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Removing Master Cylinder Without Paint Damage

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Legal Bill

Jedi Knight
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I need to remove the brake master from my fully restored BJ8. The master appears to have locked up internally immediately after I bled the brakes to remove all the old fluid. I used Castrol dot 4 brake fluid for the flush and now the system is full of it and I can’t pump it out. Is dot 4 not compatible with the seals??? I installed this master about 12 years ago. It came from Moss and was not very expensive.

I plan to try to empty the reservoir can as much as possible first. But after that I’m pondering how I’ll remove the lines from the brake master and avoid getting brake fluid anywhere on the paint. I’ll remove the rear carb air filter to make room to operate. Because I can’t just pump the lines dry I could just open the bleeders and let them drip for a while. I’m not sure how well that would work or how long it will take.

I plan to break the fitting at the master first to make sure they will unscrew easily and then snug them back up. Then I’ll disconnect the actuator rod and the two mounting bolts from inside the footwell. Then I’ll return to the brake line connections and remove them. Once removed, how can I catch the dripping fluid that remains as I work the old master cylinder out? Wrap them in rags? Plastic bags?

If any of you have a tried and true method to avoid brake fluid contact with the paint in this situation, please share.
 
After first suctioning brake fluid from the reservoir, I protected paintwork with plastic sheeting (large plastic bags taped into place). Still, I managed to spill some brake fluid on the paintwork ( none got on any exterior panel surfaces). As a precaution, I had the garden hose ready and carefully hosed contaminated surfaces down with plenty of water at low pressure.
 
I got one of these. I haven't tried it yet, but I have a similar, much larger contraption for sucking oil out of engines and it works a treat (running off a compressor). I never had much luck with MityVacs, for whatever reason, but if you have a compressor this should work well. After getting as much BF out as possible wrap the M/C with bunch of rags before pulling it; if you're careful most will stay in the M/C but you'll get some out of the pipes. Castrol, or Girling, BF has always been the 'go to' for brake fluid, but my understanding is it is not being produced anymore, and I've had better luck with silicone than glycol. If you spill some--you will--wash the area with copious amounts of water; glycol loves water.

 
Thanks Bob and Nevets. Girling dot 4 can still be ordered on line. I'm not going to replace my whole system so silicone isn't really an option for me.

I just suctioned out all the brake fluid from the reservoir with a turkey baster. There was a bit left in the bottom and I got that to with a bulb and hose type syphon. I looked on line and found some brake line and fitting caps advertised. I'm going over to the local parts store to take a look.
 
Well, the master is out. I managed to siphon off everything from the reservoir and was able to pump a couple of ounces out of the right front brake bleeder. There was a bit inside the master, but I slid it out without dumping any. I capped the lines with rubber vacuum line caps that are working well.
The master had oozed a bit over the years. I found the areas below the flange were peeling both in the footwell and under the hood. I tried to post pictures but I’m having trouble doing it from my phone.
 
Below are pictures of brake fluid extraction, the caps I used to block off the brake lines after they were removed, a bit of bubbled paint that was found underneath the master cylinder flange when I removed it, and the face of the master cylinder with the boot removed. There was also an area of paint bubbling inside the footwell below the hole where the M/C is mounted. Looks like it had a bit of a leak!


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Here are some pictures of the M/C piston, seals and the cylinder bore. I'm thinking the piston got stuck in the cylinder while we were bleeding it last night. In retrospect, I'm glad it did. I didn't know it needed servicing and I would have driven it like this if it didn't get stuck. Time to order a new one.

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While I'm waiting for the ew M/C, I'll take some time to clean up the area around the mounting hole, prime Andy bare metal, and use some touch-up paint to dress it up.
 
Legal Bill .... looking at the condition of the master cylinder bore and piston, I have to ask; how often have you flushed the hydraulic system with fresh fluid?
 
Bill, Since you live in MA, where it's relatively humid, and using DOT 3, 4 or 5.1 fluid, I wouldn't go more than 5 years without a rebuild.

(We have dry air here, and I use silicone, so I can go much longer.)
 
Scargo said:
Legal Bill .... looking at the condition of the master cylinder bore and piston, I have to ask; how often have you flushed the hydraulic system with fresh fluid?
Click to expand...
About every four years. The car lives indoors in a heated garage. I probably put 200 miles a year on it. Troubling, isn't it?
 
A tip for neutralizing brake fluid. Don't use water. Buy some denatured alcohol and put it in a small spray bottle. It will absolutely neutralize brake fluid instantaneously. It is not harmful to your paint or your skin. It takes very little.
When I do a tech session on brakes I demonstrate it like this. I pour a small amount of brake fluid into the palm of my hand and rub my hands together. I then wipe my hands with a paper towel but my hands are still oily. I then spray some denatured alcohol onto my hands and wipe. Clean as a whistle and fresh as a daisy.
 
Good point; I hadn't heard that (glycols and alcohols are chemically related, not suprising they'd be miscible).

That looks like iron rust in that cylinder; I received, at least once, what appeared to be an iron cylinder as a replacement (OEM was aluminum). If so, you could probably clean it up, hone it and put a kit in it (but it may not be worth the trouble).
 
One hint I received after the last time I replaced the MCs on out BT7 that I will pass on. When installing the new MC, I would suggest you make up the tubing connections to the cylinder before bolting the cylinder to the firewall. It is a lot easier usher the tubing nuts into place when the cylinder is free to move about a bit as the lines tend to have a bit of spring in them. Make up one connection but do not snug it up then make up the other. Then bolt the cylinder into place and snug up the tubing nuts.
 
Bob_Spidell said:
....

That looks like iron rust in that cylinder; I received, at least once, what appeared to be an iron cylinder as a replacement (OEM was aluminum). If so, you could probably clean it up, hone it and put a kit in it (but it may not be worth the trouble).
Click to expand...
I was very puzzled by that, but then I had a recollection. I need to check my old receipts, but I believe I sent both masters to Apple Hydraulics and had them sleeved. I forget what they use. I seem to recall it was a brass sleeve, but perhaps it was steel.
 
Boyracer is spot on - denatured alcohol is your best friend when working with glycol brake fluid - keep a spray bottle handy and have no worries.
 
Do you have an alternative product for us Californians? Denatured alcohol is banned here. When I need to thin shellac, the manufacturer suggested I use acetone. Would that work with brake fluid As well ?
 
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