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R&R of Clutch Master Cyl on Later Model 6er

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ScottAndrews
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R&R of Clutch Master Cyl on Later Model 6er

Post by ScottAndrews » Mon Nov 29, 2004 3:03 am

I finally got around to replacing my clutch master cylinder in my 88 today..Yikes!.. THAT was a PITA!

Took me about 2 hours to R&R the MC, and then another hour, at least, to figure out how to bleed it properly..bleeding with this process is about a 15 minute affair..so read on oh happy 6er fan...

A couple of helpful hints...

DO NOT remove the MC bolts until you have removed the hydraulic line fitting on the end that pokes through the firewall. These bolts are necessary to hold the MC in place while you trun the line fitting nut.

The MC hydraulic fitting nut is really hard to reach, and there is not much room for a wrench, let alone my trusty, but longish, flare nut wrench. Rather than risk rounding the nut , I undid the hard line where it mates to the flex hose to the slave cylinder.
I then snaked an 11 mm BOX wrench onto the line and got it up to the business end of the MC.

This wrench is rather short, and the box can't slip off the fitting, so it was simple matter to then unscrew the line fitting from the MC. At that point removal was a cinch.

The only other hard part was installing the reservoir feed fitting into the top of the MC. I ended up removing the MC again, and snapped in the elbow while I was holding it. It is MUCH easier to attach the elbow to the filler hose than to try to snap the elbow mounted to the hose into the MC. There is just not enough room..that and you are on your back with the pedals in your face...

As for bleeding.. The primary issue I found was that I was pumping air.. I didn't realize that having the car jacked up on the left side tilts the brake fluid reservoir to the right, so the reservoir level is almost even with the filler hose. Once I realized this. I bled according to this process: I removed the slave cylinder. Using an old Holley 2BBL carb spacer, I clamped the output pin of the slave so it was depressed. I did this by I clamping the slave to the carb plate so the pin was poking through one of the carb holes (A 3/4 inch thick block of wood with a large hole would work as well). I then placed a plate of metal over the opposite side of the plate so that it pressed the pin in. I clamped this in place so the pin was depressed and I didn't have to hold it. I then lowered this assembly until the bleed fitting was the lowest point. I attached a hose and fed UP to a jar of fluid that had the other end of the hose submerged under the fluid. The jar needs to be higher than the slave.. I then slowly pumped the pedal by hand and watched all the bubbles come out. I refilled the fluid reservoir several times and ended up wasting about 2/3 of a cup pf ATE Super Blue fluid.. I pumped until I had no more bubbles, and the whole mess was clearly reacting to the pedal. I then closed the bleed fitting, removed the plates and clamps and re-installed the slave. This whole process took an hour, but the actual bleeding only took about 5 minutes..once I worked out the process (and filled the reservoir properly).

The clutch is solid and smooth, and it doesn't stick in the down position now...

So. Let me know if you have any additional questions on this one.

S
---
80 Euro 635 aka Rosanante - Don Quixote's steed...ready to carry me off to dream the impossible dream... La Verdad...the Truth.

Scott Andrews
Petaluma, CA

GRNSHRK
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Brian, this should be posted as a tech article!!!

Post by GRNSHRK » Mon Nov 29, 2004 6:27 pm

This excellent write-up done by Scott should be posted as a tech article for all to benefit from.

In addition, I have personally met Scott recently and can attest to his vast knowledge of our cars, both the E12 and E28 versions. He runs an '80 Euor model while his son is the apparent owner of the '88 :?

Nice job Scott!
:mrgreen:
Bobbo
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Post by bcadmin » Mon Nov 29, 2004 8:20 pm

Scott gets a BigCoupe T-shirt!

Sharkie

Post by Sharkie » Thu Feb 26, 2009 4:56 am

Need to replace clutch in my 1988 M6(E24)...looking for any/all tech guides and/or diagrams to provide process and sequence for friend, who knows how to drop trannies and replace clutches on other vehicles.

The Sixer Kid

Post by The Sixer Kid » Thu Feb 26, 2009 12:57 pm

Wrong section Pal. Replacing the clutch M/C doesn't have anything to do with replacing the clutch itself, except for the bleeding part of things.

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ScottAndrews
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Post by ScottAndrews » Thu Feb 26, 2009 1:55 pm

To replace the clutch you will need to remove the engine or trans. Removing the trans is about 100x easier. it requires some skill to line up the input shaft properly so it all goes together, and the bell housing bolts will require a double ujoint and two long socket extensions...
It's a bitch either way, but nothing that can't be done in a weekend if you have all the parts.

WHile the trans is out I'd replace the seals, especially the selector shaft seal.

S
---
80 Euro 635 aka Rosanante - Don Quixote's steed...ready to carry me off to dream the impossible dream... La Verdad...the Truth.

Scott Andrews
Petaluma, CA

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Post by wjtesquire » Sun Jun 27, 2010 11:22 am

Scott was dead on when he said this project is a PITA! I also chose to unhook the connection at the slave cylinder flex hose, but instead of snaking the wrench up the line, I pulled the MC through the firewall enough to get to the connection inside the footwell. Hooked up the line and then my 7 year old son pushed the new MC back in the firewall turning it left and right while I got underneath and grabbed at the line. Reattached at the flex hose and went after that feed line elbow. After wasting an hour of trying to "snap" it back into the rubber grommet, I ended up prying the grommet out of the new MC, snapping the elbow in and pushing the grommet back in with a broad tipped screwdriver. I borrowed my neighbor's pressure bleeder to finish up. The online manuals were a great help in showing you how to do this simple project if you have superhuman strength of if your car does not have the pesky steering and brake components installed. Otherwise, get your best cuss words ready.

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Re: R&R of Clutch Master Cyl on Later Model 6er

Post by Rondel Fan » Sun May 12, 2019 2:48 am

Having just tackled this today I would add the following. For some reason I could not get an 11mm flare wrench to grip the hard line pressure fitting on the end of the MC. I used a crow foot with about 3 x 3/8s extentions that I finally put a wrench on up by the alternator. I broke the nut open and was able to turn loose the fitting with the stub of the crow foot by hand from the top of the engine.

I placed the new soft hose and fitting into the MC before inserting it back behind the pedal cluster.

I left the hardline disconnected from the slave and fitted it by hand into the master, then to the slave.

One of the harder parts was fully seating the new fluid feed line from the reservoir to the master.
Pressure bleeding from the top went great save one small detail.

Unfortunately I got an M6 slave cylinder line vs a 635 line and it leaked badly at the union. Hope to have the right part and buttoned up in a few days.

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Re: R&R of Clutch Master Cyl on Later Model 6er

Post by JCS » Mon May 13, 2019 12:48 pm

Fellow Members,

I would like to add that this is one of the harder jobs I have yet encountered.
I even replaced the flex hose, at the last minuet, during the task.
And to get the correct size of hose, both id and od, was a problem.
It also needed to be the proper rubber for brake fluid.
The hose I got was a little over size od and it was to tight to go thru the firewall hard rubber grommet.
I had to cut away a little rubber from the grommet.
And last but not least, I should have removed the drivers seat.
Because I am an older guy, most of my body weight pressed my back lower rib cage on the front edge of the drivers seat, and I fractured a rib.
I was still able to finish as it happened at the end, and I just had the install the new slave, and bleed the system to finish.

Best,
Jay
'88 M6, Red/Tan
To view my newest website, with 16 website links
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Re: R&R of Clutch Master Cyl on Later Model 6er

Post by Rondel Fan » Mon May 13, 2019 8:10 pm

By "flex hose" I assume you mean the fill hose from the reservoir to the MC and not the one attached to the slave. The BMW PN for black braided line is 21521163714. I had some BMW blue braided line left over from some e30 work. I couldn't find a BMW number but a lot of cars use it and VW sites have it listed as # n203501 which I think was printed on mine.
I also would have removed my seat if I hadn't removed the power relay board in search of an issue with the seat rails positioned over the rear hold down bolts. DOH!
JCS wrote:
Mon May 13, 2019 12:48 pm
Fellow Members,

I would like to add that this is one of the harder jobs I have yet encountered.
I even replaced the flex hose, at the last minuet, during the task.
And to get the correct size of hose, both id and od, was a problem.
It also needed to be the proper rubber for brake fluid.
The hose I got was a little over size od and it was to tight to go thru the firewall hard rubber grommet.
I had to cut away a little rubber from the grommet.
And last but not least, I should have removed the drivers seat.
Because I am an older guy, most of my body weight pressed my back lower rib cage on the front edge of the drivers seat, and I fractured a rib.
I was still able to finish as it happened at the end, and I just had the install the new slave, and bleed the system to finish.

Best,

Rondel Fan
Posts: 39
Joined: Mon Apr 29, 2019 12:31 pm
Location: North East

Re: R&R of Clutch Master Cyl on Later Model 6er

Post by Rondel Fan » Thu May 16, 2019 11:52 pm

In need of some help on this project. I just plumbed in the new slave flex line and it leaks badly at the union to the hardline to the master. I'm guessing the seat might buggered. The hard line, PN 34326755562 is NLA even though it crosses to many models.
Does any one have a good source for BMW flares line stock? Is it a "normal" flare? I am more familiar with Audi which in manuafacturer specific.
Thx
Mike
Last edited by Rondel Fan on Wed May 29, 2019 11:58 am, edited 1 time in total.

Sechserreihe
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Re: R&R of Clutch Master Cyl on Later Model 6er

Post by Sechserreihe » Tue May 28, 2019 3:36 pm

I'm in need of this flexline myself. You are correct that it's NLA. Is there an alternative?
Thanks,
Mark

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JCS
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Re: R&R of Clutch Master Cyl on Later Model 6er

Post by JCS » Tue May 28, 2019 5:44 pm

Sechserreihe wrote:
Tue May 28, 2019 3:36 pm
I'm in need of this flexline myself. You are correct that it's NLA. Is there an alternative?
Thanks,
Mark
I got this hose from summit racing
https://www.summitracing.com/search?Pag ... TIL-74-214
Jay
'88 M6, Red/Tan
To view my newest website, with 16 website links
Please read the instructions in RED, then on page 2,3,4 to view the info panel (CAPTIONS)
http://bigcoupe.com/phpBB3/viewtopic.php?f=24&t=28245

Rondel Fan
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Re: R&R of Clutch Master Cyl on Later Model 6er

Post by Rondel Fan » Wed May 29, 2019 12:09 pm

To be clear, the part I referenced that is NLA, is the HARD line from the clutch master to the slave flex line. The Hose that goes from the slave to the hard line from the master is available everywhere after market. PN= 21521153512 . I got a FEBI for ~$21 delivered. To replace the hard line I got a 12" straight piece from NAPA with the correct flare and shaped it. The only difference is the size of the ferrule head @12mm vs 11 and the fact that the shoulder sits a bit higher so it does not quite fully draw the line against the body stop. But it does not leak!

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Sechserreihe wrote:
Tue May 28, 2019 3:36 pm
I'm in need of this flexline myself. You are correct that it's NLA. Is there an alternative?
Thanks,
Mark

Sechserreihe
Posts: 64
Joined: Sun Jun 26, 2016 7:10 pm
Location: Columbus, OH

Re: R&R of Clutch Master Cyl on Later Model 6er

Post by Sechserreihe » Wed May 29, 2019 12:15 pm

Excellent. Thanks for clearing that up.

Mark

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