Question about breaks / master cylinder
 

Hi guys, this is my first jeep. I have an 01 WJ with 95k. I think my master Cylinder is either going or shot. When I press on the brake pedal, there is about 4-5 inches of travel before there is any brakeing power at all. Then in the next 1-2 inches of brake pedal travel the brakes grab hard. I find myself having to be very careful on the highway because I either dont stop in time or as happened last night in the rain, i locked up the tires causing the ABS to kick in.

Prior to owning the jeep Ive had 6 other cars and 2 suvs over the last 20 years. I drive 20-25k year so I think I know how to drive and how a vehicle should respond to having its brakes applied. This just doesnt seem right so, I wanted to get someone elses opinion before I start replacing parts.

Do your brakes come on almost immediatly and gradually (as most cars) or is there some pedal travel before any braking power kicks in?

Our '04 has 88,000 miles since purchased new and except for the recall/TSB for rotor & caliper replacement hasn't had any brake problems. It doesn't exhibit the symptoms you describe, and I suspect it may be your master cylinder (or the vacuum supplying it) as you mentioned. JMO
Dan

X2 on what Dan said...Tj

Sounds to me like your lacking power assist (brake booster) check to make sure you have vaccum to your booster. Try this. run engine for a minute or so, turn off and let it sit for a couple of minutes. Then with the key off pump the brake pedal 4-5 times, it should get harder each time, this will tell you if you are holding vaccum, dont let off the pedal. Then start the Jeep and the pedal should fall an inch or two slowly. If it does this you have sufficient vaccum.

Wouldnt lack of vacum make depressing the pedal difficult? Its 01:30 right now. I will try your suggestion in the morning.

I was just trying to give you a starting point. To find out whats wrong you start with whats not wrong.

Update, pedal does not sink once depressed. With truck turned off, pedal will become firm in 3-4 pumps and hold. Within a second or so of turning the truck on, the pedal sinks to the floor. So, got vacum!

Checked the fluid, was a tad low and a little darker than I would like. So, Im going to bleed the system to see if that helps. Otherwise I picked up a MC and a MC bleeder kit brand new for $60 from AutoZone.

Also, building a DIY pressure bleeder to make the process go a bit faster.
http://faculty.ccp.edu/faculty/dreed...eder/index.htm