to the caliper with 1no pan head screw.

Corrosion occurs between this plate and the caliper body pushing the plate outwards and jamming the brake pads.

These plates are very difficult to remove due to
A: small torx slot. Aka undersized
B: steel bolt in alu caliper body
C: the interstitial corrosion makes the bolt tighter!!

Some members may have encountered this before - any tips for removal of these bolts please?

I my first thought is to try welding on a nut over the screws in order to get proper heat into the bolt and get purchase on it. Threads may come too though!

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Screenshot_20200801-093426_Gallery.jpg
 

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2007 E220CDI, 1990 300E-24V, 1987 W124 3.6 AMG build 1993 E500 W124, 94 320CE, 1997 W140 S280
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Discussion Starter #2
Confession- the last time I was checking / lubricating the brakes on my S600 I discovered this. In fact this very issue if causing the pads to bind most likely contributed to the excess rust and damage to the rear side of its front brake discs.

But since the discs on the front were not good and I planned a new brake job anyways I sanded the edges of the old pads down until they were a nice sliding fit again and that let me away on a temporary basis.

But now I have new discs and pads to go in I want to try to get these stubborn plates off and make the new pads fit again like they are supposed to!

I have never had luck drilling bolts out so want to avoid that route. I guess if the weld but trick doesn't work I'll bring both calipers to a machine shop and let them deal with it
 

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W220 Moderator
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6,823 Posts
I take it the Tx internal head is rounded then ?

If not first thing I would do is rake out all corrosion from that and then using a GOOD quality, eg Snap On etc Torx Bit and bash it into the Bolt with a hefty copper mallet, 2 or 3 sharp clouts will do, then, a high percentage will undo. If not, and you can weld decently, yes my second move would be to weld a nut on the head securely, wait for it to cool from red heat, then 98% will come out.
After that, yeah, drilling, helicoiling etc.

Always use new bolts on this kind of thing and always copperslip the threads well then they come apart next time ;)

HTH, :)
 

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S500 4Matic 2005
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956 Posts
I ran into the same issue on one of my friends W220 during this last winter. The head was destroyed and couldn't get it out. @Dave2302 is the right way to get it out but I can't weld and had to drill it out. They do sell those special bits to use but I used a regular metal bit and had to use an electric drill. Made sure that the bit was a tad smaller than the screw itself and went to drilling. Thank God it came out all in one piece and did not damage the threads. Not to crazy about the procedure and hated doing it since it was not my car but I was outside on his driveway and didn't have to many options. Good luck.
 

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2003 S500
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IF I had time to do this, my first approach would be to whack the heads repeatedly (corrosion is usually brittle), and apply PB Blaster or a 50/50 mix of acetone and ATF then let them sit for a few days. I would repeat the process a couple of times, then try removal using Dave's approaches.
 

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2007 E220CDI, 1990 300E-24V, 1987 W124 3.6 AMG build 1993 E500 W124, 94 320CE, 1997 W140 S280
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Discussion Starter #6
I take it the Tx internal head is rounded then ?

If not first thing I would do is rake out all corrosion from that and then using a GOOD quality, eg Snap On etc Torx Bit and bash it into the Bolt with a hefty copper mallet, 2 or 3 sharp clouts will do, then, a high percentage will undo. If not, and you can weld decently, yes my second move would be to weld a nut on the head securely, wait for it to cool from red heat, then 98% will come out.
After that, yeah, drilling, helicoiling etc.

Always use new bolts on this kind of thing and always copperslip the threads well then they come apart next time ;)

HTH, :)
Not rounded (yet) but previously it snapped off several torx bits! Yes I'll get better quality torx bits for when I attempt this in a couple of days.

Did try smacking it with a heavy hammer before and no difference at all. They are in there TIGHT. Like you've never seen.

I have an impact driver. I may try and put a torx bit into that instead of a regular ratchet. Should help to get that sucker started at least.

Yes I am an experienced welder so I'd be able to get a nut red hot and one there really well if all else fails. I have a heilcoil set but I find them shite - in particular for the likes of m6 or under size.

If required I'll get a threadsert Kit of the appropriate size from Wurth to repair these.
 

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2007 E220CDI, 1990 300E-24V, 1987 W124 3.6 AMG build 1993 E500 W124, 94 320CE, 1997 W140 S280
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Discussion Starter #7
Copaslip at the ready 😛
20200730_230624.jpg
 

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Maserati Quattroporte, CL600, S500, BMW 330cic, E65 BMW 750LI. Dodge Ram
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901 Posts
I would grind a line down the center and use a very fat flathead screw driver and back it out. Or a half inch impact with a flat head bit and back it out.
 

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2007 E220CDI, 1990 300E-24V, 1987 W124 3.6 AMG build 1993 E500 W124, 94 320CE, 1997 W140 S280
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Discussion Starter #10
Thanks for the suggestions everyone- all very helpful! I will tackle this some evening during the week. Want to get one bolt off the car first so I can check thread and dimensions and order 4x new ones.

@Dave2302 what penetrating oil spray do you recommend that I could get on ebay etc within the UK please? I have tried many and not really found any to be effective. There was one by Lucas - toolbox buddy. That stuff was actually good! But a local auto parts store tends to get random stock in and that came and went fast unfortunately.
 

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W220 Moderator
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Did try smacking it with a heavy hammer before and no difference at all. They are in there TIGHT. Like you've never seen.
Bearing that /\ /\ /\ in mind, I think I would now proceed with heating the bolt, or straight into the welded nut technique ;)

My experience of a screwdriver slot is that if they are that tight the head just snaps off making it harder or impossible to get a good weld for the welded nut trick ;)

HTH,
 

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2006 S600
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These things are a nightmare, and one of the systematic problems that the S600 in particular suffers from.

The problem is that mud and salt accumulates behind the stainless steel thrust plate, and corrodes the alloy underneath, which swells significantly. You need to get the corrosion out.

The first sign is that the lower pads are difficult to get in, and you end up forcing them in, which causes brake binding.

I tried hammering a torx bit in, grinding a slot in the head, etc but something always breaks.

They're a bitch.

Nick :-(
 

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2007 E220CDI, 1990 300E-24V, 1987 W124 3.6 AMG build 1993 E500 W124, 94 320CE, 1997 W140 S280
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Discussion Starter #13
Thanks Nick, yes I cant see me actually getting these out. They will most likely snap off before they will come undone.

If that does happen then I'll likely pull the calipers and give to a local machine shop as I'd rather pay their time than spend hours unsuccessfully trying to drill them out myself. Never had luck with that especially dealing with an expensive aluminium part and small fastener I dont want to attempt it.

Tried getting the corrosion out before but they are so tight and packed it was hopeless.

I'll check EPC and see if the stainless plates are obtainable separate. If so I could use a dremel and sacrifice the old ones in order to free the tension on these bolts perhaps....
 

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2007 E220CDI, 1990 300E-24V, 1987 W124 3.6 AMG build 1993 E500 W124, 94 320CE, 1997 W140 S280
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Discussion Starter #15
On this now to try and get one bolt out to see if I can at all and start ordering new replacements since EPC shows nothing in terms of the plates and or bolts.

It is actually a very small allen slot. And crucially there are 3 per plate o_O o_O o_O

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Smacked them HARD again several Times with a punch and steel lump hammer.

Tried the appropriate micro sized Allen and immediately rounded out. Surprised? No what a sh#te design by MB.

Bashed a torx in then and it sheared off with the remains helpfully lodged in there. Again - totally as anticipated.

Just got started welding a large washer on there. When the bucketing rain monsoon subsides for a minute I'll weld a large nut on there too.

Something is either going to loosen or shear off.

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Place your bets now
 

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2007 E220CDI, 1990 300E-24V, 1987 W124 3.6 AMG build 1993 E500 W124, 94 320CE, 1997 W140 S280
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Discussion Starter #16
Got one out - for ref they are M5 x 9mm thread.

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Caliper threads appear salvagable with a tap and my plan is to snug them up only and remove / check/ every service to stop from happening again.

The recessed ones will be more of a challenge. I'll be stuck with m8 size nut welded internally which will require several attempts to get enough purchase on the stuck bolts. Will try one recessed now too.

Ultimately when I go to complete this I want the calipers on my workbench.
 

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2007 E220CDI, 1990 300E-24V, 1987 W124 3.6 AMG build 1993 E500 W124, 94 320CE, 1997 W140 S280
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Discussion Starter #17
OK so more looking at this and the internal bolts will be really really hard to remove. But - you dont have to!

Having the outer bolts off allows you to gingerly fold the plate back inwards and the old packed corrosion drops out.

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Then I will then carefully scrape, dremel and clean these areas thoroughly followed by caliper paint left 24 hrs to dry in those problem areas.

Then coat with brake grease for additional protection and fit a new bolt to the plate bending it back down in place. Final step is to use a nylon drift and hammer to reshape the metal plates so they are no longer bulging.

Now your new pads will fit in there properly! (Tested the above theory and it works 100%) phew!

Checked all 8 pistons on this caliper and they press in easily with my fingers. No issues there.

Here is what the sticking pads / bulging plate syndrome does do your discs :(

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2003 S500
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I am immensely thankful that I live in a rust-free part of the world. The bottom of my 2003 S500 looks like new - no trace of rust anywhere...
 

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2007 E220CDI, 1990 300E-24V, 1987 W124 3.6 AMG build 1993 E500 W124, 94 320CE, 1997 W140 S280
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Discussion Starter #19
I am immensely thankful that I live in a rust-free part of the world. The bottom of my 2003 S500 looks like new - no trace of rust anywhere...
I understand that this might look rusty but for here this is a clean car! Dust shelds etc all in good shape. I will carefully clean and paint these areas now including the dist shields and chipped parts of the caliper just for now and get the new brakes on and all functioning properly.

This S600 has all new looking / recent ABC dampers on it and many hoses replaced. It's in rude health and in the coming months the entire underside will all get cleaned and waxoyled to maintain it since I intend to keep this car for a very long time
 
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