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Braking problem

717 views 15 replies 4 participants last post by  Uniblurb 
#1 ·
Hello first post , I have a 1998 Jeep Grand Cherokee the problem is I don?t have enough pressure through the system and have tried bleeding, and I?ve pin pointed what I think is the problem but you guys tell me if this part would even be a problem because I can?t seem to find this part for sale online. Thanks
 

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#3 ·
thats your ABS system, (exact term escapes me now),
do you have a ABS light or a brake warning light in dash?

The hydraulic should do a conventional bleed - tell us history, any ABS codes and status of dash lights.
 
#4 ·
HCU - hydraulic control unit,

did you do a conventional bleed?
any issue?

the system will need a scanner to complete the bleeding - operating the valves in HCU.

Tell us the history and issues and brake work done?
 
#5 ·
Thank you for replying I really appreciate that! , well when pressing the brakes (when going slow speeds 5-20) the pedal would be very soft almost to the floor (when going at higher speeds 25+) the pedal is alot harder but even when pressing the pedal full force with my leg it won?t come to a complete stop. I attempted to bleed the brakes no fluid would leak out, not one drop. I took off the rear right caliper and checked to see if the pads were just finished but they were fine, while there I checked to see if the brake on the caliper was getting pushed out when the brake pedal was pushed, it was not. I then pressed the brake pad down to see if the brake fluid would come out of the (nipple where you bleed the brakes) once I pressed down fluid shot out perfectly fine. Sorry for the big paragraph, this help at all?
 
#7 ·
The front calipers bleed great the rear brakes are the ones with nothing coming out , I thought the same thing and I followed the lines all the way to the master cylinder so then I replaced the brake booster ( was ripped a little but seems like a common issue with the brake boosters rubber trimming) anyway also cleaned the masters cylinder and I mean CLEAN used carb cleaner, air compressor , some real strong cleaning stuff for the resovior, but should I have not done that to the master cylinder? Also cleaned the small brake lines that connect the master cylinder to the proporting valve and the lines that connect to the HCU with a air compressor. So how I I think it?s the HCU is I pumped the brakes There was pressure coming out of the master cylinder and the proporting valve, once the lines went in the HCU that?s we?re there was no pressure coming out
 
#9 ·
The front calipers bleed great the rear brakes are the ones with nothing coming out , I thought the same thing and I followed the lines all the way to the master cylinder so then I replaced the brake booster ( was ripped a little but seems like a common issue with the brake boosters rubber trimming) anyway also cleaned the masters cylinder and I mean CLEAN used carb cleaner, air compressor , some real strong cleaning stuff for the reservoir, but should I have not done that to the master cylinder? Also cleaned the small brake lines that connect the master cylinder to the proporting valve and the lines that connect to the HCU with a air compressor. So how I I think it?s the HCU is I pumped the brakes There was pressure coming out of the master cylinder and the proporting valve, once the lines went in the HCU that?s we?re there was no pressure coming out
When you cleaned the master cylinder reservoir with all those strong chemicals did you have the reservoir removed from the master cylinder? Hopefully you did since you'd just push all that dirt/scale crap into the MC. Also I probably wouldn't have used carb cleaner in the MC along with blowing high-pressure compressed air through it.

Did you do a bench bleed on the MC before attaching the lines? If not you likely have air in it and you may have some pressure but not enough if there's air trapped in it. You can 'bench bleed' the master cylinder still attached to the booster and I'll post a diagram of the lines used.

It's fairly difficult to get air in the ABS when doing brake work around it. It needs to be activated in order for air to enter. But if you blew air into the lines still attached to the HCU you could have forced air into it.

As already mentioned a DRB scan tool is needed to remove air from the ABS. I wouldn't assume that pricey part is bad w/o having any air removed from it.

As was already asked, do you have the ABS light on the dash on?

Below is the diagram for the bench bleeding lines. They sell plastic lines with fittings at parts stores as bench bleeder kits. Just have somebody else pump the pedal while you watch for air coming out of the lines in the bottom of the reservoir. This is the first thing I'd do and you may not have air in the ABS if the dash light isn't on. Good luck.
 

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#11 ·
You're welcome and just a couple tips if you bench bleed the MC with it still attached to the booster. Most don't have the fittings (may be metric) which go into the 2 MC ports or the lines/tubes to go inside the bottom of the reservoir.

Many parts stores have those bench bleeder fitting/hose kits. But on my WJ I bought a new Cardone master cylinder w/reservoir at a local parts store which comes with the exact fittings/hoses. I used these fittings/hoses on my old MC, was able to get the air out, blew the hoses/fittings out with brake cleaner, then returned the whole MC with bleeder hoses for a full refund. Lol, but the MC was never used and I didn't harm the fittings/hoses a bit.

After bench bleeding when pulling those hoses out of the reservoir keep them higher than the level of brake fluid. Then put a couple layers of household kitchen wrap like saran/glad wrap under the cap and screw it on tight. This will prevent all your brake fluid from streaming out of the ports since you've created somewhat of a vacuum in the reservoir. Then disconnect the bleeder hoses and install the OE fittings/line fairly quickly. You'll need to do a full 4-caliper bleed (right rear, left rear, front right, left right) after this. Good luck.
 
#12 ·
Big thanks to all you guys, it worked, so let me start with what was (replaced/worked on) first of all the brake booster?s rubber trimming was torn(made a hissing noise) once replaced noise stopped. Second, the jeep has been sitting in one place for bout a year and a half, I don?t know if the owners before me have bled the brakes or kept up with maintenance. When it came to the brake lines I did not ?clear them out? while they were connected to anything. Now once everything was on and I was ready to bleed the MC what I did was use lines from another MC for the ?bleeder lines? and pointed the end of the lines into a cup, when the lines were under brake fluid (making sure the reservoir stayed full) once the bubbles stopped coming out I put everything back, bled the calipers in the correct order, took it for a test drive and ran great!! Thank you guys I really appreciate it!!!!
 
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