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Has anyone replaced/rebuilt their Master Vac?


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Looks like I have a leaking master vac. Have lost all power boost to the brakes (brakes themselves are OK.) I hear a noticable hiss upon depressing brake pedal (and for some reason, engine RPM increases). When I disconnected the vaccuum hose from manifold to the master vac, the sound disappeared.

There's not much info in the Chilton manual I have about the master vac.

Is is worthwhile rebuilding it? Are bebuilt ones available. How difficult is it to remove? I can see a real problem working in the tight space under the steering wheel. I'm wondering if it's best to hire this out.

Any comments appreciated.

Jon

thebigboy@earthlink.net

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Originally posted by Jon, the BIG boy:

There's not much info in the Chilton manual I have about the master vac.

Is is worthwhile rebuilding it? Are bebuilt ones available. How difficult is it to remove? I can see a real problem working in the tight space under the steering wheel. I'm wondering if it's best to hire this out.

Jon, I was in the same boat quite awhile ago. But, I made the decision to purchase a rebuilt master-vac from Motorsport Auto. They did a decent job (although they sent me the wrong push rod).

I ended up repainting it. But, the unit itself worked great.

The master vac isn't a very easy task to rebuild. It includes a fairly large spring under stress. If you aren't careful, you could release the spring and damage anything in its path. smile.gif

I decided against it because I didn't have the tools or the nerve to take it apart.

If I did it wrong... I might be w/out brakes someday. Is that something you really want to chance? I didn't.

Anyway, if you have the tools/patience/strength to take it apart and replace all of the components.. so be it. Otherwise, leave it modular and get a new/rebuilt one.

[m]

------------------

Mike Gholson

1971 240z, Mikuni Carbs, Tokico 5-way Adjustable Struts, Ferarri Yellow, Stock Engine, 15x9 wheels w/50 series Falken tires, Currently being restored.

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  • 3 weeks later...

Hi Mike,

Sorry for not acknowledging your reply any sooner.

I took your advice and bought a rebuilt master vac from M/S--they had it to me with 24 hours. Their catalog part number was wrong--this may be why you received the wrong part. There was a mixup with 71s and 72s.

Anyway, the part came and the operation was a success.

Thx a bunch,

Jon

Originally posted by Mike:

Jon, I was in the same boat quite awhile ago. But, I made the decision to purchase a rebuilt master-vac from Motorsport Auto. They did a decent job (although they sent me the wrong push rod).

I ended up repainting it. But, the unit itself worked great.

The master vac isn't a very easy task to rebuild. It includes a fairly large spring under stress. If you aren't careful, you could release the spring and damage anything in its path. smile.gif

I decided against it because I didn't have the tools or the nerve to take it apart.

If I did it wrong... I might be w/out brakes someday. Is that something you really want to chance? I didn't.

Anyway, if you have the tools/patience/strength to take it apart and replace all of the components.. so be it. Otherwise, leave it modular and get a new/rebuilt one.

[m]

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  • 5 years later...

I am having the same problem. My brakes don't seem to work very well unless I pump them. If I pump too much, every thing locks up (so I have to be careful).

When I am idling I can press the brake pedal and watch the tach go from 1100 to 1700. The hissing starts when I press the brake pedal.

I have totally new front and rear brakes. I have bled and bled and bled.

Until this moring, the brakes were working fabulously.

Do you think that the master vac is gone? Could it possibly just be a vaccuum leak somewhere?

I am REALLY getting frustrated with the mechanics of this car. I rebuilt everything (engine, suspension, brakes) and now its BODY and interior time.

Yet.. new mechanical things keep popping up. ARRRRRRRRRRRRRR. :sick:

Should I just replace every auxillary component under the hood?!

Excuse me while I go kick my Z in the pants. :disappoin

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I got mine from Victoria British. Came with instructions on how to adjust push rod to master (I used plumbers putty, worked great). Also, if your master is older than 5 years, might as well replace/rebuild while your at it. It's off during the procedures anyway.

Be prepared to send in your core. Clean it up before! (Don't worry about any rust, rebuilder dips/blast units before rebuilding them.)

It came raw metal so you will want to paint it with quality paint to keep it looking right (not rusting to ugly real fast). I used high temp enamel. Reason is the metal on the rebuilt units is rough (but clean) and high temp is more fluid (thiner) and flows better to get into the "pors" of the rough metal. Take your time and give it several coats. You will not want to take it off later to repaint.

Be advised, as with many parts on the Z's, they are year specific, i.e. you must match the vac unit to the master cylinder. The obvious difference is the length of the rod from the vac unit to the master cylinder. My new vac unit came with a longer rod than the old one but I replaced the master cylinder when I replaced the vac unit and they matched up so I got lucky.

Remember, time is money. Not taking your time and doing it right the first time is more time and more money (and on brakes: maybe worse).

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