I have a 2008 Jeep Wrangler JK. It has 230K + miles on it. Having an issue with the brake pedal going almost down to the the floor. When I start the care in the moring, I have to pump the brakes to get pressure to build up. I have checked the following.
- Checked the brake pads: F: 6 MM / B: 5 mm - Brake pads are good. But will be replacing them next month.
- Check brake fluid: The brake reservoir is not low.
- Checked for leaks in the break lines: No leaks were discovered. traced the lines from the master cylinder to each brake.
- Air in the lines: I had no way of checking this.
- Bad Master Cylinder: No way to really check. Saw no leaks from the master Cylinder.
Had a mechanic look at it, and the master cylinder was leaking into the Power Brake booster. Had both replaced, and still having issues with the brakes to the bottom of the floor board. Is there something that I am over looking ?
Thanks -
Scott
That is typically caused by air in the brake lines, or possibly ballooning of worn rubber brake lines. Another possibility would be an internal master cylinder leak. (These days it is not unusual for new parts to be bad right out of the box.)
Make sure the brakes are bled with a scan tool to actuate the ABS. I know from personal experience about brake master cylinders going bad. I have a 1979 Pontiac Catalina, and while I was getting it road worthy again, I had to replace the brake master cylinder three times before I got one that functioned, both brand new and remanufactured. I even got the brand-new AC/Delco part through Amazon, and that failed as soon as I started the car up.
You had a new OEM master cylinder installed and if that didn't correct or change anything I would start looking at the ABS module next because if it's bad it can give you the same symptoms as a bad master cylinder does. Most new OEM master cylinders tend to work fine (Fully recognizing that @justin-shepherd experience with several master cylinders on his Catalina has been quite different)I guess I can look at the brake line and have them replaced.
I'm linking a few videos from Scotty that should help below.
After ruling out visible leaks, Scotty notes 2 common causes in this video: Sinking Brake Pedal in Your Car (Brake Master Cylinder)
Another video by Scotty explains how you can test your master cylinder, old or new, to see if it has an internal leak: Bad Master Cylinder, Leaking Internally
Thank you for the response. I hope the OEM Master Cylinder I bought is not bad. I guess I can look at the brake line and have them replaced.
But thanks again for your help.
If you had a mechanic look at it and it still didnt fix it then take it back and have them fix it right or demand your money back
@bobthehatking Only true if the mechanic supplied the part. If he didn't furnish the defective part he owes you nothing.
You're right about the parts, but he also paid for diagnostics. the mechanic found a leak which was a valid probable cause of the issue, but after the parts were replaced, he failed to confirm that the parts replaced were the root cause the problem, and he did not check to make sure that the problem was not still there. So the labor for the mechanic to re-diagnose should be no charge. the parts were leaking and needed to be changed either way so the customer is responsible for it, unless as you mentioned the mechanic supplied a faulty part