Bleeding The Hydraulic Clutch System

A simple tip that might solve your clutch bleeding frustration.

Written by Mike Maddux – 2010-05-13
How-To Library > Brakes and Clutch Section

Generic automotive clutch hydraulic system diagram and components

Clutch Bleedings Tips

As an experienced mechanic, I will never be more humbled than I was by this simple solution to a problem that caused me many a wasted evening.

OK. New clutch master and slave cylinders. Install. (This is the crux, but read on.) Add fluid. Crack slave bleeder, attach tube, put in bottle. Pump clutch pedal ten times. Look in bottle. Nothing. Repeat ad nauseum. Zippo.

Tried gravity bleeding. Kinda, but not really. Zippo.

Get out Mity-vac. Set it up. see a little fluid. Repeat, ad nauseum. Zippo. Open beer and give up.

Finally, online, I found this:

"I think the biggest reason it is so hard to bleed the clutch system is because the bleeder valve is lower than the incoming fluid line. Gravity bleeding will work to clear the clutch line of air, but there will be a bubble left in the slave cylinder. What I found that works is to simply unbolt the slave cylinder and hold it such in a way that the bleeder valve is at the highest point, relative to the incoming line. Holding it this way, the air bubble in the cylinder will naturally float up and out by gravity, e.g. the slave will fill up from the bottom and push the air out the top. Since gravity is doing all the work, this is a one man job. When the air bubbles stop, close the bleeder and attach the slave to the bell housing."

Slapped myself in the forehead and caught a lesson in humility.

Tip by Mike Maddux

— Bleeding The Hydraulic Clutch System —

Written by Mike Maddux – Created 2010-05-13 Published 2010-05-13
Contents © Copyrighted and published under the following terms:
Released under the terms of the CC Attribution-NonCommercial-ShareAlike 2.5 License

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Member Comments on Bleeding The Hydraulic Clutch System ↵

Rated 8.3 out of 10 based on 3 ratings

2010-06-04 18:57:01 # 2035

Comment by Brian M

Hey Mike,
the bleeder valve SHOULD ALWAYS be above the inlet hose. But, you shouldn't have
to unbolt to achieve this.
This is a very common happening. I can't post a pic right now, because I'm using my
iPhone, but, if your bleeder screw is below your inlet hose, you need to remove them
both and swap places.
For some crazy reason, these are packaged incorrectly, it has been like this for 30
years. Take a look at your manuals, you'll see the picture of what it should look like,
or do an archive search of my name "BManBrian" and "slave cylinder" and you'll see a
picture.
Why they package them wrong, I'll never know, about 50% of MGB enthusiasts miss
this. It'll only happen once though! Hahahahahaha

Brian

2010-06-04 19:27:47 # 2036

Comment by Mike Maddux

Brian....Well, that gets to the heart of it, doesn't it? Same npt threading, of course. Live and learn. An other example of making assumptions and being too smart to see the obvious. Mike

2012-10-18 17:53:34 # 7852

Comment by JON ERIKSSON

Rating: 6/10

I'm having the same problem, I have replaced the lockhead master cylinder [2x], new clutch hose, new copper washers, new slave cylinder, ....! I get some pedal pressure. and then I start to see a pencil pointsized air bubble coming up from the master.

I have gone thru this system 6 times anyways ans yet this is the only thing holding me back.

The car ran and drove for about 2 miles and then I had an instant dead pedal. I also tried the first suggestion of removing the slave, tapiny it up so the piston does not pop out and bleeding it....did'nt work. If any one near Concord, NH can fix this, I will pay for it gladly!!!!! Call Jon Eriksson 603-226-0106

Sincerely,

Jon

2012-12-11 10:21:36 # 8418

Comment by Alex Oliver

I've written a short article on hydraulic help - it works and has saved me years of grief

2013-07-15 13:12:39 # 11059

Comment by kim gibson

Rating: 9/10

It is not that the bleed screw and inlet pipe are reversed, it is because a part of the slave cylinder body IS above the bleed screw when it is bolted to the bell housing. I unbolted it and tipped it slightly until the bleeder was uppermost, and a small bubble did come out of the bleeder. Very helpful article.

2013-08-03 09:34:44 # 11272

Comment by Roger N

Didn't work for me !!

2013-08-03 14:09:39 # 11275

Comment by Brian M

Kim & Roger,

The Slave Cylinder comes packaged incorrectly. The bleeder screw needs to be removed
from the lower INLET, and screwed into the UPPER hole.
I am posting two pictures on the MGB forum right now, as, I can't seem to figure out how
to post pics here.

email me if you can't get it, and I can help:
BrianMasek@hotmail.com

2013-08-05 19:17:03 # 11308

Comment by Roger N

Mine was packaged right. Bleeder is on top. Friend got it bled for me.

2013-09-21 23:11:10 # 11984

Comment by Brian Radich

On a Jaguar E Type the bleed screw is at the bottom of the cylinder and the hose at the top. This is because the slave cylinder is so high up in the tunnel it would be impossible to get a spanner to the bleed screw if it was on top.
Any gravity bleeding or pressure bleeding is no good for expelling all the air. Once you have most of it out, open the screw fairly wide and get a helper to push down heavily on the clutch pedal the quickly close the screw. Repeat one or two times if necessary. The force of the clutch pedal being firmly depressed is enough to drive all the air out.

2013-09-23 15:24:07 # 12000

Comment by Brian M

I am not an expert on E-types, but, the bleeder screw should ALWAYS be at the top of the
set-up, ALWAYS! I bet if you look at the two holes they are identically threaded, just switch
the hose & bleeder screws. Originally, if memory serves me here, the clutch slave cylinder
on those cars had both bleeder and hose holes on the top, but, subsequent part
substitutions have one on the top and one on the bottom. The bleeder screw MUST BE ON
THE TOP, ALWAYS. Good Luck

2013-09-23 16:28:32 # 12001

Comment by Brian Radich

Yes Brian, the bleeder screw should always be on the top (makes semse - air on top of fluid) but..... on the E Type it is on the bottom. The parts manual clearly shows it on the bottom and the hose on top. And the method I suggested for expelling the air works fine. You just have to have the bleeder opened quite wide and have someone firmly push down on the pedal. Email me at brian_radich@yahoo.co.nz and I can show you the illustration in the parts manual. All E Types (3.8 and 4.2 anyway) were set up like this.

2014-02-12 07:27:13 # 14091

Comment by Gary Griffin

An alternative is to turn the car upside down and bleed the slave
cylinder. Hahahahahaha

2014-04-03 07:57:26 # 14762

Comment by Lorraine M

Do you have any photos? If I dont know what I'm looking for, where can I find the bleeder valve? Is it on the Slave Cylinder and where is this cylinder located?

2014-07-13 18:08:48 # 18826

Comment by KC Allen

MG guy telling a jag guy how it should be. He speaks not from experience but from know it allness. Jag bleeder is on the bottom from the factory no other way to do it on an Etype.My E is on the bottom my B is on the top I know this from experience not from a book or web spot.

2014-07-14 16:19:40 # 18854

Comment by Brian Radich

Exactly! So long as you have someone to depress the clutch pedal hard as you control the bleed valve, you will get all the air out. You can't do this with any pressurised bleeding system. Just A good hard push on the pedal.Can you imagine trying to get to the bleeder if it was on the top?

2014-08-23 19:51:42 # 19915

Comment by Rick Lewis

Rating: 10/10

My nephew and I tried bleeding the clutch on my '76 Midget to no avail. Now he works on helicopters in the Coast Guard so I just had to trust he knew what he was doing under there as I was the one pushing down the pedal & filling up the M/C.After reading several of these forums for a couple of days and the use of common sense I decided to try this: I ordered a 7/16 20mm Speed Bleeder for Advanced Auto (for those that are not familiar, a Speed Bleeder, once it's screwed out one revolution will allow fluid/air to come out but the SS ball in the check valve will not allow anything to come back in. It's often called a one-man bleeder. I then got some oxygen tubing (just the right size) and slipped it over the bleeder nipple and using as short of a piece necessary to come out next to the front left tire and put that end into a collection container (clear is best so you can see how much fluid has come through). Then there is the problem with the hydraulic line being higher than the clutch master cylinder (where pe

2014-08-23 20:11:51 # 19917

Comment by Rick Lewis

(where pesky air bubbles like to hide). Remove the M/C from the mounting bracket, you will have to take the mounting bracket loose in order to get to the bottom nut of the M/C. with one hand hold the M/C above the hydraulic line. With your loose hand you will be topping off the M/C with fluid. Push the piston in and watch the fluid/air come out of the clear tubing. Keep repeating this process until there are no more bubbles. Reassemble, tighten the bleeder. You will then have all the clutch you need.Be 10% smarter than whatever you are working with and always use common sense.Rick

2014-09-02 11:54:43 # 20143

Comment by Bob Ickrath

OK...I clicked on this because I replaced my clutch slave last week and had a hard time bleeding it. Went out and looked at my TR-6 and sure enough, the bleed is on the bottom! Looked at my shop manual and and lo and behold, the drawing has it on the top. Guess when it gets below 90 degrees in my garage I will try to switch it...Thanks!

2015-12-07 11:52:15 # 30772

Comment by Ray Rawlinson

I bled the clutch this weekend after switching the bleed nipple and the clutch line and it bled in a few minutes, no problem. I had not read this thread until now and when I was under the car for the first time the positioning of the bleed nipple just seemed wrong to me so I switched them around everything works just fine.

2017-01-16 04:21:23 # 39734

Comment by Jim H

How do you get to the clutch reservoir? My Morris Minor 1000 reservoir is inside the rrame rail. I cant even touch it and i can barely see part of the cap from under the hood.

2017-01-16 10:58:06 # 39744

Comment by Gord Smith-Ritchie

To Jim H, the 1000 did not have a hydraulic clutch, but if someone added one and used the brake master cylinder as the reservoir, you have to go inside the car and pull up the carpet and you will see the access plug on the floor.

2017-05-27 11:38:30 # 42512

Comment by Brian Lake

just did the search mentioned above by Brian M. and "No Results Found"

2018-05-25 07:25:49 # 50358

Comment by charles durning

There is an easy way to bleed. First replace the bleeder screw with an easy bleed. The thread size is 1/4-20. Then compress the slave piston all the way into the slave cylinder bore and use a zip tie to hold it in place. With the bleeder cracked open have someone fully depress the pedal once. While the pedal is fully depressed close the bleeder. Release the pedal, check, and top up the M/C. Repeat as necessary.Fully depressing the piston is critical. That makes the displacement inside of the slave as small as possible. That way there is no place for air bubbles to hide. The speed bleeder keeps air from getting in through the bleeder.

2018-05-27 06:37:52 # 50409

Comment by Steven Pignataro

Thanks...always gaining so much from this forum!

2018-07-27 08:30:28 # 51392

Comment by Jim Christian

The clutch line on my MGB GT comes out of the Master cylinder and is routed higher that the reservoir as it goes toward the front. This creates a perfect place for air to be trapped. My solution was to buy a piece of clear plastic vinyl hose, at the hardware store, that would just go over the MC cap threads. I cut it about three inches long and clamped it to the MC. Then I filled it to level above the MC steel line and pumped slowly until the last bubbles disappeared. I had previously bled the slave cylinder, but I did it again just to be sure. Worked for me.

2018-07-31 17:00:21 # 51438

Comment by Chuck Tompkins

Should the clutch pedal resistance be firm somewhere near end of travel? My clutch pedal goes to the floor but I am able to change gears.

2019-05-27 09:44:33 # 57154

Comment by JAMES CAMPBELL

It worked after several hours of trying to bleed with my "assistant", wife, could use gravity method by unbolting and making sure bleeding screw is at top, and open, I dont see how you could switch ports , as one is a different diameter'

2019-08-31 13:42:15 # 58933

Comment by Torbjrn Eriksson

Your method of detaching the slave cylinder worked! After 10 summer weeks of bleeding attempts In the garage I finally have a clutch that opens...Thanks

2019-09-12 09:56:53 # 59123

Comment by Richard Harcourt-Brown

Your solution of removing and rotating the slave cyl until the bleed valve is uppermost , then allowing gravity feed to displace trapped air absolutely solved the problem. 5 previous attempts including 2 with the help my local garage (who kindly let me use their ramps) had all failed.!!... thanks for the tip

. Rich

2020-08-19 13:18:52 # 65450

Comment by Don Renollet R

I registered just to add to the discussion. Indeed the clutch slave cyl on my 79 MGB, came from the vendor with the bleeder screw on the hose port. I checked my old slave, and checked the Haynes manual to verify this. At least on my old leaking slave, the bleeder port and hose port ARE threaded the same. So i need to switch ports if i wish to be like the Haynes manual and the part i removed off the car which i believe is oem. hope to update later.

2023-07-17 15:05:59 # 87311

Comment by Wal Parnel

Used a spray bottle pump. Took off nozzle, put on bleeder hose connect to nipple. Put brake fluid in bottle. Removed about 1 oz, fluid from slave. Couple pumps, pushed bubbles up and out slave. Closed nipple, topped off slave, done.

2024-09-30 03:41:47 # 92267

Comment by Michael Marzi

Great advice on this thread, thanks guys. Ive had my MGC GT for nearly 40 years and have always had trouble blending the clutch and purging air from the slave cylinder. When I read that the bleed valve should be at the top I checked the workshop manual and sure enough, the bleed valve is shown to be at the top as suggested. Presto! It now bleeds properly and problem solved.

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