brake bleed question,help needed

[mike weyman]

hi guys, replaced 4 calipers and 3 lines(back 3). the front brakes bled no problem, the back passenger side took about an hour, but i have yet to get fluid to the drivers side, this doesn't seem right to me. i'de guess the fluid should have gotten to the drivers side first(closer).the fluid level is dropping,so it's getting there eventually.
question is,would it be a fair assumption that the flex line is on it's way out??maybe not letting as much fluid through??
once i get all fluid i'll test them to see if they release properly.
does anyone have any experience with this?? please let me know. mike

 

[vmrod]

I did not replace my steel brake lines, but I did replace my flex lines and calipers. It took a while to get the brakes bled. It sounds like you are on the right track. Just keep adding fluid as needed. Once they were acceptable, I drove it around the block a couple times. (Physically driving the car really didn't do anything, but it was fun for me.) The car sat up a couple weeks, then I rebled them. They seem very good to me right now, but then again, I haven't even sat in the car for several months.

 

[cwerve74]

Just completed a 4 wheel brake rebuild plus several lines. It took just over two hours for the fluid to reach the back using just gravity to move it along. I just opened one of the bleed valves and put a hose and a collection bottle on and let it sit. When I got fluid I moved to the next wheel. Sounds like yours is taking a lot longer. Is the valve in the bake distribution block (the one on the frame rail under the master cylindar) open to the back? If the flex lines were not replaced and they are more than 5 years old I would also look there.

 

[mike weyman]

should there be more volume of fluid in the front as opposed to the rear??
I just finished bleeding the lines and there's copious fluid in the front, but there's less volume in the rear , but all four rear bleeders are consistantly slower ,and the two front are the same.is this what a proportioning valve does??brakes work in the rear , but have to be applied hard to get it to stop turning with the bar on the studs to hold it.maybe someone knows more about this,even if someone's done the same and it was fine , i'd be glad to know so i can commence the paint aspect soon as the sun is shining and i want to get this thing mobile.mike

 

[Vettehead Mikey]

There should be no difference, front to rear. The piston in the master cylinder is the same diameter throughout, so flow should be the same.

'75s don't have a proportioning valve, (common misunderstanding) they have a manifold equipped with a pressure/flow differential indicator. The indicator switch turns on the red brake warning light. There is no device that proportions pressure front to rear or side to side. Later years DO have a true proportioning valve, but I'm not sure in which year this started.

It is possible the pressure differential piston is jammed in it's bore and is restricting the flow to the rear.

 

[Culprit]

Howdy,

I recommend replacing the flex hoses - they are the weak link in the chain. The extra cost is almost nothing compared to what I'm sure it cost you to replace the calipers and steel lines.

I also highly recommend a product called speed bleeders and a vaccum pump. Here is the link to a similar past brake thread. Read my two posts in the thread and I hope it gives you some good info. http://www.corvetteactioncenter.com/forums/showthread.php?t=44819&highlight=speed+bleeders

Semper Fidelis,
Culprit

 

[mike weyman]

since it's all bled i'm going to put the wheels on and see how it works. if the rear brakes stick or act badly, i'll put in the lines.mike

 

[brusso]

The indicator switch turns on the red brake warning light. There is no device that proportions pressure front to rear or side to side. Later years DO have a true proportioning valve, but I'm not sure in which year this started.

It is possible the pressure differential piston is jammed in it's bore and is restricting the flow to the rear.

I think that you are on to something there. I had the same problem with mine. After I finally finished bleeding, I started the car and stepped on the brakes. I could feel the little spool valve "center" and then the brake light went out. I rebled the rears and noticed better flow.

 

[mike weyman]

i thought as much, the manual i have says if you break a line it automatically switches to the other set of breaks. the back bakes were capped off when i got it.mike

 

[Robin7TFour]

hello, anyone here use the vaccum pump type power bleeder. i just bought one yesterday to check my vac. advance. i am curious on how effective and fast it is.

thanks

Robin

 

[IH2LOSE]

From a person who hates to bleed brakes.


What type of fluid are you using? if its silacone it airates very very fast,Once the air is in it it takes a day to let it gas out.Meaning if your bleeding your brakes and catching the fluid in a container then pouring the caught fluid back into the master your wasting your time.

I have invested in a power bleeder from motive products.It takes an all day 2 person (if you lucky it will only take one day) frustating job of bleeding brake down to a perfect bleed in less then an hour.http://www.motiveproducts.com/05specials.html

 

[mike weyman]

dot 3 from a sealed container.just like on the lid.lol.i didn't recycle the once thru stuff,that's what zorb all is for, and besides i couldn't find a tube.

 

[Hib Halverson]

'75s don't have a proportioning valve, (common misunderstanding) they have a manifold equipped with a pressure/flow differential indicator. The indicator switch turns on the red brake warning light. There is no device that proportions pressure front to rear or side to side. Later years DO have a true proportioning valve, but I'm not sure in which year this started.

Far as I know, no disc brake C2 or C3 had a rear proportioning valve unless the car was optioned with J56. Non-J56 cars relied upon the smaller piston diameters in the rear for proportioning.