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Install new brake master cylinder

Posted by 74B 
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Bill Haney
Rocky Mount, NC, USA   usa

I'm finally getting around to replacing my leaking brake mster cylinder. This is my first installation. I know I'll need lots of patience (which I seem to have less of every year) but I was wondering if there are any "tricks of the trade" that I should know. I'm trying not to make a one hour job into 3 or 4 hours! I'm going to read the repair manuals and Hayes and Chilton's and I know they probably won't cover every thing I should know. My new unit from the B Hive included two brass washers in a separate package. Will it be obvious where they will fit?

Thanks in avance for all your suggestions


Dwain Avatar
Dwain Fitzpatrick
Norcross, GA, USA   usa
Check on previous posts, there are a couple of tricks..............

Painting Bumpers In Atlanta

Too many Cars... not enough time...

Tom Bedenbaugh Avatar
Memphis,Tn, USA   usa
First take all the mount bolts out of the pedal box. This will allow you to wiggel the master cyl. out. The second thing that will make the job easier is to install a hella coil in the bottom mount hole of the master cyl. Also mount the hard line first after mounting the master to the pedal box loosly. This helps getting the fittings started. Pay attention to the angle of the banjo fitting before you transfer it to the new master.

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Bill Haney
Rocky Mount, NC, USA   usa
Thanks Tom, appreciate your advice. What is a hella coil? Do you use it to line up the M/C?

I had go go get my shades after looking at your engine bay. WOW!!! That is absolutely beautiful. I hope you've taken a picture, blown it up, framed it and placed on a wall. That's worth it! Congrats.

Thanks, Bill

Bill Haney
Rocky Mount, NC, USA   usa
Oh, another question. I've always used Castrol GT-LMA Dot 4. Now my parts store is closed. Wondering if I can use Valvoline synthetic High Performance exceeds Dot 3 and Dot 4?



Tom Bedenbaugh Avatar
Memphis,Tn, USA   usa
Hella Coil is a thread insert. The kit comes with a tap that threads the hole to install threads in the hole eith a tool that also comes with the kit. It allows you to install the master cylinder without having to use a nut on the back side. That bottom nut is some what of a PITA to get started without removing the pedal box. It's not imposible, but inserting a hella coil in the bottom hole makes it MUCH easier.

When you change over to synthetic you are suppose to replsce or rebuild the intire brake hydrolics. The two are not compatable.

PaulP Avatar
Paul Peterson
Seattle, WA, USA   usa
1973 MG MGB GT
1974 MG MGB
Tom - I don't mean to highjack Bill's thread, but since it's all MC related, I'll give it a shot.

The one mistake I made when reinstalling my MC (on a '74 chrome bumper) was I left the banjo bolt a bit loose so I could line up the rear brake hardline and tighten evertything up once the line was connected. The problem (as you know) is I couldn't get a wrench in there to tighten it after the MC is attached to the pedal box bracket.

Over on BCF someone was trying to tell me it was possible to tighten the banjo bolt after the MC is installed.

I can see if you had a earlier car where the banjo bolt faces rearward you could reach it from the cockpit side of the firewall.

Am I correct in thinking you have to tighten the banjo bolt before the MC gets attached to the bracket?

Thanks - Paul

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Tom Bedenbaugh Avatar
Memphis,Tn, USA   usa
I've done it both ways. I find that you can eyeball it and get it close enough. That's the reason I connect both hard lines before tightening any thing down. The wiggle factor helps get them started.

flash75 Avatar
Clifton Gordon
Summerfield, Florida, USA   usa
Valvoline SynPower DOT 3/4 is is an excellent replacement for Castrol LMA. I think Tom was thinking about silicone DOT 5 fluid in his comment.


Bill Haney
Rocky Mount, NC, USA   usa
Is a 12 ounce can enough to refill it with? I'd like to flush all the lines out when bleeding. I'm also going to install two rear wheel cylinders which are beginning to leak.

Thanks for all your advice. I couldn't find much on the search thingy but I only did it for 1 year. Took forever to read.


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