Loss of brake pedal pressure

[Strato56]

I've had this issue for a while now, I have brakes but the pedal goes almost to the floor. When I bleed them I get a good pedal again, but over time, 4-5 months, it losses pressure again. I just checked all the lines, reservoir, and master cylinder and don't see any evidence of leaks. All pads are adjusted properly, ebrake is also adjusted properly. I did not pull all the drums to check slave cylinders. When I restored the car, I did not bench bleed the master cylinder. Would that be the issue? Any help would be highly appreciated!

[66brm]

Are you driving the car much or is it just sitting for extended periods? I find if I don't use my cars often the same thing occurs, but after a couple of applications the pedal comes back to me, so to speak
_________________
Aust. RHD 66 Type 1
Aust. RHD 57 Type 1 Oval

[Strato56]

[andk5591]

My cars are parked all winter (November to March) - never have an issue with brakes. So I don't buy this coming from the car sitting. Bench bleeding wouldnt be an issue at this point. BUT are you getting air in the lines when you bleed them? Wonder if you have a loose connection.
_________________
D-Dubya Manx clone - 63 Short pan,1914.
Rosie 65 bug - My mostly stock daily driver.
Woodie 69 VW woodie (Hot VWs 7/12).
"John's car" 64 VW woodie - The first ever
Maxine 61 Cal-look bug - Cindy's daily driver.
Max - 73 standard Beetle hearse project - For sale
66 bug project - Real patina & Suby conversion
There's more, but not keeping them...

[128vw]

Do you have to add fluid before you bleed them? If not, you might have a bad master cyl.

[Strato56]

[Center Pin]

When you bleed them... more air from one corner? Same from all four? Is it an original style master or has it been upgraded to a dual circuit? What is the fluid level in the reservoir doing over time dropping/rising?

[Strato56]

[Strato56]

Ok, need some more help on this. Bled the brakes again and the left rear won't go down very easily. Very little fluid comes out also. Also the left front there is so much air and it never goes away, maybe one bleed and then it's back. Very small air bubbles. Seems like I have a leak somewhere sucking air into the system, I just can't see where. All the lines are tight and I don't see any evidence of leaks. Any thoughts on where to start? Would prefer to not replace all the brake lines and cylinders if possible... Thanks.

[Aussiebug]

The flexible fuel lines tend to swell internally with age, restricting fluid flow; so if they are more than about 5 years old that might be the cause of the hard-to-bleed rear wheel. Or there's crud behind the bleed valve.

It's just possible that a cracked flexible line might be causing the problem with the bubbles in the front wheel too, but unlikely - using the brake pedal would almost certainly cause a fluid leak at any crack. So the bubbles for the front are more likely to be coming from the MC itself - the pushrod activates the front brakes first, then the rears, so air COULD be getting in past a bad seal nearest the pedal. The left front getting more air into it is probably because it's a shorter run on a LHD car than the right front.

I presume that the brakes are properly adjusted so there is a few mm of freeplay in the MC pushrod? If not, the pushrod wont return completely to uncover the compensating ports to return fluid to the reservoir, and that can cause problems with bleeding the brakes.
_________________
Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.vw-resource.com

[3foldfolly]

I would remove all the drums and inspect the wheel cylinders.

[drscope]

Start by pulling your wheel cylinders. You live in a high humidity area and brake fluid will absorb moisture, so it isn't uncommon to have water in the fluid.

It usually sits in the wheel cylinders where it rusts or corrodes the inner walls of the cylinders.

Or, sometimes the bore of the cylinders just gets nasty enough that the piston actually sticks. If you have a sticking piston, it can result in the same sort of symptoms you are describing.

And while you have it all apart, if it's been a while since the flex lines were replaced it may be a good idea to replace all 4 of them as well. As already pointed out, they are a multi layer hose and you can't see what may be coming apart internally to restrict the flow.

Sometimes they won't allow pressure to go to the wheel cylinder and other times they won't allow it to return. They are cause of a lot of seemingly unusual brake problems.
_________________
Mother Nature is a Mean Evil Bitch!