where is the air bubble trapped?

[mykwikcoupe]

I have gone through nearly a gallon of brake fluid bleeding my brakes. I am doing the old fashioned way with 2 people. I got into a hurry once and didn't fill up the reservoir in time and ran it dry. Since then i have gone through tons of fluid and am getting no bubbles from anyplace but I have no pedal pressure either. Is the bubble maybe trapped in the master cylinder? I need to swap in the sei prop valve now anyways so I need to bleed it but its either a dead master cylinder or there's air in it some crazy place. Do I need to bench bleed the master cylinder or something? HELP

[Hauntd ca3]

bleed the MC then the rest of the system

[mykwikcoupe]

how do you just bleed the MC when you release the pedal it would suck in fluid correct? I guess loosen up nut and bleed but re-tighten before pedal gets to the floor?

[Hauntd ca3]

pretty much the same as bleeding the wheels.
have someone sit in the car and slowly push the pedal down while you crack open one of the unions on teh mc, and when the pedal hits the floor, get them to hold it there and tighten up the union.
when there is no more air coming out and its just a steady flow of brake fluid, move on down the line.
just keep a good supply of rags to catch the brake fluid that will come out

[mykwikcoupe]

sweet thanks. Since I am using different calipers should I think about using a different MC like something newer with more flow to the calipers. I am using type r calipers up front and legends out back so the piston area is much larger then stock?

[2oodoor]

I ususally bench bleed MC by chucking it in a bench vise and using plastic fittings that screw into where the lines would be. Attached to those fittings are rubber tubes that go back into the reservior of fluid.
Using a big phillips head screw driver to immulate the pedal rod, I push in the spool to push out the air into the fluid. It is the only way to truely get all the air out and replace it with fluid.
Start with long strokes, several to get it good, then finish with shorter and shorter strokes, um yes ha ha its slightley a gratifying task....
\Normally the spool is never pushed all the way in max just with your pedal rod as the MC is installed in the car. This is why bench bleeding is done.

[cygnus x-1]

sweet thanks. Since I am using different calipers should I think about using a different MC like something newer with more flow to the calipers. I am using type r calipers up front and legends out back so the piston area is much larger then stock?

Most likely you will need a 15/16" MC. If the rear pistons are larger diameter than stock, for sure. Which Legend calipers are these?


C|

[lostforawhile]

if you ran the master dry, you need to bench bleed it, you need to do this because you have to push the piston further then the rod on the booster pushes it. See roodoos post, you can get the plastic metric fittings in a kit at the auto parts store, you screw them into the ports on the side of the master, and run tubing into it, fill it with brake fluid, and use something that fits in the hole in the back to push the piston slowly all the way forward, do this until you don't see bubbles. now install the master with the fluid still in it, and connect the lines, making sure it doesn't run dry. If you ran it out, unless you do this, you will never get out the air. once it's back in the car, bleed the brakes diagonally, left front/right rear right front/left rear. how are you bleeding them? are you using a jar with clean fluid and running the tube into it? if you are just hooking up a tube and opening the bleeder, you are going to suck air back in every time. the theory behind this, is air rises, push the air bubbles out, they rise to the surface of the brake fluid, and escape. all that is sucked back in is fluid

[mykwikcoupe]

I bleed from furthest to closest myself. I always use a new bottle of brake fluid and never dot 5 unless the cap says so. I didn't realize the pedal travel isn't make full use of the piston rod travel. My car is an 89 coupe so I believe it has the 15/16th MC already but I will check. Thanks for the help in the bench bleeding. Will the auto parts kit say import master cylinder bench bleeding kit? I have a 3 ft length of tubing from a mighty vac kit I bought that I use the catch bottle and tubing from. I place the bottle higher then the caliper so I can see the bubbles rising and how many bubbles come out.

[Dr_Snooz]

For some strange reason, the bleeding sequence on these cars is different from every other car out there. You start with the front left wheel (closest to driver on USDM cars) -> right rear -> right front -> left rear. I don't know why they did it this way and it probably doesn't matter if you don't follow it, but that's how it's supposed to be done.

[gp02a0083]

I bleed from furthest to closest myself. I always use a new bottle of brake fluid and never dot 5 unless the cap says so. I didn't realize the pedal travel isn't make full use of the piston rod travel. My car is an 89 coupe so I believe it has the 15/16th MC already but I will check. Thanks for the help in the bench bleeding. Will the auto parts kit say import master cylinder bench bleeding kit? I have a 3 ft length of tubing from a mighty vac kit I bought that I use the catch bottle and tubing from. I place the bottle higher then the caliper so I can see the bubbles rising and how many bubbles come out.

you should have the larger MC being its a 89, the 88's and 89's regardless of trim have the same hardware( SE-i's have the same MC and front brakes, the rears are diffrent and the prop valve), the 86-87's are different. You cant use a 86-87 MC with the 88-89 brakes, the brake pedal will have too much travel.

This happened when i did the 88-89 front brake swap on my 87 lxi hatch, i didn't have enough hydraulic pressure

[lostforawhile]

I bleed from furthest to closest myself. I always use a new bottle of brake fluid and never dot 5 unless the cap says so. I didn't realize the pedal travel isn't make full use of the piston rod travel. My car is an 89 coupe so I believe it has the 15/16th MC already but I will check. Thanks for the help in the bench bleeding. Will the auto parts kit say import master cylinder bench bleeding kit? I have a 3 ft length of tubing from a mighty vac kit I bought that I use the catch bottle and tubing from. I place the bottle higher then the caliper so I can see the bubbles rising and how many bubbles come out.

usually they have a kit with a bunch of different fittings in it,since they are plastic, you can force one that is close and not hurt the master cylinders threads, an alternate idea is to go to the yard and cut off some pieces of metal line with the fittings on them

For some strange reason, the bleeding sequence on these cars is different from every other car out there. You start with the front left wheel (closest to driver on USDM cars) -> right rear -> right front -> left rear. I don't know why they did it this way and it probably doesn't matter if you don't follow it, but that's how it's supposed to be done.

these cars,like every other car on the road since about the mid 70's, has a diagnol split braking system, one bore in the master cyl is right front,left rear, the other is left front/right rear. this is so you don't lose both front,or both rear brakes at the same time, it helps to keep the car under control in an emergency stop with one of the master cyl circuits failed.
if you try to bleed both fronts,or both rears you are just pushing air around

[mykwikcoupe]

so this brake bleed kit talked about earlier in the thread has both metric and SAE fittings, 15 in all. a few lengths of tubing and some cheap hose clamps. it cost me $9 at oreilly auto parts today. looks very straight forward. thanks for all the help.

[apache07x]

Sounds like either the Master Cylinder is not putting enough fluid out for the calipers, this happened to me before with my race car. It had a brand new MC but it just wasn't big enough for the four disc brakes I upgraded to. Or it could be your proportioning valve is not centered / lined up correctly. Did this start after your upgrades? If it's the proportioning valve only way I've ever got one centered is to open all four bleeders stomp it to the floor and have someone tighten all the bleeders back up while your holding the pedal to the floor. Then see if it's better if it is try bleeding again.

[lostforawhile]

oh if anyone is wondering how the master cyl can be a dual circuit, and appear to have one bore, there are two pistons, a primary and a secondary, the primary pushes on the secondary,if the primary fails, it slides forward to push on the secondary, if the secondary fails that circuit simply doesn't work