[sparkyj]

Hi,
I am planning on replacing my master cylinder in my 1984 B150 van. The pedal is slowly smooshing to the floor and occasionally the break light stays on and you have to smash it all the way down to make it reset. There is a drop in the booster pressure after turning the car off, so i think the booster is fine.

Any tips on replacing this? it has been a while since my last master cyl job. I assume there is a bleed order to which brakes get bled, correct? And I assume when disconnecting the brake lines from the master, you are essentially introducing are "way" up stream, so pushing that air bubble out is mandatory.

Would a quart of fluid do the trick for this job, once it cycles through?

This will be a one man job, btw;-)

thanks for any help

 

[alloro]

Bench bleed the MC before you install it, then bleed the brake lines starting with the one furthest away from the MC and working your way closer. Usually the order is RR, LR, RF, LF.

 

[sparkyj]

Thanks, that makes sense.
Is there any trick to prevent the air from getting into the line at where you connect lines to the master?

 

[alloro]

You can minimized but never fully eliminate air getting into the system as you reconnect the MC lines.

 

[sparkyj]

can this be performed with the parking brake set? Problem is I have an angled driveway where I will be doing the work.

 

[alloro]

can this be performed with the parking brake set? Problem is I have an angled driveway where I will be doing the work.

I would suggest doing it with the front of the van facing downhill so you're not fighting against gravity with the air bubbles. Leave it in park, set the e-brake, and chock the rear wheels. Most likely you'll have to remove the front wheels to access the front caliper bleeder screws.

 

[sparkyj]

Thanks! Good point about the gravity bubbles.

 

[sparkyj]

Just replaced the master cylinder. Bled the brakes staring with rear passenger, then Rear Driver, then Passenger, then driver. The rear brakes are now grabbing at the last second of a stop. Didn't do that before. Is this common? A proportioning valve issue? Still air in the line?

I took it to a parking lot and pulled some skids. Looks like drivers side is locking up into a skid but passenger side leaves no skid marks
Fronts are not leaving any skid marks.

Next steps?
Thanks guys

 

[alloro]

I took it to a parking lot and pulled some skids. Looks like drivers side is locking up into a skid but passenger side leaves no skid marks
Fronts are not leaving any skid marks.

Next steps?

An out of round drum will cause that. The shoes expand into the wide part of the drum which then causes grabbing as the narrow part of the drum rotates into the shoes.

 

[sparkyj]

Yes that is a possibility. i still had some day light left. just now I managed to get the rear drums off to have a look. Drums seemed even.
Passenger side was a tad oily. Drivers side wasn't much better but dry. Maybe the weak master was not reaching all the way back to the drums for a while and hence, maybe the inner workings were not mating well? I cleaned them off pretty good and it seems a lot better. The wheel Cyls looked greasy so probably need to replace those as soon as possible. Thanks for you input.

 

[alloro]

I managed to get the rear drums off to have a look. Drums seemed even.

We're talking thousands of an inch here, you can't tell just by looking at them.

 

[sparkyj]

Popping them off again tomorrow and turning them, along with new shoes and cylinders
Thanks for the nudge....

 

[sparkyj]

I took the van down the street and had the drums turned and wheel cylinders and shoes replaced. Not excited about how the brakes feel. I know sometimes drums can take a while to set, but I have a "rolling" stop action right now. I would expect the rears to skid but does it take about 500 miles for shoes to break in?

maybe air is still in the line? the guy made a mess out of the new master cylinder I put in and the fluid was a little bit down in side the reservoir. Makes me wonder if it bled it properly and put fluid in while bleeding it.

Also, I notice an audible Swoosh to the pedal. Maybe this is a psychosomatic symptom of expecting perfection but, is this a common issue/sound with a power brake on a B150 van? The master is brand new.

 

[alloro]

I know sometimes drums can take a while to set, but I have a "rolling" stop action right now. I would expect the rears to skid but does it take about 500 miles for shoes to break in?

There is no break-in period for drums and shoes, only for pads and rotors. I think the shoes aren't fully adjusted, or you have air in the brake lines.