I have replaced my master cylinder twice now, with salvaged cylinders, the second one looks great all seals looked good, very clean. but after bleeding all the brakes multiple times they are still going to the floor. Could it be something else or should I try bleeding again?
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When you say that the first master cylinder had no pedal, did that just suddenly happen?
A master cylinder has rubber seals inside - think of a bicycle pump - when the bicycle pump seal wears it becomes difficult to pressurise it. The same is true of a master cylinder.
A classic sign of a master cylinder with worn or perished seals is that it needs pumping a few times to pressurise but there is no leakage of brake fluid.
Prior to you changing the master cylinder had the level of the brake fluid dropped .. indicating a leak somewhere? Had you done any work on the brake pads/rotors?
Eliminate other causes of air getting into the braking system:
First thing to do is check the flexible brake hoses on each wheel. Get a friend to pump - and hold - the brake pedal while you inspect the flexible hoses. Check for leaks (obviously) but also look to see if each flexible hose 'bulges' anywhere along its length.
Also check each flexible hose to see if it is perished or wet with fluid.
A perished flexible hose can draw in air and cause no pedal/spongy pedal. The same is true with a flexible hose that bulges/balloons when under pressure.
It only takes a slight 'weeping' from a flexi hose or rigid pipe connection to allow air into the system. Check the rigid brake pipes too - especially where there is a connector/join.
Then remove the road wheels and look for the slightest fluid leak around caliper pistons.
The problem, I think, comes back to the original fault .. no pedal when your car had sat overnight. This is rather indicative of air getting into the system somewhere though not necessarily from the master cylinder.
Check for the slightest leak in the entire braking system. It only takes a small amount of air to get in and cause problems. The fact that you fitted a second master cylinder makes me think the problem could lie elsewhere.
Try bleeding the braking system. It's a 2 man job, but quite easy.
Here's a link that explains how to do it: How to Bleed Your Brakes
For some reason these vehicles you need to bleed brakes several times, had same problem, so air hangs up in lines somewhere it apears. When you say brakes sticks, describe it better, locked up, or dragging on rotors?
Hi P, The most usual cause of the brake pedal action becoming hard is a defective return seal in the brake master cylinder. When the brakes are depressed fluid is pushed into the wheel cylinders, activating the brake pads and shoes. After a few operations of the braking system the fluid fails to return to the master cylinder and with each further action the brakes become tighter. After the vehicle stands for some time the pressure gradually releases and frees the brakes. Have the brake master cylinder checked. It's good policy to replace the brake fluid once or twice a year as part of the major service. Regards John
1. What is the Brake Fluid Level?
2. Are you losing any Brake fluid at all? Are there any puddles or noticeable wetness on the ground or on the tires/wheels? With vehicle parked, the reservoir filled (overfilled), and engine running: pump the brakes and check on the ground and back sides (inside portions) of the wheels. Look for any brake fluid leaks.
3. Leaks from Calipers usually means a leak from the caliper piston. The rubber seals will be wet.
Leaks from Drums usually means a leak from the wheel cylinder.
4. In any case of leaks from the wheels - replace the calliper OR wheel cylinder.
For caliper leaks: change the brake pads, and clean the rotors with brake cleaner.
For drum leaks: clean the drum and brake hardware with brake cleaner, and replace the shoes.
5. If no leak is detected from the wheel area's: check under the Master Cylinder for wetness indicating a possible leak.
6. If no leak can be found: you MAY have a rear seal leak in the Master Cylinder which is pumping Brake Fluid into the Brake Booster (that large disk looking thing attached to the fire wall, attached to the Master Cylinder in front).
a. Use a large drip/catch pan under the Van in the area on the Master Cylinder.
b. Disconnect the brake lines from the Master Cylinder using a flair wrench.
c. Remove the two nuts (12 or 13mm?) attaching the Master Cylinder to the Brake Booster. If you have been using a lot of fluid, and have found no leaks, here is a good possibilty that all that brake fluid has collected in the Booster; so when you detach the Master Cylinder from the Brake Booster, all that fluid will come rushing out!
7. If there is Brake Fluid inside the Brake Booster: there is no cleaning that out. Brake Fluid is very caustic to the seals inside the Booster and should be replaced.
8. Of course the Master Cylinder will also have to be replaced.
9. After replacing the Master Cylinder/Brake Booster - make sure you get all that spilled brake fluid off the engine compartment area parts! I use a brake cleaner, then mild soap and then water to rinse. Clean any Brake Fluid off Paint imediatley as it will quickly dissolves finishes and paint.
10. If no leak is detected and the Booster is clear, there may be problems with the Booster One-Way Valve. This is attached to the outside of the Booster and has a hose from an "advance" connected to it. This maybe malfunctioning where you are losing power. Replace this first before deciding to replace the whole booster (in cases of NON-LEAKS ONLY). If that did not work, there may be inner seals inside the Booster that have failed. That means a new Booster.
11. In any of the above cases: Make sure you bleed the Master Cylinder correctly and bleed the brakes (at each affected wheel) correctly. Any air in the brake lines will decrease your braking proficiency or could result in brake failure.
Let me know if this helped or if you have any additional information or questions. Feel free to contact me at FixYa.com!
if you can see a good amount of wet brake fluid between the brake master cylinder and the brake booster. and you have been adding fliud often,you could have a bad master cylinder. it has to be replaced not rebuilt. you however may have a far more common problem, a rusted through brake line.have someone pump the brake pedal, than look under the car for a brake fluid leak ,repair as needed. than bleed the brakes for a good hard brake pedal
good luck chris
you can go to a salvage yard and find wrecked cars like it even the galant has the same reservior and find the diaphram chances are they won't even charge ypou for it.. good luck please rate this..thanks