loveoldtrux

Hi gang,

Son's girlfriend was allowed to drive his '98 Cherokee for a few months. See the rotor below for the condition she brought it back in. She won't fix if as she needs her money for something called "Kratom", so I'm stuck with it! Ever seen something this bad? I haven't - she said it was "making a little noise" - I told her he needs to tell he never to drive it again!!



So with the rotor worn down this far and the caliper piston extended to it's MAX, I would have thought the master cylnder would be empty on the primary side - after replacing both front rotors and pads (piston appeared to be okay) I checked the master cyl, expecting to have to add some fluid - nope it was near the top! So, we replace all the front hardware and test drive - brakes don't make me happy...the pedal stilll goes near the floor before stopping Jeep (it's a little bit creepy!!!). Jacked up rear end for a quick test - had son hold brake down as I tried to spin rear wheels - wheels spin like the brakes aren't on!! Off come the REAR wheels.... brake cylnder is leaking fluid on one side, other side; wheel cylnder is not pressing one of the shoes out to stop the drum and the shoes are worn paper thin. Replaced the drums, wheel cylnders, shoes ( and adjusted the rear brakes / shoes ), brake hardware and bled the lines. Jumped back in Jeep to find the pedal is still miserably close to floor; I'm not happy with this - my '96 brake pedal is close to the top of travel before activating brakes and it's brakes haven't been worked on! Pumping the pedal does not bring it up any or make it any firmer so I would assume no air is left in lines....

Ideas? I don't think the booster could be bad - it just gives power boost to the pedal I don't think it should go down as close to the floor like it does. With all the parts just installed that pedal should be extra firm....

Thanks,
Mark

lawsoncl

Wow, if that's just one side then I'd replace or rebuild that caliper regardless and make sure the slides were okay. If it's both sides, I'd guess the issue started more than a few months ago. If bleeding and adjusting the rear brakes doesn't fix it, I'd start suspecting the master cylinder is bad.

Turbo X_J

If it leaked fluid long enough air was sucked into the master cylinder, bench bleed is the only way to fix it.

Dave51

^^^

loveoldtrux

lawsoncl - thanks. Yeah, just the left side was like that; right side was just "normal wear". Thanks for your reply!

--Mark

loveoldtrux

Turbo X J - it's been over 40 years since I've done a bench bleed - I remember the good ole days when I used to overhaul these things (Pontiac had seal kits)!!

I don't have the LARGE vise I had a Boomershine Pontiac - I can do a bench bleed while attached to the brake booster right?... just disconnect the master cylnder line, hold finger over hole and have son pump brakes until any suspected air is gone - first primary side, then secondary... then bleed the 4 wheels?...

Thanks much for that reply!
--Mark

Dave51

The (an) important consideration is that the MC needs be level-- not the reservoir but the cylinder itself, so that might require parking on a hill:


I'd also like to be a little contrary here. I don't believe bench bleeding is mandatory. AAMOF, I believe that you could replace the entire brake system without putting fluid anywhere and through careful bleeding be absolutely fine. That's not to start an argument about the merits of bench MC testing, but rather based on what you describe (MC always had fluid, you bled the system and the pedal still goes to the floor) that SCREAMS faulty MC.

But hey, no worries. As long as it get fixed, that's the important part.

And certainly, if you're taking an MC right out of the box, then go ahead and bench bleed (and you can "bench bleed" after you install it). You "bench bleed" because you don't want to introduce unnecessary air into the system when installing a new MC. Once you start pumping that pedal, that air is going to come out of the MC no matter how you bleed.

Dave51

If you want to do it that way, just crack those connections, don't disconnect them. Use a rag to collect the mess.

Turbo X_J

Don't concern yourself with the second method this guy uses, it's not ready. You can grab a couple of brass pipe plugs and keep in your tool box for future use if you don't have the fancy plastic ones. If you bleed it in the vehicle just make sure that the master cylinder is level.

gat

"I would have thought the master cylnder would be empty on the primary side - after replacing both front rotors and pads (piston appeared to be okay) I checked the master cyl, expecting to have to add some fluid - nope it was near the top!"
Did you check the fluid level prior to replacement? Prior to replacement is when the fluid level would be low. Once you have replaced the rotors you have shoved the pistons rearward which displaces the fluid back into the reservor.
If only one side had that issue, then there was highly uneven wear. She couldn't have been driving with both feet on both pedals. There has to either be a stuck piston or stuck slides because I don't think that you have a proportioning valve. Maybe a pinched line at that size.
If you plan to keep the vehicle for a while, then I recommend that you replace something on both sides when you replace something. You can buy the bleeding kits with the plastic pieces for extremely affordable prices at your local parts stores. Bleed the master cylinder, then gravity bleed rear right, rear left, front right, and finally front left. If you go thru 1 quart between the four, then you will have come close to completely replacing the system.
Complete aside- Kratum is a drug derived from an eastern plant. It is often quaffed as a tea. It is a very mild pain killer with no known side effects at all. If you have ever watched one of Chris Bell's documentaries, then you'll enjoy his one about Kratum. https://m.imdb.com/title/tt8412232 I don't know the ages of your son and his girlfriend, but I think that Kratum and Cannibinoid Oil are all the rage for teens and early twenties drug consumers. I can't drive a day in my life without passing a ****ing drug shop any more.

Scott91370

Honestly I would replace everything that was part of the system, you've done most of it already:
lines, calipers, cylinders, springs, adjusters, rotors, drums, pad, shoes, and all new fluid. And anything else I may have missed.