Lotus Elan

Clutch bleeding

PostPost by: b-havers » Sat Jun 02, 2012 4:32 pm

Thanks, I'll untighten it a bit, then :oops:
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PostPost by: rgh0 » Mon May 09, 2016 12:17 pm

I just finished reassembling my Elan with a new clutch and new slave cylinder and rebuilt master cylinder. As usual bleeding the clutch was a pain and by 7:30 pm I had not got it right and there was still air in the system and I needed to knock off for the night. So I decide to try the method I had seen recommended by others, that is to wedge the pedal down overnight with a length of wood and come back in the morning and it would be OK.

I have never really believed this as i could not understand how it worked but I had nothing to lose so i thought give it a try. To my surprise when I came back the next morning the clutch was perfect :shock:

SO how does it work?
My only theory is that the air is mainly in the top of the slave cylinder as the bleed port is horizontal and not at the top. Overnight with pressure on the system the air under pressure in the slave cylinder can leak slowly past the seal while the fluid cannot. For it to work you need to have most of the air out of the system so you get some pressure when you wedge the pedal down. Thus by morning all the remaining air is gone :D

Whatever the reason it worked for me

cheers
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PostPost by: gjz30075 » Mon May 09, 2016 2:32 pm

Interesting! I've heard of this, too. So, does the pedal need to be wedged to the floor? Is the cap on the
master removed? Or loosened?
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PostPost by: Robbie693 » Mon May 09, 2016 6:12 pm

Cap off or on but I tend to leave it on incase of unexpected squirts. This method always works for me, in fact I've given up doing the repetitive bleeding I used to do and now just give it a quick go with the Easybleeder and wedge the pedal down. Unfortunately you have to wait while it does it's thing...
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PostPost by: billwill » Tue May 10, 2016 1:33 pm

Since the clutch slave is in a circular hole. The slave can be rotated so that the bleed screw is ABOVE the incoming hydraulic pipe. It is then a bit more fiddly to get the bleed pipe on the nipple and open and close it, but you don't get any problems with trapped air.
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PostPost by: Craven » Tue May 10, 2016 4:06 pm

Must have been a while since you did one Bill, the body of the cylinder has flats on it which locate against the dagger plate stopping rotation. Having said that it can be fitted with the bleed nipple at the highest point.
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PostPost by: seniorchristo » Tue May 10, 2016 11:23 pm

It was my good fortune this topic reappeared as I was in a quandary as to how to properly bleed my clutch slave cylinder after a recent rebuild. I used a mity vac with some success, tried the 150 pump trick and then enlisted my brother to pump the clutch and then slowly bleed while pushing down on the pedal. This improved the operation but I still had a problem, most evident when starting the car after it sat for a while. My problem stemmed from the fact I couldn't get enough swing on the wrench to open and close the bleeder screw without fumbling around while air seeped back in (I guess). Tonight I propped the pedal to the floor and will see if it solves the problem.
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PostPost by: rgh0 » Wed May 11, 2016 10:01 am

Hi Chris
Getting a decent swing on the bleed screw is a real challenge especially with a big diameter set of headers. I have a cutoff 7/16 ring spanner that i can fit to the bleeder so i can easily open and shut it as I have someone pump the pedal. Alternatively you can fit speed bleeders that have a check valve in them so you open them and pump as you don't need to shut them off on the pedal up stroke.

But if you have the slave cylinder in it's designed orientation as constrained by the flat on the cylinder and the flange on the steel plate between the block and bell housing you will always result with some air left in the cylinder usually unless you can pump hard enough to sweep the air out. This is due to the bleeder at the side rather than top of the slave cylinder. You can modify it to rotate the slave cylinder 90 degrees to put the bleeder at the top but that puts the inlet pipe at the bottom and uncomfortably close the exhaust header.

I will be very interested to see how the "wedge it down overnight after bleeding as best you can" technique works for you

cheers
Rohan
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PostPost by: patrics » Wed May 11, 2016 9:27 pm

Hi,
Last time I bled mine I did it in an easy way.
Mine has hose going from master cylinder to slave and was partially bled.
1. Remove slave from housing and pull the unit back up to where the reservoir is
2. With the slave in the vertical position - inlet / bleed screw at the top
3. Remove the bleed screw completely
4. Use a syringe to top the slave up
5. Gently tap side to get the air out and repeat until fluid level in slave no longer sinks inside.
6. Refit bleed screw
7. Job done

Easy, quick and cheap as will only use a few ml of fluid

Regards
Steve
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PostPost by: seniorchristo » Wed May 11, 2016 11:37 pm

The wedge method didn't work for me. After the car sits for a while the pedal has 3-4 inches of free play before pushing fluid versus about 1 inch when pumped up. Also after cruising awhile in the 3rd gear the 4th gear upshift was very difficult. I have a long steel braided hose from master to slave and I think air is trapped in the big loop up top. What I didn't do was pump up the pedal before wedging. I think I will do that now and check back again tomorrow. :)
Later
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PostPost by: rgh0 » Thu May 12, 2016 10:05 am

Yes i think you need to have the minimum freeplay so you get maximum pressure in the system when wedged overnight and the only significant air is in the slave cylinder. Mine had been bleed to the point that I only had about 1 inch of freeplay

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PostPost by: prezoom » Thu May 12, 2016 4:09 pm

I bleed mine before installing the slave cylinder on the bell housing. It is on a -4 AN line, and being flexible, I can raise it above the master cylinder, and orient the cylinder so the bleed is at the top. I made a tool to capture the piston, preventing it from being pushed out of the cylinder. A C/G clamp and a short block of wood inserted in the bore would accomplish the same thing. Without needing the pressure to operate the clutch, the air can be expelled merely pushing the pedal with your hand, using a speed bleeder. I leave the tool in place until I am ready to install the cylinder in the bell housing ring. After removing the tool, the piston seal provides enough resistance to keep the piston in the bore for the amount of time it takes to install the circlip, adjusting rod and spring.
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PostPost by: seniorchristo » Thu May 12, 2016 11:28 pm

I drove the car again today and the clutch was better but not 100%. I pumped it up about 25 times and wedged it again. Will try again later this week. :)
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