I'm replacing the master cylinder on my 1995 del Sol si, but can't get the old one off the brake booster. I already disconnected the lines and unbolted both 12mm bolts and tried to yank off the MC but only got a good wiggle going so far enough to see a small gap and spray wd40 in it (all I have) and tapped it with hammer wiggled and yanked it as much as I could..its old and was corroded together but feels like its stuck in the middle

also, I read with everything connected and bled, you can hit the brakes with the 12mm bolts loose and it will break the MC loose from the booster? . but even if u have a bad mc stuck on there?

 

Mine just slid off but it's a southern car. It should only be held onto the booster by two nuts and slide off. It sounds like yours is getting stuck on a thread of the booster.

Try something better than wd40 on rust, pb blaster is what you should try next

 

 

This is going to sound really stupid, so stupid that it may actually work.

Go press the brake pedal down a few times. Did the master cylinder fall off on it's own?

If yes, then hooray for my stupid idea.

If no, then make certain everything is undone.

@TomCat39

 

^worth a try

A rubber mallet may also help.

 

I didn't try that with the lines connected yet, but im sure I would have to bleed them too. I already emptied the mc too. I don't know if I should reattach the lines bleed the system just to try to pump the brakes with the MC mounting nuts loose and brake it free. wondering If that works

also I tried a rubber mallet too, we can get it to wiggle with lots of force but it feels like its stuck inside somehow but it is corroded bad I can take pics tmrw in sunlight ill try to find pb blaster if I think I can yank it off but tried for a hour

 

Well then remove the brake booster and take the whole thing apart once you get it off. If it's that bad you're probably going to need a new booster anyways

 

yea the booster still works tho idk I'll try again now. I'll let young guys know thanks

 

thanks I got my hands on some pb blaster and after a hour soak it came right off