Repairing Brake Master Cylinder

Reply Subscribe

Thread Tools

Search this Thread

Nov 5, 2018 | 07:12 PM

EcbJag

Thread Starter

Senior Member

Joined: Jun 2010

Posts: 535

Likes: 198

From: Napa Ca, United States

Repairing Brake Master Cylinder

I noticed while detailing the engine bay last night that the brake master cylinder in my car has been leaking from where it meets the servo unit and brake fluid has run down the inner fender well and dissolved the paint down to bare metal over a fairly large area.

After a quick web search I found that the master cylinder is NLA so I ordered the seal kit. Has anyone rebuilt their master cylinder? How difficult is it? Any tips? Any special tools needed?

Also any advice on how to prep the bare metal surface of the inner fender well to prevent rust before I go about repainting it? Any product recommendations for this?

Thanks in advance!

Nov 5, 2018 | 09:13 PM

Jagsandmgs

Senior Member

Joined: Mar 2017

Posts: 699

Likes: 415

From: Jaffrey, NH

You can still get a master cylinder from rockauto.com. But the kit is cheaper... And no big deal. Just lube the seals up with brake fluid so they’ll slip over the piston end. You’ll want ring clip or circlip or whatever clip pliers if you’re not ambidextrous. Sometimes the kits don’t include the plastic nipples that go in the top so don’t break them before you know you have new ones.

Nov 6, 2018 | 10:54 AM

JigJag

Veteran Member

Joined: Mar 2016

Posts: 1,333

Likes: 583

From: North Carolina

Also there is a retaining bolt preventing the piston from coming out. Don’t forget to remove it. In the front well if I recall properly.

Nov 6, 2018 | 11:29 AM

EcbJag

Thread Starter

Senior Member

Joined: Jun 2010

Posts: 535

Likes: 198

From: Napa Ca, United States

How do the plastic fittings come out of the top? Do they just pull out?

Nov 7, 2018 | 10:10 AM

sidescrollin

Veteran Member

Joined: Jul 2010

Posts: 2,459

Likes: 695

From: Key West, FL

The fittings just pull out. They they have barbs on them. When I bought a kit, it came with replacement barbs. If yours does, you can cut the rubber seals a bit to help it out, since the originals will be very stiff at this point.

Clean everything and lube the assembly with brake fluid when reinstalling.

Remove loose rust on the damaged panel with a scotchbrite pad. Spray Ospho on area and wipe off residual after 30 minutes or so. come back and scuff panel again 24 hrs later. Prime, paint, done.

Try to see if any fluid has gotten back into the booster.