ABS Brake Bleeding

abs
brakes

#1

1998 Pathfinder SE, 3.3L, 116K. I need to bleed the brake system (the pedal is a bit spongy - probably got some air in when I let it go for too long with low fluid level).



I’m just about to get one of those pressure bleeding systems (I already got one of those “suction” guns that you pump to suck the fluid out of each bleeding valve, but it doesn’t work so well: the connection between the valve and the bleeder hose is obviously not airtight, so when I “suck” the fluid out, air bubbles also get sucked into the hose, making it impossible to see if bubbles are coming out of the actual brake line. Furthermore, I want to do a complete fluid purge, so the pressure system is the way to go).



I have two questions:



1) Let’s assume I got air into the master cylinder: do I HAVE to bench-bleed it? Or will pressure-bleeding rid the master cylinder of air bubbles? Associated question: should I cycle the brake pedal while doing this to insure that trapped bubbles are released within the piston assembly?



2) This car has an ABS controller between the master cylinder and the rest of the circuit. Is there anything I need to do with the ABS system to insure a complete, effective bleeding process?



Thanks in advance.


#2

The bleeding process of an ABS system varies with each vehicle. Some require no special procedures while others require that special steps be followed. Obtain the bleeding procedure for the ABS on your vehicle. Failing to bleed the ABS properly can result in inoperative brakes and a trip to the dealer to correct the problem.

Tester


#3

The 98 Pathfinder does NOT require any special equipment to bleed the brakes…I’ve done it several times on my 98 Pathfinder.


#4

i prefer the old fashioned soda bottle bleeder

the fancy pumps, suctions and pressure gizmos are great, but what are you going to do with it the other 364 days a year?

put it up on ramps, so the front end is lifted. pumping the pedal will get out the air. full strokes. starting with the RR, LR, RF, LF.

make sure you DON’T let the reservoir get emptied though, or you have to start over again.


#5

Cappy’s method will work fine. You will need 2 people, one to open and close the bleeders and one to pump and hold the brake pedal. Check and refill the master cylinder after every wheel…


#6

Thanks for the comments so far. I’ve already done the soda-bottle bleeder - many times (on cars and motorcycles) - and in fact on this very car! (which has failed to fix the problem). This leads me to believe that the air is much “higher” in the brake circuit - i.e. around the ABS actuator or the master cylinder. My proposed solution: change the fluid in the whole system (not a bad thing to do on a 10 year-old car). This is where the pressure bleeder comes in: for ~$60, this thing should be MUCH faster (and also easier on my wife, who doesn’t particularly enjoy playing amateur mechanic’s assistant).


#7

Aren’t you going to find and repair the brake fluid leak, first? Examine the brake lines and hoses throughout the truck for leaks. Look at the tires. Are there streaks on the inside sidewall on any tire? If there are streaks, this indicates a brake fluid leak. Remove wheels and examine the brake parts.


#8

Hellokit, I’m reasonably sure that the air was introduced after I had done a slight “maintenance bleeding” after changing the front pads. Following this bleed, I forgot to refill the reservoir. After going up some pretty steep up and down terrain I got a brake light indicator on the dash… which led me to check the fluid. That’s when I noticed it was really low. I topped it off, but the damage is done: I probably sucked some air in the circuit while braking and going downhill with low fluid in the reservoir.


#9

one more thought:

have you by any chance replaced the MC? if you have the adjusting rod needs to be adjusted so it gets full throw.

if you have NOT replaced the MC, then just pumping with full strokes of the pedal (but ALOT of them) is what is needed to clear out all air bubbles.

i personally think the soda bottle is the best. but as you pointed out it does require two people. i have a friend who swears that he does it one handed, making sure there is always enough fluid in the bottle to ensure it never sucks air on the upstroke.


#10

I agree with your friend. The bottle should be 1/2 filled with fresh fluid and hung as close to the bleeder as possible, and the bottle end of the bleed tube should be immersed in the fluid. The air in the tube then “burps” out the fluid in the bottle and any rebound of the caliper piston draws in only pure fluid.

You can also buy a device to hold the pedal down while you work.


#11

well i dont know about your pathfinder , but i can tell you GM doesnt recommend the use of suction or pressure type bleeding apparatus.the best way i have found is using two people one at the bleeder valve and one inside working the pedal. do not pump the pedal. foot OFF of the brake pedal, open the bleeder valve then have the assistant slowly push down on the pedal till it reaches the floor when it does they need to hold it down till you get the bleeder closed then slowly let the pedal out and wait for 10-15 seconds for the system to settle out and do it again and repeat on all wheels till all air is removed cappy’s wheel order is correct always start with the one furthest from the master cylinder and work your way back. in the absence of an assistant you can gravity bleed them this will require leaving the m/c cap off so that atmospheric preesure can be allowed to push down on the fluid.if the cap is left on it wont work. do not forget the cap is off and go pushing on the brake pedal BIG MESS!!! i have had success with both methods .


#12

i HAVE to ask… i have NEVER heard of the “gravity method”. more info please.

thanks!

i ask since i have two weeks at home to try this!


#13

I never used any bottle. What I would normally do is take off the m/c lid , crack open a bleeder and let it bleed itself. Just make sure the m/c is kept full. Never had a problem doing this.


#14

needless to say if you are bleeding the entire system it is defenitely the longer of the two methods but if you dont have anyone else to help it is an alternative. basically as i said take off the cap fill the resovoir leave cap off and open your bleeders one at a time letting atmospheric pressure do the work for you. if there is alot of air in system it will require patience but it will work. i replaced a wheel cylinder on a car today and bled it that way. having only replaced the one wheel cylinder and of course not losing hardly any fluid there was only a need to bleed that one cylinder just removed the cap open the bleeder and waited for it to flow in this case didnt take too long.


#15

I have to vouch for this method, it’s the only way I bleed brakes.

Fill the m/c and leave the lid off

Remove a b/s and wait for the fluid to drip. While waiting clean the b/s for crud and debris with a pin vise or something like that. After the fluid comes out install the b/s but don’t tighten, it still needs to bleed. You will be able to see when the bubbles stop but wait for clean fluid to bleed through. tighten when good.

Do this to all others. Now is the time I clean up.

Fill the m/s, install the lid and start the engine ( simply for the booster ). Slowly depress the pedal a few times until you get a good pedal.

Fill the m/c.