Help Bleeding Brakes (Non Aviation)

SkyHog

SkyHog

Touchdown! Greaser!
Joined
Feb 23, 2005
Messages
18,510
Location
Middle of nowhere Texas
Display Name
Everything Offends Me
Home Airfield
KLUD
A few weeks ago, I had the distinct pleasure of putting my race car into the wall at nearly 100MPH. Hurt like a bastard, but thankfully, the damage was limited to the upper and lower control arms, the wheel, the shock, the upper and lower trailing arms, the spindle, and the tie rod (basically, everything that isn't frame in that corner).

Also - the brake line sheared in half.

I got everything put back together, but once I put the brake line on, I have absolutely no front brakes when I press the pedal, and the pedal is very spongy. Makes perfect sense, as the brake line is filled with air, not fluid.

So I filled the front master cylinder reservoir with fluid, popped the bleeder, and started pumping the brakes. But nothing happened. No fluid came out, and the fluid in the reservoir didn't even move up and down like I would have expected.

Anyone know if there is something special you need to do to purge an entire brake hose of air?
 
Nothing special, but the technique you describe is not purging the air.
Open bleeder w pressure, close bleeder, let off pressure - repeat, repeat, repeat. Takes many more cycles than I always expect.
 
Master cylinder piston seals are shot.
 
SkyHog said:
A few weeks ago, I had the distinct pleasure of putting my race car into the wall at nearly 100MPH. Hurt like a bastard, but thankfully, the damage was limited to the upper and lower control arms, the wheel, the shock, the upper and lower trailing arms, the spindle, and the tie rod (basically, everything that isn't frame in that corner).

Also - the brake line sheared in half.

I got everything put back together, but once I put the brake line on, I have absolutely no front brakes when I press the pedal, and the pedal is very spongy. Makes perfect sense, as the brake line is filled with air, not fluid.

So I filled the front master cylinder reservoir with fluid, popped the bleeder, and started pumping the brakes. But nothing happened. No fluid came out, and the fluid in the reservoir didn't even move up and down like I would have expected.

Anyone know if there is something special you need to do to purge an entire brake hose of air?
Click to expand...
Fill a metal oil squirt can with fluid, attach a hose that will also go over the bleed valve, pump in from the caliper to the master cylinder. Since you already have the master full, you'll want to get the fluid from there.
 
N801BH said:
Most probably...

Good chance the OP had his foot on the brake pedal during the impact and that will usually hurt the seal.. IMHO..
Click to expand...

Could be, I'd rid the possibility of it being an airlock first though.
 
Been there, done that, had the cast to show for it....

Sounds like the master cylinder took a shot too. If you had your foot on the brakes at the moment of impact then the master cylinder could be damaged.

But you need to bleed the master cylinder first. I always did that on the bench, then installed it.
 
I' d be very surprised if the frame is still straight at this point. :yes:
 
Thanks everyone...some answers to questions so far:

1. I hit the wall at full speed. Foot was on the brake but I was smart enough to tuck before impact so not full pressure on the pedal. I did hit hard enough to bend the foot support tho so it is possible I jammed the brake pedal in on contact.
2. There are two master cylinders, one for the front brakes and one for the rear, with a brake bias dial to allow me to adjust which wheels get more brake.
3. No frame damage. There is one part of the front frame that was partially bent, but it was an easy weld fix as is most stuff on this car.
4. I bled the master cylinder and it held pressure enough to bleed. I think there is just a massive amount of air between the cylinder and the wheel since it is all new brake line from the T to the hub.

I am going to try a vacuum pump to see if maybe I can suck the air out of the line instead. I welcome any other advice though.

As to type of race car, it is a Pro Chassis Dwarf Car (Classic Lite). Picture below.
 
You shouldn't be having that much trouble, how far away from the front master cylinder do you have the T fitting to go to each wheel? What type of fluid are you running? What type of lines are you running?

I ask because I had an F1000 that had a brake issue only to realize the Castrol SRF we run was eating away the inside of the lines and clogging the T fitting that led to one caliper providing uneven clamping force between the two calipers.
 
I've found with lots of air the best way is to release pedal, then press pedal all the way down, have someone close bleeder while still holding pedal then repeat. Being a race car without all the bs involved in a normal car it should bleed very easy. I'm going with blown master.
 
Maciej said:
You shouldn't be having that much trouble, how far away from the front master cylinder do you have the T fitting to go to each wheel? What type of fluid are you running? What type of lines are you running?

I ask because I had an F1000 that had a brake issue only to realize the Castrol SRF we run was eating away the inside of the lines and clogging the T fitting that led to one caliper providing uneven clamping force between the two calipers.
Click to expand...

I run DOT3 fluid - the master cylinder is in the cockpit, above the brake pedal. There is a 3 ft line from there to the front end of the car, where a T splits it to two 30" flexible brake lines that run to each wheel. So not very long - maybe a total of 7 feet of brake line I need to fill.
 
For single handed bleeding, fill the master cylinder full, crack open the bleeder screw, wait, wait, wait. Let gravity do most of the work. Sometimes that's all you need.

Next step (if necessary) is to press /hold the pedal with the bleeder closed. Hold the pedal (somehow) open the bleeder screw, let air out, close screw. Repeat until you get only fluid. (Shop manuals like to tell you to put a hose on the screw and put the other end in a jar of fluid, but I've never found that to be necessary.) If that doesn't work, you gots other problems.
 
Dwarf cars can get up to 100 mph..???? :lol::lol::lol:

Dwarf car classes is one of the most competitive classes going now. Always fun to watch.

My last encounter with the wall was in a full size late model on pavement. That was the start of the end of my not so great racing career. I should have stayed with local dirt tracks. :yes:
 
Get a vacuum brake bleeder. They are magic for one person bleeding.
 
Capt. Geoffrey Thorpe said:
For single handed bleeding, fill the master cylinder full, crack open the bleeder screw, wait, wait, wait. Let gravity do most of the work. Sometimes that's all you need.

Next step (if necessary) is to press /hold the pedal with the bleeder closed. Hold the pedal (somehow) open the bleeder screw, let air out, close screw. Repeat until you get only fluid. (Shop manuals like to tell you to put a hose on the screw and put the other end in a jar of fluid, but I've never found that to be necessary.) If that doesn't work, you gots other problems.
Click to expand...


Used this method quite frequently.
It works, and removes a lot of other single-operation hassles (and less expensive than buying bleeding equipment). Just make sure that there is a couple of inches of fluid in the container, not just a coating.
 
An oil squirt can is what, $5, the hose is <$1? You'll be done in 5 minutes, I don't know wh this has to be expensive, difficult, or a day long ordeal.:dunno:
 
You must log in or register to reply here.
Back
Top