I have a 1987 Honda Accord 2 door hatchback. 2.0 fuel injected 4cyl automatic. 220.000 miles. No one and I mean no one can figure out what's wrong. When the car is NOT running, the brake peddle will pump up, but as soon as I start the engine it goes to the floor. I have replaced the 2 rear wheel cylinders in the rear drum brakes. There are no leaks in the brake system at all. I have put a new power brake booster in, and a new Master brake cylinder in it. The brake peddle still goes to the floor when the engine is started. Can't drive it until the brakes work again. It's been 4 weeks now. No mechanics here can fix it. PLEASE HELP US figure it out. I don't know of anything else to replace. Thank You, Gary.....P.S. Love your youtube videos.
Where did you buy your brake master cylinder? I got made from Advance Auto. I had problems with the brake master cylinder three times in my '79 Pontiac, before I got one to work. They're made in Mexico, and apparently they're not very reliable. I even bought an OEM model off of Amazon that was brand new, and that didn't work, either.
Brake hoses can fail internally, or balloon out under pressure, when they get old despite looking OK on the outside. If original the brake hoses on that car are way overdue for replacement after 37 years.
It has all metal lines. Does that make a difference?
It has all metal lines. Does that make a difference?
What about the lines going to the wheels? Have the stock rubber hoses been replaced with aerospace-grade flexible hydraulic lines?
Oh, Right. I forgot about the short rubber hose going to the front disc brakes. They would need then because the wheels turn. What a dummy I can be sometimes. I am 70 so I can use that as a reason that I forgot, LOL. I will check them in the morning. Thank You for reminding me.
There will be rubber hoses in the rear as well due to movement of the rear suspension. All should be replaced due to age whether they are the cause of this particular problem or not.
Hmmm interesting. Since you have drum brakes did you adjust the drum brakes so the drums are not loose? You can easily tell if your drum brakes are loose by engaging the emergency brakes. If the emergency brakes are loose then you need to tighten and adjust the drum brakes. Also did you bleed air from the brake lines? Air trapped inside the brake lines can cause brake pedal to go to the floor. Check and make sure you did these following tips down below as well.
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Brake Fluid: Ensure the brake fluid reservoir is filled to the correct level. Also, check for any air bubbles in the brake fluid. If air is present, it can cause a soft brake pedal.
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Bleeding the Brakes: Even if you've replaced components, air could still be trapped in the brake lines. Bleeding the brake system can help remove any air. Ensure proper bleeding procedures for your vehicle, including bleeding all four corners.
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Master Cylinder Bench Bleeding: When you replaced the master cylinder, did you bench bleed it before installation? Bench bleeding helps remove air from the master cylinder before it is installed in the car.
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Proportioning Valve: Check if your vehicle has a proportioning valve. If it does, make sure it is functioning correctly. A malfunctioning proportioning valve can cause improper brake pressure distribution.
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Brake Booster Check Valve: Ensure the check valve on the brake booster is functioning correctly. If it's faulty, it can allow air to enter the brake booster, affecting brake pedal feel.
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Brake Lines and Hoses: Inspect all brake lines and hoses for any signs of damage or leaks. Even a small leak can allow air to enter the system.
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Wheel Cylinder Adjustment: Double-check the adjustment of the rear drum brake wheel cylinders. Improper adjustment can lead to a soft pedal.
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Caliper/Piston Issues (Front Brakes): If you have front disc brakes, check the calipers and pistons for proper operation. Sticking or malfunctioning calipers can cause brake issues.
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ABS System (if equipped): If your vehicle is equipped with an Anti-Lock Braking System (ABS), there could be an issue with the ABS system affecting brake performance.
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Professional Inspection: If the issue persists, it may be beneficial to have a professional mechanic or brake specialist inspect the vehicle. They may use specialized tools to diagnose and pinpoint the problem.
I have done all of the things in the answer, except I do not have ABS. Still does not work
Ok that's definitely a strange one. I would email Scotty for advise and if not then I would book appointment with Scotty and hopefully he will be able to fix your issue.
So Scotty does not answer on this site? How do I email him? I live in Washington State. That might be kind of far away from where he is at.
he answers a handful of questions online, and some get picked to be answered in a video, but he can't answer them all. He's just one man 🙂 No promises.
https://carkiller.com/scottykilmer/postid/211972/