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Old 07-29-2022, 10:05 PM   #1
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Total loss of service brakes

Just had a total loss of service brakes yesterday. Lucky for me, it was after parking overnight, and I was just testing the brakes as I do every morning : After I released the parking brakes, the bus started rolling forward slowly whereas I was pumping the pedal several times. I immediately stopped it by putting my parking brake back on (almost crashed my face into the windshield).
This is a 2008 IC CE300 with full hydraulic brakes.
The day before, I went down some serious hills in the Smokey Mountains, and I had a yellow ABS light go on, but no braking power issue. As I parked to spend the night, I noticed some strong brakes fluid smell in rear left. I checked the fault codes on dash and it showed an issue related to the rear left ABS sensor. I looked under and the ABS sensor had popped out of its socked on the brake housing, was half melted and thin copper wiring hanging out. Obviously dead. However, this I believe has nothing to do with the service brakes loss, bt I still mention it, just in case.
I got it towed to a shop that services school buses. The first thing they checked is the master cylinder and they indicated that no pressure is coming out of it as the brakes pedal is activated. Which explains the zero brakes response while pressive/depressing the pedal). They removed teh master cylinder, dismantled it and the o-rings were very very soft. They showed me the brake fluid they emptied and it is made of TWO liquids not mixing with each other : pinkish at bottom and greenish on top, with a clear separation between both. They do not recognize the top green liquid and believe that it is responsible for deteriorating the o-rings. The master cylinder is less that a year old. The last people who worked on my brakes are an international dealership 7 months ago due to brakes locking up (they replaced 2 deteriorated hoses and flushed the system. I drove >2000 miles after that with no issue).
My questions are :
1) any idea what this green fluid can be ?
2) when the brake system is flushed, is all the brake fluid replaced, or only a replenishement ?
3) If this green fluid has contaminated my system, could I have much more extensive damages on other components with O-rings/gaskets such as the complete Wabco HCU, calipers, etc...) ? This is freaking me out now.
Thanks for some insight.

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Old 07-30-2022, 08:39 AM   #2
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Quote:
Originally Posted by Seb1 View Post
Just had a total loss of service brakes yesterday. Lucky for me, it was after parking overnight, and I was just testing the brakes as I do every morning : After I released the parking brakes, the bus started rolling forward slowly whereas I was pumping the pedal several times. I immediately stopped it by putting my parking brake back on (almost crashed my face into the windshield).
This is a 2008 IC CE300 with full hydraulic brakes.
The day before, I went down some serious hills in the Smokey Mountains, and I had a yellow ABS light go on, but no braking power issue. As I parked to spend the night, I noticed some strong brakes fluid smell in rear left. I checked the fault codes on dash and it showed an issue related to the rear left ABS sensor. I looked under and the ABS sensor had popped out of its socked on the brake housing, was half melted and thin copper wiring hanging out. Obviously dead. However, this I believe has nothing to do with the service brakes loss, bt I still mention it, just in case.
I got it towed to a shop that services school buses. The first thing they checked is the master cylinder and they indicated that no pressure is coming out of it as the brakes pedal is activated. Which explains the zero brakes response while pressive/depressing the pedal). They removed teh master cylinder, dismantled it and the o-rings were very very soft. They showed me the brake fluid they emptied and it is made of TWO liquids not mixing with each other : pinkish at bottom and greenish on top, with a clear separation between both. They do not recognize the top green liquid and believe that it is responsible for deteriorating the o-rings. The master cylinder is less that a year old. The last people who worked on my brakes are an international dealership 7 months ago due to brakes locking up (they replaced 2 deteriorated hoses and flushed the system. I drove >2000 miles after that with no issue).
My questions are :
1) any idea what this green fluid can be ?
2) when the brake system is flushed, is all the brake fluid replaced, or only a replenishement ?
3) If this green fluid has contaminated my system, could I have much more extensive damages on other components with O-rings/gaskets such as the complete Wabco HCU, calipers, etc...) ? This is freaking me out now.
Thanks for some insight.
I posted some Wabco service manuals in this thread, post #13.

I hope you find some good info there to fix your problems?
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Old 07-30-2022, 11:43 AM   #3
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Sorry that you're having this problem.

I was curious about the mention of a strong brake fluid smell near the left rear. Did you track that down? A strong brake fluid smell would suggest that you've lost system seal at that location. Of course if a contaminant has caused o-rings to break down in the master cylinder then it might have affected the caliper seals as well, something you might want to discuss with the mechanic.

Obviously you need to figure out where the contaminant came from. What are the chances that the last shop that worked on the brakes put the wrong brake fluid into it?
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Old 07-30-2022, 12:33 PM   #4
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so with these WABCO controllers are you guys saying that if I get hit in the side of the bus and the electrical system gets knocked out that I would no longer have any brakes at all?? or just loss of power assist.. i cant believe a complete "brake by wire" system would ever be DOT approved?
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Old 07-30-2022, 01:05 PM   #5
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If power fails, you ideally have around 2k psi in your accumulators. The PB is supposed to engage as a failsafe as well

I wonder why there are no codes. I guess you aren't sending a signal to the HCU from the MC, but does Wabco Toolbox recognize that the brake pedal is being depressed? If so, why isn't that a trigger for a fault? I guess it is a hydraulic signal from the MC to the HCU.

I hope you're able to figure it all out. Wabco diagnostic support techs are super helpful and you should encourage the shop to open a ticket with them if there is any confusion or questions.
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Old 07-30-2022, 01:15 PM   #6
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This must be a complicated system for hydraulic brakes. When you say that it had two fluids in the master cylinder-- the first thing that crosses my mind would be red power steering fluid and clear or greenish brake fluid. I assume it uses power steering hydraulic pressure to operate the brakes when the engine is running?
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Old 07-30-2022, 01:46 PM   #7
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This must be a complicated system for hydraulic brakes. When you say that it had two fluids in the master cylinder-- the first thing that crosses my mind would be red power steering fluid and clear or greenish brake fluid. I assume it uses power steering hydraulic pressure to operate the brakes when the engine is running?
I read that about Bosch hydromax, but on my Wabco HPB system, there isn't the power steering feature. When you contact Wabco, what manual do they tell you to use? If you were near Massachusetts, I would try to swing through and plug in my software. It has a pretty thorough diagnostic procedure that should pin point the issue.

Keep us posted.
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Old 07-30-2022, 06:12 PM   #8
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Here is a picture :
HTTPS://drive.google.com/file/d/1pbX...w?usp=drivesdk[
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Old 07-30-2022, 06:15 PM   #9
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Hi Oldyeller, yes, I am afraid my rear left caliper seals are shot. I just hope that it is not due to this green thingy. Because then it means that more brake parts will fail sooner or later.
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Old 07-30-2022, 06:18 PM   #10
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Quote:
Originally Posted by Samarath View Post
If power fails, you ideally have around 2k psi in your accumulators. The PB is supposed to engage as a failsafe as well

I wonder why there are no codes. I guess you aren't sending a signal to the HCU from the MC, but does Wabco Toolbox recognize that the brake pedal is being depressed? If so, why isn't that a trigger for a fault? I guess it is a hydraulic signal from the MC to the HCU.

I hope you're able to figure it all out. Wabco diagnostic support techs are super helpful and you should encourage the shop to open a ticket with them if there is any confusion or questions.
Hi Samarath, I also find weird /a bit annoying that the Waco system would not return a message on dash, even though the Pedal activates the MC and then the Wabco HCU.
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Old 07-30-2022, 06:51 PM   #11
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Quote:
Originally Posted by PorchDog View Post
This must be a complicated system for hydraulic brakes. When you say that it had two fluids in the master cylinder-- the first thing that crosses my mind would be red power steering fluid and clear or greenish brake fluid. I assume it uses power steering hydraulic pressure to operate the brakes when the engine is running?
Now that you mention it, my bus has the Bosch hydraulic brake system. If anyone has been following my thread about resealing my HPOP, you'll know that my system has a belt driven hydraulic pump above the HPOP that provides boost for the power steering AND power brakes. That pump uses power steering fluid. Nothing running through either that system or the brake system is green.

I have the Bosch Hydromax Booster manual as a PDF if you need a copy. It has diagrams which accurately reflect what I have.
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Old 07-30-2022, 07:32 PM   #12
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From the pic it looks like brake fluid with antifreeze floating on top.
If someone put coolant in the MC it would definitely cause a loss of braking.
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Old 07-31-2022, 08:21 PM   #13
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So, I have reading a bit more to educate myself on brakes fluids, and I came across reading that DOT 5 is silicon based, and that if an idiot has poured some in there it is not compatible with any other DOT fluids that are glycol based. DOT 5 can deteriorate seals and is not to be used with ABS systems So that got me freaking out because my master cylinder seals were very soft. However, DOT 5 is of deep purple color : none of my 2 colors… so there is hope that a different mistake was made, maybe not as catastrophic.
I went thru the past 2 years of shops receipts when work on my brakes was done and they all show DOT 3 was used (even though something else may have been used by mistake).
In couple days, the shop will do a full flush. Then will see if rear left caliper seals are dead. If that turns out to be the case, that weird fluid then may have indeed done extensive damage to the whole system.
Meanwhile, I’ll look for where I can get the 2 liquids analyzed.
Will keep you all posted.
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Old 08-02-2022, 10:01 AM   #14
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You're absolutely right about the diff between DOT 5 & 3/4/5.1. I ran into this issue more than once servicing bikes where 5.1 is popular as a high-performance fluid, and 5 gets routinely confused with it. Whoever thought throwing a silicone-based 'dot 5' into the mix should be flogged. My recommendation was always to rebuild the entire brake system. On a bike, that's not too involved (though still no joyride). On a bus... yeah... I hope that's not the case with you.

DOT 5 is mandated to be purple in color, unlike the other variants that can span a range of colors. So the good news is maybe that's not the case with you. The bad news, however, is that I can't think of too many other liquids I wouldn't be almost equally as concerned with being mixed in as DOT 5.

If I were you, and I suspected this was done during a prior service, I'd try to find my receipts, or ask for copies, to see if anything like brake fluid was itemized. EDIT: I see you already did. Sorry.

FYI Hydraulic Mineral Oil is green, and I can see where this might have been used by someone a bit clueless. I don't know much about it, but it states here it's incompatible with synthetic brake fluid. Also says it's safe for all seals, so if this is what it is, that might be a little ray of hope? Here's an example:

https://www.mandsmachinery.com/produ...l-brake-fluid/
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Old 08-02-2022, 10:18 AM   #15
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Sniff it- is there ANY sweetness or antifreeze smell to it? I know it would be really stupid but I still think someone goofed and put coolant in there.
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Old 08-02-2022, 11:01 AM   #16
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Quote:
Originally Posted by Seb1 View Post
So, I have reading a bit more to educate myself on brakes fluids, and I came across reading that DOT 5 is silicon based, and that if an idiot has poured some in there it is not compatible with any other DOT fluids that are glycol based. DOT 5 can deteriorate seals and is not to be used with ABS systems So that got me freaking out because my master cylinder seals were very soft. However, DOT 5 is of deep purple color : none of my 2 colors… so there is hope that a different mistake was made, maybe not as catastrophic.
I went thru the past 2 years of shops receipts when work on my brakes was done and they all show DOT 3 was used (even though something else may have been used by mistake).
In couple days, the shop will do a full flush. Then will see if rear left caliper seals are dead. If that turns out to be the case, that weird fluid then may have indeed done extensive damage to the whole system.
Meanwhile, I’ll look for where I can get the 2 liquids analyzed.
Will keep you all posted.
Quote:
Originally Posted by TheHubbardBus View Post
You're absolutely right about the diff between DOT 5 & 3/4/5.1. I ran into this issue more than once servicing bikes where 5.1 is popular as a high-performance fluid, and 5 gets routinely confused with it. Whoever thought throwing a silicone-based 'dot 5' into the mix should be flogged. My recommendation was always to rebuild the entire brake system. On a bike, that's not too involved (though still no joyride). On a bus... yeah... I hope that's not the case with you.

DOT 5 is mandated to be purple in color, unlike the other variants that can span a range of colors. So the good news is maybe that's not the case with you. The bad news, however, is that I can't think of too many other liquids I wouldn't be almost equally as concerned with being mixed in as DOT 5.

If I were you, and I suspected this was done during a prior service, I'd try to find my receipts, or ask for copies, to see if anything like brake fluid was itemized. EDIT: I see you already did. Sorry.

FYI Hydraulic Mineral Oil is green, and I can see where this might have been used by someone a bit clueless. I don't know much about it, but it states here it's incompatible with synthetic brake fluid. Also says it's safe for all seals, so if this is what it is, that might be a little ray of hope? Here's an example:

https://www.mandsmachinery.com/produ...l-brake-fluid/
It is my understanding (no personal experience thankfully) that mixing DOT 5 brake fluid with the other types results in the coagulation of the mixture in the system. If that's true (I can neither confirm nor deny) then that's not what happened here.

The advantages of DOT 5 brake fluid is it is hydrophobic, heat resistant and doesn't harm paint, something more important on a bike given the location of the front master cylinder.

I bought an old 1998 Honda Valkyrie basket case a couple years ago while wintering in Florida and rebuilt it while I was enjoying the nice weather. When it came time to overhaul the brake system I converted it from DOT3 to DOT5. That consisted of overhauling the master cylinders and calipers and flushing the lines with alcohol. DOT5 brake fluid isn't harmful to O-rings or other 'rubber' components or Harley wouldn't have used it for the last 50 years.
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Old 08-02-2022, 11:29 AM   #17
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You're correct, oldyeller. The problem is in getting all that gunk out of a contaminated system. Personally, I wouldn't trust it to all be gone without completely rebuilding the MC, calipers, & lines (thinking non-abs systems here), just like you did. As you obviously know, a tiny bit of coagulated gunk finding its way from behind a piston seal and maybe travelling up to clog a tiny port in the MC could cause a very bad day. Hygrophobic, yes. Heat-tolerant... not compared to high-performance versions of DOT 4 & 5.1. And the main problem: it's compressible, which may result in acceptable performance in a cruiser-style bike, but it's not something you'd want in anything where brake feel and maximum stopping power are critical.
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Old 08-02-2022, 12:05 PM   #18
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You're correct, oldyeller. The problem is in getting all that gunk out of a contaminated system. Personally, I wouldn't trust it to all be gone without completely rebuilding the MC, calipers, & lines (thinking non-abs systems here), just like you did. As you obviously know, a tiny bit of coagulated gunk finding its way from behind a piston seal and maybe travelling up to clog a tiny port in the MC could cause a very bad day. Hygrophobic, yes. Heat-tolerant... not compared to high-performance versions of DOT 4 & 5.1. And the main problem: it's compressible, which may result in acceptable performance in a cruiser-style bike, but it's not something you'd want in anything where brake feel and maximum stopping power are critical.
I wouldn't disagree with your points but the boiling point of DOT5 is around 260 degrees centigrade (500 degrees fahrenheit) which is higher than that listed for standard DOT3 and 4 which is what I assume you'd find in any bus. The average rider/driver likely doesn't bother to flush his/her system regularly so DOT5 would probably hold up better to heat over the long haul given it's hydrophobic tendencies.

Yes, I'd do a lot more research before I decided to put DOT5 in my bus. In a motorcycle I wouldn't think twice about it. If you're tracking your bike then do whatever you think is best but for riding on the street it wouldn't be a big deal. I never rode my Valkyrie with DOT5 in it - because the brakes were completely frozen at both wheels and the master cylinders were full of snot balls but I'm fine with the brake performance now that both ends are rebuilt and filled with DOT5.

Of course I'm old and I ride slow so my needs are modest with regard to sustained braking.

Here's a link to my rebuild thread on the forum Valkyrie Riders Cruiser Club. If you're into motorcycles you might find it amusing.

http://www.valkyrieforum.com/bbs/ind...,114932.0.html
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Old 08-02-2022, 12:21 PM   #19
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It's obvious you know your stuff. Yeah, I admit I'm splitting hairs on the temp thing, but most of the 5.1 we ran was near or above 600-degrees dry. Of course, just like you said, you had to change it out every month or it would take on so much water it was near worthless. Whatever you didn't use got thrown in the trash. Sometimes I could squeeze partially-used bottles until the liquid reached the top of the cap and then tighten them down to hold a vaccum, but most of the time you'd come back and they were garbage after sucking in air. I included DOT 4 only because there are a couple I've seen (but not used) that advertised wet boiling points ~500F.

I'd love to check out your thread. Thanks!!!
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Old 08-04-2022, 04:06 PM   #20
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LHM is green, mineral oil based, and absolutely incompatible with rubber parts common in systems designed for polyglycol ether fluids (e.g DOT 3 and 4) or silicone fluids (DOT 5)
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