Master Cylinder, Rebuild or Replace?

[timemachine]

I haven't been losing brake fluid. Not one drop of fluid hits the ground with this car. I've also checked the entire engine bay. I'm praying the brake booster is ok. You guys are starting to scare me. Now I'm wondering if the stumble at idle has anything to do with the faulty master cylinder.

Nah, don't project. Sounds like you came out on the good side on this one and can stick to plan. Be grateful.

Jim

[74Opel1900]

So I managed to get my hands on a brand new master cylinder for only $58.50 including shipping but..... the old reservoir does not fit. I'm thinking an earlier model reservoir may fit or maybe one from a GT. Does anyone have any advice based on this picture? If someone has a reservoir they think might fit and is willing to sell it please let me know.

http://i250.photobucket.com/albums/g...ercylinder.jpg

[hrcollinsjr]

It looks like a regular Opel M/C to me. How about some measurements? I usually remove good resevoirs and toss the M/C if it looks really bad.

Harold

[RallyBob]

Probably an F.A.G. (Manta B) replacement. Beck Arnley used to sell these, drove people nuts because the reservoirs are different than the Delco-Moraine M/C. IIRC, there is a VW reservoir that fits...but it's been 15 years since I've seen a new one of those M/C's, so I don't remember which model it came from.

[74Opel1900]

The inside diameter for the reservoir on the new MC is 21mm and the old reservoir is 24mm.

[hrcollinsjr]

The inside diameter for the reservoir on the new MC is 21mm and the old reservoir is 24mm.

What's the measure between the two points where the resevoir 'plugs in'?

Harold

[74Opel1900]

I should have those measurements later today.

I know quite a few people need or are going to need a new master cylinder. As soon as I get the reservoir sorted out I will provide the details on where I got mine. I don't want to recommend this part if there is an issue with the reservoir that can't be resolved.

The good news is that there was no fluid in the brake booster just a lot of rust in the master cylinder so the brake lines needed to be flushed.

[74Opel1900]

What's the measure between the two points where the resevoir 'plugs in'?

Harold

From each of the center points it's 93mm. If anyone knows of a reservoir that may fit please let me know.

[jerseydave]

I am old school.

93 millimeters = 3.66141732 inches

[74Opel1900]

I'm being told by the seller that not all Opels have this problem with the old reservoir not fitting. Does anyone have an older (1971 - 1973) reservoir they can measure. Maybe one from an ATE Master Cylinder. I understand that older Mantas used them.

[RallyBob]

I'm being told by the seller that not all Opels have this problem with the old reservoir not fitting. Does anyone have an older (1971 - 1973) reservoir they can measure. Maybe one from an AT Master Cylinder. I understand that older Mantas used them.

The older ATE master cylinder reservoirs are definitely NOT compatible with either the Delco-Moraine or the F.A.G. master cylinders. Been there, tried that!

[74Opel1900]

The older ATE master cylinder reservoirs are definitely NOT compatible with either the Delco-Moraine or the F.A.G. master cylinders. Been there, tried that!

Damn it! Ok, so I guess I have to return the part and hunt down another M/C. I was reading the thread about the GEO M/C. I may go that route unless someone has another idea (besides sending it out for reconditioning, mine is totally shot with rust on the inside). I would really like to find a reservoir that fits this one.

[BQS4]

Damn it! Ok, so I guess I have to return the part and hunt down another M/C. I was reading the thread about the GEO M/C. I may go that route unless someone has another idea (besides sending it out for reconditioning, mine is totally shot with rust on the inside). I would really like to find a reservoir that fits this one.

Brian;
Here's another idea, takes some work, but, seeing as you're willing to do the Geo M/C, this would still keep it all Opel. If you can only locate a 71-73 Manta/Ascona M/C, you can swap out the brake booster from the 71-73 Manta/Ascona, it's a direct bolt up swap but, it'll allow you to use a new 71-73 M/C. I have done this a couple of times.

[RallyBob]

I modified this Strange Engineering M/C to fit a 1975 Sportwagon. Had to alter the mounting pattern a bit, make an extension button to meet up with the plunger in the booster, and alter the brake lines a bit. The bore is 1.0625", which increases the fluid volume a bit...therefore the pedal effort usually goes up. But since the car it's on is a 1975 (bigger booster), and it has the bigger 3/4" wheel cylinders and bigger 1.625" 4-piston Wilwood front calipers, the ratio works out nicely. Cost was just over $100.

The other M/C is from a BMW 320i. It has the same bore diameter and mounting pattern as a stock Opel ATE master cylinder (so it fits early Manta/Ascona), but the fluid outlets are on the opposite side. So I made some extensions for the hard lines. I tried to get a reservoir from a junkyard, but they wouldn't sell me just the reservoir. And a new reservoir from the dealer is over $80! So I got some Tilton racing reservoirs and 'made them fit'.

Both M/C's here are aluminum, so rust will never be an issue again. They can still corrode internally, but I change fluid frequently so that's a non-issue as well.

[opelwasp]

Damn it! Ok, so I guess I have to return the part and hunt down another M/C. I was reading the thread about the GEO M/C. I may go that route unless someone has another idea (besides sending it out for reconditioning, mine is totally shot with rust on the inside). I would really like to find a reservoir that fits this one.

Brian;
Here's another idea, takes some work, but, seeing as you're willing to do the Geo M/C, this would still keep it all Opel. If you can only locate a 71-73 Manta/Ascona M/C, you can swap out the brake booster from the 71-73 Manta/Ascona, it's a direct bolt up swap but, it'll allow you to use a new 71-73 M/C. I have done this a couple of times.

I have tried to mount the Geo M/C in the Manta/Ascona but I don't see how it can be don without MAJOR modifications. They are not similar in any way. The holes don't line up, the pushrod in the back is way too long.

[74Opel1900]

All I really need is a reservoir that fits the M/C I have. Ideally I need to find one that fits because the shop has already installed the M/C and now they are going to have to pull it. Not a huge task but it still costs money.

Bob, what's your best guess at which VW reservoir might fit? I know you said it's been a while so you can't recall but I'm willing to try. If I can find one that fits then this new M/C would be a nice option for those in need.

[RallyBob]

Damn, I just re-read this thread....I thought I had a solution for you. I found a used ATE Manta B master cylinder in my shop today, pulled the reservoir off and cleaned it with the intent to send it to you. Then I read that the center-to-center dimension of your M/C is 93 mm, with a 21 mm top inlet. The one I have is 85 mm c-to-c with 19 mm top inlets. Oh well....

As far as the VW reservoir, I truly have no idea. This happened about 1989-1990 or so, and even then I never knew the correct make/model. Smitty found an application because he had an auto parts store as well as C & R at the time, so he just started opening boxes 'til he found something that matched! I just remember he had one installed on his Sportwagon.

[jerseydave]

I saw that Bob had mentioned a VW reservoir may fit, how about a trip to a VW dealer and check out the parts department and open a few boxes and take some measurements. On one of the searches I found a forum and they steered the guy to go to the dealer and get one for a MK1 Rabbit (late 70's-early 80's)

Might be worth a try.

[74Opel1900]

Bob, I didn't take those measurements myself and it wouldn't surprise me if they were off. Don't rule out that ATE reservoir yet. If you would be kind enough to send it I'd like to give it a try. I'll send it back to you if it doesn't fit. I PM'd you my address and I'll pay for the shipping of course.

Dave, I'll try to chase up an MK1 reservoir and see if it fits. Thanks.

[jerseydave]

Brian I also saw a volvo reservoir on ebay, that is probably from the FAG company. It is a shame that they don't post the measurements for our convience in trying to find something that fits.