Trouble bleeding rear brakes

[JimZRyd]

Hey guys! I'm attempting to bleed the brakes on my 94. Starting with the right rear. I've got new calipers from Mid America, stainless lines and speed bleeders from Russell. Using a Motive pressure pump AND a Mighty vac. I can barely get any fluid flow. When I open the bleeder screws I will get about an inch or so in the tube but that's it. I wait about 5 minutes and the tighten the bleeder back down and check the Motive pressure, pump the brake pedal a couple times, feels firm, and then go crack the bleeder screw again and all I get is just a trickle of fluid. I've removed the bleeder and it still trickles. I disconnected the line itself and get flow, not a lot but it does flow.

Am I not giving it enough time? I've bled many a brake, even Corvettes, and always had steady flow of fluid during my bleeding process. This is the first time I've tried a C4. Could I have gotten some sort of air lock? I'm stumped! Any advice will be greatly appreciated! TIA!!

[Billy Mild]

Try with the engine running.

[-=Jeff=-]

The way I do it now:

Speed bleeder with a piece of clear tubing into a container, tubing goes into a bit of brake fluid in the container. I then open the bleeder and pump the brakes and watch the tube for bubbles (I have my son pumping the pedal). I repeat at each caliper and then sometimes repeat the process a second time..

[JimZRyd]

These are new calipers so I assumed that I would have to wait till fluid flows freely in order to know I've filled the caliper with fluid and all air has been removed. I've been at this for days off and on and would have thought I'd see results by now.

I haven't tried it with the engine on. Always thought with an ABS system, with the engine running you are pressurizing the abs system and traditional bleeding of the brakes won't work. I might be wrong.

Shouldn't I be seeing a free flow of fluid at some point using both a Motive pump and a Mighty vac?

Thanks guys!

[-=Jeff=-]

I was having trouble with the mighty vac. I went old school gravity bleed.. Car off. That seems to work best for me

[JimZRyd]

Jeff, were you able to get a free flow of fluid or just a trickle? All I get is a trickle and seems to be better with the Mighty vac. I've tried it back and forth many times. With my last Vette, a C5, all I had to do was crack the bleeder and it flowed freely. Could easily do all 4 in less than 30 minutes. This being my first C4 I was wondering if I was missing something unique to these. I've read some say it took a little time to get them to bleed but good gracious how long should it take?!?! My 94 only has 11.5K miles on it so this is probably the first brake bleed she's ever had. Would that make a difference?

[-=Jeff=-]

no I don't recall it flowing.. it needed 'help'.. If you have a helper, have them pump 3-5 times and hold the pedal, then crack the bleeder.. OR

do what I said and pump it yourself a bunch of times, I actually use the mity vac container with the mity vac hose, the hose connects to the lid with the internal tube.. all self-contained minimal mess

[JimZRyd]

Mines Definately not flowing. When I did my C5 the whole tube would fill and flow and there was a definate change from old to new fluid. Maybe it'll just take some time. I've waited as long as 15 minutes and barely got out an once. Hopefully there's nothing blocked, that's my fear. Everything mentioned thus far I've tried. Thanks for all the advice. Anybody got anything else to try, I'm all ears!

[Billy Mild]

Have you taken the bleed screw completely out?

[JimZRyd]

Yes Billy. After my first attempt today with little to no results I took the speed bleeder completely out and blew air through it to make sure it wasn't clogged. I got a small trickle of fluid from the hole. I then disconnected the brake hose from the caliper and got decent flow, not a flood or anything. I did remove the brass washers thinking they might be displacing the hose and/or the bleed screw. Put it all back together and then using the motive/mighty vac I was able to get about and ounce or so out over 10-15 mins. Think I should just give it more time ? These calipers are brand new so they are dry. How much will one hold?

[Mystic ZR-1]

Using the Mighty Vac backwards, as a pump. With flex hose disconnected
from the caliper.
Back fill thru the the bleed screw to ensure the caliper
is full. Reconnect hose and bleed normally after you're happy that the
caliper is full. You'll have to put the stock bleed screws back in to do this
as the Speed Bleeders have a check valve that may not let you do this.
FWIW: a friend once bought new calipers for his C3 and the holes for the
bleed screws weren't drilled thru... :cry:

[JimZRyd]

Using the Mighty Vac backwards, as a pump. With flex hose disconnected
from the caliper.
Back fill thru the the bleed screw to ensure the caliper
is full. Reconnect hose and bleed normally after you're happy that the
caliper is full. You'll have to put the stock bleed screws back in to do this
as the Speed Bleeders have a check valve that may not let you do this.
FWIW: a friend once bought new calipers for his C3 and the holes for the
bleed screws weren't drilled thru... :cry:


Wouldn't that method, if the caliper has air in it, force the air further up the system and into the lines requiring more of a bleed procedure in order to draw that air back through the caliper and out the bleed screw?

[Mystic ZR-1]

Not if you disconnect the flex hose and bleed normally after you reconnect the hose.
True, the vent screw is on the top, but if you flush enough, you'll know
if there's restriction in the caliper.
Here's the best advice:
Worse comes to worse... maybe follow the instructions in the FSM?

[JimZRyd]

Now I got what your saying! Take off the brake hose from the caliper. That Definately would be a way to refill the caliper. Thanks! It'll be Friday before I can get back to it. Very well might try that! Thanks again!

[mbabbitt]

I've bleed my brakes probably 40 times doing track events over 6 years. I've boiled my fluid many a times. I gone thru brake pads like butter. Whatever you do, NEVER use CarboTech pads. They cost a lot and wear like butter. I went thru one set a weekend.
Get rid of the Mighty Vac and speed bleeders. They are a waste of money. The Motive is all you need. Make sure the caliper is floating on the pins. Get a piece of plastic tubing long enough to hit the bottom of your favorite empty bourbon bottle. Fill the bottom of the bottle enough to cover the end of the plastic tube. Keep the end covered with fluid. Make sure the reservoir is full, pump up the Motive to 30 lbs (make sure it is holding the pressure) and crack the bleeder until you see new, bubble free fluid You need to keep an eye on the reservoir at all times after that first crack of the right rear bleeder.
Good luck,

Mark

[Billy Mild]

I would try to gravity bleed it for a few hours. Maybe crack the bleeder and wait a while.

[gbrtng]

I've bleed my brakes probably 40 times doing track events over 6 years. I've boiled my fluid many a times. I gone thru brake pads like butter. Whatever you do, NEVER use CarboTech pads. They cost a lot and wear like butter. I went thru one set a weekend.
Get rid of the Mighty Vac and speed bleeders. They are a waste of money. The Motive is all you need. Make sure the caliper is floating on the pins. Get a piece of plastic tubing long enough to hit the bottom of your favorite empty bourbon bottle. Fill the bottom of the bottle enough to cover the end of the plastic tube. Keep the end covered with fluid. Make sure the reservoir is full, pump up the Motive to 30 lbs (make sure it is holding the pressure) and crack the bleeder until you see new, bubble free fluid You need to keep an eye on the reservoir at all times after that first crack of the right rear bleeder.
Good luck,

Mark

What he said - except my Motive is Wifey on the brake pedal - push, hold, release while I open and close the bleeder. tres simple ...

[-=Jeff=-]

What he said - except my Motive is Wifey on the brake pedal - push, hold, release while I open and close the bleeder. tres simple ...

That is what I do too, except my son on the brake pedal

[JimZRyd]

Thanks guys. I actually have been trying all the above suggestions, except trying to back fill the new calipers. Might try that if I continue to have problems. Billy might have it pegged as I might not be waiting long enough. In all the brake jobs I've done it's never taken much time and I always have seemed to get much better flow when bleeding. Ill get back on it by the end of the week and update then.

[JimZRyd]

Finally got the rears to bleed well! Found a thread on another site where guys were having a problem with their C4's brakes leaking from the bleeder screws. They were all using speed bleeders, as was I, and the speed bleeder screws weren't seating right in the caliper allowing them to leak. I wasn't having any leakage problems, just couldn't get them to bleed. So I compared my Russel speed bleeders with the oem ones and sure enough the speed bleeders were longer and had a more pointed tip. So I removed the speed bleeders and replaced them with the oem and BAM! That did it! They both bled fine. The right rear was a little sluggish but the left rear flowed fine. Bled approx 50cc through each and buttoned them up. Firm pedal! Now to move on to the fronts!

[Bmak77]

If you have a air compressor go to Harbor Freight Tools and get a Pneumatic Brake Bleeder Item number 92924. It makes bleeding and flushing a snap. I have used it on several of my cars with ease. The cost about $30.00.

[JimZRyd]

Hey thanks! I'll check it out. I normally use my Motive pressure pump and a Mighty Vac. Always worked like a charm till these speed bleeders got in the way.