Brake Problemo
03-07-2013, 10:42 PM
#1
Dailydriving300ci-of-fury
Thread Starter
Brake Problemo
Sup guys, I'll start out by saying I've already searched for my problem, but I kind of have a combination of what all the other guys (posting about brake problems) have.
My problem is the brake pedal likes to slowly bleed down really close to the floor. I'll usually have to let off the brake and press it again if I dont want to have to stand on the brake to get the truck to stop moving. This is especially bad in 4 low when the truck likes to lunge forward. I'm not loosing any brake fluid at all. I had a leaking wheel cylinder about a month back, but I replaced it and bled all the lines. Also from time to time the rear anti-lock light and the emergency brake light will come on. Another thing is, when the truck is running and I do hold down on the brakes I hear a whirring type air noise that corresponds with brake pedal action. Sooo, I'm not sure whether or not to replace the master cylinder, or the brake booster, or anything do do with the proportioning valve or any brake sensors. Could just use a little help diagnosing my problem cause I don't want to throw parts at it. Thanks guys.
My problem is the brake pedal likes to slowly bleed down really close to the floor. I'll usually have to let off the brake and press it again if I dont want to have to stand on the brake to get the truck to stop moving. This is especially bad in 4 low when the truck likes to lunge forward. I'm not loosing any brake fluid at all. I had a leaking wheel cylinder about a month back, but I replaced it and bled all the lines. Also from time to time the rear anti-lock light and the emergency brake light will come on. Another thing is, when the truck is running and I do hold down on the brakes I hear a whirring type air noise that corresponds with brake pedal action. Sooo, I'm not sure whether or not to replace the master cylinder, or the brake booster, or anything do do with the proportioning valve or any brake sensors. Could just use a little help diagnosing my problem cause I don't want to throw parts at it. Thanks guys.
03-07-2013, 11:06 PM
#2
Senior Member
Sounds like the diaphragm in the booster is leaking. Check your booster to see if it holds vacuum. There's a special tool to do that, that you may be able to rent.
03-08-2013, 12:40 AM
#3
Senior Member
A leaky booster will cause a hard pedal not a leak down or spongy. Try flushing and leading the system. Brake fluid absorbs moisture which evaporates and causes gaps. If that doesn't do it you may have a bad seal on the master cylinder push rod. Basically replace it. You can try this test. Pump up the pedal quickly and smoothly. Have a buddy remove the reservoir cap then quickly release the pedal. You should see a small rush if fluid back in. If you see a fountain of fluid and/or bubbles you have air in the lines. For the next test someone please correct me if I am wrong I haven't done it in a while. Pump the pedal slowly then press it to the floor. If the fluid level rises the pushrod seal is bad. Anytime you work on the breaks its good practice to clean and inspect each wheel. Always use new fluid from a sealed bottle.
03-09-2013, 12:01 AM
#4
Dailydriving300ci-of-fury
Thread Starter
A leaky booster will cause a hard pedal not a leak down or spongy. Try flushing and leading the system. Brake fluid absorbs moisture which evaporates and causes gaps. If that doesn't do it you may have a bad seal on the master cylinder push rod. Basically replace it. You can try this test. Pump up the pedal quickly and smoothly. Have a buddy remove the reservoir cap then quickly release the pedal. You should see a small rush if fluid back in. If you see a fountain of fluid and/or bubbles you have air in the lines. For the next test someone please correct me if I am wrong I haven't done it in a while. Pump the pedal slowly then press it to the floor. If the fluid level rises the pushrod seal is bad. Anytime you work on the breaks its good practice to clean and inspect each wheel. Always use new fluid from a sealed bottle.