Two Brake bleeding question.

[Buffalosports]

As you can see in my previous couple posts, I have been having trouble with my brakes. I appologize if I am getting annoying with these posts. My brakes where barely working and the peddle was soft. I went through and lubricated all the sliders on my calipers with no better result. Next, I went through and bleed all the calipers by pumping up the brakes and opening the bleeder. No air came out, fluid would squirt everywhere with no spitting or signs of air. Again, same result, very soft peddle. Next, I went on to replace the master cylinder. The master cylinder was bench bleed and all breaking lines are now reattached. Obvisouly, I need to bleed the system again but this time, I would think it should be much more difficult. I think I am going to go and pick up a Mightyvac (or something similar ex.: Harbor freight cheapo).

my First question is, how do I do it with the pump? What Psi am I looking for?

Second, does the ABS pump need to be blead? How would I go about doing this. My explorer is a 98 sport with 4 wheel disc brakes.

Third, I know the order in which I should bleed the calipers. Should the master cylinder be bleed first or last?

 

[nssj2]

I can offer a little help. You need to bleed the master cylinder first, before you install it. You will unfortunately need to bleed the ABS pump. That involves picking up a $200+ scan tool, or taking it to a qualified shop to bleed the whole system on the truck.

 

[Buffalosports]

Just got done talking to a Ford Mechanic and he said that the Abs pump does not need to be bleed but it does take a real long time in pumping all the air out of the lines. So hopefully that question was answered.

 

[Maniak]

Which "pump" method are you thinking of?

Are you talking about pulling a vacuum on the bleed screws for each cylinder or bleeding it "backwards" through the master cylinder?

I use an old r-12 venture style vacuum pump for both methods.

Here is a pic of it bleeding the clutch (master cylinder for the brakes is also for the clutch on the 2006 mustang).

vacuum_clutch_bleeding 002 by maniak_az, on Flickr


For brakes, Its similar. I have a cup with a top on it that has 2 vacuum lines coming out of the top. One line goes to the vacuum pump and the other goes to the bleed screw. I put bearing grease around the bleed screw and around the vacuum lines in the cup top. The "cup" was made for brake bleeding, but you could use a jar with 2 holes in the lid.

That vacuum pump can pull 28" of vacuum which is what I do. When I bleed brakes I let it pull a vacuum for 1-2 minute and viola, its bled.

Thats the only way I have been able to bleed brakes by myself. As for the ABS module, I can't comment on that, I've been very lucky and haven't had to bleed that yet (only have rabs on the explorer)

~Mark

 

[Buffalosports]

Ok, I replaced the master cylinder and brake lines need to be disconnected to do so. Everything is reconnected but obvisouly there will be atleast some air in the line because the closed system was broken when I took of the break lines from the master cylinder. I went and bought a Mightyvac so I guess I can technically "pump" air out of the break lines. The mightyvac is what I meant by pump. Sorry if that was unclear. The Mightyvac comes with a gauge on the top. How do I use the mightyvac to get the air out of the lines?

From what I have read on a Hyundai Tiburon website, you attach the hose to the bleeder without opening it. Pump the vac up to about 25psi and open the bleeder. Allow brake fluid to draw through the lines until 5psi. At 5 close the bleeder and start the process over until there are nolonger any air bubbles in the line. Does this sound correct?

 

[Maniak]

I know what your doing now. The "cup" I was talking about came with my mityvac (sp?) brake bleeding system. I retired my miyvac since I was using it as a vacuum gauge for a while and broke it.. I found my venturi r-12 pump works better.

When I had the mightyvac I would use it with the cup between the vac and the bleed screw. That way the vac won't suck brake fluid into it which will hurt the diaphragm. I would connect the vac to the cup and the cup to the bleed screw and put bearing grease around the bleed screw so air won't get around it. Then I'd open the bleed screw and pump away on the hand pump. It would take a while, but it would pump out the air But only if you have good seals at the bleed screw and at the cup type thingy.

If you want to connect the pump directly to the bleed screw I'd use a long clear hose and keep the pump higher than the bleed screw. That way you can stop before you suck brake fluid into the pump and it won't "run" into the pump by gravity.

This is a different brand, but this is basically what my kit came with.

~Mark

 

[Buffalosports]

Ya I was orginally going to get this exact model until I found the actual Mightyvac at Harbor freight for $40. I think that is a decent a price. Hopefully this little thing is powerful enough to get all the air out. I have been told by a neighbor that it does take a while. I would assume that pumping the brake peddle is not needed with mightyvac and would probably be bad for it. The only time the directions mention touching the peddle is in the case of dirt build up.

 

[waskly]

abs needs to be bleed. i wont go into why since thats a really long post there is a reason for it. you can get away with it but again abs should be bleed also.

now to bleed brakes considering you bleed the master, you start with the longest run first then 2nd longest 3rd and 4th. so you would start with right rear/ left rear/ right front/left front.

if you get no pedal at all, bleed the left front first. then do the 4 in the order.

also a bad abs pump can act like a bad master cylinder. you really want to bleed it so no bubbles comes out. remember that long lines will take time before the air in the lines moves all the way to the caliper.

 

[2000StreetRod]

soft pedal - engine on or off?

Before you replaced the master cylinder:

With the engine off, did the pedal continue to drop all the way to the floor? That would indicate a bad master cylinder.

Was the pedal soft with the engine off or only when the engine was running? If only when engine running, I think that indicates a defective booster. If you bleed the brakes until the pedal is firm with the engine off but the pedal goes soft with the engine running I suspect that you have a bad booster.

There are valves, reservoirs and a motor in the ABS unit. If the ABS is activated and air gets into one of the reservoirs then the ABS must be cycled during the bleeding process to purge the air. This is normally done with a scan tool in conjunction with a pressurized bleeding system.

I have experienced poor results when bleeding with a vacuum hand pump. I've had better results by elevating the bleed tube and cup above the bleeder valve, opening the valve a small amount, and then pumping the brake pedal making sure not to bleed more fluid than is in the specific master cylinder reservoir.

 

[2000StreetRod]

excellent idea!

. . . I would connect the vac to the cup and the cup to the bleed screw and put bearing grease around the bleed screw so air won't get around it. . . ~Mark

A very clever trick which I intend to use in the future!

 

[Buffalosports]

Before you replaced the master cylinder:

With the engine off, did the pedal continue to drop all the way to the floor? That would indicate a bad master cylinder.

Was the pedal soft with the engine off or only when the engine was running? If only when engine running, I think that indicates a defective booster. If you bleed the brakes until the pedal is firm with the engine off but the pedal goes soft with the engine running I suspect that you have a bad booster.

There are valves, reservoirs and a motor in the ABS unit. If the ABS is activated and air gets into one of the reservoirs then the ABS must be cycled during the bleeding process to purge the air. This is normally done with a scan tool in conjunction with a pressurized bleeding system.

I have experienced poor results when bleeding with a vacuum hand pump. I've had better results by elevating the bleed tube and cup above the bleeder valve, opening the valve a small amount, and then pumping the brake pedal making sure not to bleed more fluid than is in the specific master cylinder reservoir.

I am pretty sure that a booster is quite the oposite. Since a booster helps in braking, normally a bad booster is represented by a very firm peddle.

 

[Buffalosports]

Now i'm just royally getting p!ssed. I went through and bleed the whole system. There is no air in the lines nor in the master cylinder. I started with the master cylinder and went right rear, left rear, front right, and front left. The peddle is much stronger when the truck is off but as soon as I start it, the peddle sinks right to the floor. If I hold the peddle to the floor, vacuuum kicks in and the engine idles down a bit and then kicks back up. I can not figure this out.

What I have done:
- all sliders on calipers lubricated with never-sieze
- Master cylinder replace with bench bleeding
- All lines bleed with mityvac

What could remain?:
- ABS pump (ABS light is not on)
- Brake booster (peddle is not firm)
- Leak (do not think it is a leak because I can not see any visable leaks and the fluid level never changes)
- Caliper pistons shot (when the breaks slightly worked, I do not pull in any direction)

My next guess would be the ABS pump seals are bad and leaking when pressing on the brake. Any other ideas?

 

[Buffalosports]

Is there a ABS bypass valve that possibly have gone bad? If so, where is it located? Thanks.

 

[waskly]

the car cant stop short right? i been thinking if you can get an abs event going, it should tell you. but

as long as you have a firm pedal with the car off. and it goes to the floor i would say the abs hcu has open dump valves.

 

[Buffalosports]

the car cant stop short right? i been thinking if you can get an abs event going, it should tell you. but

as long as you have a firm pedal with the car off. and it goes to the floor i would say the abs hcu has open dump valves.

I was sent an email containing something about this earlier today. I believe it said that dirt sometimes causes these valves to stay open. This means the module needs to be replaced, correct?

 

[Buffalosports]

What is this? It is located on the furthest back brake line of the master cylinder. I needed to reuse when replacing my master cylinder. Would have anything to do with a soft pedal?

 

[YBCold]

when i replaced my brake line i just gravity bled my system. but i also bypassed the ABS valve. but ive read on here from some other people that u dont always have to get a scanner to sequence the valves inside it to bleed it.

 

[Buffalosports]

when i replaced my brake line i just gravity bled my system. but i also bypassed the ABS valve. but ive read on here from some other people that u dont always have to get a scanner to sequence the valves inside it to bleed it.

According to my haynes manuel, 96 and older need to be taken in and bled with a scanner. Now, if the hole ABS module is replaced, I am not sure if that is still the case.

 

[YBCold]

hmmm u may have a point

 

[waskly]

I was sent an email containing something about this earlier today. I believe it said that dirt sometimes causes these valves to stay open. This means the module needs to be replaced, correct?

correct. you will also need to do an abs bleed on the vehicle.