My problem started a couple weeks ago. The ABS light came on, aprox
1/2 hour later my brakes were not working properly. The pedal felt all wrong (goes all the way down with no pressure) and it sounded like the breaks were intermittingly stopping (like skidding) when they did work... very dangerous to drive this way.
I took the truck home and checked the fluid, it turns out the fluid is low, so I replaced it, still no puddles in the driveway and from checking the inside (quick look) and around the wheels no leaks.
I took it up to the garage where I bought the truck and the guys up there (without looking at it) say it sounds like it need's a master cylinder. What is your opinion? Is there anything else I should check into before I buy a MC and try to install it myself? Any advise about installing a Master Cylinder?
I bought this truck used and I really fell in love with it. I'd like to do the repairs myself when possible, but I donot have a ton of experience with this type of thing, so it is a learning process for me. Any kind of insight will help!
"kevin" snipped-for-privacy@gmail.com wrote in message news: snipped-for-privacy@4ax.com...
Kevin, Replacing a master cylinder is fairly easy. Its pretty much just a swap out kind of deal. Just remember to prime the new master cylinder before you install it. You do this by pushing the plunger rod in and out a couple of times to get the air out of the primary and secondary plungers. Once you have done that, just install in the reverse order that you took the old one off, and bleed ALL of your brakes to get any air out of the system. You also have a choice of brake bleeding styles. The most prominent one is pressure bleeding. Have a friend pump the brakes 2-3 times, or until solid. When your friend says they are solid, have your friend hold down on the pedal, and open the bleed valve. Close the bleed valve BEFORE your friends releases the brake pedal. Keep doing this until you get no more air in the system, and watch your resevoir.. You have to keep fluid in it at all times, or you have to start over. The second style is the gravity bleed. Basically you just open the bleed valve, and let the fluid drain out. This takes a long time, and again, you have to keep an eye on the resevoir. Also with this system, you probably only want to do one at a time. It might help speed up the process. That's it, thats all you need to do. Oh, and one more thing. Buy a chilton/haynes manual for your vehicle.. When it comes to repairs by a DIY, or a professional. You can't beat a good tech manual.
Bad master cylinder. Internally the master cylinder has pistons and cylinders that move in and out as you press and release the brake pedal. The pistons and cylinders fit tightly together but, eventually, they wear and as you step on the pedal, fluid leaks past the pistons causing the brakes to not work properly and causing the pedal to feel strange. However, because the leak is internal to the master cylinder, nothing will spill out onto the ground for you to see.
Replacing the master cylinder is a simple swap-out. Find someone who has done it, or, do a Google search for replacing master cylinder. The new one will have plastic caps on the inlet and outlet ports. Open these caps and fill the new master cylinder with fluid -- pump the rod in and out a few times to prime the master cylinder with fluid. You'll still need to bleed the brakes after replacing the master cylinder.
How low was the reservoir? It may take more than a "quick look" to find the leaking component. Until you determine where the fluid went, all we can do is speculate.
I had a Toyota truck that slowly lost it's master cylinder. No evidence of fluid leaks anywhere but all symptoms pointed to the master cylinder. Only when I replaced it did I discover where the fluid went... Into the vacuum booster and down the inside of the firewall where it saturated the carpet pad.. Never noticed because of the rubber floor mats I had down.
That is exactly my point. Brake fluid doesn't just suddenly disappear for no reason. If you lose fluid, there's a leak somewhere. It's just a matter of finding it.
I appreciate all the advice and it really does help. Unfortunately I can only do a little at a time, so yes this weekend I need to check the pads as well as the other suggestions that have been made. I want to rule out every possibility before I replace the master cylinder.
I understand your feeling (re have a pro do it), but I like this truck and want to learn everything I can regarding it's repair and upkeep Im no mechanic but I need to start somewhere. I am not going to learn anything if I bring it someplace and have it done for me. Fortunately I have some free time and I can keep the truck off the road so I have the luxury of learning as I go. Luckily I you guys have taken the time to point me in right direction too.
I did and everything is fine, infact I wont have to worry about replacing anything for another year. I also re-checked the brake fluid and it has remained at the same level (since I replaced it, altho Ive driven only 2 miles aside from the driveway to garage and back a couple times since I refilled it) , so I believe this indicates a master cylinder prob right? I've checked everywhere (including the firewall which someone sugg today) for any possible signs of leakage and nothing. If the MC goes is it possible for the fluid to get low and then no further leaking?
I've pretty much run out of things to do except replace the MC or is there something else Im overlooking?
Kevin, An internal leak in the MC will NOT cause fluid to go low. The reason for this is because the brake system is hydraulic and has a finite amount of room. IF there is no external leak, then the fluid should not go down, EXCEPT for wear on the brake pads and shoes.
As for a bad MC, it will feel spongy, but then fall to the floor slowly. Now the ABS light will come on if the resevoir gets low. Thats because the resevoir indicator will signal the ABS and turn the ABS off in case it completely drains out. This protects the ABS from burning up because it doesnt have fluid in it.
I say check your brake cylinders on the rear again. Just to make sure of no leakage. In fact I would wipe them out with a rag, and then check them again after a few miles of driving. But if your brake pedal feels like what I have described above, then I suggest a new master cyliner anyway.
I am ASE certified for brakes. ASE # OP3GR7RM1KURTZ You can verify this number with ASE through their website I believe. Pk
Shayne, I dont know if you have noticed, but there is a reason that the vacuum line on the brake booster is located at the top of the booster. Your truck can not suck the brake fluid into the engine by way of the vacuum. If it is going anywhere, its just staying in the brake booster, or leaking down the firewall. I would prefer to say that it is staying in the brake booster, especially if you havent had to add more than a few ounces of fluid. The vacuum side of the booster is sealed, so as to hold the vacuum, the only place for the fluid to get out of the vacuum side and into the passenger compartment is through a valve in the center of the diaphram on the booster, and that would require several ounces of fluid to achieve that, also it would require almost a half gallon of DOT3 fluid to fill the booster enough for the engine to suck it back into the engine.
Thanks I am definetly going to take your advice and do a thorough check of everything later this week or this weekend. So what you are saying is there has to be a leak someplace? Can you answer one more question, is there anything special I need to do or any special tool I need to bleed the brakes when I replace the MC?
If you havent noticed a significant drop in fluid level, then I doubt you have a leak. That is to say that if you check your fluids once a week, and its taken a month or two (dependent on driving conditions, and how often you use your brakes) for the level to drop, then its not a leak, its going down due to use. If this is the case, it should not be refilled, but the front pads probably need replaced cause they are worn. As you use your brakes, on a truck its typically a 60/40 frt/rear ratio, the pistons have to slide out to make up the space between your rotor and the pad. This is done so that the next time you hit your brakes, they react quickly, and not take 2-3 sec to contact the rotor. There is a square o-ring on the piston that will pull the piston away from the rotor about 2MM. The reason you see the brake fluid go down is because its in the piston on your brakes. The rear brakes act differently, and wear on them wont be noticed by a loss of fluid in the resevoir. Their slack is actually taken up by a mechanical slack adjuster installed in each rear drum, UNLESS you have 4-wheel disc brakes. Then it will act the same as the front. As a rule of thumb, I change my rear shoes every 3rd time I change the fronts. More so if I haul heavy loads. It depends on how much wear they get. My bet is that your frt pads are sitting about an 1/8 to 3/16 of an inch off your rotors and this is what caused the fluid to go down. If that is the case, its time for new pads on the front.
*** IF YOU HAVE 4 WHEEL ABS, TAKE IT TO THE SHOP**** No special tools unless you have 4 wheel ABS. If you have RABS (Rear ABS) only, then you can do this at home. Definitely get a tech manual for the vehicle you are working on. I have my tech manual for 93-00 Rangers in front of me, and it adimently states NOT to do this if you have 4 wheel ABS. Do make sure you pump that piston a couple times with fluid in the resevoir before you install it, this just primes it and gets the air out of the MC.. If you have RABS, then there is a special procedure to bleed the air out of it. You have to bleed the ABS pump as well as the other 4 brakes. Buy the Haynes Tech manual if you havent done so. This is all covered in Chpt 9, under Brakes. But I cant say it enough, if you have 4 wheel ABS dont do this. In the end you will have to have it towed to the shop to get the ABS bled. It requires an expensive special tool, that would not be worth you buying it. If you arent sure if you have 4wheel ABS, dont do this.
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Thanks so much, your detailed reply really helps. I am lucky enough to have access to a bay at a local garage on saturday so I will be able to check all this easily. I really appreciate you explaining how the system works.
So if you are right about the pads, why would the master cylinder and the brakes seemingly go all at once?? One minute I am pulling into a gas station and I notice the ABS light, aprox 10 minutes later the brake's are spongy and Im barely getting any braking at all??!?? Is this commen for your pads and MC to go at the same time?
It sounds like you had a sticking piston, and when it finally came loose and moved out in its bore, it was enough to pull the fluid level down in the system. That stuck piston coming loose might have allowed the plunger to travel down the bore farther in the MC to a spot that was getting rusty (DOT3 brake fluid is moisture absorbent, thats why its in plastic bottles, and is supposed to stay sealed to keep moisture out). The rust could have possibly knicked the rubber seal, and created a leak in the MC plunger seals.Also, alot of pluger seals, are cup seals, so when the have pressure against them, they spread out to hold the fluid in the system, if one came loose.... Again, who knows how it happens, and there are several ways it can happen, and to really find out what did happen you would have to disassemble the MC and inspect the parts, but suffice it to say. If the MC goes out, you dont want to have to stop too fast..
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