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Discussion Starter · #1 ·
I've been driving the car almost everyday lately with no problems..until now. Looks like the MC started leaking..or the Booster. Don't see any leaks around the lines going into the MC, or any leaks where the reseavor goes in....of course, the wind is blowing all the fluid around as I drive the car. but it looks like it might be coming from where the MC goes into the booster, then goes to the bottom of the booster, then to the bellypan. Is there a gasket here?? It doesn't leak fast enough to where I can see the leak while the car is parked and someone pushing on the brake. Other than this, the brakes still work good.
 

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boomerang opeler
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if its comming out of there you will have a leak from the rear of the mc you will have to pull it to see and while its off you may as well change the seals anyway only other way is if the rear seal has spun and now faces the wrong way(dont ask i cant remember :) i think its wide part forward) [if you dont have a wide part its worn]
 

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Discussion Starter · #3 · (Edited)
Looks like I'm ready to dive into this task. ANy words of wisdom on how to remove the resevor, and reinstall on the new one...so I don't break it??

Thanks.
 

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Brake MC removal

Use flare nut wrenches on the lines coming into the master cylinder and be sure to catch any brake fluid before it hits the painted surfaces of your car so use a drop cloth of some sort. Also, be careful removing the nuts that hold the master cylinder to the vaccum booster and you should be fine.

Good luck.
 

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Take the bolts loose first for the MC and carefully pry it off. on install it help to wet the seals with brake fluid to get them in. If you break it don't worry, I have more of those than I care to mention and my car doesn't use that type.
 

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yes that is the way to do it.
 

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Discussion Starter · #8 ·
thanks, got everything off pretty easy. Must been leaking in the back, cuz the booster had some fluid in it. Got it all cleaned out. PO supposedly had a new MC to put in it, when I found the box, it looked clean, but obviously not new..in fact still had traces of fluid in it and was missing the seals on the top. I guess I will just order another one from OGTS just to make sure.
 

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Discussion Starter · #9 ·
No peddle

Just got the (supposed) rebuilt MC back in the car, all hoses hooked up, fluid, etc. I can pump all day long on the peddle, but it never gets harder. I didn't have a way to bench bleed the MC, so I thought I could just push the air through the lines then out at the caliper...but I'm getting no peddle to do so. Had the wife pump the peddle, and I could see air bubbles going into the reseavior. Could not bench bleeding the MC cause this??

Thanks.
 

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bozkm said:
I can pump all day long on the peddle, but it never gets harder. Could not bench bleeding the MC cause this?? Thanks.
Yes, but just bench-bleed it in place. Simply fill the reservoir, remove the brake lines at the MC, and depress the pedal. Have a container and a bunch of rags handy to catch the fluid (it will eat through paint if left). When you are sure you are getting fluid out of both brake line connections, re-attach them and bleed the lines normally.

HTH
 

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Lotsa emphasis on rags and clean up the brake fluid immediately, to include using lots of brake cleaner or more of Simple Green or another cleaner. Brake fluid will eat the original enamel paint in no time. I can't understand why you didn't get the fittings, hoses, and instructions to bench bleed the MC, unless it was from a private concern. One reason why I keep all the extraeneous stuff that come in parts boxes for the cars. When you think you have all the brake fluid cleaned up, do it again, because there will be residual hiding in the nooks and crannies to eat the paint there too.

Ron
 

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Discussion Starter · #12 · (Edited)
Thanks. I just checked NAPA onlone, and they sell the MC bleed kit for only 9 bucks. I think I'll pick one up tomorrow. Still do it in the car, but get the hoses so they'll go back into the MC. Should the lines going back in the reservoir be submerged?? Also, Keith, you mentioned to make sure fluid is coming out of both connections..I'm assuming you meant all three...

One of the reasons I didn't do it out of the car, was because of the reservoir, since you have to remove it to put the MC back in. I wasn't real sure that the MC would keep its prime if you remove the fluid then the reservoir after you bled it. Thanks.
 

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Yes, the hoses need to be submerged in the reservoir or they will suck in air when you let the piston go back, or take your foot off the brake pedal. Just remove one line for the front brakes at the front of the MC and hook up one bleed hose there and remove the one for the rear brakes at the rear of the MC, then slowly push the piston forward and release slowly, until only fluid comes out of the hoses. Then bleed the brakes normally at the calipers and wheel cylinders. BTW, I never had a problem removing the MC with the reservoir attached, but maybe I have more room in my 72. :confused:
 

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Discussion Starter · #14 ·
Thanks guys. Bought the kit last night..5 bucks. Bled the MC while in the car. Works like a champ now.
 

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90% chance you'll be doing this again!!!

If your fluid was being sucked into your brake booster, you're probably going to need a booster, as your diaphram is bad! Have yours rebuilt, or see when Opel GT. Source expects to get some more rebuilds in stock!!! Just responded under bad booster or vacuum leak.....If about a week from now all your brake fluid is gone, it's the booster... ;)
 

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Discussion Starter · #16 ·
With the way my luck has been going, I will probably have to replace...but I thought the leaking of the fluid into the booster was caused by a bad rear seal on the MC. If I have a new MC, I'm not seeing how fluid could be sucked into the booster anymore.
 

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New or not, the vacuum is on both sides now!

Think the title says it all! Vacuum is supposed to be on the one side and is isolated by the rubber diaphram from the rear seals on the Master, Vaccuum getting through a bad seal puts vacuum directly to your master cyclinder seals!

Hey I just did it twice, second time around I was able to get a rebuilt booster! We shall see, time shall tell. I think i'm done screwing with my brakes and the fliuid will stay put now! :D I had heard of this before, first car I've had do it!!!
 

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Rick, your statement that vacuum in the booster in only on one side, presumably, the rear, from what you said, caused me to refer to my manuals for a description of how the booster functioned. There was nothing in the Clymer's Opel Manual, but in my Camaro manual, the description in quite clear. There is vacuum on both sides of the booster diphragm and when you depress the brake pedal it allows atmosphere in the rear chamber with the vacuum on the front chamber assisting pedal action. I don't wish to infer you are wrong, just wanted to check and clear up in my mind, how the system works. Bozkm, is correct in the idea that with new seal in the MC, he shouldn't be losing brake fluid into the booster, but if he continues to loose fluid and it is not leaking externally, it probably is because of bad seals in the MC. JMTCW.
 

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Hummm? Thanks for the clarification!

Ron, I also was unable to find out much in the Opel manual! But I did however change out my master cylinder first with a rebuild from Opel GT Source, one week later my resvoir was empty??? Two weeks later OGTS got 5 rebuilt boosters and I had to go through the process again, this time replacing the booster??? I'm watching and waiting to see if the problem is fixed right now. My mechanic at Action Axle Suspension and brake said it has always been a replacement of the brake booster when he finds fluid in the booster! Sorry if I've steered anyone wrong as I've heard of this before, just never experianced it until now...I have two other parts cars, didn't waist my time pulling one of the other boosters as I wanted to do it right the first time and ended up doing it twice anyway.

I talked to Gil today at OGTS, he confirmed that I must have got a bad rebuilt master cyclinder from them and will send me out a replacement. This would be fine if I hadn't already spent $205.00 in labor to have a mechanic work on my brakes two times now, and the $242.00 for a rebuilt Booster!!! :mad: I have only driven my GT two times so far, total of 16 miles and the fluid seems to be staying put in the resivoir at present. My mechanic did say it's always been his policy to change the Booster and master at the same time if fluid got into the Booster because of moister in the fluid tha will cause rust and shorten the life of the Booster??? He also added that when he vacuum bleeds brakes he's had fluid pull around the cups in a new wheel cyclinder if the vacuum is too strong. He believes that if you have too much vacuum IE: a bad booster diaphram there wont be atmopheric pressure on the back side of the diaphram, but vacuum and the excess vacuum can compromise the seals in the Master and pull fluid past good seals if the vacuum is too strong! ??? Either way, I have spent a fortune so far in parts and labor and still looking at replacing the Master again I guess :confused:
And the labor is on me, not OGTS. If my mechanic could have got the parts via one of his sources, say NAPA. It would all be reimbursed through them!!!
Thanks Ron for your imput, I learn something new all the time!
 

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That's a lot to think on Rick, but for the most part pretty easy to follow. I've pulled air in from the wheel cylinders using a hand vacuum pump trying to bleed the brakes too. Not to hard to figure out when you look at the seals, they are fairly soft, have no reinforcement spring and flexible, so air gets in easily under a vacuum. They are designed to have pressure applied to them from the back side and a vacuum deforms then enuff to create a leak. Your mech is right, brake fluid is a sponge to moisture in the air and will accelerate rusting. Brake cleaner is the way to go to remove it as soon as possible, it will remove the brake fluid and evaporate quickly leaving no residue. Can you use it on the booster and if so will it get all the fluid out. I think so, but there could be residual fluid in the booster in the nooks and crannies. I don't understand the too much vacuum in the booster statement, the boosters are designed to operate at engine vacuum, some even have vacuum reservoirs to help maintain vacuum and there is the check valve at the inlet port. I'm lost there. The seals on the piston of the MC are designed so as not to have leaks of fluid into the booster, but some times you just get bad seals or worn or rusty pistons that will eat the sealing surface. I coat the seals and piston rods with a bit of commercial grade Vaseline to help lube the seals a bit but only on the outside of the piston rod and seal. Anyway, this has been a good excercise in how things can sometimes get a bit muddled and to get opinions on how to fix stuff.
 
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