65 C10 Brakes Question

[Daron Craig]

On my 65 I installed a new master cylinder. I bench bled it first. I ran all new hard lines. There are 3 soft lines one at each front wheel, and one that transitions from the hard line along the passenger side frame to the a tee that goes to each rear wheel with hard line. Trying to bleed the system I cannot get the rear to flow. It moves fluid, but does not come out like the front. I cannot get a good brake pedal feel either. Am I missing anything?

[scottofksu]

You might add what style of brakes you are running - like have you converted anything to disc brakes or are you still running a full drum setup. You might also want to provide the specifics on the master cylinder you purchased. They have different bore diameters for different applications and will include a proportioning valve for disc applications even if only the fronts have been converted to disc brakes and especially if it has been converted to discs all around. Additionally, powered versus manual brakes like different leverage ratios from the pedal (i.e., 6:1 to 7:1 for front drums and 4:1 to 5:1 for front disc brakes).

[Daron Craig]

It is still drums all around. Stock size. I replaced all the components, springs, shoes, wheel cylinders, and so on. Master cylinder is stock replacement from orielly's. No booster or anything.

[1964FarmFreshC10]

That's a very simple 1 circuit system so you would need to identify where the restriction is.

The rear brake line is smaller than the front so flow will be slightly lower but still should be good.

If both rear cylinders are the same I would start by disconnecting the flex line at the rear axle and see if you get decent flow there. then move forward to the T junction at the right front wheel.

[Daron Craig]

Front flow is great. Rear wheels are hardlined to the wheel cylinder from the tee on the axle. There is flow, but it doesn't FLOW out like the fronts. I don't see any leaks anywhere either.

[theastronaut]

Originally Posted by 1964FarmFreshC10

That's a very simple 1 circuit system so you would need to identify where the restriction is.

The rear brake line is smaller than the front so flow will be slightly lower but still should be good.

If both rear cylinders are the same I would start by disconnecting the flex line at the rear axle and see if you get decent flow there. then move forward to the T junction at the right front wheel.

Flow through a smaller line has the same volume of fluid because the master cylinder is moving a fixed volume of fluid on each stroke, and that amount has to move through the line no matter what size the line is. 3/16 vs 1/4 isn't enough of a restriction to slow down the fluid enough to matter at the pressure and volume the brakes work at.

[Southcity]

If I understand the info provided to date correctly, all new hard lines but the soft line (rubber hoses) have not been replaced? If that is the case, inspect the condition of that rear rubber hose. Given that you have replaced just about everything except the rubber hose in the system, do a careful inspection of them, consider potentially replacing them as well if they are old/brittle etc.

[jayoldschool]

The rear soft line, frame to axle, plugged when bleeding my brakes after a wheel cylinder replacement. Changed line, bled out perfectly. Couldn't blow through the line after I took it off.

[Daron Craig]

So, all hard lines, soft lines, tees, and fittings are all new as well. Basically all components of the brake system are new.

[jayoldschool]

Originally Posted by Daron Craig

So, all hard lines, soft lines, tees, and fittings are all new as well. Basically all components of the brake system are new.

Disconnect the soft line that connects to the splitter on the rear axle. Try and bleed, see what you get. Troubleshoot based on flow results.

[64shortbox]

On the hard lines you replaced - did you use stainless steel brake lines? If so, I've read read where some people weren't able to get the flared ends to seat properly and they were sucking air. Just a thought.

[Daron Craig]

Originally Posted by 64shortbox

On the hard lines you replaced - did you use stainless steel brake lines? If so, I've read read where some people weren't able to get the flared ends to seat properly and they were sucking air. Just a thought.

Yes sir I got the stainless line kit from classic industries. I did use line wrenches and torqued each connection pretty good. I don’t see any leaks. Are you saying could be sucking air even with no leaks?

[64shortbox]

Yes, that's what I read in a couple of posts on my Pontiac site. That stainless lines might not leak brake fluid but could still suck air. I too planned on using stainless brake lines on my 62 Pontiac until I read several posts about people having problems with stainless brake lines. Something about the flair ends not being perfect and no amount of tightening could get them to seal properly. I'll dig through the archive's on my Pontiac site and see if I can find the reviews & I'll post them here for you.