Brake lines clogged?
Rennlist Member
Joined: Oct 2010
Posts: 4,932
Likes: 481
From: fairfield, CT
Just to put this out there....
Our car has one line to the rear, not two. There is a junction underneath the car just ahead of the axles on the chassis...where it splits to the two rear brakes. The right rear is all of one foot or so longer...
So pressure to both rears should be more or less the same. Typically when you have a slow bleeder, it's only the bleeder that is clogged. So check that first before getting crazy.
Our car has one line to the rear, not two. There is a junction underneath the car just ahead of the axles on the chassis...where it splits to the two rear brakes. The right rear is all of one foot or so longer...
So pressure to both rears should be more or less the same. Typically when you have a slow bleeder, it's only the bleeder that is clogged. So check that first before getting crazy.
Racer
Joined: May 2006
Posts: 290
Likes: 5
I know a few cases of it having been pushed through the entire system but it was used as a last resort with the alternative being replace everything. On a C2 I would be concerned about getting it completely out of the brake master cylinder? I have only used it on calipers prior to rebuilding. If your pedal is hard and your pads are wearing evenly, or the issue is the spring plates, I would just stick with 2 liters of DOT4 to flush the brake & clutch lines. Can't imagine introducing a fluid as preventative maintenance that has the potential to contaminate the entire system.
I wouldn't be comfortable with anything besides brake fluid, but I have read about using DA. I too don't like the idea of getting anything else in the master cylinder, and in our case the ABS unit. I'm no chemist, but isopropyl and denatured alcohol seem to have minimal lubricity compared to brake fluid, and I'd worry about any rubber seals getting wonky.
1st Gear
Joined: Sep 2018
Posts: 1
Likes: 0
The hard lines can always be flushed or blown out clean with air. Most likely the reduction in flow you noticed while bleeding is caused by the rubber flexible hose either delaminating or swelling or deforming in some other manner, thus reducing the ID of the hose. I have personally experienced this several times, and the fact that you've already replaced the flexible lines makes them even more suspect. For some reason it seems like the OEM hoses last far longer than any replacement I have tried.
You are correct that hydraulic pressure in a closed system will equalize and will not compress, but the second you opened the bleeder screw you have an open hydraulic system which will flow at different rates depending on pressure applied and length and diameter of lines. Most likely that caliper that bled slowly has a restricted supply of fluid and is slow to apply and then slow to release, which could explain the noise you speak of coming from the rear of the car. Being a rear caliper, as opposed to a front, you may not notice any uneven braking performance from a hose that is restricted, and possibly even blocked completely.
Also brake fluid will absorb moisture in the form of humidity from the air, which will eventually render it into the jelly someone spoke of. It can be flushed from lines with new fluid, but always keep fluid in a sealed container with as little air space as possible (I.e, a new bottle as opposed to one with only 20% left in it). The only exception to this is the high performance silicone brake fluids which are not compatible with a traditional DOT1-5 system.
Just wanted to jump in and share my experience with everyone, hope this helps.
Cheers,
NB
You are correct that hydraulic pressure in a closed system will equalize and will not compress, but the second you opened the bleeder screw you have an open hydraulic system which will flow at different rates depending on pressure applied and length and diameter of lines. Most likely that caliper that bled slowly has a restricted supply of fluid and is slow to apply and then slow to release, which could explain the noise you speak of coming from the rear of the car. Being a rear caliper, as opposed to a front, you may not notice any uneven braking performance from a hose that is restricted, and possibly even blocked completely.
Also brake fluid will absorb moisture in the form of humidity from the air, which will eventually render it into the jelly someone spoke of. It can be flushed from lines with new fluid, but always keep fluid in a sealed container with as little air space as possible (I.e, a new bottle as opposed to one with only 20% left in it). The only exception to this is the high performance silicone brake fluids which are not compatible with a traditional DOT1-5 system.
Just wanted to jump in and share my experience with everyone, hope this helps.
Cheers,
NB