why elevated as opposed to lowered? looks to me like raising the rear moves the top of the piston cylinder above the bleeding screw....where lowering it raises the bleeding screw above the top of the piston cylinder?

edit: i see that i'm not alone thinking this way and i will pull a rear wheel and try to envison what Dep is saying this weekend

 

Again...on the back of the car the caliper sits on a 30 degree angle facing towards the BACK of the car. When you ELEVATE the rear it REDUCES the amout of angle to make it closer to vertical. There are THREE bleeder screws on the back caliper. Two facing front and one facing rear. The rear-facing screw and the piston it bleeds need to be elevated in order to get the air to move CLOSER to the bleeder screw so that it can be bled out.

Bob: Thanks for going to the effort of checking it out. When you take off the wheel you will see what I am talking about.

Dep

 

THREE bleeder screws?

Well, I might just have to concede to being the dummy here. I thought mine only had two. I guess I'll have to crawl back under later & check it out.

 

One on the outside front half facing forward. One on the inside front half facing forward. One on the outside rear half facing backward.


Dep

 

nope my back facing are plugs...

i still believe that raising the rear creates a high spot in the cylinder that can trap air.... i don't see how it can move out with the rear up...air will always rise and stay there....i'm out of town but will look at this and try to see your way on saturday.

 

That's odd. I have 3 bleeders on each caliper on the rears.

Okay....try this. Get a ball and fill it with water till it's 2/3 full. Now tilt
the ball so that the hole is at a 30 degree angle, but not so the water leaks out. See the air in there? Now with the ball still in that position picture putting more water coming in from a different hole while still keeping the original hole tilted at 30 degrees. What happens? The water comes out of the first hole but the air bubble REAMAINS.
Now...turn the ball so the first hole is facing straight UP. Now picture more water coming in from that second hole. The air is pushed OUT of the ball by the incoming water because the air can ESCAPE.

Mr. Wizard

 

Some had plugs, some didn't.

I have a collection of OEM GM plugs for show & tell.

 

Lorin,
Just curious as to where you are with your bleed sitution right now? I see your post of 5/3 but nothing more was said after it was answered a number of times. I don't agree with the posts about raising the back end of the car or what have you. GM doesn't tell you to do this when bleeding your Corvette. I think I mentioned to you that I had a similar problem with my 73' trying to get a good pedal bleeding it manually. I had nothing but problems. I also think I mentioned to you about the $50 Motive Pressure Bleeder. I will mention it again. That tool is a life saver and worth every penny. In the 23 years since I have owned my 73' I never had such a good brake pedal like I have now since purchasing the Motive Bleeder. I agree with Tom that gravity bleeding is another good way to bleed but having pressure going into the system as with using the Motive bleeder will make problems show up such as any leaks you may have in the system. Doing it with gravity you really need to know there are no leaks to begin with such as in the calipers or lines before you start to bleed the system using the gravity method.

Hey Tom I'm also 54 and another oldster who has been messing with these cars for the last 37 years. Because of my interest in muscle cars unlike you opening up a repair shop I chose to open up a Carquest Auto Parts Store back in 78'. Sold it in 83' and became a wagon jobber ever since to this day. At this point in time it gives me more time to play with my collector cars as I have been slowing down.

 

The pressure bleeder is a great tool to have...

But...

The pressure generated by the brake pedal is how much?

Much more than the pressure bleeder (even a professional diaphragm type) will ever generate. Any leaks that you have will be evident long before using a pressure bleeder, just by stepping on the brake. It ain't rocket science.

Just pull back the seals & take a peek.

If you just gotta have a neat toy.... well then.... yeh.... it's cool to have a pressure bleeder.

But I can do the same job with a piece of rubber hose & a coffee cup.
Local Vette people have watched me do it and drove home with a smile on their face. Personally, I consider it "over-kill" because I can do brake jobs without it. But if you can't, then by all means, buy one.


PS- I also worked in an autoparts store.... United Auto Parts on Main St in Endicott NY. It's still there I believe. Fun job, but pay sucked. And we sold Delco parts so I never had any take-home pay. LOL

Tom

 

Thanks Tom!!! And here I thought I had "special edition" rear
calipers

Hey everyone....Tom still uses a crank in the front of his car to start his engine too!!!
Dang whippersnappers and their newfangled inventions. Next they'll be flying through the air in those flying machines.

Dep

 

Yes... but she seems to like to do that for me.
I am fortunate.

 

we are accomplishing the same thing...however if you raise the front above the top of the piston cylinder the air will seek to go up and out as opposed to being forced down and out...and air naturally will want to rise...anyway ..i'm back in town now and the house is filled full of mothers and inlaws and a returning college kid whos smarter then me now.....yikes i just may sleep out inthe garage...oh yeah to my point i may just play around alot out there this weekend with a level and digital camera and make a photo documentary...

 

My son and I stayed with the manual bleeding . At the beginning we
were getting fluild . Then we got some real bubbles they came out so
fast the brake hoses in the back begin to jump . We went around the car
three times , got good brakes , the best I ever had . Replaced both of
the rear hoses I notice the one had a bulge in it . Didn't realize so much
air got suck up in the system . I do want to thank you all for the helpful info .
I am going to purchase a Motive Bleeder . I'm sure there will be a next
time , the help that was given is greatly appreciated . I have
only two bleeders on each rear caliper . Thanks again .

 

Ok guys, i have a 76 and am sticking with my coffee cup and bleeder hose. I have gone around the car three times, i am getting clear fluid, no bubbles, but my pedal is spongy. I just put in all new metal and rubber lines and new calipers. Did not replace the master cylinder. I realized I forgot to bench bleed the master cylinder. :o
do I still need to try to bench bleed the MC?

 

you need to do this all over again.....bench bleeding at the MC will ensure there is no air left in it. There probably isn't any but you don't want to do this for a third time....

 

I don't see where you need to bench bleed the master cylinder again unless you let it run dry when replacing everything. Do you have manual brakes or Power? I see this is a new brake problem from another member. Maybe you should of started your own thread for this problem. Others trying to help out may think this is the original thread.

 

Dep well i'll stick to my original contention, heres a picture of drivers side rear with the car level....raising the rear of the car would make the caliper more horizontal compounding the air getting stuck in the top of the piston bores... i doubt you could raise it high enough to make it vertical without the car being flipped over... raising the front would move the front of the caliper up and lowering the rear which in fact would make it more vertical just as you are saying.....and my back "bleeder" is a plug. [IMG][/IMG]

 

Thanks for the pic Bob, but I am sticking to the FAQ of raising it 1 foot.
The closer to the top TOP of the pistion is WHERE you want the air because that's where the bleeder channel is.
We will have to agree to disagree

Dep