Opel GT Source brakes

[jmbinjax]

I just finished installing the M/C Booster combo. I sure wish I had an extra elbow in my arms when working on my GT.

Anyway, everything's great except while idling I sometimes get a very hard pedal and the engines revs if I keep my foot on the pedal.

Is this an indication of a problem with the vacuum check valve?

[grslightng02]

I'm not an expert but this is what I found from my experience.

Somewhere in the vicinity below the original air filter housing the vacuum booster hose that goes to the brake booster off of the exhaust manifold, there should be a small grey and white plastic valve. This ONE WAY valve allows pressure (warm air from exhaust) to go into the hose and assist with booster pressure but not return back. (If you install this valve backwards you lose all pressure and your braking will seem like you only have 25% braking left. ) However if this valve is going bad and not doing it's job correctly you can get a build up of pressure between the valve and brake booster that may actually be leaking backwards and possibly causing this backpressure and interfering with your idle.

My suggestion is to order a replacement valve... probably less than $10 and easy to install.... just make sure you install it so the air flow goes from exhaust manifold FORWARD toward the radiator and brake booster. I believe there's an arrow on the valve.

[grslightng02]

OK so I've been advised to correct an error from my previous entry. The vacuum booster hose goes FROM the INTAKE manifold TO the Brake Booster to provide extra pressure. (I had previously said it went from the exhaust manifold)

[markandson]

OK so I've been advised to correct an error from my previous entry. The vacuum booster hose goes FROM the INTAKE manifold TO the Brake Booster to provide extra pressure. (I had previously said it went from the exhaust manifold)

If you really want to get technical it does not supply pressure; it supplies vacuum to one side of the diaphragm and then atmospheric pressure does the actual "assist" to the brake pedal pressure applied.

[73Manta72gt]

I think the new OGTS booster has an internal check valve and you don't need the inline one in the vacuum hose. I would suspect a bad hose if it hasn't been replaced. They tend to crack near the manifold nipple where the hose bends 90 deg. If the hose is good the booster might be defective

[jmbinjax]

Thanks for the feedback!

I replaced the hose about three years ago. I didn't have the problem prior to replacing the booster and M/C.

I'm leaning toward a weak check valve. I have one coming. It only happens while at idle. It's a very hard pedal, harder than just no assist and the idle increases significantly if I keep pressure on the pedal when it happens.

[jmbinjax]

If anyone cares, Gil and I felt it was probably the booster. He exchanged it with no problem and I installed it last night and everything works great.

As usual, Gil and OGTS was great!

[jayhawkjesse33]

thats great to hear! i am slated to have my combo installed on thursday, hopefully it all goes smoothly...

[Yoda]

Working on this upgrade now myself. My FSM is in a box somewhere and I don't see any tips in OGTS instruction sheet that address getting the old booster out of the car once it's disconnected. I did remove the four nuts and have separated the booster push rod from the pedal linkage so it's loose. It's just binding on the hood hinge and/or the brake lines.

Will I need to remove one of the hood hinges or will the linkage from the booster separate from the booster? I've pushed the brake lines out of the way a bit, but it doesn't seem like a good idea to really start bending them.

[thescifiguy]

It was pretty fussy for me to get out, too. Make sure to remove the 4 nuts at the booster, the 2 at the cylinder, all 3 brake lines, and fully unscrew the nut fastener at the push rod. The offset fluid reservoir is supported by a bracket mounted to the driver's side cylinder-to-booster bolt, while you're jiggling the cylinder off it might snag on this. Reach underneath and over and pull the bracket off the bolt.

At this point I pulled the booster and cylinder sideways until the cylinder was pointing 45* towards the passenger side and jiggled and fussed until I worked it off the 2 bolts. I did all this while laying across the fender and radiator from the passenger side. Get used to this position. Maybe park next to a wall so you can put your feet against it. I didn't have to remove the hood. Puts LOTS of rags under the cylinder. You'll definitely have to do some bending of two of the lines because they enter the cylinder from side you're going to bend it towards. If you don't have tubing bending pliers, just make sure that you spread any bending with your hands over a long area. I have the pliers, but I chose use my hands because my lines are relatively new. Getting the lines lined up and screwed back in, I must've tweaked certain ones over a dozen times until the fitting finally started screwing in. I had to look up through the grill to see that my angle was off a bit. Don't feel like a knucklehead if it takes you HOURS to do it.

[Yoda]

Thanks for the tips. Got the master cylinder & reservoir out with out too much trouble (hour or so), it's just the booster that's sort of stuck.

After the nut fastener is disconnected can it be separated from the booster?

As I type, something (now) obvious just occurred to me. The nut fastener should push at least an inch or two into the booster. If I compress it this way, it should give me enough clearance to get it out.

I'll give that a try.

[jayhawkjesse33]

I had mine installed on Friday and my brake pedal is weak/limp. I have to depress it (without much effort at all) about 2/3 down to get any braking. Also, if I pump the brakes when in park, the idle will jump around a little bit as well.

The pedal issue is a bigger deal to me at this point, the idle isn't a large deal as its only a 200-300 rpm difference at worst.

Any thoughts or suggestions on these issues is always welcome.

Eric

[thescifiguy]

Any thoughts or suggestions

Eric

If it wasn't for your mention of idle speed changing, I'd say check that your lines are tight on the cylinder. I had soft pedal until I rechecked one of my brake lines and found it to be loose. You might still have bubbles in your cylinder or lines.

Another member had a similar experience and I think OGTS gave him a new booster. Assuming that your one way valve in the vacuum line to the manifold is still intact and correctly oriented and the hose clamps are all tight and there's no hose leaks, it has to be the booster itself causing your idle to change. I really don't understand how a faulty booster can change the idle. Unless the diaphragm inside is intact when at rest and somehow a tear or something in it opens and lets air leak as you press. I suppose it's possible that the push rod in the booster isn't seated in the cylinder shaft and you're not actually pressing the shaft in until the last minute.

Just as a point I'd like to bring up, the white vacuum line fitting on the booster is a source of concern for me. It seems to dislodge easily and cock on an angle. I don't know how that fitting maintains it's seal, but it worries me.

It's tough to guess because YOU didn't do the work. There's no telling what the mechanic who did it may have done or forgotten. If I had done the work myself and those were the symptoms, I'd think I had a vac leak AND bubbles. Since you PAID for the work, I'd say take it back and have them bleed the system again and check things out.

[jayhawkjesse33]

If it wasn't for your mention of idle speed changing, I'd say check that your lines are tight on the cylinder. I had soft pedal until I rechecked one of my brake lines and found it to be loose. You might still have bubbles in your cylinder or lines.

Another member had a similar experience and I think OGTS gave him a new booster. Assuming that your one way valve in the vacuum line to the manifold is still intact and correctly oriented and the hose clamps are all tight and there's no hose leaks, it has to be the booster itself causing your idle to change. I really don't understand how a faulty booster can change the idle. Unless the diaphragm inside is intact when at rest and somehow a tear or something in it opens and lets air leak as you press. I suppose it's possible that the push rod in the booster isn't seated in the cylinder shaft and you're not actually pressing the shaft in until the last minute.

Just as a point I'd like to bring up, the white vacuum line fitting on the booster is a source of concern for me. It seems to dislodge easily and cock on an angle. I don't know how that fitting maintains it's seal, but it worries me.

It's tough to guess because YOU didn't do the work. There's no telling what the mechanic who did it may have done or forgotten. If I had done the work myself and those were the symptoms, I'd think I had a vac leak AND bubbles. Since you PAID for the work, I'd say take it back and have them bleed the system again and check things out.

I called the shop when I got back and am going to be taking it back in to have them go over everything again. They stand behind their work and will make sure everything is up to the customers satisfaction. And I took it to a shop to do the work because I didn't trust myself with doing brake work! There are things I'm comfortable with and there are things that terrify me, and messing with my brakes is something that I have zero experience with. Thanks so much for the advice and I'll update the situation as it progresses.

Eric

[hrcollinsjr]

I'm sure they were certain that the system was well bled. Wonder if they know to adjust all four rear brake shoes. Brake shoes out of adjustment can cause excessive pedal travel.

Harold

[runs5k]

Hi,

I actually started the thread but I kind of got side tracked. I bought a set of addco sway bars and decided to drop the diff and clean it up before tackling the brakes. I'm also in the process of cleaning the bottom of the car before putting everything back together with the new rear brakes and new rear cylinders. I even had the drums turned. I should be able to go to the front brakes next weekend. I hope I don't have any problems with my booster.

[jmbinjax]

I had mine installed on Friday and my brake pedal is weak/limp. I have to depress it (without much effort at all) about 2/3 down to get any braking. Also, if I pump the brakes when in park, the idle will jump around a little bit as well.

The pedal issue is a bigger deal to me at this point, the idle isn't a large deal as its only a 200-300 rpm difference at worst.

Any thoughts or suggestions on these issues is always welcome.

Eric

It sounds like the system has air in it. As far as the idle, this is completely different than what I had and pumping it will deplete the vacuum and a slight idle change would be expected. The new booster has a built in check valve and the inline one is no longer needed, according to OGTS.

[jmbinjax]

Thanks for the tips. Got the master cylinder & reservoir out with out too much trouble (hour or so), it's just the booster that's sort of stuck.

After the nut fastener is disconnected can it be separated from the booster?

As I type, something (now) obvious just occurred to me. The nut fastener should push at least an inch or two into the booster. If I compress it this way, it should give me enough clearance to get it out.

I'll give that a try.

If you have it seperated from the radiator support and it's hanging up on the lines, you need to get them out of the way. Bending them slightly is ok as long as you don't kink them. Getting the old one out should not be too much of an issue, it's getting the new in that can be a little challenging. You can try opening the hood all the way without the use of the prop rod, this can give you a little more room.