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olskool4x4 · 01-04-2017, 03:55 PM

History of brake issue: 12 Dec, 2016
My 2008 Adventurer Limited (UFO/R26) had 33,000 miles on it. I was going down the road and my ABS, ATC lights came on and my dash displayed a Hydraulic Brake Failure. When I parked the vehicle, I left it in “N” without applying the Park Brake, I didn’t want it to engage and not release. When I shut the vehicle off the P-Brake (SAHR) automatically applied preventing the RV from moving. I needed to remove the SAHR cable to move it to the storage area. I blocked the wheels, started the vehicle and lowered the jacks to ensure the vehicle wouldn’t move when the SAHR cable was released. After I removed the SAHR cable by loosening the locking nut (15mm) and unscrewing the cable 3 inches with an (8mm) wrench. I started the vehicle and the jacks automatically retracted because the system recognized the PB was disconnected. I could move the RV but all the warning lights were on. I again tried to activate and deactivate the PB and I could hear it working. So I crawled back under the RV and hooked it back up to see if it would work. Before I crawled under it, I blocked the wheels, turned the key on (not running) and ensured the HCU was pressurized and pushed in on the PB to disengage it. It’s easy to reconnect the cable if the PB is disengaged. I screwed the cable back into the SAHR by hand (no wrench needed) and used the 15mm to lock the locking nut. I started the vehicle, pulled the PB knob to engage the PB and it worked! I pushed in on the PB and it disengaged! Everything was back to normal, no warning lights and I drove it to the storage area.
Conclusion ?: I’m not sure, but when the HCU is maintaining 2000-2300 PSI going down the road the seals are leaking and bypassing the valves reducing the PSI. (My OEM HCU is currently 100% functional, No warnings)
I ordered the TOOLBOX software and NEXTIQ USB Link-2 to check the system. The faults were still stored but inactive (No warning lights).
Bottom Line: I order a new HCU $4,000, AND it was “DEFECTIVE” it would not maintain REAR PSI, and the ATC light was on, I had to removed it and currently waiting for the UPS info to send it back. I reinstalled my old OEM HCU to validate the New HCU was bad. My old HCU is reinstalled and works perfectly with no issues or warning lights, but I know the seals will probably leak again that’s why I want a new one. 4 Jan, 2017
The PDF show's the steps to remove and install the HCU. (First time 6 hrs, second time 3 hrs)

DriVer · 01-04-2017, 04:47 PM

olskool4x4

I just wanted to let you know that your article has been added to the listings in the: "Workhorse Important Discussions"

This reference will provide invaluable assistance to R-26 owners that encounter the need to resolve or understand their HPB braking system on their UFO Chassis.

CJ7365 · 01-04-2017, 06:27 PM

Awesome write up, with plenty of pictures

Brazel's RV Performance · 01-04-2017, 09:00 PM

Wow Duane, this is an awesome write up and will help not only UFO owners but I'm sure a lot of repair shops as well!

DriVer · 01-04-2017, 09:35 PM

Quote:

Originally Posted by Ultra RV Tech

Wow Duane, this is an awesome write up and will help not only UFO owners but I'm sure a lot of repair shops as well!

I've not seen such a well prepared article like this in a long time.

olskool4x4 · 01-08-2017, 09:31 AM

Update, I received my (second) New HCU, installed it and everything works great (Thank You Utra RV “Jon”). I would like to note a couple things:
1. After bleeding the system leave your Pressure System hooked up to the Master Cylinder.
2. Turn the key on to pressurize the system, the HCU pumps will run for approximately 1 minute.
3. You will have two warning lights on ATC, and ABS. The ABS light is on because the SAHR cable is disconnected (Parking Brake). The ATC light will stay on until you drive the vehicle.
4. Leave the Key on, after the system is pressurized put your foot on the brake and put the transmission in “N”, and disengage the PB by pushing in on the brake switch (yellow knob). This makes it easy to reconnect the SAHR Cable. This pressurizes the SAHR canister and extends the connecter by 3 inches, when you screw the cable in there’s no tension on the cable.
5. Turn the key off or put the Trans in "P" and the SAHR (Parking Brake) will automatically engage.
After driving the UFO Adventurer the brakes worked awesome, the vehicle stops on a dime.
My observations: New HCU vs Old HCU
Old HCU:
1. When holding the Brake at a stop light (30 sec or more) the vehicle would start to move forward slightly and I needed to press a little harder on the pedal. I had to remember after I was sitting for 30 sec or more to add more pressure to the pedal.
2. After the vehicle sat overnight all the brake fluid would return to the Master Cylinder reservoir (MAX line). I’m thinking this is an indicator the fluid was bypassing the seals because of debris in the fluid getting stuck under the seals or the seals were going bad?
3. When I had to pull the New (Faulty) HCU back out, I installed the Old HCU again and completely re-bleeding the system for the second time! The Old HCU brakes worked great, and the next morning the MC reservoir level was in the middle between (MIN and MAX). I’m thinking that pushing 10 new bottles of brake fluid through the system cleaned out all the debris and cleaned the seals?
New HCU:
1. Brakes hold great at stop lights, no additional pressure needed after 30 sec.
2. Stopping is better and the pedal is more firm, my old pedal was a little spongy but not bad.
3. I haven’t checked the MC reservoir yet to see were the brake fluid level is.
Conclusion: I’m now a believer in changing your brake fluid every 2 years! I also think RV brake fluid gets abused when braking 20,000 plus lbs going down mountains. I recommend replacing your brake fluid with DOT 5.1, not DOT 3. DOT 5.1 has a 90* higher wet boiling point. You can mix (DOT 3, DOT 4 & DOT 5.1) “Don’t use “DOT 5”
Note: Dry Boiling Point is fresh Brake Fluid, Wet Boiling Points is brake fluid that’s been in the vehicle exposed to moisture / condensation.
DOT 3 Dry Boiling Point 401* Wet Boiling Point 284*
DOT 4 Dry Boiling Point 466* Wet Boiling Point 311*
DOT 5.1 Dry Boiling Point 518* Wet Boiling Point 374*
It’s hard to find DOT 5.1 so I order it from Amazon, $14.05 Wagner Dot 5.1 SEVEREDUTY Brake Fluid, 32 oz; 946 ml</SPAN>
https://www.amazon.com/Wagner-Dot-SEVEREDUTY-Brake-Fluid/dp/B000C92RDC/ref=sr_1_3?ie=UTF8&qid=1483891973&sr=8-3&keywords=dot+5.1

CJ7365 · 01-08-2017, 06:09 PM

Quote:

Originally Posted by olskool4x4

Update, I received my (second) New HCU, installed it and everything works great (Thank You Utra RV “Jon”). I would like to note a couple things:
1. After bleeding the system leave your Pressure System hooked up to the Master Cylinder.
2. Turn the key on to pressurize the system, the HCU pumps will run for approximately 1 minute.
3. You will have two warning lights on ATC, and ABS. The ABS light is on because the SAHR cable is disconnected (Parking Brake). The ATC light will stay on until you drive the vehicle.
4. Leave the Key on, after the system is pressurized put your foot on the brake and put the transmission in “N”, and disengage the PB by pushing in on the brake switch (yellow knob). This makes it easy to reconnect the SAHR Cable. This pressurizes the SAHR canister and extends the connecter by 3 inches, when you screw the cable in there’s no tension on the cable.
5. Turn the key off or put the Trans in "P" and the SAHR (Parking Brake) will automatically engage.
After driving the UFO Adventurer the brakes worked awesome, the vehicle stops on a dime.
My observations: New HCU vs Old HCU
Old HCU:
1. When holding the Brake at a stop light (30 sec or more) the vehicle would start to move forward slightly and I needed to press a little harder on the pedal. I had to remember after I was sitting for 30 sec or more to add more pressure to the pedal.
2. After the vehicle sat overnight all the brake fluid would return to the Master Cylinder reservoir (MAX line). I’m thinking this is an indicator the fluid was bypassing the seals because of debris in the fluid getting stuck under the seals or the seals were going bad?
3. When I had to pull the New (Faulty) HCU back out, I installed the Old HCU again and completely re-bleeding the system for the second time! The Old HCU brakes worked great, and the next morning the MC reservoir level was in the middle between (MIN and MAX). I’m thinking that pushing 10 new bottles of brake fluid through the system cleaned out all the debris and cleaned the seals?
New HCU:
1. Brakes hold great at stop lights, no additional pressure needed after 30 sec.
2. Stopping is better and the pedal is more firm, my old pedal was a little spongy but not bad.
3. I haven’t checked the MC reservoir yet to see were the brake fluid level is.
Conclusion: I’m now a believer in changing your brake fluid every 2 years! I also think RV brake fluid gets abused when braking 20,000 plus lbs going down mountains. I recommend replacing your brake fluid with DOT 5.1, not DOT 3. DOT 5.1 has a 90* higher wet boiling point. You can mix (DOT 3, DOT 4 & DOT 5.1) “Don’t use “DOT 5”
Note: Dry Boiling Point is fresh Brake Fluid, Wet Boiling Points is brake fluid that’s been in the vehicle exposed to moisture / condensation.
DOT 3 Dry Boiling Point 401* Wet Boiling Point 284*
DOT 4 Dry Boiling Point 466* Wet Boiling Point 311*
DOT 5.1 Dry Boiling Point 518* Wet Boiling Point 374*
It’s hard to find DOT 5.1 so I order it from Amazon, $14.05 Wagner Dot 5.1 SEVEREDUTY Brake Fluid, 32 oz; 946 ml</SPAN>
https://www.amazon.com/Wagner-Dot-SEVEREDUTY-Brake-Fluid/dp/B000C92RDC/ref=sr_1_3?ie=UTF8&qid=1483891973&sr=8-3&keywords=dot+5.1

Wow some more great info, especially about the Boiling points of the different types of Brake Fluid.

DriVer · 01-08-2017, 06:43 PM

Of note with DOT5.1 is that its hygroscopic properties work overtime.

Oemy will advise to change your brake fluid annually and use DOT3. I have to agree with him however I'll go 2 years and hopefully no more than that. The point I expect is that changing the fluid more often increases the reliability of the braking system and assures that the fluid will bring the vehicle to a stop within design parameters.

If I am not mistaken, DOT 5.1 is recommended for use in recent Ford F-Series Super Duty F-53 Chassis.

olskool4x4 · 01-08-2017, 07:00 PM

I agree Driver, that's why I'll test the brake fluid with a brake fluid test and flush it ever 2 years.

I just checked my Master Cylinder and the fluid was between the MIN and MAX marks. The new HCU has maintain pressure overnight, my old HCU would release the fluid back into the MC.

51chevy65 · 01-15-2017, 05:05 PM

I want to say that I was having issues 18 months that lasted for 5 months. there where times I had atc/abs lights on and off, times park did not want to release, rear flashers staying on (both) low pressure warnings on dash, cruise control not working no brake lights just flashing. Couple shops wanted me to sign over my 401K before they would attempt to repair. After talking to Wabco tech guy and him telling me what could be problem, I found that my master cyc. what the fault. There is a micro switch mounted to base of master cyc. That switch is not just a open/close switch. The master cyc. had small leak and was playing havick with everything mentioned above. changing master cyc. with new switch aprox. $300 made the fix.

olskool4x4 · 01-16-2017, 06:50 PM

I drove the RV with the new HCU towing my Jeep CJ7 and no issues, everything worked great. Here's a 10 min video I did when installing the HCU it's not great but it might help someone.

https://www.youtube.com/edit?o=U&feature=vm&video_id=GVdycOiDWWk

olskool4x4 · 01-16-2017, 06:58 PM

Here's another short video on replacing the HCU electric pump motor.

DriVer · 01-22-2017, 10:07 PM

Cool beans! Thanks for the video.

YngRvrs · 04-06-2017, 01:21 PM

well, Ihave not been here for sometime. We had a HCU issue back in 2014. Without going intoalot of detail, we had 2 defective units sent to our repair facility(Gramps-Terry LaBonte Chevy). Finally I was told it was ready. The day we picked it up the ATC light was on and has stayed on. My advisor at Terry LaBonte attepted to explain the light and it was not on after tehere repairs where completed the week before. We hasd to take motorhome as they had it close to six months. My Workhorse rep asked me to take it to Lazydays in Tampa to have there Workhorse chassis tech look at it. After a few calls to factory rep and engineer from Merritt Wabco they determined it was a software anomaly and as of June 2016 there was no solution. So we drive with the ATC light on.