Brakes breaking.

[amcordo]

Hey all!

I've got a dual cylinder brake system. Just recently it started losing fluid somewhere in the system (I had no pressure in the brakes when I used it today, which is the first time I've ever had to pump them). Where are the weak points in the system?

I ask because it's starting to get colder outside, so the faster I can diagnose the problem the better when I'm crawling around under it. So any suggestions that at least point me in a place to look first are welcome!

There are no noticable symptoms with a casual glance (without getting underneath). So no puddle under the truck where the MC is, and no fluid on the pedal.

[Nium]

Check the under and around the brake master cylinder. If no fluid around master check the wheel cylinders.

[greenmeanie]

This will sound facetious but the weak points are anywhere there is a seal/moving part or corrodable surface.

As far as diagnosis goes you say you managed to stop by pumping but have not noticed fluid loss.

Start with the cheap and simple stuff. Really obvious is to make sure you have fluid in the reservoir and look at its colour. Black indicates your seals are on the way out. Dark, honey brown means your fluid is old which should not cause failure by itself but the age can allow for more water in the system. Adjust your brake shoes per the manual and eliminate drum/shoe wear.

Get under the truck and examine all the lines hoses and joints for leakage. Do the same for the master cylinder. Pull the drums and inspect the brake cylinder seals. This will truly eliminate external leaks as the source of your problem. At this point, if you are an optimist, you can bleed the brakes and see if the problem goes away as it may just be an air bubble. Air, however, doesn't just get into the system magically so you will most likely be fixing something soon anyway even if you do get a good pedal.

If you still need to pump after bleeding and have no fluid leaking then it would indicate fluid is bypassing a seal preventing full pressure being applied. This puts you into the realms of stripping out and overhauling the master cylinder. Use good quality seals (I.e. avoid anything that says Britpart or suggests it has been in the company of their rubber stuff) or you'll be doing it all again soon.

Of course, I like to overhaul systems rather than subassemblies and as you will be going through the bleed process (Fun on 11" twin leading show drums) I would use this opportunity to examine and replace as necessary the wheel cylinder seals and rubber hoses too.

[amcordo]

There IS a loss of fluid, but the problem is that I don't know where it's going. The reservoir keeps getting low. Thanks for the heads up though!

This will sound facetious but the weak points are anywhere there is a seal/moving part or corrodable surface.

As far as diagnosis goes you say you managed to stop by pumping but have not noticed fluid loss.

Start with the cheap and simple stuff. Really obvious is to make sure you have fluid in the reservoir and look at its colour. Black indicates your seals are on the way out. Dark, honey brown means your fluid is old which should not cause failure by itself but the age can allow for more water in the system. Adjust your brake shoes per the manual and eliminate drum/shoe wear.

Get under the truck and examine all the lines hoses and joints for leakage. Do the same for the master cylinder. Pull the drums and inspect the brake cylinder seals. This will truly eliminate external leaks as the source of your problem. At this point, if you are an optimist, you can bleed the brakes and see if the problem goes away as it may just be an air bubble. Air, however, doesn't just get into the system magically so you will most likely be fixing something soon anyway even if you do get a good pedal.

If you still need to pump after bleeding and have no fluid leaking then it would indicate fluid is bypassing a seal preventing full pressure being applied. This puts you into the realms of stripping out and overhauling the master cylinder. Use good quality seals (I.e. avoid anything that says Britpart or suggests it has been in the company of their rubber stuff) or you'll be doing it all again soon.

Of course, I like to overhaul systems rather than subassemblies and as you will be going through the bleed process (Fun on 11" twin leading show drums) I would use this opportunity to examine and replace as necessary the wheel cylinder seals and rubber hoses too.

[Sputnicker]

If you don't see evidence of fluid leaking anywhere else, it may be a leaky master cylinder that is leaking into the servo. Try unbolting the master from the servo and pull it back a ways (with brake lines still attached and see if the fluid runs out.

[amcordo]

Great! Thanks!

If you don't see evidence of fluid leaking anywhere else, it may be a leaky master cylinder that is leaking into the servo. Try unbolting the master from the servo and pull it back a ways (with brake lines still attached and see if the fluid runs out.