Archived Brake problem

[seafish]

Hey guys, yesterday I finally installed my BrakeSmart trailer brake controller. I followed the instructions, including bleeding the newly installed brake fitting 3 times, but now my brake pedal slowly goes almost to the floor as I press and hold it AND there is a fairly loud hissing sound coming from underneath the dash as it sinks almost to the floor. I realize that the pedal sinking means that I did not get all of the air out from the brake lines, BUT I am confused by the hissing from under the dash... there is no fluid leaking, only the noise.



The truck and trailer and brake controller continue to drive, operate and stop well, BUT I need to know what the hissing is...



Tomorrow I will bleed the brake lines all the way around instead of just at the fitting...



While I know all the basic bleeding rules and techniques already PLEASE do tell me any important bleeding instructions SPECIFIC for our trucks.



Also, I have a small MityVac with fluid reservoir that I have never used yet... Will this get rid of the air as well or better then the press and hold technique??



I also need to know what fluid I should buy.



I need to get this done tomorrow so that I can leave with the trailer on Wednesday. Thanks in advance for all the info. Oo.

 

[Loren]

C. Fish,



I haven't had good results with my MityVac. I prefer to replace the bleeder valves at each wheel with Speed Bleeders. They have a check valve built into them and allow one-man bleeding. You can find them here:

Speed Bleeder Bleeding Brakes Bleeding Motorcycle Brakes Automotive Bleeder Screw Brake Bleeder



I have a BrakeSmart controller on my truck. You will never go back to anything else after you've used this one.



Now, regarding your brakes... If your pedal is going to the floor and there is no brake fluid leaking anywhere, there can be only one cause: an internal leak within the master cylinder.



My son-in-law's truck had this problem recently and we found that changing the master cylinder is a very easy job. The part wasn't too expensive, I think. It seems that it was around $100. I didn't pay for it, so I don't remember for sure.



We bled the master cylinder on a bench, per the instructions that came with it, installed it, and bled all the wheel calipers. It was a quick and easy fix.



My guess is that the hissing is the fluid squirting past the seal inside the master cylinder.



Best of luck,

-- Loren

 

[seafish]

Loren, thanks for the heads up... I don't understand how the installing the Brakesmart could have ruined the master cylinder... it worked fine before I did the install and was then leaking right after the install. Do you have any ideas??

PS--the controller is working great... I calibarted it today, by now I have to replace the master cylinder before I lieave if I can even find the part at the local dealer...
Do you know if the cylinder can be repaired??
Can I even drive the vehicle??

Thanks again!!!

 

[Loren]

C. Fish,



I don’t think the BrakeSmart ruined the master cylinder. One possibility is that bleeding the brake system did it.



When you bleed the brakes, the pedal goes all the way to the floor, where it usually never goes. This will drive the master cylinder piston into parts of the cylinder that may have corrosion or other rough surfaces. That may cause the piston seal to get scratched and create a leak.



This would occur when the brakes are bled, too. Now that I think about it, we had just changed the brake fluid on my son-in-law’s (Steve’s) truck not long before his master cylinder failed.



Changing the brake fluid will wash out the old fluid that has absorbed water (which causes corrosion and lowers the boiling point of the fluid) and replace it with clean fluid, which is safer. It’s something you should do periodically, but most drivers don’t. I try to change the fluid in my truck about every two years at least.



I’m sure that the master cylinder can be rebuilt if you can find the kit with the parts. We weren’t able to find a kit, so Steve bought a rebuilt unit from the local NAPA store. The first one was bad, but NAPA stood behind it 100%.



As far as driving the truck, that’s your call. I would say that if it takes ten seconds or more for the pedal to creep down to the floor you can probably get away with driving it. Just remember to pump the brakes occasionally while you are stopped at red lights.



If the pedal thumps to the floor in two seconds or less, I wouldn’t drive the truck. In either case, it’s your decision, just be sure you’re safe.



Good luck,

– Loren

 

[BFoughty]

It has been my experience that it is as cheap to buy a new master cylinder as it is to rebuild one. Same goes for break calipers.

 

[seafish]

C. Fish,



I don’t think the BrakeSmart ruined the master cylinder. One possibility is that bleeding the brake system did it.



When you bleed the brakes, the pedal goes all the way to the floor, where it usually never goes. This will drive the master cylinder piston into parts of the cylinder that may have corrosion or other rough surfaces. That may cause the piston seal to get scratched and create a leak.





– Loren

Well Loren, that is probably what did it. The truck is 5 years old... just recently I went to Dodge and asked them what the recomended brake fluid/system flush interval was and they looked it up and said "there is no recomended interval. " I was going to do it soon, just wanted to get the brake controller installed before my trip on Wednesday. Now I'll have to replace the master cylinder and flush and bleed the brake system before I leave. #@$%! Thanks for the help, I really appreciate it.



PS-- any recomendations on brake fluid??

 

[seafish]

Well... I re-bled the master cylinder at the brass fitting that I installed, also worked my way around all of the wheels and bled them twice around... air definitely came out of all of them. The brakes work without sponginess now, BUT if I keep a steady pressure on the pedal while at a dead stop, it SLOOOOWWWWLLLYYYY sinks towards the floor and after awhile a much quiter hiss is heard from uner the dash. My take on it now is that that maybe somehow one of the piston seals in the hydraulic booster or master cylinder was damaged damaged while originally bleeding the system, like Loran suggested. In any case, I feel confident to drive the truck now, and will take it buy the dealer when I get back.

PS --the Brakesmart Controller is a joy to use and drive with. If interested, check out the pics of the install here--

https://www.turbodieselregister.com...0158-brakesmart-controller-3.html#post2148502

 

[Loren]

PS-- any recomendations on brake fluid??

C. Fish,



I have read (maybe in the TDR) that if a brake fluid meets the specification for whichever DOT level it has then it's okay. I usually buy the cheapest, brand-name fluid from Wal-Mart, but the last time I bought NAPA's brand from the NAPA store because it was handier.



I use DOT-3 fluid. I'm pretty sure that's what is required.



I told you you'd love the BrakeSmart. I sure love mine.



-- Loren

 

[sag2]

It is not uncommon to have the pedal go slowly to the floor if you hold fairly hard steady pressure. The hissing is the power steering fluid passing through the booster when you have the pedal depressed. Perfectly normal.

I do agree with Lauren, the seals probably got roughed up when you bled the brakes and allowed to piston to travel to a spot in the bore it had never been. As he said, as long as the pedal holds for several seconds, and I'm assuming it never starts rolling no matter how long you hold, you should be fine.

Any DOT 3 fluid is fine.

 

[seafish]

OK, Thanks everyone for their explanations and help!!!