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Hi guys, new to the website here. I bought a 74 Manta ralleye that had been in my neighbors garage for 28 years. Don't get too exited because he left gas in the tank and that with the welding and relining cost me a cool $350 off the start, plus replacing the fuel pump and all the steel lines. Anyway, got it started and it wouldn't stop.........

The front brakes are fine, I put on new rotors, pads and hardware, and had the calipers rebuilt. Bled the system with no issue.

Here's my issue. No fluid going to rear brakes, dryer than a popcorn fart when trying to bleed. I pulled the line off at the master, and there was no fluid there at all. So I hooked up a line from the single rear outlet on the master, and fed the line back into the reservoir. Had my son depress the pedal slowly, and it's never ending cycle of push air out, suck fluid back up, then push air out again.

I've bled many a brake system this way, but can't get rid of the air. Any suggestions would be helpful since I'd like to not but a new master cylinder if possible.
 

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Über Genius
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I'm having a hard time understanding what you mean by you fed a line back to the reservoir.

The Opel MC is a dual piston design. As you depress the pedal, one piston builds pressure enough to push the other piston. Once they are equalized they press harder into the caliper and wheel cylinder.
When you bleed the front, if the rear piston is dry, then the rear piston is fully collapsing onto the front piston. If the spring broke between the front and back pistons then you'd probably get the condition you describe but I've never seen a spring break that way.

What happens if you blow air into the brake wheel cylinder bleeder?
 

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Discussion Starter #3
What I meant was I disconnected the rear line and put a fitting in the master with a hose returning to the reservoir, as if I was bench bleeding. So the fluid is now pushing out right back into the reservoir.

I'll open up a rear bleeder and blow air into that and see what happens. But will that push back through the proportioning valve?
 

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What I meant was I disconnected the rear line and put a fitting in the master with a hose returning to the reservoir, as if I was bench bleeding. So the fluid is now pushing out right back into the reservoir.

I'll open up a rear bleeder and blow air into that and see what happens. But will that push back through the proportioning valve?
You have a proportioning valve?
My 73 GT doesn't.

So, bench bleeding. It seems like the two pistons are frozen together.
Have you tried choking the line on the return.

Push pedal in, lock line so air can't go back in, retract. Repeat a few times..
 

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Make absolutely sure you have the correct connection on the master cylinder piped to the correct lines. I had a frustrating experience with my GT restoration over this issue. I was absolutely positive, but I was wrong. This may seem obvious, but the MC reservoir is actually two reservoirs. Make sure that both have fluid. If these aren't the problems, call Opel GT source and order a new MC. They're not that expensive and the new ones are an upgrade from the OEM.
 

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It boggles the mind how some people will spend a couple thousand dollars on getting their car to go. A few more thousand making it look great. And then go cheap on the brakes.

That's what I say to myself in the mirror when I cheap out on my brakes. LOL

The OGTS MC and Booster combo is AWESOME!! Well worth it!
 

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Discussion Starter #8
Definitely didn't mix up the lines because I only took off the rear. Each caliper has it's only line on the master. I attached a pic of the mc with the bench bleeder set up.

Not going cheap on the brakes, just want to hunt down the failure to make sure it doesn't there aren't any other issues. Been doing some reading, will the Opel GT source mc have the wire connection on it, and if not, is that really needed?

Thanks for all the help, I'll let you know how it goes after I get the part.
 

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Definitely didn't mix up the lines because I only took off the rear. Each caliper has it's only line on the master. I attached a pic of the mc with the bench bleeder set up.

Not going cheap on the brakes, just want to hunt down the failure to make sure it doesn't there aren't any other issues. Been doing some reading, will the Opel GT source mc have the wire connection on it, and if not, is that really needed?

Thanks for all the help, I'll let you know how it goes after I get the part.


It won't have the connection and in my opinion it's not needed. I can tell that you know cars and specifically brake systems. You'll know if you develop a problem with the system without the warning light.

Your problem has nothing to do with the brake booster, but don't be surprised if you find it bad also. You're dealing with an old car and old components. OGTS often runs deals on the two components together.
 

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I'm not sure if OGTS has Delco replacement master cylinders for a 74 Manta. Most of the commentary here is from GT owners, and OGTS certainly has the parts for those cars covered.

Even 20 years ago, finding replacement Delco stuff was a challenge. We usually swapped to Manta B master cylinders and reservoirs, though on occasion I would have a Delco MC resleeved by White Post Restorations if i could find a good rebuild kit, and I would put the MC together myself.

HTH
 

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Opeler
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Brakes

The manta Ascona masters are different than the GT,so after talking to Gill they don't have masters or booster for the Manta.Took apart 5 masters none looked good enough to rebuild.There are rebuilt ones from rock auto and on the internet but may need to use a different fluid reservoir.Ford ranger I believe.The other option is the Geo conversion, an find that here on the sight.The switch is not needed and has a habit of causing problems.
 

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Wow, if Gil doesn't know where you can find one, that's not good. I would suggest trying another source. Maybe Opels Unlimited has one. They buy up old inventory and occasionally run across NOS parts.
 

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Did you try using vacuum to pull the fluid to the rear? If you can fill the lines and wheel cylinders with fluid, you will then know whether you have an internal problem if you still don't have rear brakes. I think you need back pressure on the rear circuit or it won't do anything. This is the safety feature that gives you some braking if the front or rear circuit blows out.

It was pain bleeding the brakes on my car and I had to use a combination of vacuum and someone pumping the pedal.

There are threads about using Geo Metro parts but you must also replace the booster.

This is the very part I fear most about going on my 74.
 

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Interestingly enough, the MC on my 74 Manta was replaced some time in the past by a PO with one from a 1982 Ford F-150. Why that was chosen I have no idea!
 

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Well you obviously have an old line there, did you replace the rear flexible hose? At this point I would take the line loose at the brake hose or at both wheel cylinders and blow air through that way. No proportion valve on this, but the fitting at the cylinder works as something similar. You need to verify the line is clear and the hose is good. Then I would bench bleed them with the cap off! I just recently had a bleeding issue due to a cap not venting
 

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Discussion Starter #17
good news bad news

Good news - got the new Centric master from Rockauto in about 3 days for $71. All the line fitting receptacles match up perfectly. Bad news is the reservoirs don't fit because the new mc doesn't have an area for the reservoir seals to seat. In fact, new mc has no area cut out for seals.

Any recommendations besides sending it back? 1982 Ford F-150 ?
 

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Discussion Starter #19

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Opeler
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Master

Ive talked to Gill regarding replacing my 75 master and in case it wasn't clear in my earlier post ,its Centric part number 130.36201 with a r24556 reservoir.Will need to cut the bottom extra plastic off but will work.Good luck
 
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