[johnlennox]

I have a new 5th wheel trailer with Dexter disc brakes and electro/hydraulic actuator installed by the trailer manufacturer, NuWa. My truck has a BrakeSmart controller purchased and installed around mid-2008.
After about 2000 miles on the trailer, I have consistently experienced about a 2 second delay between truck brake application and trailer brake actuation. This delay is consistent at about 2 seconds whether heavy or light brake application.
I have tried different settings of gain and preact on the BraksSmart with no effect on the delay.
Is this normal? (I hope not)
Any suggestions on how to minimize or eliminate this delay?

John

 

[fulltimer50]

Be sure the "pump mode " is set to on in the setup??

 

[johnlennox]

Thanks for the reply George
The BrakeSmart does recognize that it is connected to an electro/hydraulic actuator.
It turns out that the likely culprit is air in the disc brake calipers. Depending on their orientation on the axle, the bleed fitting may be at the bottom of the caliper. In that position all of the entrained air in the caliper may not be purged. In that case I will need to loosen the brake line connection at the very top of the caliper. This according to the brake system manufacturer, Dexter.
Dexter says that if the system is functioning properly I should feel the brakes taking hold almost immediately. To build up enough pressure to lock up the wheels takes about 3/4 second.
John

 

[fulltimer50]

Seems to me if you bleed from the brake line, there will still be air in the caliber.

 

[Believer45]

Seems to me if you bleed from the brake line, there will still be air in the caliber.

Not if the brake line is at the very top of the caliper as it is installed.

 

[Wren]

Take the caliper off and turn it over to drain it.

Get all that air out of the brakes.

 

[davydee]

John, let us know if that fixes it. We've got dexters on a different brand trailer, but haven't towed yet to see if we have a similar issue. David

 

[johnlennox]

The calipers are plumbed so that the inlet brake line is atteched to the top of the inside of the caliper. Then, at the bottom of the caliper, there is a short line that connects the bottom of that side of the caliper to the bottom of the other side of the caliper. The bleeder valve is at the top of the other side of the caliper.
This is the type of caliper that has brake pads pressurized from both sides of the disc.
From the way the caliper assembly is plumbed, I can see that is is next to impossible to get all of the air out of the caliper assembly by the normal bleeding procedure. What Dexter has suggested, and what I will be doing tomorrow (with the help of Dear Wife who will be the brake actuator) is to first bleed the side with the bleeder valve is case there is air entrapped there, and then loosen the incoming brake line on that side and see what comes out there. After that I will give the brake line itself a good flush to ensure that there is no air in the line.
Then on to the next wheel....
Since I have to remove the wheel to get at the bleeder, I figure it will take me about 2 hours to do all four wheels (these things always take longer than you think).

Then a road test to see if the problem is cured.
I'll let you know how it goes.

John

 

[johnlennox]

OK I did it! .....and what a job - 5 hours!
There was air in the inside half of the caliper on both brakes of the rear axle.
I messed around with a bleeding procedure that would get air out of the inside half of the calipers since that was the area most likely to have entrapped air (inlet line connected to the top, bleeder on the outside half at the top.
First, activate the E/H Actuator pump and open the bleeder slightly to insure that there is no air in the top of that half of the caliper.
Then move on to the inside half of the caliper.
I ended up disconnecting the inlet line from the inside half of the caliper, using a short length of clear hose (tygon tubing, 1/8 id) slipped over the end of the inlet line and over the end of the bleeder (first activate the E/H Actuator pump to fill the line with fluid and insure that there is no air in the inlet line). Another longer length of tygon tube (1/4" id) forced into the female fitting the the inlet line screws into. The other end of that line into a container. Activate the E/H Actuator pump and the reverse flow through the caliper assembly should carry out any air entrapped in the inside half of the caliper.
Result -
- On one inside caliper half the intrapped air came right out when the fluid started flowing.
- On the other inside caliper at the other end of the axle no air came out while the fluid was flowing. But as soon as I shut off the E/H Actuator, air began bubbling into hte line our of the inside caliper. I waited until the air bubbles stopped, turned on the Actuator again, no bubbles, stopped it and more bubbles entering the line. Repeated again and this time no bubbles when the Actuator turned off.

That was it. Brakes now actuate with no perceptable delay.

John

 

[fulltimer50]

You Done It. Good Job.

 

[davydee]

Thanks for letting us know! David

 

[94_turbo]

and they let the trailer out of the factory that way--:icon_rolleyes::icon_rolleyes:

 

[johnlennox]

Letting out of the factory I can understand. It's hard to tell until your out on the road.
What I don't understand is how it got to the dealer without some mention of malfunctioning brakes.
Anyway, fixed now.
I'll tell you what........disc brakes are awesome!!!!! You stay "stop!"......they stop----period. These discs are bigger and thicker, and pads are bigger, than on my F-350 dually.

John