Master Cylinder lid leaks

[Turbogus]

Hi gang,
Now that the Speedometer project is nearing completion (along with fine tuning the carburator) I've had a small leak from the lid of the power brake M/C. I've replaced the lid and gasket once and verified flatness of the surface of the top of the M/C.
Still a small leak persists. I'd hate to hassle in a new M/C if this issue can be addressed.

Has anyone else encountered this?

 

[JPNinPA]

Thinking about this. If you have the old style metal lid held by the flip over spring clip,Or a newer screw on plastic type and it leaks.. How is the fluid getting pressurized to leak out? I could see general sloshing around with a loose lid leaking but if it shows a seal the only way s pressure or expansion. Does your lines run near the exhaust or is the master cylinder in a hot zone?


Second do you know it is the lid?


Regards,
JPNinPA

Sent using TapTalk

 

[Turbogus]

Thanks for your quick response JPN, BB has the old style metal lid held by the flip over spring clip. I replaced the lid once (came with gasket) but I'm afraid it may have been a miC (made in China) part, and after the debacle I had at NAPA with a thermostat cover it wouldn't surprise me if the casting of the lid is slightly off. The Master Cylinder is right above the steering column on this '78, and as the lines they appear stock and are routed far enough away from the motor and headers. When I get home tonight I'll take a photo and post.

 

[Turbogus]

Well, broke down and bought a "new" BMS from Napa, noted that it was MIC (made in China) so before I left the shop I checked against their counter top and an L.E.D. flashlight in order to detirmine flatness of the BMS body~it looked good. I'm in the process of bench bleeding now and I spent about 15 minutes before dinner pumping the dingus but there's still bubbles, (not the stripper kind either) could this be unusual?

 

[k-2]

Sounds like you are doing the steps, bench bleeding - using the tubes*? - try when spool depressed lightly tap on master might help purge any air... but its often a 1,2,3 done, so I might suspect new component is NFG...

To follow along what year and model jeep?

* could the bleeding tubes be the source of air?

 

[Turbogus]

Hi K-2 'Black Betty' is a '78 CJ 5 w/360. It didn't occur to me to tap the MC sometime I can just feel those donkey ears spring up.

 

[Turbogus]

Yep, tapped it with the handle of my 5 pound cross pien hammer and I was done in four minutes. Now to mount the dingus up without spilling brake fluid all over the place.

 

[Turbogus]

Got the BMS installed last night, I was expecting a larger mess with brake fluid leaking out of the line ports when I removed the plugs. In preperation I got an aluminum roasting pan from the Dollar Store to catch any but it turned out even with the plugs removed and the resivoirs filled the seepage was minimal. Going to be out of town during my short break today so may bleed the wheel cylinders on Sunday.

 

[Turbogus]

No bleeding on Sunday too many honey do's maybe next week. Pressed the brake pedal a couple of times and no leaks so far.

 

[Turbogus]

Got the brakes bled with my trusty little Harbor Freight brake bleeder, worked pretty good as long as the resivoir stays vertical. I noticed the hold down on the BSM lid was a much tighter fit than the old one but since the other one was crusty I thought no harm in proceeding. Didn't have a chance for a road test until today and it seems to be holding water (brake fluid).