Lost brake pressure after m/c change - Page 2 - LotusTalk - The Lotus Cars Community
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post #21 of 28 (permalink) Old 10-12-2015, 07:54 PM
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So you are saying adjust from where the brake pedal connects to the brake booster and give it more slack/play? Would this be because the old m/c was a bit more worn and the new one is in well... new condition/not worn out. Do you happen to know where exactly to adjust it, because from looking at the old m/c there doesn't seem to be anything to adjust on it. Also would loosing the m/c from the booster do any good?
If your brakes are locked loosen the master cylinder to booster nuts and the brakes should release if it is the booster x dimension. You should not have had to draw the master cylinder down to the booster with the nuts, that is a wrong part. The master cylinder should have easily sat flush to the booster with no effort. That pop you heard was bad. Like broken booster bad.

Adjusting play at the pedal end will only work if the brake booster is being applied by the pedal which only happens if something is holding the pedal down.

Was the new master cylinder identical to the old one? At the back of the master cylinder the depth the booster pushrod engages the master cylinder is critical. Did the booster output rod pull out when you removed the master cylinder?

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post #22 of 28 (permalink) Old 10-12-2015, 08:15 PM
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I just watched your master cylinder install video. That part where you have to push on the master cylinder and it springs in and out, and you have to hold it in to start the nuts, that is your problem. Lucky you got it to bleed at all because it is applied as far as you pushed it into the booster. The old one did not look like it came out that way. Part is wrong or built out if spec. If the old one came out that way (hard to tell in the video) then the booster was applied or broken. I am still concerned about the pop noise you heard, might have broke the booster power piston.

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post #23 of 28 (permalink) Old 10-12-2015, 10:18 PM Thread Starter
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Quote:
Originally Posted by Wmangm View Post
If your brakes are locked loosen the master cylinder to booster nuts and the brakes should release if it is the booster x dimension. You should not have had to draw the master cylinder down to the booster with the nuts, that is a wrong part. The master cylinder should have easily sat flush to the booster with no effort. That pop you heard was bad. Like broken booster bad.

Adjusting play at the pedal end will only work if the brake booster is being applied by the pedal which only happens if something is holding the pedal down.

Was the new master cylinder identical to the old one? At the back of the master cylinder the depth the booster pushrod engages the master cylinder is critical. Did the booster output rod pull out when you removed the master cylinder?

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Originally Posted by Wmangm View Post
I just watched your master cylinder install video. That part where you have to push on the master cylinder and it springs in and out, and you have to hold it in to start the nuts, that is your problem. Lucky you got it to bleed at all because it is applied as far as you pushed it into the booster. The old one did not look like it came out that way. Part is wrong or built out if spec. If the old one came out that way (hard to tell in the video) then the booster was applied or broken. I am still concerned about the pop noise you heard, might have broke the booster power piston.

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The m/c I ordered was from mylotusgarage, and is identical to the one I removed. I take it next step is removing m/c and re inspecting things. I didn't see any rod coming from the brake booster when I installed the new m/c.
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post #24 of 28 (permalink) Old 10-13-2015, 08:07 AM
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The m/c I ordered was from mylotusgarage, and is identical to the one I removed. I take it next step is removing m/c and re inspecting things. I didn't see any rod coming from the brake booster when I installed the new m/c.
When you pull it apart measure the depth of the cup where the booster pushrod engages to the mounting flange face (booster contact part) of the master cylinder and compare it to the master cylinder that came out. It would not be the first time a part was made out of spec. If it is the same between parts then the booster output rod is pushed out for some reason. There should be minimal or zero preload on the master cylinder. Any preload causes the master cylinder to be applied and the result is the issue you are having. I don't know if lotus might have cheated using a little preload to shorten brake pedal stroke but your video looked to be a half inch or more which is way too much. There is a chance that the booster output rod is adjustable but if it was not mentioned in the manual it is preset and don't mess with it.



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post #25 of 28 (permalink) Old 10-13-2015, 02:26 PM Thread Starter
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So obviously I am new to brake systems, can someone tell me what is broken inside the brake booster and what it does and how I probably caused this to happen? Does this mean my old m/c might not have been bad and this part of the system was already broken or did I just mess it up by installing m/c incorrectly? I'm getting the vibe I did it, so feel free to lay it on me.

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post #26 of 28 (permalink) Old 10-13-2015, 02:34 PM Thread Starter
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and here it is...
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post #27 of 28 (permalink) Old 10-13-2015, 08:39 PM
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That is the input rod and power piston assembly. It did not slide into the master cylinder when you installed it. The pop you heard was when it snapped. I am actually amazed and a little concerned that you were able to drive it at all. The booster needs replaced, the master cylinder may have rear seal damage and may need the input cup replaced so it will nest into the booster. See if there is any brake fluid leaking at the back of the master cylinder. If not then maybe ok but better if you can get a seal kit. The old master cylinder input cup may be able to be swapped into the new master. Take the old master cylinder and give it a pull and see if it comes out nice. Sh*t happens, chalk this one up to experience and now you know what not to do next time.

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post #28 of 28 (permalink) Old 10-13-2015, 10:20 PM Thread Starter
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That is the input rod and power piston assembly. It did not slide into the master cylinder when you installed it. The pop you heard was when it snapped. I am actually amazed and a little concerned that you were able to drive it at all. The booster needs replaced, the master cylinder may have rear seal damage and may need the input cup replaced so it will nest into the booster. See if there is any brake fluid leaking at the back of the master cylinder. If not then maybe ok but better if you can get a seal kit. The old master cylinder input cup may be able to be swapped into the new master. Take the old master cylinder and give it a pull and see if it comes out nice. Sh*t happens, chalk this one up to experience and now you know what not to do next time.

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You actually made me laugh when you said you were amazed haha. I'm just glad the mystery up to this point is over, my next question is do people cross reference the p/n off parts like the m/c and booster so it can be purchased locally or is this an actual Lotus part? I will have to go down tomorrow to see whats entailed in actually removing the booster, as once again, I've never done it before. I will also check my manual
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