Brake pedal tiny rattle/engagement gap on zero pressure - LotusTalk - The Lotus Cars Community
 
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post #1 of 5 (permalink) Old 09-03-2019, 05:11 PM Thread Starter
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Brake pedal tiny rattle/engagement gap on zero pressure

Hi there. My brake pedal has about 1mm of play before it fully engages, which is enough to be noticeable and make a small rattling sound when going from zero pressure to any pressure. Climbing around under the dash, it seems like it’s just that small bit of play around the yoke, where the pin runs through the yoke. I’ve done all the adjustment I can think of to get it a bit tighter, I am thinking now that I need to do something to make the pin slightly bigger or maybe need a new bushing or something. Does anyone know what I’m talking about, or have any other thoughts? This write up gives a good summary of what the yoke looks like and how to adjust it generally, but this doesn’t address the very small bit of play in the yoke itself: http://www.sandsmuseum.com/cars/elise/experience/maintenance/brakes/brakeadj.html

Thank you!
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post #2 of 5 (permalink) Old 09-04-2019, 07:21 AM
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The play and rattle is likely in the pin that holds the yoke to the brake pedal. No amount of adjusting the length of the push rod will change the play on the yoke pin. I would try removing the pin and putting a small amount of grease on it to dampen the rattle. There has to be some small amount of play in that joint for it to operate smoothly.
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post #3 of 5 (permalink) Old 09-04-2019, 01:14 PM
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The brake pedal on my '05 seems to have a lot of lost motion before braking begins. I'm wondering if the pedal pushrod is adjusted too short.
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post #4 of 5 (permalink) Old 09-05-2019, 12:21 PM
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Quote:
Originally Posted by steelypip View Post
The brake pedal on my '05 seems to have a lot of lost motion before braking begins.
Not sure how much "a lot" is, but there has to be some amount of pedal travel. The master cylinder has a hole between the cylinder bore and the reservoir. This does two things. 1- It allows fluid from the reservoir to automatically top off the system as brake pads wear down. 2- it allows expansion of hot fluid. When you press the brake pedal, the master cylinder piston is pushed past the hole (lost motion) and seals the system, that is when pressure is allowed to build and operate the brakes. When heat from the brakes heats up the fluid, the fluid expands. If the piston does not move back and open that hole, the expanding fluid will pressurize the system, applying the brakes and locking them.

If your lost motion is more than normal, it could be due to old fluid, air in the lines, or the caliper pistons being knocked back from warped rotors or bad wheel bearings.
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post #5 of 5 (permalink) Old 09-07-2019, 10:38 AM Thread Starter
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Originally Posted by TedR View Post
The play and rattle is likely in the pin that holds the yoke to the brake pedal. No amount of adjusting the length of the push rod will change the play on the yoke pin. I would try removing the pin and putting a small amount of grease on it to dampen the rattle. There has to be some small amount of play in that joint for it to operate smoothly.
Thank you for the reply I think youre right. Is everyones like this or is the looseness in mine unusual? Ill try a little grease, I suppose in theory I could buy a new Clovis and pin with tighter tolerances somewhere but not the most straightforward thing...
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