Flat Towing, unexpected brake lockup.

[73Corvetteman]

So was the problem active brake boost making the auxiliary brake system too active or did the Bronco apply brakes independantly?

There auxiliary system is adjusted for no boost, if boost activates the auxiliary system applies pedal too far due to lack of resistance of the brake pedal so the first one.

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[sfearnow]

Details:

2022 Ford Bronco Outer Banks Sasquatch 2.7
Flat Towed with professionally installed air brakes. (Demco Air Force One with Blue Ox tow setup)

Just had my parking brake engage while flat-towing yesterday. On my return trip, second day of travel and had not been in or touched the Bronco at all.

180 miles into the day, we stopped for 20-30 minutes with RV engine still running, but parked.

Pulled out of the rest area in Shepherdsville, KY and saw a cloud of smoke behind me. Pulled over and saw long rubber tire trails all behind me. Both rear Sasquatch tires flat as can be from being dragged.

When I got in to disconnect flat-towing and disconnect so the tow truck could load, there were no errors on dash, still properly in flat towing mode and gear still in Neutral. The only thing of note was a red PARK indicator on.

This was not manually engaged, and took me a while to find where to disengage it as we live in a flat suburb of Austin, TX.

Had roadside assistance tow me to a tire shop—which of course doesn’t have the stock Goodyear Sasquatch tires that are on the rest of the Bronco. Will go mismatched from here and rotate old to rear.

Now in the unenviable position of not being near a Ford dealer—with family and dogs still a three-day drive from home.

Trying to decide whether to unplug the power to the rear brakes on the Bronco (tire tech recommendation) and rely on front only plus RV brakes to continue or try to find the rear e-brake/parking brake relay.

Thankful to find these threads as the only other solution I could fathom was someone nefariously engaging the brake at the Rest Stop. Really not a reasonable conclusion, but at my wits-end as it has been working flawlessly until….it wasn’t. Now one day behind in travel and out the cost of two tires (so far), plus a tow. Will have to consider whether to upgrade to remaining three tires to match when I get home—so cost will exceed $2,300 even if it doesn’t fail again on my way back to the Austin metro.

 

[dgorsett]

There should be a fuse to pull to disable parking brake or unhook wires at actuators at calipers . This would disable only parking brake and not service brakes. But might send a code to the Bronco causing a freak out.

I had brakes set (never new if service or parking) inexplicably off road once, never has happened again.

BTW I never use the parking brake during the flat tow set up process or while flat towing nor do I let anyone help me set up (anymore). A friend helped with my old Wrangler once and set the brake, not as bad as your result but anyway...

 

[Bsenecal]

Details:

2022 Ford Bronco Outer Banks Sasquatch 2.7
Flat Towed with professionally installed air brakes. (Demco Air Force One with Blue Ox tow setup)

Just had my parking brake engage while flat-towing yesterday. On my return trip, second day of travel and had not been in or touched the Bronco at all.

180 miles into the day, we stopped for 20-30 minutes with RV engine still running, but parked.

Pulled out of the rest area in Shepherdsville, KY and saw a cloud of smoke behind me. Pulled over and saw long rubber tire trails all behind me. Both rear Sasquatch tires flat as can be from being dragged.

When I got in to disconnect flat-towing and disconnect so the tow truck could load, there were no errors on dash, still properly in flat towing mode and gear still in Neutral. The only thing of note was a red PARK indicator on.

This was not manually engaged, and took me a while to find where to disengage it as we live in a flat suburb of Austin, TX.

Had roadside assistance tow me to a tire shop—which of course doesn’t have the stock Goodyear Sasquatch tires that are on the rest of the Bronco. Will go mismatched from here and rotate old to rear.

Now in the unenviable position of not being near a Ford dealer—with family and dogs still a three-day drive from home.

Trying to decide whether to unplug the power to the rear brakes on the Bronco (tire tech recommendation) and rely on front only plus RV brakes to continue or try to find the rear e-brake/parking brake relay.

Thankful to find these threads as the only other solution I could fathom was someone nefariously engaging the brake at the Rest Stop. Really not a reasonable conclusion, but at my wits-end as it has been working flawlessly until….it wasn’t. Now one day behind in travel and out the cost of two tires (so far), plus a tow. Will have to consider whether to upgrade to remaining three tires to match when I get home—so cost will exceed $2,300 even if it doesn’t fail again on my way back to the Austin metro.

Good luck with everything. Bummer about the parking brake coming on.
BTW, nice coach.
Brian

 

[Fordified1]

Details:

2022 Ford Bronco Outer Banks Sasquatch 2.7
Flat Towed with professionally installed air brakes. (Demco Air Force One with Blue Ox tow setup)

Just had my parking brake engage while flat-towing yesterday. On my return trip, second day of travel and had not been in or touched the Bronco at all.

180 miles into the day, we stopped for 20-30 minutes with RV engine still running, but parked.

Pulled out of the rest area in Shepherdsville, KY and saw a cloud of smoke behind me. Pulled over and saw long rubber tire trails all behind me. Both rear Sasquatch tires flat as can be from being dragged.

When I got in to disconnect flat-towing and disconnect so the tow truck could load, there were no errors on dash, still properly in flat towing mode and gear still in Neutral. The only thing of note was a red PARK indicator on.

This was not manually engaged, and took me a while to find where to disengage it as we live in a flat suburb of Austin, TX.

Had roadside assistance tow me to a tire shop—which of course doesn’t have the stock Goodyear Sasquatch tires that are on the rest of the Bronco. Will go mismatched from here and rotate old to rear.

Now in the unenviable position of not being near a Ford dealer—with family and dogs still a three-day drive from home.

Trying to decide whether to unplug the power to the rear brakes on the Bronco (tire tech recommendation) and rely on front only plus RV brakes to continue or try to find the rear e-brake/parking brake relay.

Thankful to find these threads as the only other solution I could fathom was someone nefariously engaging the brake at the Rest Stop. Really not a reasonable conclusion, but at my wits-end as it has been working flawlessly until….it wasn’t. Now one day behind in travel and out the cost of two tires (so far), plus a tow. Will have to consider whether to upgrade to remaining three tires to match when I get home—so cost will exceed $2,300 even if it doesn’t fail again on my way back to the Austin metro.

supposedly the flat tow procedure from Ford has been updated with the added need to pull two fuses related to the brakes. I was thinking it was mentioned in this thread somewhere. I did not go back and look.. If not here it’s in another. Make sure you have the latest version of the Bronco flat tow procedure.

Also my rear monitor has a microphone and I always turn up the volume when I first set out on my way to make sure I don’t hear any strange sounds. It actually saved my Jeep gladiator tires as the parking brake locked up on it one time. That rear microphone also clued me in that a safety chain had come loose and dragging while towing a trailer.

 

[grtharris]

There should be a fuse to pull to disable parking brake or unhook wires at actuators at calipers . This would disable only parking brake and not service brakes. But might send a code to the Bronco causing a freak out.

I had brakes set (never new if service or parking) inexplicably off road once, never has happened again.

BTW I never use the parking brake during the flat tow set up process or while flat towing nor do I let anyone help me set up (anymore). A friend helped with my old Wrangler once and set the brake, not as bad as your result but anyway...

The parking brakes are controlled by the ANATI-LOCK BRAKE SYSTEM (ABS) MODULE. The fuses that power that module are F28 60A and F29 60A which are the ones Fords said to pull when flat towing.
By the way my bronco is at the Ford dealer, my extended warranty is about to end and I have a small oil leak around the right side of the rear axle, so I took it in to get as many of the recalls done as possible. I also added the brake issue of the EBB randomly coming on when flat towing.
Going to send the service writer a leak to this thread.

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