MatraSport Forum

Each model => Murena => Topic started by: Jon Weywadt on May 23, 2010, 11:00:16 am



Title: Problem with Green Stuff brake pads
Post by: Jon Weywadt on May 23, 2010, 11:00:16 am
This winter I bought Grenn Stuff brake pads for front and rear braes. Yesterday replacing the old pads finally reached top of the to-do list.

After cleaning off the caliper I made sure the frame holding the pads would slide back and forth with ease. Then when installing the pads I discovered that the outer pad hit the corner of the frame and rested at an angle instead of flat and parallel with the other pad.  >:(

When I compared the pad with the one I took out, I could see that the tabs holding hte pad in the frame were 4 mm closer to the wheel center than on the original. This caused the pad to sit further outward and even though it has the sam beveling on the outside corner, it could not be inserted all the way flat against the frame. ??? ??? ???

The previous owner had replaced the calipers all the way around and the disks are new as well. The old pads produce a perfect wear on the disk to within 1 mm of the rim. If I got the Green Stuff pad to lay flat in the frame it would actually extend over the rim of the disk. That could not be good???

Finding this on the first wheel I worked, I only did the same cleaning on the other front wheel and did not try the rear wheels.

I was wondering if any of you have run into similar problems? I have the correct Green Stuff pads, according to Roys alternative parts list. So I wonder if there are differences in the front calipers and disks on the different year, or model Murenas??

Are there other cars, whose calipers fit the Murena front wheels and disks? I am speculating that the new calipers, that the previous owner had installed, perhaps are not a 100% identical to the originals.

One major reason to try the Green Stuff pads was to reduce the black dust that quickly coats the front wheels. Fortunately the current pads have plenty of wear left in them, so I have time to figure out what to do.

One thing seems clear.  :D I will have a set of Green Stuff pads for a Murena for sale. At least for the front.


Title: Re: Problem with Green Stuff brake pads
Post by: Anders Dinsen on May 23, 2010, 12:43:24 pm
I run Green Stuff on all four wheels, and have never had any problems. I think EBC just put the wrong set of pads in the right box. Or the wrong box outside the right pads, and shipped you someone else's. Or... well you know ;)

Feel free to drop by and compare your pads and calipers with mine! (although you will have to take the wheels of the car yourself ;) )

/Anders


Title: Re: Problem with Green Stuff brake pads
Post by: roy4matra on May 25, 2010, 09:54:10 am
This winter I bought Grenn Stuff brake pads for front and rear braes. Yesterday replacing the old pads finally reached top of the to-do list.

After cleaning off the caliper I made sure the frame holding the pads would slide back and forth with ease. Then when installing the pads I discovered that the outer pad hit the corner of the frame and rested at an angle instead of flat and parallel with the other pad.  >:(

When I compared the pad with the one I took out, I could see that the tabs holding hte pad in the frame were 4 mm closer to the wheel center than on the original. This caused the pad to sit further outward and even though it has the sam beveling on the outside corner, it could not be inserted all the way flat against the frame. ??? ??? ???

If you have the correct pads Jon, were the originals correct?  A 4 mm difference in the locating tab is the difference between front and rear pads - see my brake booklet or website for a side by side diagram of the front and rear pads.
Front pads are 4 mm closer to the hub.  Consequently fronts will not fit in the rear.  Rear however will fit in the front but are 4 mm further out and the edge of the pad will be off the disc.

Quote
The previous owner had replaced the calipers all the way around and the disks are new as well.

If the calipers have been replaced, are they correct.  You can fit a later Bendix Talbot caliper but it is not quite the same.  Maybe these were fitted?

Quote
I was wondering if any of you have run into similar problems? I have the correct Green Stuff pads, according to Roys alternative parts list. So I wonder if there are differences in the front calipers and disks on the different year, or model Murenas??

No Jon, all Murena came from the factory with the same calipers.

Quote
Are there other cars, whose calipers fit the Murena front wheels and disks? I am speculating that the new calipers, that the previous owner had installed, perhaps are not a 100% identical to the originals.

As I stated above this is a possibility.

Roy


Title: Re: Problem with Green Stuff brake pads
Post by: Jon Weywadt on May 25, 2010, 10:49:35 am
If you have the correct pads Jon, were the originals correct?  A 4 mm difference in the locating tab is the difference between front and rear pads - see my brake booklet or website for a side by side diagram of the front and rear pads.
Front pads are 4 mm closer to the hub.  Consequently fronts will not fit in the rear.  Rear however will fit in the front but are 4 mm further out and the edge of the pad will be off the disc.
-
If the calipers have been replaced, are they correct.  You can fit a later Bendix Talbot caliper but it is not quite the same.  Maybe these were fitted?
---

Roy
Hi Roy.

I compared the Green Stuff front and rear pads and can see the 4mm difference you mention. However, the front pads have a round disk mounted on the outside of one tab, just like the ones that are mounted now. This is not on the other Green Stuff pads. That is why I am assuming the one with the disk is meant for the front. There is also an inward rounded cutout on the tabs I removed, just like the ones I tried to fit.

I did not remove my rear disk pads after running into the problem, but this coming weekend I will do that and compare the pads.

It would be nice (though annoying) if I have just managed to get the pads swapped in their boxes.  ::)

One set of Green Stuff pads has a contact for the brake wear sensor, the other set does not. None of my current pads have this and the wire in the right rear is just hanging loose. On the left front, where there should be both a sensor wire and ground wire, someone has just cut them off at the inner fender. >:(
The connector on the pad looks like a small clip-on button type, but no matching wire is included, nor is there a matching plug on the loose wire.  ???

I looked at the drawing on your site and will compare with my Green Stuff pads. I should have known better than to attempt the job, without first checking your website.  ;) ;) ;)


Title: Re: Problem with Green Stuff brake pads
Post by: roy4matra on May 25, 2010, 11:24:56 am
Hi Roy.

I compared the Green Stuff front and rear pads and can see the 4mm difference you mention. However, the front pads have a round disk mounted on the outside of one tab, just like the ones that are mounted now. This is not on the other Green Stuff pads.

Oh I think I know what you are talking about now.  It is riveted in the hole in the tab yes?  Simply use a pin punch and knock them out.  This can be removed and thrown away Jon!  Or re-rivet them in the correct side...

These round studs were meant to be a wear indicator, as they are soft material, and as it touches the brake disc it makes a noise, but doesn't damage the disc.  So you get a warning before the pad is completely worn out.

The problem is, the people fitting them don't seem to know what they are for and, if they are fitted at all, have often fitted them the wrong side so the stud is on the back, instead of the same side as the pad material!

Quote
There is also an inward rounded cutout on the tabs I removed, just like the ones I tried to fit.

The small cut out on the corner of the tab is for the anti-rattle spring.  Sometimes these cut-outs are missing.  If that is the case, simply file the corner off for the spring to fit.

Quote
It would be nice (though annoying) if I have just managed to get the pads swapped in their boxes.  ::)

Look at my side by side comparison again Jon.  The front pads should be more rounded at their lower corners which distinguishes them from the rears which have a sharper corner.  The rears should also have a pip on the back whilst the fronts do not.  However, these are not really necessary and don't worry if they are missing, *as long as you make sure the slot in the rear piston is horizontal*.  The pip on the back forces the slot to be horizontal because of its position.  These pips are not to stop the piston rotating as is often mistakenly quoted!  They are there simply to make you align the piston slot correctly.

Quote
One set of Green Stuff pads has a contact for the brake wear sensor, the other set does not. None of my current pads have this and the wire in the right rear is just hanging loose. On the left front, where there should be both a sensor wire and ground wire, someone has just cut them off at the inner fender. >:(
The connector on the pad looks like a small clip-on button type, but no matching wire is included, nor is there a matching plug on the loose wire.  ???

The brake wear sensor wires in the boxes I find inconsistent!  Sometimes they are there and sometimes they are not!  Since the Murena only has one on the LH front and one on the RH rear, as long as you have one box with two in it, you have enough.  The end of these wires have a black plastic end with a ridge.  You push these through the hole in the tab from the back until the ridge locks them in.  it should be in the top of the inner pad nearest the wire on the car.  When the material wears down to the last bit, the disc touches the plastic and wears it off and touches the wire inside, earthing it, and bringing on the warning light.

If those studs were fitted on the pad side of the tabs, they can be used too, and are more reliable since the wire sometimes breaks and therefore you get no warning.  There can also be one on each pad giving you a warning no matter which pad wears first (as they don't always wear at the same rate).  With the wiring system you only have a warning on the LH front and RH rear inner pads.

Quote
I looked at the drawing on your site and will compare with my Green Stuff pads. I should have known better than to attempt the job, without first checking your website.  ;) ;) ;)

Thanks.  I have tried to cover most common things.

Roy


Title: Re: Problem with Green Stuff brake pads
Post by: Jon Weywadt on May 26, 2010, 09:49:46 pm
Or re-rivet them in the correct side...
---

Look at my side by side comparison again Jon. 
---
Thanks.  I have tried to cover most common things.

Roy
Hi Roy.
Thanks again. Mystery solved. I did have the pads swapped around. :-[
This weekend I will take pictures of the front pads that are on the car now and you will see why I did not realize the swap.
and those disks riveted onto the tabs,... they ARE on the wrong side and just makes it nearly impossible to install the pads. I was wondering about that, since I had never encountered such a difficult task of installing pads before. If I cannot get the electrical sensors to work, I will just move the disks to hte correct side, so I will get the audible warning.


Title: Re: Problem with Green Stuff brake pads
Post by: Philbert on May 29, 2010, 05:43:13 pm
Now that I have successfully replaced the front pads with Green Stuff, I am stumped by the rear calipers.
I have skimmed through Roy's Brake tutorial and read the Repair manual.

From what I can gather I have to loosen the bleed screw and then turn the piston clockwise with a ratchet wrench. When I do that and check the position of the piston, it has not retracted at all. 10 turns of the piston and no more clearance between the pads. What am I doing wrong. Do I have to hold on to the pin sticking out under the hand brake mechanism? and how would I do that?

PS. This is actually Jon Weywadt posting from Jan's PC, since I am working in his garrage today, while we also work on a LED high brake light.


Title: Re: Problem with Green Stuff brake pads
Post by: JL on May 30, 2010, 11:07:52 am
You need to apply some pressure to the face of the piston while turning it. Try doing it without opening the bleed nipple first, as long as the brake fluid resevoir is not too full there should be room for the fluid to just get pushed back through the master cylinder into it; if that does work or the resevoir is too full, open the bleed nipple but you may need to bleed the brakes afterwards.

Good luck.

John


Title: Re: Problem with Green Stuff brake pads
Post by: Oetker on June 04, 2010, 09:01:02 am
Indeed some pressure is needed when turning, but I would check the pistons first.
Most of them are pretty damaged and pitted after all these years.
(http://img9.imageshack.us/img9/2222/remoud1medium.jpg)
I took them apart compltely and rivised them to Roy's tutuorial.
(http://img5.imageshack.us/img5/1621/p1000453mediumfx0.jpg)
Also I didn't use the Green stuff but Ferodo's.
Other compounds of the pads can give worse results.
The Ferodo's work fine.


Title: Re: Problem with Green Stuff brake pads
Post by: roy4matra on June 05, 2010, 06:18:07 pm
Now that I have successfully replaced the front pads with Green Stuff, I am stumped by the rear calipers.
I have skimmed through Roy's Brake tutorial and read the Repair manual.

From what I can gather I have to loosen the bleed screw and then turn the piston clockwise with a ratchet wrench. When I do that and check the position of the piston, it has not retracted at all. 10 turns of the piston and no more clearance between the pads. What am I doing wrong. Do I have to hold on to the pin sticking out under the hand brake mechanism? and how would I do that?

No you don't need to hold the pin Jon.  In fact the pin cannot rotate unless the wedge link has been knocked out.

First let me explain why you need to rotate it.  The piston has a one way 'ratchet' mechanism inside it so that as the pads wear down, and the piston has to move further out to apply them, this mechanism rotates around the centre pin which has a coarse spiral like thread.  As it rotates it will pass a 'tooth' and cannot go back past that point any longer, so the piston stays out and it therefore 'self adjusts' to keep the pads close to the disc and the hand brake in correct adjustment.

When you wish to push the pistons back in to fit new pads, you cannot, since it is held in position by this one way mechanism.  However, you can rotate the piston to wind it back down the spiral, but you must apply pressure as you rotate the piston, and since the frame stops you using a conventional wind-back tool it is a little more difficult, particularly when on the car.

If, as Oetker says, the pistons are corroded on the area outside the housing, this makes them especially tight.  If there is corrosion in the frame grooves, the piston housing will be slightly oval also making it difficult to both rotate the piston as well as push it in.

You should never need to open a bleed nipple to get the piston to go back in, since the reservoir should have room to take all the fluid it pushes back (unless the system has been topped up with the brakes worn and pistons out!)  You should never top up a brake system with worn brakes.  If the reservoir was correct when all pads were new, it has sufficient fluid to allow for maximum wear.  The low level of fluid is actually another easy visual indication of worn pads, and will return to correct level when new pads are fitted.  The only other time a system should need fluid is if you had a brake fluid leak or you are changing it for new.

A point about the brake piston one-way mechanism.  If the spring end was to break off inside, the mechanism could possibly rotate - the 'self adjustment' might not work, and it might be impossible to rotate the piston back in, but I have not come across this so far and I have seen some very corroded and seized units!  However, if you do ever have the mechanism out, please make sure you put it back in correctly.  I have done at least two caliper overhauls where the mechanism was incorrectly assembled and it would be almost impossible to bleed all the air out.

The piston has a small cut out at the top in the back which is the same point as when you have the piston groove horizontal with the smaller groove uppermost.  This is where the air finds the highest exit point.  I have seen the internal bar which should be horizontal, blocking this exit point!  If you have never stripped the brakes totally, you probably won't understand this so don't worry, but if you have had the pistons out and cleaned everything, please bear this in mind.

Final observation - your overhauled calipers look good Oetker, but the pistons are incorrectly positioned at present.  Since they are not on the car this is no problem, but when you do fit them to the car the pistons will need to be rotated to bring the groove horizontal 'in fitted position'.  So if these are being left on the shelf for a while I would rotate them now whilst the seal is not stuck on the piston.

Roy


Title: Re: Problem with Green Stuff brake pads
Post by: Oetker on June 05, 2010, 07:16:37 pm
Quote Roy.
--------------
I would rotate them now whilst the seal is not stuck on the piston.
===================================================
Yes I noticed that when mounting them, but they are already fitted right after overhaul, and work perfectly.
(http://img22.imageshack.us/img22/5682/p1000481mediumei3.jpg)
(http://img24.imageshack.us/img24/8545/p1000485mediumgh4.jpg)


Title: Re: Problem with Green Stuff brake pads
Post by: Jon Weywadt on June 05, 2010, 07:17:47 pm
Thank you Roy for the explanation. You are right I do not understand the part with the spring or inside groves, since I have not had my calipers apart. Fortunately the previous owner replaced disks and calipers on all four wheels, so they are in good shape with no corotion on hte pistons.

I will try to perform the operation tomorrow, but just hod much pressure is needed? I am considering concocting a special tool from an old ratchet wrench and a spring. Since the piston housing is still attached to the frame, I cannot apply pressure directly. But if I can wedge a spring between the frame and the wrench, perhaps it will be a simple mater. We shall see.


Title: Re: Problem with Green Stuff brake pads
Post by: Oetker on June 05, 2010, 07:26:36 pm
I had them out, and it went fairly easy.
However last week I worked on the car from a fellow member and replaced pads.
Needed some force to push and turn them in.
We used a special tool to do it (sorry no pic at hand from that tool).
Best to do with 2 men.
Put 2 screwdrivers crosswise to apply force to the tool.
The tool looked like the original tool.
(http://img143.imageshack.us/img143/3849/p1020304medium.jpg)
Before I get critics, I never hang calipers like that, but was done to catch clean piston  and pads in one shot.


Title: Re: Problem with Green Stuff brake pads
Post by: roy4matra on June 09, 2010, 11:50:39 pm
Quote Roy.
--------------
I would rotate them now whilst the seal is not stuck on the piston.
===================================================
Yes I noticed that when mounting them, but they are already fitted right after overhaul, and work perfectly.

I wasn't sure Oetker if you had two sets of calipers with one set on the car and one set which you had just overhauled, and would leave stored as spares.  If cleaned calipers are stored for some time the seal can stick to the pistons, but as you have already fitted them that's good.  It will be a pleasure to use the car with the rear brakes and handbrake working correctly.

Roy


Title: Re: Problem with Green Stuff brake pads
Post by: Oetker on June 10, 2010, 12:10:42 am
That and the overhaul of the steering rack including ball joints and shocks was much progression in the driving experience of the car.
It made my car so much better.
Your tutorial was much help for me, otherwise i would never have separated the cylinder from the caliper.
No more sticking brakes (NB: the reason why the car was sold by the previous owner).
I have a spare set for overhaul now, and will set the piston in the right position, because they will be stored.

Thanks


Title: Re: Problem with Green Stuff brake pads
Post by: roy4matra on June 10, 2010, 12:14:27 am
I will try to perform the operation tomorrow, but just hod much pressure is needed?

Sometimes it can be quite considerable at the beginning.  I have a special Facom tool made for this particular job!  It's like a large pliers but it operates in reverse - as you squeeze the handles the jaws are pushed further apart not together.  The jaws are made with a section that fits the groove in the piston.  The other jaw pushes against the inside of the frame opposite the piston.  So you can squeeze the handles to push the piston inward and at the same time you can rotate the piston using the pliers as the lever!  I'm not sure if it is still available but I think it was D60A

Quote
I am considering concocting a special tool from an old ratchet wrench and a spring. Since the piston housing is still attached to the frame, I cannot apply pressure directly. But if I can wedge a spring between the frame and the wrench, perhaps it will be a simple mater...

No sorry, I doubt a spring will be strong enough, since it would have to be very strong and start compressed to try and apply enough force.

However, if you don't wish to separate it from the car and take it to a bench and vice, then you really need two people, one to hold the caliper whilst the other works on the piston.  You need a piece of square bar that fits well in the groove in the piston.  Then you need a piece of wood that almost fits the space between that square bar and the opposite frame.  Finally you need a wedge to push between the square bar and wood, a chisel is often ideal.  Tap the wedge into the gap between the wood and bar applying pressure to the piston, and then rotate the bar 90 degrees to rotate the piston.  Tap the wedge a bit more, then rotate the bar, keep doing this alternately.  It should start to wind back down and once you have it started, you can probably dispense with the wood and wedge and just keep rotating the piston with a bit of hand pressure.

Roy


Title: Re: Problem with Green Stuff brake pads
Post by: Jon Weywadt on June 10, 2010, 11:58:04 am

Sometimes it can be quite considerable at the beginning.  I have a special Facom tool made for this particular job!  It's like a large pliers but it operates in reverse - as you squeeze the handles the jaws are pushed further apart not together.  The jaws are made with a section that fits the groove in the piston.  The other jaw pushes against the inside of the frame opposite the piston.  So you can squeeze the handles to push the piston inward and at the same time you can rotate the piston using the pliers as the lever!  I'm not sure if it is still available but I think it was D60A

---

Roy
Thanks Roy.

That is an excellent idea for a tool. If I can't find it I will definitely make a similar one myself.  :)


Title: Re: Problem with Green Stuff brake pads
Post by: Jon Weywadt on September 26, 2010, 11:16:33 pm
----
When you wish to push the pistons back in to fit new pads, you cannot, since it is held in position by this one way mechanism.  However, you can rotate the piston to wind it back down the spiral, but you must apply pressure as you rotate the piston, and since the frame stops you using a conventional wind-back tool it is a little more difficult, particularly when on the car.
---
Roy

I finally had to do this work on the rear calipers. The reason being that it would fail the biannual MOT (Syn, in Danish), because the hand brake was unable to hold the car to the point of stalling the engine. That is about the braking power it needs to hold a car on an 18 degree sope as the law calls for in Denmark.

Part of the work consisted of replacing the outer hand brake cables from the caliper to the chassis. Last year I replaced the inner cable with a stainless one. (Still looking for stainless outer cables) ??? the old ones were so rusted that they compressed when pulling the hand brake.

The rest of the work, and the hard part, was to screw the pistons back in, to fit the Green Stuff pads I skipped last time. With help from Jesper, who held the caliper with a huge pipe wrench and applied pressure to the piston with a long 19mm wrench, I was able to turn the piston and it actually retracted. The left one took a lot of pressure and many tries, while the right one moved fairly easy, using the same tecnique. I naturally had the dust seals removed while doing this. ;)

With the new pads installed and the brake applied to seat the piston, I could adjust the hand brake to the correct tension. It now can stall the engine, if you try to start in 1st gear with the brake pulled tight.

It has never worked this well.  ;D


Title: Re: Problem with Green Stuff brake pads
Post by: Oskar on September 27, 2010, 11:35:32 pm
ive manage to screw it up. I thought it just had to be turned 45degres and then pushed in and after that turn it another 45degres so it would sit.  ???


Title: Re: Problem with Green Stuff brake pads
Post by: Jon Weywadt on September 28, 2010, 10:03:54 am
Success  :D

The car just passed the MOT (bilsyn) with flying colors. ;D

Releasing the clutch, with the car in first gear and the hand brake pulled, will stall the engine. :D

If I try to drive, with the hand brake pulled, the rear end will settle down about 3"-4".  ;D


Title: Re: Problem with Green Stuff brake pads
Post by: RazorbackNOR on September 28, 2010, 10:22:16 am
Congrats Jon!!  ;D