Clutch Master and Slave Cylinders

[JohnH]

Went to give Daisy a run round the block the other day and dicovered the clutch pedal flat to the floor. WHAAATT.

I always leave the car in neutral when I park up, whether it stayed down after I put it in neutral, or it magically happened when she was standing for a few days, I dont know. Anyway I lifted the pedal up, started the car and move the gear lever into first and pulled forward a couple of feet, then reverse and moved back. All seemed well. I did check the fluid level and it may have dropped a bit, I'm not sure. Couldnt see anything under the car.

Got thinking about it and decided I might as well overhaul the hydraulics so purchased a Master cylinder overhaul kit from BiggRed (£10) and a replacement Slave cylinder from Febi Bilstein (£20). Both of the original cylinders have been on the car since 1986, so maybe a sensible move.

I'll start work on it in the next few days, SWMBO permitting.

If anyone has done this before, any tips will be gratefully accepted.  

 

Edited July 29 by JohnH

[JohnH]

 Removing the Clutch Master Cylinder on a RHD car is very straight forward. Theres just one bolt to undo on the clutch pedal and two on the bulkhead accessed from the engine compartment.

You need to remove the lower cover to get acess to the various bits.

A 17mm spanner to hold the bolt head and a 13mm ratchet spanner to undo the nut. Ease the bolt out and that will release the clutch pedal. 

There was a bit of fluid leaking shown in the above pic and below from a differnet angle.

Now head under the bonnet

really easy to get at when you havent got an engine and other bits and bobs in the way.

see below for the real deal,

Put a towel or in my case and old vest under the master cylinder to stop any of the brake fluid getting on the inner wing. It is a very efficient paint stripper.

Using a large syringe suck the brake fluid from the resevoir. 

Detach the resevoir rubber pipe by prising it off with a screwdriver and undo the pipe leading to the slave cylinder. You will need an 11mm brake pipe, flare nut spanner.

Next undo the two bolts holding the master cylinder to the bulkhead. The top right is very straight forward and the bottom left is very slightly more challenging.

Remove the master cylinder, bearing in mid it still has a bit of fluid in it, so wrap it in your old vest and put it on your workbench.

remove the circlip using the appropriate pliers, then extract the piston assembly. As you can see the spring is broken. My replacement kit doesnt one so I have ordered another kit that does (£10). It will be here in a few days.

In the meantime I'll sort out the slave cylinder, tomorrow. Stay tuned in for more exciting updates!

Edited July 29 by JohnH
spelling

[JohnH]

Well tuesdays been and gone. SWMBO had me doing gardening, but I did get a couple of minutes to strip down the master cylinder piston. I had some concerns about how one would do this and a bit of internet surfing brought up an excellant article on E28 Goddies website.

https://e28goodies.com/check-brake-thats-not-clutche/

You need to go 2/3s of the way thru until you come to the bmwfans.info parts diagram. This is for a LHD vehicle, infact every diagram known to man, including BMW's own service manuel (Blue book) and Haynes 1560 E28 520i and 525e manual use this diagram. Though the external appearance of the LHD and RHD are different, the internal compodents, apart from the lenght of the piston, are the same.

I used E28Goodies guide with a couple of excepetions. I didnt want to pull the rod out of the piston by using a screwdriver in circular rod end fitting, because this appears to be plastic on the RHD rod and I thougt this may break it, so I inserted a thin screwdriver between the piston and collar in the other end of the rod. It popped  out whithout much effort.

The other thing was removinf the toothed restraing washer from the end of the piston. I tried to use a pair of pliers but all it did was bend the teeth. I didnt have a spare so I popped the piston in the vice and used a prizzer to pop it off. See below.  

 

Popped the new seals on, lugricated with red rubber grease;

The BiggRed seal kit I ordered didn't have the internal piston spring included within the kit (I knew that as the picture didnt include it), so I ordered a FrenTech kit off ebay that included a spring within the picture. It turned up the next day and it too didnt include a spring. I contacted the seller and got an immediate refund and apology! So I've done what I should done in the first place and purchased a complete LHD E21 Clutch Master Cylinder from Autodoc for £23 plus postage £12. So we wait, for how long, I dont know. Days, weeks, life times. I dont know. What I do know is that Autodoc aren't the fastest. 

In the mean time here's a picture of the tools used so far (excluding flat bladed screwdriver).

Anyway we sit, and wait. Maybe I'll do the Slave cylinder, weather permitting. Two nice days then it rains according to George III. The weather forcasts threatens Thunder and Lightning, very very frightening today. We'll see.

[JohnH]

Well we did have a bit of T&L early thursday evening. They said we had 2" of rain over a 2 hour period..

Anyway took the opputunity on Saturday to inspect the Slave Cylinder;

I remember now, that The guy a bought the gearbox from about 12 years ago had fitted a new slave using the method that was in fashion then, to fit it upside down to aid bleeding. A close inspection didnt spot any leakage. In fact it looked very new and inpart, shiney. Desided to leave well alone.

Studying the Blue Book diagram,

shows that the bleed nipple draws air from the top of the cylinder, when its installed correctly. I seem to recall that I had to remove the slave from the gearbox and hold it vertically with the bleeder uppermost to get the air out. 

Anyway, still waiting on Autodoc. From what I can see from the tracking info they sent me, they still havent despatched anything yet. Hey Hoo.

[Ordnator 2]

On 26/07/2024 at 11:59, JohnH said:

Went to give Daisy a run round the block the other day and dicovered the clutch pedal flat to the floor. WHAAATT.

I always leave the car in neutral when I park up, whether it stayed down after I put it in neutral, or it magically happened when she was standing for a few days, I dont know. Anyway I lifted the pedal up, started the car and move the gear lever into first and pulled forward a couple of feet, then reverse and moved back. All seemed well. I did check the fluid level and it may have dropped a bit, I'm not sure. Couldnt see anything under the car.

Got thinking about it and decided I might as well overhaul the hydraulics so purchased a Master cylinder overhaul kit from BiggRed (£10) and a replacement Slave cylinder from Febi Bilstein (£20). Both of the original cylinders have been on the car since 1986, so maybe a sensible move.

I'll start work on it in the next few days, SWMBO permitting.

If anyone has done this before, any tips will be gratefully accepted.  

 

Hi John,

I have always had auto's so not much manual E28 knowledge to be able to share.

The system is about as simple as an hydraulic system can be though, get the air out and keep the fluid in the correct areas.

Worn seals will likely be a good start point for any issues as the only wear part.

Following with interest.

Best regards.

Mick

[JohnH]

Hi Mick,

Thanks for your thoughts.

As chance would have it I have been thinking about fitting an auto box as I'm getting fed up with clutches! I have an EH box that I removed from a 525e parts car I used to have. I put the engine into Daisy when she started smoking a little bit, together with a 5sp manual a bought from a chap how was breaking an E30 325i. I fitted Daisies M20B20 731 cylinder head and intake manifold onto the M20B27 from the 525e. I also fitted Motronic 1.3 from an E30 325i. All in all its an excellant combination and in retrospct would work very well this an auto. I used to have an E36 325TDS Auto which had a 5speed box. I think thaat would work really well.

Regards

John.

The Autodoc parcel arrived yesterday. Heres the LHD E21 master compared to the RHD E28 version.

The internal componets apart from the length of the piston are identical, but as chance would have it, 2nd FrenTeck kit that also came included a spring,

I will use this sping. Old broken compared to new shiney.

 

they look identical, accept the wire diameter, 1.25mm old and 1.29mm new. It looks more but its probably just the colour deceiving me. 

So the next step is refitting the master. Stay tuned.

[JohnH]

Continued rebuilding the Clutch Master Cylinder. 

Inserted the rod into the cylinder and tapped the nut downwards, very gently and it snapped into place.

inserted the piston into the cylinder. I had previously wiped a bit of red rubber grease onto the piston seals and the top of the piston, which helped it to just slip in.

next fit the U washer and circlip

Its a bit fiddly. Press down on the rod with the palm of your hand and pull the rubber back with you fingers!!!

The object of the exercise is push the piston in a bit so the U washer will drop into position, and then insert the circlip. Make sur the circlip snips into the cylinder ring properly.

Next refit the Master Cylinder. Put a small amount of sealant on the cylinder mounting face. All the mechanical brake bits on bobs on the bulkhead get in the way so insert the lower left bolt into the cylinder and hold it in place with a socket with an extension. See photo somewhere above. Engage the screw, get the cyinder centered and pushed into position. Do it all the way up. Insert the top right bolt. Re-attach the metal pipe fitting using 11mm spanner and the resevoir pipe. 

Now for the hard bit, attaching the cyinder rod to the clutch pedal.

   

Insert the rod attachment bolt though the rod circular end fitting and the clutch pedal. That was the easy bit. Now for the bit that really tests your patience and ribs. Fitting the nut. You cant get you fingers in there, everythings in the way. You can get a spanner in there, no problemo, but a normal spanner wont press the nut into position, it just slips though the head of the spanner into the floor. There is a solution, use a ratchet spanner that has a nut holding head. see my trusty Carolus ratchet spanner below.

As you can see, the haed of the spanner has a fitting partially covering the teeth. You can only insert nut from the underside of the picture.

So leaning over the seat, using your left hand to hold the bolt in place, carefully lift the spanner and nut combo into place and slowly and patiently, as your chest implodes and shoulder muscles are at screeming point, carefully get the nut to engage. Use your third hand to help press the nut into position. Breath slowly and ratchet the nut up until it snugly into position. Job done. Now roll backwards onto the ground, breathing deeply, rubbing your aching thighs and any other body parts as required. You've done it. Good job. Ten minutes of your life that you will never get back, but worth it.

The next exciting installment is about Bleeding the Clutch.  

Edited August 12 by JohnH
spelling

[JohnH]

I came across a very interesting video explaining, clutch bleeding.

In short you do it from the bottom up, not from the top down, as I've previously done it.

The first couple of comments on this vid suggest using the brakes to get the fluid into the system, rather than using an oil can. I didnt have a usable oil can, so decided to use the brakes method. The only down side of this approach is that you need someone other that you, to pump the brake pedal, so hello swmbo.

Because I was taking this approach I decided to flip the slave cylinder to it correct orientation, then hook up the pipework.

Front brake, complete with spanner.

   

Slave with spanner.

Check that the brake reservoir is full. Now open both bleeders and get swmbo to press the brake pedal slowly to the floor and hold it there. Close the bleeders and get swmbo to release the brake slowly. do this 3-4 times and check the brake reservoir. Top it up and continue the routine. It took 12-14 brake presses to get the clutch reservoir half full. Also topped up the brakes two further times. I used about 150 ml of brake fluid. The whole process took no more than half an hour.

Took the car for a spin. The clutch was perfect. Much better than before and strangly the brakes seemed better as well.

Would I bleed it this way again, yes, but I would get a oil pump to do it as per the video. Much easier. No wriggling aound under the car, no peddle pumping and you can keep an eye on the clutch reservoir. No more than ten minutes as well.  

Observations. If I had had the correct master cylinder kit in the first place, the whole process would have taken no more than a couple of hours. The only onerous part of the process was getting the damn nut back on the peddle bolt. It helped having all the right tools as well.

Edited August 12 by JohnH

[Sir Anthony Regents Park]

Those early master cylinders are a real problem now. Later cars from 1986 onwards had an E30 style cylinder that bolts to the side of the pedal box........which is different to the pre '86 cars. 

 

The oil can method looks good. I used a pressure bleeder with gentle pedal pumping but the oil can idea looks better.