mrmossyone

Looks like I have a slow seep where the master cylinder bolts on to the power brake booster. Is there a seal/gasket or something there that could be bad and the cause of this leak? Seems like there is a small dent/cut/crease right below where master cylinder bolts into it. Any help would be appreciated.

transmaster

Replace the master cylinder (MS) RIGHT!!!!!! NOW!!!!!!!!, It is leaking past the internal seals you are going to very soon have No brakes period. The only place the fluid can come out is where you see it, and You are damn lucky you can see it at least you have warning. I honestly would not drive the truck until you replace the MS. Don't bother to rebuild it, just purchase a re-manufactured one, a rebuild kit costs about 30 dollars, the brake cylinder hone another 18 to 25 bucks. It just doesn't make sense to redo one of these things yourself. You didn't mention the year and model truck you have but a rebuilt MS should cost you less then 40 dollars at NAPA parts.

Assuming you want to replace the MS yourself, very easy at least the removal and replacement part. To make the rest so much easier this would be a good time to add some brake tools to your tool box. flare fitting wrenches, and a pressure bleeder.

On the left is a flare nut wrench from KD tools it costs about 10 dollars, you really can't properly loosen or tighten a flare fitting without one of them. These wrenches can be purchased at Sears, and any Parts store. On the right is a Motive Product pressure bleeder. I have one of these and I purchased mine from Motive Products, a first rate outfit . Believe me these pressure bleeders are the greatest device to work on braking systems sense the twist off cap for a bottle of beer. go here for the bleeder; http://www.motiveproducts.com/02bleeders.html

NGM

Definantly replace the Master Cyl. When its off look into the hole in the brake booster and make sure its dry in there. If its wet in there replace the brake booster because the brake fluid will eat up the diaphram in there.

wde3477

Just changed mine out a month or so ago - saw a rust trail down the booster underneath the master cylinder bolt-up. IIRC, the rebuilt master cylinder and two rear wheel cylinders (broke the bleeder screws off the last time) came to about $65 after the core return. As NGM recommends, inspect the booster for any fluid on the diaphragm - long as you got things apart, may as well do it right.

Took the opportunity to change the brake fluid all the way around - some recommend to do this every 3 years or so. Pretty nasty fluid and some crud came out, so probably a good thing. Took a little over 2 quarts of fluid.

A little time-consuming, not too difficult. Soaked the fittings and bolts with penetrating oil during the week before - everything came apart pretty easy. Toughest parts were bench-bleeding the new master, and getting all the air out of the RR cylinder.

transmaster

This is where the pressure bleeder is worth it's weight in gold. You don't have to bench bleed the master cylinder, install it fill it with fluid. clamp or screw the adapter from the bleeder which is full of brake fluid pump it up and go around to each bleeding point and let the brake fluid flow until all the bubbles stop and the brake fluid runs clear. and you are done and you don't have to ask somebody to mash the brake pedal for you. You also don't have to worry about running the master cylinder dry during the bleed out because of extra quart or two of brake fluid in the bleeder's tank.

Honestly I spent years bleeding brakes the two person way. I purchased the pro model which holds a half a gallon of brake fluid, in retrospect I would have been just as happy with one of the smaller models. When I first used it, it was like I had discovered a hundred dollar bill stashed in the pocket of a coat I had not worn in years. This device makes bleeding brakes and flushing out the brake fluid a easy one man operation. I felt like putting this thing on an alter to the Brake God and worshipping it.

Oh, here is a tip I learned from a racing mechanic. When you are flushing out the brake system use a colored brake fluid. The one I use is Ate Super Blue, or Gold, Racing High Performance Brake Fluid. Which is can be purchased from the same place that makes the pressure bleeders, They also happen to have the best price. There is no difference between the two except for the color. When you are flushing the brake fluid you can tell by the color change when the fresh fluid has replaced the old. Believe me replacing the brake fluid every 3 years, more often if you live in a area with high humidity is the ticket for keeping your braking system healthy.

smp5937

Thanks for this info!! I am getting ready to do my brakes soon, and I had never seen one of these tools...I will be shopping really soon for one...

mrmossyone

Thanks for all of the help, I really appreciate the advice.

UJRock

Well i have a stroy to go with this and it JUST happened today. This morning I get ready for school, I do my usual routine and i get ready to take off. I back out of the drive way and all is good. I usualy dont push to hard on the brake shifting form Reverse to drive. Well I start to hot rod it and I get to my first stop sign. This is a some what busy intersection, alot of buses go through it, well i step on the pedal and it just drops, not all the way, enough to wake me up form my coma. I think thats not good, and i should have listened to the mechanic. Ive been having brake problems before and new one were on the list. Lets just say the pay check I just got is spent. Well I proceed normally and come to the next stop sign and downshifted D-2-1. first got to a crawl. I pull out and go, this road is a small highway, so i cant really go slow.I get to school and Im not allowed to park at school because I did donuts in the parking lot, so I park across the road at Kinneys. I got lucky I didnt have to stop and wait to cross, I proceeded to coast through the parking lot, found my spot and had to use the snow bank and my brakes. That got a few peoples attention, so much for me laying low. I left school early so I could beet the traffic, drove home under 30 the whole way. First gear was pretty handy slowing me down. I tried adding new fluid and bleeding it but the pressure would build and then drop when i hit the pedal. Both of my lights are on(brake, ABS). So I looked for leaks found some new ones and you guys already answered my question. Anyways after reading the thread It sounds like I too need a master cylinder. I tried refilling the resivor thing and it just kept draining. Their is a newer looking stain on the wheel well so im going to have to say thats it.

mrmossyone

Okay I changed the master cylinder and the brake booster and something isn't right. When you press the brake pedal it travels pretty far and the front of the booster pushes out also when you press on the pedal. Does this mean I didn't bleed the brakes enough or I need to adjust the rod on the booster? If it's an adjustment does anyone know an easy way to adjust it, what distance etc.? Thanks.

UJRock

check for leaks. I replaced mine and didnt have any pressure and one of my calipers was leaking.