Brake hose failures

[prgynt]

I have a 2004 F150 5.4L towing a 16ft travel trailer with dry weight of around 4500lbs. Been towing it over mountain passes for years.

This last weekend when going over a low pass, my passenger rear brake hose ruptured. I managed to get it down the hill into town before I lost all fluid. I figured it was 20yrs old, just failed. A brake shop replaced the hose, bled all the brakes. Not sure what brake hose they used. Got to my destination including going down another pass. 2 days later driving home, new hose pops off where crimped. Had to disconnect trailer, get truck towed to auto parts store. No repair shops open on Sunday. Figured it was a bad hose. Bought a new one at NAPA, installed it myself, bled brake line. 50 miles later going down another low pass, hose pops off same as earlier. Brake fluid is very hot. That is 3 hoses in 48hrs.

Don't know make of brake controller offhand. Was thinking if trailer brakes getting old, not sharing the load and putting too much stress on truck brakes? Maybe fluid getting too hot and causing failure at weak point (where hose is crimped to connector)?

[Grit_dog]

I’d guess 500+ deg (guessing) of full throttle exhaust could cook a brake hose. Although that doesn’t explain it popping out of the crimp, twice, I think?
But it’s the only plausible explanation.

[time2roll]

Yes that broken muffler would be a very odd road hazard. 😉
Thanks for the follow up.

[prgynt]

time2roll wrote:
This is the hose mounted on the solid rear axle and the only real flex is the very slight movement of the caliper? Do I have that right? If so there should be virtually no mechanical stress on the brake line. Either the line is defective or an incredibly odd road hazard. Any pictures?

I would be getting my next hose direct at a Ford dealer.

So I found the exhaust line had broken at the muffler. My theory is hot exhaust overheated the brake fluid,made the hose fail. I just replaced the entire exhaust line and muffler, will need to take trailer out to test it. I think the exhaust got really hot going up the mountain pass pulling the trailer, then hose failed on downward side.

[time2roll]

This is the hose mounted on the solid rear axle and the only real flex is the very slight movement of the caliper? Do I have that right? If so there should be virtually no mechanical stress on the brake line. Either the line is defective or an incredibly odd road hazard. Any pictures?

I would be getting my next hose direct at a Ford dealer.

[mkirsch]

I agree. Those hoses are designed to withstand all the pressure. Now whether the cheap aftermarket hoses you've been installing are built to that specification, that's another matter altogether. Cheap aftermarket, because that's all there is for your 20-model-year-old-in-another-month truck. OEM hoses were likely discontinued 10 years ago.

The pressure in the hoses is proportional to the pressure you put on the pedal. You would have to be pushing on the pedal like an 800lb gorilla to have the slightest hope of bursting a brake hose. I'm not sure the master cylinder can even produce that much pressure. I'd like to think you'd have noticed something like that though, and mentioned it in your post.

In other words, if the trailer brakes were not "sharing the load" you would have to be pushing on the truck brakes harder than normal to stop, VERY hard, in fact. You'd notice that, though with a ~5000lb-ish trailer behind that truck it should have more than adequate brakes on the truck alone to stop the whole rig.

Brakes work by converting motion into heat, so everything is going to get hot including the brake fluid. So the brake fluid being hot may not mean anything.

A hung caliper that is causing burst hoses is going to be literally SMOKIN' HOT. Uncomfortable to get within a few inches of. Again, something I'd hope you would have noticed at the time and mentioned in your post.

Bad batch of hoses is where my money is. If they all came from the same parts supplier...

[Grit_dog]

It’s an old truck. Do you have a hung up caliper that is boiling brake fluid? Only plausible reason (even though I’ve never seen that happen in 35 years of doing a lot of stupid human tricks with little trucks and heavy trailers) besides defective.

[Grit_dog]

Edit
Edit edit.
The rear brake caliper hoses can’t get pulled or twisted during driving. They’re in a fixed position unless removing the caliper.
As unbelievable as it sounds, you may have hit the bad brake hose lottery!
Would think something safety related would not have that chance of failure, but I’ve returned complete sets of wire rope rigging because all the swathes just pulled apart. Luckily they were bad enough that they didn’t take any significant loads before cutting loose.

[Krusty]

Brake hoses are pretty robust and generally overbuilt for their use. I dont think a brake system would ever be able to generate enough pressure to damage one. Same with heat unless it is contacting an exhaust pipe or something. I agree there has to be something causing it to stretch or chafe etc.

[prgynt]

BILDER wrote:
Look for some type of over travel of axle. Made lot of hoses, pulling apart at the crimp is not a normal failure from pressure. more of stress from alingment, twist or pull

That is a really good idea, thanks!

[BILDER]

Look for some type of over travel of axle. Made lot of hoses, pulling apart at the crimp is not a normal failure from pressure. more of stress from alingment, twist or pull