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Discussion Starter #1
Where did it go?

Catherine drove up yesterday, about 60 miles, and said the brake warning light had come on and braking was becoming progressively more difficult. Ah ha! A leak in the system! But all four corners were dry, and there were no wet spots anywhere. She's got new wheel cylinders in back, new hard and soft brake lines, and rebuilt calipers in front. The master cylinder and booster are original.

Could the fluid have gone into the booster? On Rob's car I replaced the M/C and booster and the booster was full of fluid, so it seem that can happen.

I was wondering if anyone had experienced this before I remove the M/C and booster.

Catherine is here for a replacement engine so we are up to our elbows in that already.

Mike
 

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It’s pretty common. I wouldn’t trust 45+ year old hydraulics, that’s for sure!
 

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My original master / booster had a similar problem. Everything leaked into the booster.

I also had the problem where all of the fluid would drain from the master and I would have zero brakes (pedal to the floor) on the first pump.
 

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The booster in mine looked okay from the outside, but didn't work right. When I pulled it to replace the master and booster it was easy to see how shot it was inside. The new OGTS booster and MC work great and have a more modern feel. Total pain to get it all in there though with the tight area to work in. I ended up bleeding the MC in the car since I couldn't manage to get it in without dumping brake fluid everywhere.
 

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Opeler
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I have experienced failures of MC seals on older cars soon after bleeding the brake system from air bubbles. What happens is that the piston normally moves only through the limited stroke keeping that area swept and rust free. When pumping the pedal during the bleeding process, the piston will slide much further and reach the area of the cylinder that is corroded. Rough surface will damage the seals.
 

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UngerDog
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Brake booster oil leak has happened to me on more than one car. What you can do is check the inside of the booster by rotating the brake booster fitting 45 degrees counter clockwise and pull it away from the booster. Then, insert a long thin rod with an absorbent attachment at the end into the booster and get that into the bottom side of the booster, pull it out and see if it has brake fluid on it.
 

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Can Opeler
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Thanks all.

Followup question, once fluid leaks into the booster, is it toast?

Mike
I doubt it if it hasn’t been leaking too long. Give it a try. It will be obvious if it starts leaking vacuum
 

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Discussion Starter #10
It started leaking yesterday, as far as we can tell.

Minor correction, the reservoir for the rear brakes is empty. Catherine mentioned brakes getting progressively worse with is probably due to a more gradual failure in the front section, the rust-on-rubber thing PJ mentioned.

Mike
 

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If you are doing the whole engine thing and the rest of the braking system has been refurbished then I would just bite the bullet and put in a new master and booster.
 

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Years ago I inspected a wrecked automobile that had been involved in a fatal collision.
The owner had previously complained of 'bad' brakes. The 'Dealer' mechanic couldn't find any leaks
anywhere in the brake system, but refilled the reservoir more than once IIRC according to testimony.
...It didn't end well.... The missing fluid was hiding in the booster. Not doing any good there.
So you obviously have a leaking seal somewhere between the master cylinder and the booster.
The diaphragm in the booster may be damaged, it's old by now.
Better to be SAFE, replace it . ...Reminds me, I have a new booster, will replace it soon !
 

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Über Genius
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I've never seen a booster ruined by brake fluid.

In my first GT, the MC leaked into the booster. It was only 12 years old.

The only bad thing that will happen to the booster is it could lose vacuum. It won't happen catastrophically though so it's not exactly a danger.
 

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Can Opeler
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I've never seen a booster ruined by brake fluid.

In my first GT, the MC leaked into the booster. It was only 12 years old.

The only bad thing that will happen to the booster is it could lose vacuum. It won't happen catastrophically though so it's not exactly a danger.
Also the booster is not necessity. I disconnect mine occasionally. The pedal feel is much better disconnected and you can still threshold brake without too much force.

But then again I have extra springs on all of my pedals. I really like heavy pedal feel.
 

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Opeler
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Brake Booster

Over the years I had leaks from the master cylinder into the brake booster in various Opel GT's. In all cases, because I had very little money, I would swab out the brake booster after removing the master cylinder. I went in through the vacuum hose connection using either strong paper towels or cloth rags. Then I replaced the master cylinder (usually with a rebuilt one due to cost). I never had a problem with the dried out brake booster failing. (rebuilt master cylinder failures are a different story)
 

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Discussion Starter #16
Also the booster is not necessity. I disconnect mine occasionally. The pedal feel is much better disconnected and you can still threshold brake without too much force.

But then again I have extra springs on all of my pedals. I really like heavy pedal feel.
We've disconnected ours for rain races.
 

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Normally the MC shouldn't leak straight into the booster. The input rod has two rubber seals between the brake fluid and vacuum sides.
Inbetween the seals the MC has a weep hole that exits on the bottom of the MC near the booster. If the the first seal leaks, brake fluid should run out the weep hole instead of filling the booster. Apparently, on your MC the hole is clogged up.
Thomas
 
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