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motovate 03-26-2020 08:54 PM

Brake System Questions
 
I actually never gave this much thought until I got a 2005 Nissan Frontier 4x4. I always thought all mfg's had the system split front/rear. Front on one side of the master cyl and rear on the other. I just found out this little Nissan is a "X". LR/RF and RR/LF so you are supposed to start say on the LR to bleed (Farthest away) then go to the RF, jump to RR and then to LF.

I just wanted to be sure my 2003 Jeep Rubicon was front on one line and rear on another line - so if I just did the front calipers ( which I did) All I have to bleed is LF ( farthest away) then RF. This is correct - correct!:surprise: If I then do the rear it is bleed RR then LR. Systems are closed to each other in case you loose front brakes you still have both rear brakes.????????????????????

I've always bled RR to LR then RF to LF farthest to closest to master cyl.

Also I have a 2003 Rubicon - no anti skid light comes on when the key is turned on but I saw where someone with I think was a 93 Jeep had anti skid on it?? Do I have it and don't know it and if so what do I need to do different when bleeding??

Thanks:smile2:
LBM

JFM626 03-27-2020 09:51 AM

If you have "anti-skid" there will be a module near the drivers side fender with a bunch of brake lines coming out. You are bleeding the brakes correctly with the following caveat. You run a risk of contaminating the brake system if you do not pre bleed the brake calipers before compressing the caliper piston.

motovate 03-27-2020 11:37 AM

Quote:

Originally Posted by JFM626 (Post 40914435)
If you have "anti-skid" there will be a module near the drivers side fender with a bunch of brake lines coming out. You are bleeding the brakes correctly with the following caveat. You run a risk of contaminating the brake system if you do not pre bleed the brake calipers before compressing the caliper piston.

OK- not quite sure about the pre bleeding of the calipers. Are you saying to open the bleeder valve when you push the piston(s) back into the caliper to allow it to slide over the rotor??? So old brake fluid is not pushed back down the line?? Sounds like a good thing to do at any time although I never really did that before. In my case I changed calipers so they were empty to begin with.

Also Did any 2003 Jeep Rubicons have anti skid??

Thanks - LBM

JFM626 03-27-2020 12:17 PM

No not quite. Because type 3 brake fluid is hydroscopic it will absorb a certain amount of water while in the braking system, as the calipers are the areas that get hottest and often at the lowest point any water and the resulting "crud" will form at the bottom side of the piston bore. By not pushing the pistons back initially, but just bleeding the brakes through the bleed screw you could mitigate the chance of any of this "crud" traveling back up into the system, with possible unwanted results (blocking valves in your anti- lock system), or finding its way back into your caliper after replacing it and/or your brake pads. By pre bleeding you can lessen but not totally eliminate the possibility of caliper piston seizure in the near future.

motovate 03-31-2020 12:23 AM

OK what you are describing I always thought of as flushing the system to get all the old brake fluid out. You are just suggesting do that before pushing the pistons back into the caliper. Bleeding the system for me was always to get all the air out. My 2003 Rubicon calls for type 4 brake fluid and in this case I replaced front calibers & rotors and will replace the rear calipers & rotors. Then bleed out all the old fluid until it is clear and no bubbles on the rear which is what I did on the front. As far as I can tell this 03 Rubicon does not have anti - skid. I have an old 88 Chevy 3/4 T 4x4 that has all the extra stuff hanging down just below the master cyl - don't see that just a junction block between systems.

Thanks - LBM


Quote:

Originally Posted by JFM626 (Post 40914609)
No not quite. Because type 3 brake fluid is hydroscopic it will absorb a certain amount of water while in the braking system, as the calipers are the areas that get hottest and often at the lowest point any water and the resulting "crud" will form at the bottom side of the piston bore. By not pushing the pistons back initially, but just bleeding the brakes through the bleed screw you could mitigate the chance of any of this "crud" traveling back up into the system, with possible unwanted results (blocking valves in your anti- lock system), or finding its way back into your caliper after replacing it and/or your brake pads. By pre bleeding you can lessen but not totally eliminate the possibility of caliper piston seizure in the near future.


JFM626 03-31-2020 08:45 AM

Type 4 brake fluid is also hydroscopic. Yes you will still have bleed your brakes to remove any air trapped in the system after installing new components. The pre- bleeding is just to lessen the chance of any contaminates remaining in the system.


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