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I have changed the Master cylinder twice because the first one had a peddle, and when it sat over night it had no peddle. The second one has no peddle. Bench bleed. Seems like not enough pressure comes out of the lines at master? Pressure bleed the system and no air. All with car not running.
I read your comment about having power-bled the system and not finding any air coming out. This is one hell of a braking problem you have..
Ok, some years ago I had the same problem as you are experiencing (I'm in the UK). After a whole week of messing around continually bleeding and re-bleeding the system (and finding no air) I pumped the brake pedal until it pressurised and put a big, heavy bit of metal on it to keep it depressed overnight.
The next morning I removed that big lump of metal from the brake pedal and quickly checked it - it was rock hard. Two minutes later, the brake pedal was spongy again.
I then started on the wheel furthest away from the master cylinder. I removed the wheel and removed the brake pads and forced the brake piston right back into the calliper unit. I then used wooden wedges/wrenches in between the lip of the piston and the brake rotor to jam the piston calliper in place. The piston could not move outwards when the brake pedal was pumped.
I then bled the calliper unit on that wheel. It's a two man job: You want somebody to pump the pedal and keep it held down as you tighten the bleed nipple. Replace the brake pads and see if the pedal remains firm..
If not, move onto the next wheel (2nd furthest away from the master cylinder) and repeat the process. As a rule of thumb air finds its way into the longest runs of brake pipe simply because there's more unions/connectors in a longer length.
In my case after removing the brake pads, pushing the piston home and wedging it, then bleeding the calliper, the brake pedal became rock hard - it worked! And no, I didn't see any air bubble(s) in the bleed tube.
It's worth a shot - do it with every wheel in turn.
Another thing you can try first is to raise the rear of your vehicle on ramps/jacks (don't let a vehicle on ramps tick over .. the engine is oil is at an angle and won't be picked up by the oil pump.. you'll damage the engine. Put it on ramps and then switch it off..).
With the rear of the vehicle 'high' pump the brake pedal until it becomes hard then put something heavy on it to keep it depressed overnight. Slacken the bleed ******* on each rear calliper, put a cloth over them and 'hope' that because the rear of the vehicle is higher than the front end that the air will travel uphill and find its own way out. Yes, you'll lose a little fluid overnight.
In the morning tighten the bleed ******* and the pump the brake and pray ..
If not, try removing the brake pads and wedging them as described above..
You seem to know what your doing with tools in your hand. Keep going. Sometimes it's very difficult and time consuming, but you'll get there in the endI read your comment about having power-bled the system and not finding any air coming out. This is one hell of a braking problem you have..
Ok, some years ago I had the same problem as you are experiencing (I'm in the UK). After a whole week of messing around continually bleeding and re-bleeding the system (and finding no air) I pumped the brake pedal until it pressurised and put a big, heavy bit of metal on it to keep it depressed overnight.
The next morning I removed that big lump of metal from the brake pedal and quickly checked it - it was rock hard. Two minutes later, the brake pedal was spongy again.
I then started on the wheel furthest away from the master cylinder. I removed the wheel and removed the brake pads and forced the brake piston right back into the calliper unit. I then used wooden wedges/wrenches in between the lip of the piston and the brake rotor to jam the piston calliper in place. The piston could not move outwards when the brake pedal was pumped.
I then bled the calliper unit on that wheel. It's a two man job: You want somebody to pump the pedal and keep it held down as you tighten the bleed nipple. Replace the brake pads and see if the pedal remains firm..
If not, move onto the next wheel (2nd furthest away from the master cylinder) and repeat the process. As a rule of thumb air finds its way into the longest runs of brake pipe simply because there's more unions/connectors in a longer length.
In my case after removing the brake pads, pushing the piston home and wedging it, then bleeding the calliper, the brake pedal became rock hard - it worked! And no, I didn't see any air bubble(s) in the bleed tube.
It's worth a shot - do it with every wheel in turn.
Another thing you can try first is to raise the rear of your vehicle on ramps/jacks (don't let a vehicle on ramps tick over .. the engine is oil is at an angle and won't be picked up by the oil pump.. you'll damage the engine. Put it on ramps and then switch it off..).
With the rear of the vehicle 'high' pump the brake pedal until it becomes hard then put something heavy on it to keep it depressed overnight. Slacken the bleed ******* on each rear calliper, put a cloth over them and 'hope' that because the rear of the vehicle is higher than the front end that the air will travel uphill and find its own way out. Yes, you'll lose a little fluid overnight.
In the morning tighten the bleed ******* and the pump the brake and pray ..
If not, try removing the brake pads and wedging them as described above..
You seem to know what your doing with tools in your hand. Keep going. Sometimes it's very difficult and time consuming, but you'll get there in the end
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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
I did change both hoses I power bead the hole system, and there does not seem to be any air?I did change both hoses I power bead the hole system, and there does not seem to be any air?
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Most likely a failed master cylinder or vaccume leak to the booster. Here is how to check for a bad brake booster first with the vehicle off depress the brake pedal usually once or twice is sufficient but however long it takes to make the pedal as firm as possible now with your foot on the brake pedal pushing down start the car if the pedal moves your boosters not at fault it's your master cylinder or another problem if it doesn't move its most likely a booster problem
The first thing that comes to my mind would be whether or not you bled the master cylinder before you put it on the car? A lot of people don't know that needs to be done first.
If you didn't, then disconnect it from the brake system and bleed it until the fluid is bubble free. then reconnect it to the brake system and bleed the rest of the brakes. Hope this helps.
Yes and No...Replacing the master cylinder is a good idea, however, giving the vehicle that much pressure with old lines attached may blow out the old rusted lines. If you are going to replace the master cylinder, you may just want to replace the brake lines as well.
You need to check wheel cylinders, the only way that the brake peddle will go to the floor like that is if there is a lose of fluid pressure somewhere .
Unbolt, master cylinder from booster, the brake lines from the master cylinder, will flex enough to where you can put it over to the side, where you would be able to remove the booster.Then unbolt the 4 bolts under the dash and unhook linkage to brake peddle.
I just went to Brake Masters this morning and had them replace the Master Cylinder since I was experiencing the pedal very spongy and going to the floor. When they replaced the Master Cylinder and they gave me back the car, the brakes were still spongy and going to the floor. I addressed this to them and they took another look at it, but when I took it for a second time, the brakes were extremely spongy. It was almost like they gave me back my car in worst condition to when I brought it in. Can you help?
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.
I read your comment about having power-bled the system and not finding any air coming out. This is one hell of a braking problem you have..
Ok, some years ago I had the same problem as you are experiencing (I'm in the UK). After a whole week of messing around continually bleeding and re-bleeding the system (and finding no air) I pumped the brake pedal until it pressurised and put a big, heavy bit of metal on it to keep it depressed overnight.
The next morning I removed that big lump of metal from the brake pedal and quickly checked it - it was rock hard. Two minutes later, the brake pedal was spongy again.
I then started on the wheel furthest away from the master cylinder. I removed the wheel and removed the brake pads and forced the brake piston right back into the calliper unit. I then used wooden wedges/wrenches in between the lip of the piston and the brake rotor to jam the piston calliper in place. The piston could not move outwards when the brake pedal was pumped.
I then bled the calliper unit on that wheel. It's a two man job: You want somebody to pump the pedal and keep it held down as you tighten the bleed nipple. Replace the brake pads and see if the pedal remains firm..
If not, move onto the next wheel (2nd furthest away from the master cylinder) and repeat the process. As a rule of thumb air finds its way into the longest runs of brake pipe simply because there's more unions/connectors in a longer length.
In my case after removing the brake pads, pushing the piston home and wedging it, then bleeding the calliper, the brake pedal became rock hard - it worked! And no, I didn't see any air bubble(s) in the bleed tube.
It's worth a shot - do it with every wheel in turn.
Another thing you can try first is to raise the rear of your vehicle on ramps/jacks (don't let a vehicle on ramps tick over .. the engine is oil is at an angle and won't be picked up by the oil pump.. you'll damage the engine. Put it on ramps and then switch it off..).
With the rear of the vehicle 'high' pump the brake pedal until it becomes hard then put something heavy on it to keep it depressed overnight. Slacken the bleed ******* on each rear calliper, put a cloth over them and 'hope' that because the rear of the vehicle is higher than the front end that the air will travel uphill and find its own way out. Yes, you'll lose a little fluid overnight.
In the morning tighten the bleed ******* and the pump the brake and pray ..
If not, try removing the brake pads and wedging them as described above..
You seem to know what your doing with tools in your hand. Keep going. Sometimes it's very difficult and time consuming, but you'll get there in the end
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