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I recently replaced the brake master cylinder as the brake pedal had
no pressure when pressed. The brake light also stayed on?
I purchased a new cylinder
I bleed the cylinder. Same problem after install. I guess I need a new
brake booster? No luck finding this part? 1979 Chevy Monza 3,2
Anyone know where I can get the Brake Booster

Can you bleed the brakes? If it is your booster that is bad you will still get a firm pedal (if the master cylinder is good, and there is no air in the system, and no leaks) it will just be harder to push. The last master cylinder I replaced (on a 1969 Firebird) took me 3 master cylinders to get a good one, the new ones seem to be junk.

Are you sure you bled all the air out of the new master cylinder before installing it?

I would try to bleed the brakes - I suspect you have a bad new MC.

I never thought about that. Thank you.
I’ve owned My 1979 Monza since new.
I’ve never Bleed the brakes since I’ve
owned the car. 41 years WOW

Did the brake light go out? Why did it come on in the first place? It sounds like you had a leak in the system, did that get fixed?

I had my booster re-built as that was the only option I could find, I have a friend [I do really!] that was dating the manager at a metro Detroit area O'Rielly's she dealt with all of it for us, cost I remember as similar to a new one if I could have found one, also it was gone for more than a month, like 7 weeks IIRC, so not going to happen fast and that could be holding the pedal forward and leaving the Brake Lights on, if it is bad. That system will require a good flush as brake fluid is designed to absorb water and that lowers its' boiling point as well allowing that absorbed water to eventually do what water does to steel, we don't like to use that "R" word here [LOL]. I would make sure all of the hydraulic brake components are top notch before going much further with this repair as, if something else is amiss that will give up shortly thereafter and then you get to wash, rinse, repeat, ad infinitum, Definitely no Fun that way, you will likely have the time if the booster is bad and goes out for a rebuild, replace and steel lines that look questionable and consider doing all of them, I have played chase the line game before only one looks bad/is leaking but with in a month or two half the system has been replaced, today Inline Tube and Classic Tube I believe both offer them prebent and in either steel or stainless. If you know someone with a vacuum pump and gauges that you can cobble up, to test to see if it is leaking and or sticking, just another idea to check out, before sending it out for rebuild as rebuilding anything seems like a roll of the dice these days. Harry