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| Brake bleeding on single circuit setup http://www.international2cvfriends.com/forum/viewtopic.php?f=7&t=1572 |
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| Author: | meshking [ April 10th, 2010, 7:58 pm ] |
| Post subject: | Brake bleeding on single circuit setup |
I'm trying to bleed the brakes on my drummer, and failing dismally. I''m not getting a decent flow to the rear brakes, or for that matter, a constant flow to the fronts. I've managed to get a full bore of flow in my bleeding pipe from all but the nearside rear brake. However, the full bore wouldn't last long, and on the next up/down cycle it would be back to a trickle in the pipe. I've fitted a new master cylinder, and new wheel cylinders all round, with new pipes throughout too. Is there something obvious that I've done wrong here (probably). Maybe there is different bleeding technique for single circuit, or for fitting a new master cylinder? When I renewed the pipes and rear cylinders on my lhm car, just a few cycles of up down allowed for all the air to be removed. But I was in at least double figures and still only getting a dribble from the rears. Thanks, Ben |
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| Author: | ken [ April 10th, 2010, 8:35 pm ] |
| Post subject: | Re: Brake bleeding on single circuit setup |
Ben, if it's a single circuit master cylinder, that should be very straightforward...  All I can think of is that the push rod may not have been adjusted to suit the new master cylinder. If there's not enough free play, the port which allows fluid to move down from the reservoir into the master cylinder may not be open, or if it is, it may be restricted. The specified clearance is 0.5 to 1mm, which gives about 5mm free play at the pedal. ken |
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| Author: | meshking [ April 10th, 2010, 8:41 pm ] |
| Post subject: | Re: Brake bleeding on single circuit setup |
Good point - I didn't adjust anything, just bolted it up. I'll check that tomorrow. Thanks Ken! |
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| Author: | meshking [ April 15th, 2010, 10:35 pm ] |
| Post subject: | Re: Brake bleeding on single circuit setup |
Took a bit longer to get out to the garage, but you're right. However - it's miles out, and I run out of thread to adjust the height to. With about 1 thread located in the pedal, I've got movement halfway down the pedal movement. Comparing the old and the new, the actuator in the cylinder is really close to the end of the old one, but deep inside the new one - am I missing a bit? |
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| Author: | ken [ April 15th, 2010, 11:02 pm ] |
| Post subject: | Re: Brake bleeding on single circuit setup |
Ben, iirc, there were different lengths of pushrods with certain setups. If you could let me know approximately what length of rod you need, there's probably one still lying around here, since the long overdue clear up and throwing out session hasn't got under way yet. ken. ( Edit. Seems a bit odd if the rod end of the piston is really far inside the cylinder. Are you sure it's not sticking? Sometimes, a few gentle taps on the cylinder with a small hammer will persuade the piston to move back, but that's not the best if it's a new cylinder.)  meshking wrote: Took a bit longer to get out to the garage, but you're right. However - it's miles out, and I run out of thread to adjust the height to. With about 1 thread located in the pedal, I've got movement halfway down the pedal movement. Comparing the old and the new, the actuator in the cylinder is really close to the end of the old one, but deep inside the new one - am I missing a bit? |
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| Author: | 2CViking [ April 16th, 2010, 11:52 am ] |
| Post subject: | Re: Brake bleeding on single circuit setup |
Maybe you got the ''wrong'' master cylinder, the one with long push rod or the piston is stuck after being pressed in and wont come back to resting point.. Photos please. |
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| Author: | meshking [ April 16th, 2010, 8:35 pm ] |
| Post subject: | Re: Brake bleeding on single circuit setup |
Thanks folks. The pushrod I have is ~85mm long, it needs to be another 10-20mm or so to get the correct travel. If the piston were stuck, presumably I wouldn't be able to push it down and have it come back to the same place? That is currently, with the brakes unbled and the pushrod on it's full extent, I get resistance about halfway down the pedal movement, and I can do exactly the same on the next push. What sort of photos do you need? It's all plumbed in and I'm loathed to remove it if all I need is a longer pushrod. Looking at the old one, I can see the piston top (or whatever the pushrod pushes against that pushes the plunger) very close to the free end. However, on the new one, it's deep inside. Ben |
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| Author: | ken [ April 16th, 2010, 9:01 pm ] |
| Post subject: | Re: Brake bleeding on single circuit setup |
ben, had a scout around amongst the bits boxes today and found some pushrods, two were 85mm total length, but one was 105mm. Threads are approx 20mm on both types. Any good for a swap? ken |
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| Author: | 2CViking [ April 16th, 2010, 9:10 pm ] |
| Post subject: | Re: Brake bleeding on single circuit setup |
The master cylinder on this photo is for drum brakes before 1973 with long push rod. You can see how ''deep'' the hole is. If your car is born with the short rod (from 1973 to 1982) it can't reach the bottom of the hole Can you aim the camera at the rear of the master cylinder. No need to remove the master cylinder. The problem may be somewhere else. Attachment: 1200309.jpg |
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| Author: | meshking [ April 17th, 2010, 8:47 pm ] |
| Post subject: | Re: Brake bleeding on single circuit setup |
Difficult to get a decent shot of it insitu, but it's one of these: http://www.ecas2cvparts.co.uk/master-cy ... -1324.html Here's the pic  and the old one: 
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