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Discussion Starter #1
OGTS master cylinder leak issue
Just a word to anyone who purchased the upgrade brake booster and master cylinder for their Opel GTs. I installed both in my GT a year ago when I put it back together after having the car repainted. I have had what I would call seepage of brake fluid from under the new rubber seats which the reservoir pushes into. I made sure everything was seated as it should be and I kept my eye on it for a bit and it got worse to the point where if I filled the reservoir in a day or two it was almost empty. I took the reservoir off, and due to it not being a tight fit, the brake fluid had drawn in moisture which was pitting the area on the master cylinder where the seat is supposed to seal. Also the leaking brake fluid dripping thru the belly pan hole caused the paint to really peel up. I called OGTS and they said some of the units had developed that issue and they had new replacements rubber seats they would send out at no charge which sealed a lot tighter.
Good they stand behind it but check your system out if you have the upgraded booster and mc and you will know right off the bat what the issue is rather than waiting and trying to reseal it and eventually ending up with brake fluid damage to you paint.
 

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Discussion Starter #2
I received the replacement seats or seals from OGTS but no instructions and being Saturday cannot contact them till Monday. I don't want to put this together incorrectly so maybe a member can offer me advice. It appears both openings in the master cylinder are the same size. The seats OGTS sent me have 1 larger and 1 smaller seat. I'm guessing the larger seat goes in the rear hole of the mc where the reservoir itself sits and the smaller one (which actually pushes all the way into the master cylinder with no lip on top) would be for the front hole where the L tube would connect to the mc. Anyone verify if that is the proper set up?
 

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Über Genius
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Your thinking is backwards.

The one with the lip goes to the front of the car. It will receive the L connector.
The smaller one goes towards the firewall and engages the reservoir directly.

I do recall it being a pain and I think I put the rubber piece on the reservoir and then installed it into the MC. The L tube with the lip was easy after that.
 

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Discussion Starter #4
Reply from OGTS

Here is the reply from OGTS ( :) very happy that I got a reply on a Saturday so I can get this together). I would not have guessed the small seat went in small side up.

Hi Gordon,

The large seal goes in the one closest to the brake booster. The largest half of that seal (also the flat side) is up.

The small seal goes in the one closest to the front of the car. The smallest half of this seal goes up.



Opel GT Source
 

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Here is the reply from OGTS ( :) very happy that I got a reply on a Saturday so I can get this together). I would not have guessed the small seat went in small side up.

Hi Gordon,

The large seal goes in the one closest to the brake booster. The largest half of that seal (also the flat side) is up.

The small seal goes in the one closest to the front of the car. The smallest half of this seal goes up.



Opel GT Source
So I have mine backwards?
Oh well, it doesn't leak..
 

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Discussion Starter #6
If it ain't broken, don't fix it!

With the new smaller booster you can actually put the seats in the master cylinder as well as set on the reservoir before it goes in the car. It's tight but you can get it onto the booster as an assembled unit, just making sure that the rod in the booster goes into the master cylinder tube where it belongs before attaching to the booster.
 

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I'd run DOT 5 silicone brake fluid just in case. Won't ruin your paint. Not compatible with other brake fluid though so you can't mix them.
 

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Brake fluid resistant sealer

OGTS master cylinder leak issue
Just a word to anyone who purchased the upgrade brake booster and master cylinder for their Opel GTs. I installed both in my GT a year ago when I put it back together after having the car repainted. I have had what I would call seepage of brake fluid from under the new rubber seats which the reservoir pushes into. I made sure everything was seated as it should be and I kept my eye on it for a bit and it got worse to the point where if I filled the reservoir in a day or two it was almost empty. I took the reservoir off, and due to it not being a tight fit, the brake fluid had drawn in moisture which was pitting the area on the master cylinder where the seat is supposed to seal. Also the leaking brake fluid dripping thru the belly pan hole caused the paint to really peel up. I called OGTS and they said some of the units had developed that issue and they had new replacements rubber seats they would send out at no charge which sealed a lot tighter.
Good they stand behind it but check your system out if you have the upgraded booster and mc and you will know right off the bat what the issue is rather than waiting and trying to reseal it and eventually ending up with brake fluid damage to you paint.
I had a leak also, with new M/C at the reservoir. OGTS sent me the replacement rubber seals but I did not trust that they would would seal properly, so I put a coat of Permatex copper RTV on them before installing the reservoir, being careful nut to get any of the RTV into the M/C body. I had previously tested a blob of this sealer in a jar of DOT 4 brake fluid. After 2 weeks submerged in the jar, there was no breakdown or softening of the RTV. Although my car is still far from going on the road, the brake system has been installed for many months, and I pump the brake pedal several times at least every week. So far, no leaks. So, I recommend this particular RTV for use at the brake fluid reservoir.
 

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My new master cylinder leaked and caused alot of paint damage to the nose cavity. Complete pain in the ass to get in there and repair it. Thankfully I had painted the nose cavity in Tremclad flat black so repainting it wasn't as complex as if it was the fresh yellow paint like the rest of my engine bay.
 

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I'd run DOT 5 silicone brake fluid just in case. Won't ruin your paint. Not compatible with other brake fluid though so you can't mix them.
With that being said I would highly recommend flushing the system before installing DOT 5 fluid. I'm sure there is information somewhere on the internet on how to do it correctly.

Harold
 

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master cylinder removal tips?

We ordered the new master cylinder and booster. But we are needing to know how to remove the master cylinder. We have disconnected the brake lines. Are the 4 nuts all that hold it on to the body?
 

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We ordered the new master cylinder and booster. But we are needing to know how to remove the master cylinder. We have disconnected the brake lines. Are the 4 nuts all that hold it on to the body?
Three brake lines (two are connected both by flare nut fittings and banjo fittings). Usually the flare nut fittings are easiest, but will require a proper flare nut wrench. The banjo fittings will need to be transferred over to the new MC, and you will need new copper crush washers. OGTS provides two thicker washers for the front banjo fitting, as the original thin washers will leak, but you should also replace the rear banjo fitting washers.

Then remove the master cylinder from the booster (two nuts). The outer nut is tricky to reach, and is easiest done by either first popping off the fluid reservoir, or by reaching in through the access port behind the headlight bucket (which is in the way, so would have to be removed). I pick removing the reservoir.

Undo the push rod from the booster (big lock nut and threaded shaft).

Then four nuts on the back of the booster, and lift the booster out by sliding foward.

It's been while since I removed mine, but I just installed the new OGTS 22 mm master cylinder and big booster, so that describes the opposite of how I put it back in.

HTH
 

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We ordered the new master cylinder and booster. But we are needing to know how to remove the master cylinder. We have disconnected the brake lines. Are the 4 nuts all that hold it on to the body?
The master cylinder is removed by removing the two nuts at the master cylinder to booster.
The booster is removed by removing the four nuts at the booster to core support AND disconnecting the connecting rod that runs from the firewall to the core support.
 

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Then remove the master cylinder from the booster (two nuts). The outer nut is tricky to reach, and is easiest done by either first popping off the fluid reservoir, or by reaching in through the access port behind the headlight bucket (which is in the way, so would have to be removed). I pick removing the reservoir.
I rotate the headlights, pop off the driver side cover (3 screws), slightly rotate the headlights back and use a ratchet with a 13mm socket at the end of a couple of long extensions.

Harold
 

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22mm Master Cylinder with old Booster

Maybe with the new shorter brake booster, this is not a problem, but when installing just the 22mm MC on the old booster, all of the original lines need to be reworked slightly, as the fitting ports are in slightly different locations than the on the original MC. With the car on jackstands, I thought that I would mention that I was able to access everything on the lower end of the MC by removing the grill screening, reaching my arms in through there, and I was able to see what I was doing by looking through the nostrils. I am 6' 4", so that may be a factor. I also left the MC mounting bolt nuts loose while attaching the lines to give myself a little play to work with. Thank you, Harold, for the last tip of going through the headlight port without removing the whole headlight for the fenderside nut, as that was the only thing that I could not quite get from up front.

Officially my new least favorite thing that I have ever had to do to my GT...what a PITA.
 
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