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I have a 1990 Honda Civic lx. When I first start driving everything is fine after a while of driving and braking the calipers wll tend to engage on their own and the brake pedal becomes very hard there are times when I can keep driving and they will disengage after abit but there are times I have to pull over turn of the car and wait for a few minutes and the calipers will release and its only the front. I have replaced both calipers in the front and brakes hoses, I also replaced the rear drums shoes , hoses and brake cyliders and continue to have this problem. I put a new brake booster, master cylinder a year ago. also replaced the engine a year ago. can aytone help going nuts
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See if Eric’s comment in this post helps.
thanks I will try that. its something applying pressure to the calipers so im thinking booster or master cylinder, they were both replaced a year ago.
Could this also happen if the master cylinder seal was put in the wrong way round, or if it wasn’t connected properly to the rod that comes from the brake pedal?
I am open to all possibilities gone take off the master cylinder and take a look at it this weekend. I checked the booster for leaks and all vacuum lines not a single leak anywhere. stumpped
I would check to see if there is fluid spurting up thru the master cylinder reservoir when an assistant presses the pedal. If no fluid its a possibility your pedals out of adjustment and blocking the vent ports. Then again just having too much fluid in the reservoir,or contaminated fluid can also be the culprit. Make sure both vent ports are spurting fluid.
no squirting of fluid at all, re bleed the brakes and no problem there fluids flowing just fine. took a look at the manual and it says the brake pedal should be 6in. from floor when I check my pedal is only 4 in from floor could this be the culprit. I replaced the booster and master cylinder when I replaced the motor last year also, vent ports????? thanks
If the vent ports are blocked for any reason the brakes may self apply.Expanded hotter brake fluid needs to be able to return back into the reservoir. To check, look into the top of the reservoir while someone is pressing the pedal. If you do not see fluid returning,spurting back in they are blocked. I would adjust the pedal to a higher level if the fluids not returning. FIRST check to see if the fluid is at the right height,If the brakes are half worn the fluid should be half full.To much fluid also has no room to expand and can cause self-apply. Always DOUBLE CHECK they are working properly before you drive .
ok I will do that now the vent ports are located in the booster correct cause my MC has two lines going out to a proportioning valve then from there to all 4 brakes. my understanding is that this valve mainly supports the rear brake shoes correct. so by adjusting the brake pedal height might correct my problem and how will I know when and if its correct do I need to test it everytime I adjust it
Check out Eric’s you tube video when he did his brother’s Honda’s master cylinder swap, it has a lot of good info for you!
I know you’ve replaced a,lot of stuff in the brakes, but are you sure the caliper guide pins are lubed? That can cause it as well.
Is the fluid returning back into the Master Cylinder when the pedal is pushed? If not adjust the pedal higher until it does. If the fluid gets hot it expands.If it can not expand back to the reservoir it expands pressure on the brakes. The vent holes are where the fluid retuns in the reservoir not the booster.
You said your pedal height was only 4 inches while the specification calls for 6 inches. Can you pull the pedal up to the 6 inch height?
If the pedal isn’t returning to the full height it won’t allow the piston in the master cylinder to return far enough to uncover the return ports.
I wouldn’t adjust the pedal. Rather, I would find out why the pedal isn’t returning all the way. Is there a return spring that is broken or disconnected? Is something obstructing the pedal?
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