brake fluid leak from behind reservoir

[welcomehome]

2000 international 3800 7.3L bluebird Handibus with hydraulic brakes.

after tracking down the burnt brake fluid smell, i have discovered that i have a leak from the device behind and above the brake fluid reservoir. ive just recently tracked this leak down but have noticed it for quite a while now.
somebody looked at it and told me it had something to do with the brake master and said it was probably just a simple gasket.
the brakes continue to work fine and rarely do i have to top off the reservoir. but the leak and the smell of it burning off continue to get worse.
have any of you dealt with this leak before? was it a simple gasket fix? or did u end up having to replace the whole part?
thank you for your time.

[welcomehome]

the leak is coming from the mating surface of the master cylinder and the booster. it seems i need to replace the master cylinder as this seems to be a common leak from what my internet browsing has suggested. does anyone have any advice on doing this job? i see one at napa for around 140. does that sound like about right? is it basically as simple as taking the 4 bolts off, taking the old one off and putting the new one on and bolting it back together?

[Brad_SwiftFur]

Originally Posted by welcomehome

the leak is coming from the mating surface of the master cylinder and the booster. it seems i need to replace the master cylinder as this seems to be a common leak from what my internet browsing has suggested. does anyone have any advice on doing this job? i see one at napa for around 140. does that sound like about right? is it basically as simple as taking the 4 bolts off, taking the old one off and putting the new one on and bolting it back together?

It's been a long time since I've replaced a hydraulic brake master cylinder. You'll need to "prime" the master cylinder, work all the air out of it, before reconnecting the lines. You'll also need to bleed the air out of the lines once reconnected. Since you have the master cylinder off and replacing all that brake fluid, it might be wise to go on and flush out all the old brake fluid and have fresh fluid in the whole system. This is easiest with 2 people.

$140 for a new master cylinder doesn't sound out of line. The actual replacement procedure is relatively straightforward (assuming the steel lines aren't rusted and prove difficult to remove). It's all that bleeding of air from the system that ... isn't really all that hard (with 2 people), it's just time consuming to do.

[Booyah45828]

You got a vac booster or hydroboost? If it's a vac, replace it with the master cylinder if you have any fluid leaks there, otherwise you'll be replacing the booster relatively soon too. That fluid eats the hell out of the diaphragm inside.

[Brad_SwiftFur]

Originally Posted by Booyah45828

You got a vac booster or hydroboost? If it's a vac, replace it with the master cylinder if you have any fluid leaks there, otherwise you'll be replacing the booster relatively soon too. That fluid eats the hell out of the diaphragm inside.

7.3 engine, it's probably going to be a hydraulic boost.