Air in Brake Lines

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

avslash

Full Access Member
Joined
Nov 22, 2011
Posts
1,255
Reaction score
1,101
Location
The Lone Star State
I noticed on my last trip that my brakes were taking a bit too much pedal travel for my liking. I followed a couple of on-line tutorials and zeroed in on a bad master cylinder. No biggie. Ordered one in and replaced and bled brakes. Pedal travel was as new, and all seemed good.

Over the course of a week or two, I then noticed that pedal travel increased back to about where it had been prior to replacing the master cylinder. I thought I must have inadvertently left some air in the lines, so I bled them again and all seemed good with a nice firm pedal.

Fast forward about 8 weeks and I have repeated that process about 5 times, so I assume I must be getting air into the brake system from somewhere. No other related symptoms. Pad and rotors are good. Fluid is full (and fresh, obviously). No leaks; level stays right at max on the reservoir. When freshly bled, the brakes work like new. ABS works. No error codes. No squeaking or squealing. Etc, etc.

Any tips on how to diagnose exactly where air might be getting in? My pressure bleeder is tired....
 

ryanjl

Full Access Member
Joined
Dec 31, 2015
Posts
2,994
Reaction score
1,771
Location
KCMO
When you have to bleed your brakes, does any one caliper produce more air than the others?
 

avslash

Full Access Member
Joined
Nov 22, 2011
Posts
1,255
Reaction score
1,101
Location
The Lone Star State
When you have to bleed your brakes, does any one caliper produce more air than the others?

Good question. I should have thought of that. The two rear wheels have the most air. Both fronts are basically nothing when bleeding. Just the tiny little bubbles that tend to seep around the threads of the bleeder screws.
 

ryanjl

Full Access Member
Joined
Dec 31, 2015
Posts
2,994
Reaction score
1,771
Location
KCMO
I have no idea how the LR4's brake lines are routed. Back in the day, the front two wheels would have independent lines but the rear would share one line that ran all the way to the back axle, where it would split and run to each wheel. No idea whether the LR4 does this. Probably not. The way Rover's traction control pulses brakes makes me wonder if each back wheel has its own brake line all the way to the booster.

But if both back wheels have air and the fronts do not, makes me wonder what the rears share in common but do not share with the front.
 

Rover Range

Full Access Member
Joined
Jun 13, 2022
Posts
503
Reaction score
273
Location
Texas
You can wrap teflon tape on the bleeder fitting (correct word got censored) to eliminate the air leaks.

Also, when bleeding.

Engine running.
Install the bleed tube to the brake caliper bleed screw and immerse the free end of the bleed tube in a bleed jar containing a small quantity of brake fluid.
Hold the bleed container at least 10 inches above the caliper that is being bled.

Start with the brake caliper furthest away from the master cylinder.
1) RR
2) LR
3) RF
4) LF
 
Last edited:

avslash

Full Access Member
Joined
Nov 22, 2011
Posts
1,255
Reaction score
1,101
Location
The Lone Star State
You can wrap teflon tape on the bleeder fitting (correct word got censored) to eliminate the air leaks.

Also, when bleeding.

Engine running.
Install the bleed tube to the brake caliper bleed screw and immerse the free end of the bleed tube in a bleed jar containing a small quantity of brake fluid.
Hold the bleed container at least 10 inches above the caliper that is being bled.

Start with the brake caliper furthest away from the master cylinder.
1) RR
2) LR
3) RF
4) LF

Teflon tape is a good idea.

I'll trace the lines back next, I guess. It is getting in there somewhere. I am not an inexperienced brake bleeder. Too many years of wrenching on Porsches for that.

The service manual specifies that it be bled with the engine running, btw.
 

Latest posts

Members online

Forum statistics

Threads
36,178
Posts
216,949
Members
30,438
Latest member
MosheFrost
Top