Master Cylinder Resevoir

Ernest · Feb 2, 2025

Has anyone ever just changed the size of their master cylinder resevoir for an increased capacity one.

My idea... my '79 malibu resevoir(pic1) and thinking about swaping it out for the slightly larger resevoir(pic2) thats for '81 Buick, Cadillac, Oldsmobile and Pontiac.

I could possibly use the entire master cylinder/resevior unit, both have the same 1" bore(according to amazon description), but not sure of the mounting stud spacing, or just use the resevior only since they both look very similar along with the cap for the extra capacity, but not sure of the size and spacing of the resevior holes and mounts.

Just spit balling here... so any thoughts?

69hurstolds · Feb 2, 2025

?? Why need the extra capacity? I guess it could come in handy if you had a slight leak somewhere or never filled your system. But as long as you can keep the level is above the pistons and not suck in any air, a huge reservoir is just bragging rights.

But if it makes you happy, go for it. I believe the spacing and hole sizes are the same, but haven't verified it. If so, do what allows you to sleep at night.

Ernest · Feb 2, 2025

Like the second pic shows, "expect more"... so why not? 😀

565bbchevy · Feb 2, 2025

So my thoughts were why wouldn't they have used the taller reservoir, was there maybe a clearance issue with the Gbody?
Well I used some modeling clay to verify on my 86' Regal and there is a hood brace directly above the master cylinder and I also don't have hood insulation under my hood which would reduce the clearance even more.

Stand offs about an inch tall

After the hood closed it reduced the clearance to 5/8" on the front and 7/8" on the back.

Ernest · Feb 9, 2025

i finnally had the chance to change the master cylinder out, the old one was definately shot, pedal went easily to the floor, barely any stoping power.

I readjusted both the drum/disk brakes, bled them using the one man method using DOT3, went out for a test drive, barely touching the pedal and the car stops quickly like it should.

It has been suggested to "bench" bleed the master cylinder first so you could fully press in the shaft more properly to fill it and get the all air bubbles out, unfortunately, i dont have one, so i had to do it attached to the power brake booster, works either way.

565bbchevy · Feb 9, 2025

Ernest said:
i finnally had the chance to change the master cylinder out, the old one was definately shot, pedal went easily to the floor, barely any stoping power.

I readjusted both the drum/disk brakes, bled them using the one man method using DOT3, went out for a test drive, barely touching the pedal and the car stops quickly like it should.

It has been suggested to "bench" bleed the master cylinder first so you could fully press in the shaft more properly to fill it and get the all air bubbles out, unfortunately, i dont have one, so i had to do it attached to the power brake booster, works either way.

So is that the stock height one? And yeah your old fluid looks pretty dirty.

Ernest · Feb 9, 2025

Yes... stock unit, stock height, the other master cylinder i spoke of, was just an after thought.

The old fluid was filthy, i've had the malibu for 3 1/2 yrs now and never changed the brake fluid, since it is not a daily driver(20mile drive on sundays/car shows/swap meets/cars&coffee, weather permiting), i wasnt too concerned about the fluid, till now.

Those srtains you see aroud the flare nuts and mounting studs, a shot of PB blaster just in case, the MC was not leaking anywhere externally.

Search

Search

Master Cylinder Resevoir

Ernest

Royal Smart Person

Attachments

69hurstolds

I know nothing!

Ernest

Royal Smart Person

565bbchevy

Geezer

Ernest

Royal Smart Person

Attachments

565bbchevy

Geezer

Ernest

Royal Smart Person

Similar threads

Please support GBodyForum Sponsors

Recommended Communities