Got a problem with my brakes
I had a break fluid leak, repaired it, and bled the brakes. But now on first brake, the brakes are fine, on second brake, the brakes are soft, on the third attempt there are almost no brakes, on the fourth attempt the brakes are fine again, what can be the problem?
Astra - 1998 Opel Astra 1.8
Answers & Comments
Need more information about the brake fluid leak and what you needed to do to rectify it.
Brake pedal feel should be fairly consistent and when it isn't it does indicate something mechanical is sticking and freeing itself intermittently.
I suggest you inspect all aspects of the braking system systematically and thoroughly to ensure everything is serviceable. Pay attention also to the correct adjustment of the pedal linkage and if the master cylinder or brake booster servo has been changed at any time, the master cylinder clearance should be checked.
Check also wheel bearings for excessive free play.
How do you check the clearance on the master cylinder?
The problem might be with the rear cylinder if the spring between the pistons is missing, weak or broken. Sometimes the outer dust covers can be so strong they act like springs and pull in the pistons.
Checking master cylinder clearance is necessary to ensure the master cylinder can return fully. Manufacturers and dealers use service tool gauges to check and set the clearance but otherwise a little careful measuring is required.
Sometimes the clearance is adjusted by inserting shims between the master cylinder and booster but mostly the booster pushrod is adjustable. It is important to ensure the pedal linkage is correctly adjusted and fully returned. Basically the amount of protrusion of the booster pushrod must be around 10 thousandths of an inch (check vehicle specs for exact figure) less than the distance from the master cylinder mounting face to the bottom of the dimple in the centre of the master cylinder piston.
Sounds like you may have air in the lines. I understand that you've bled the brakes - but this is a common situation. Happens on manual transmission lines sometimes as well (both are hydraulic fluids).
The bleeding procedure for a lot of newer vehicles is changing - even on some of the older models now. You'll want to make sure you have the exact proper system at hand to use or else there can be issues.
If you are absolutely positive that your brake bleed technique is correct - your first step should be to perform the bleed again - starting with right rear (or whichever side is furthest from the master cylinder) and work your way to the other side of the back and then diagonally to the caliper directly across from master c - then on to the caliper right below it.
If re-bleed doesn't work - just comment and I'll go further.
All The Best, Justin McCartney
17 South Industries, LLC
Hi there.
When i push my brake pedal in there is a swich noice. i tested it and when you push the pedal in there are air sucked into the booster. is that right?
Yes - your brake booster helps with the vacuum of the car among other things on other models. Some vehicles it actually would be used to help the power steering pump - Older Chevys K5 Blazers, etc. While your brake booster is doing it's thing - so is your master cylinder. You should hear a spongey kind of sound when you hit the brakes without the car on (the brake system is hydraulic - so it will function with or without the vehicle on if it's in proper order). That's natural. Not only is your brake booster performing its job - when you hit that pedal the mechanism is forcing the ram into the master cylinders housing - which makes the kind of sound - like the hydraulic arms for hatchback lids - it's audible on it's own without being attached to the brake booster - bench testing.
On Ford Rangers - 90's not sure how far past - if you got air in your clutch lines - you had to remove the master cylinder completely. Behind the clutch pedal - from that arm forward - and it can get tedious. You disconnect there - and at the slave cylinder (a coupling around the input shaft of transmission in bell housing) you get the line off - and you pull out the master cylinder - piston rod, reservoir (still attached) and line that would go to transmission.
Once out? Well - the reason you have to disconnect all of that and remove it to bleed the air out of the lines is because of the way the system is routed. Air bubbles are naturally going to rise. They'll cling to the walls of the hose as well - installed - the apex of the system is wrong. This is Factory repair instructions - is to remove entire assembly - get the reservoir up higher than the rest of the assembly - and literally take a screwdriver and tap the line repeatedly up and down to the master cylinder and all the way down to the end of the line. As you do that - you'll see the air bubbles finally coming up through the fluid you'd never be able to get out if you don't pull the entire assembly.
Always have to watch fluid level in reservoir - if you're on the second brake - and the fluid gets below minimum - you can pull air into the line. The other brakes left can bleed fine, too - but once you try and test it - you'll know there's an issue. Bleed, Bleed, Bleed, Check the Reservoir and top it off.