I have a fontaine trailer, the service brakes work fine. I bought it off someone else and the abs wiring had been removed so that is not working, but when I pull the emergency/parking brake valve, the trailer brakes will set for 1 second and then release and i will not have any parking brakes. So when i disconnect, the trailer wants to roll. I cannot figure out why, i dont have a diagram for the lines or anything. Any help.
The first question is, does it have spring cans? the double brake chambers? If it does, and you disconnect the lines from the truck, and drain the trailer air tanks, do the parking brakes come on?
No it has the single type 30 chambers. And if i drain the tanks the brakes dont move. Only work when using service brake.
No springs no parking brakes. If it was the old emergency air setup, the air in the trailer tanks would hold the brakes on until it all bled off, assuming the relay valve was working correctly.
That's pretty strange, if it's new enough to have abs it should have spring brakes. Is there any extra plumbing like somebody pulled the spring brake cans?
Maybe it's missing because it never had any?
Believe it or not, and I have no idea why, but it's not unusual for Lowboy trailers to not have spring brake chambers, even those with ABS, I've seen several. :beatsme
I think in the past you could order them that way, and some people had reasons to do so, like being able to move them with dozers or whatnot with no air supply. I won't swear to it but I believe current DOT regs require them now.
I've also noticed on newer tractors it's common to see spring brakes only on the front drive axil ? That was common on 1960's & 70's trucks . *** !! Guy pays good money today on a truck with spring chambers only on one axil . Added spring chambers to a 2008 Mack last year for a customer . Now his buddy is sending me two more to do this year .:beatsme Back to the trailer brake issue ...... First thing I check if brakes are acting funky is for a mud dauber in the main line between the glad hand and relay . Unhook both lines at trailer relay & make sure you have good airflow through them . Damn Mud wasps
This sounds like a mud dauber nest to me also. But in order to know how to proceed, you are going to have to provide a simple schematic of how it is plumbed and what kind of valves it has. Model numbers and/or photos.
Gladhand screens can be your best friend sometimes. I once had to unplug and clean out a 2006 Peterbilt air system that was plugged up all the way back to the TP valve because the old trailer the guy picked up was full of bugs. Got his air working and the dumbutt hooks back up to the same trailer... Really?
Only time I've seen that done on purpose was for backing into paving machines, the apron would bust the spring chambers.
The Murray I pull has no spring brakes. The parking brake holds until the air bleeds down. If you leave it set a while, be sure to charge it up before trying to back under it. I have built an extension line, an old coiled air line with a gladhand on each end to be able to do this easily. Scraper dollies and baskets are made that way as well, so you can open the petcock to release the brakes in order to roll it under the raised rear end. The mud dauber has been my nemesis on trailers that sit a long time between uses. That will sure ruin what should otherwise be an easy trip.
It's an amazing thing that a lowly mud dauber can shut down the movement of tons of iron, but such is the case. :yup
I guess that's why they make those blanking covers for gladhands? LOL
I have had them block the tiny exhaust port of valves under the truck, making necessary complete removal and disassembly of the valve, getting covered in filth, all to poke out a bit of dirt with a wire and put it all back together. So if you really wanted to make it mud dauber proof a screen on every exhaust port would be the thing....gladhands aren't the only thing.
We certainly have plenty of dirt daubers, but we also have some kind of bug that loves to chew up leaves and pack them into the fitting right behind the gladhand, where you can't see them even if you look. As soon as you put air on the line, you fill the valve with thousands of tiny pieces of leaves. If I ever figure out what kind of bug that is, I'm going on an extermination crusade! I've started using those gladhand rubbers that have the cross slits in them.
Update: The parking brake sets and holds, if we turn the truck off they bleed off immediately. If we disconnect the trailer with the truck on, they bleed off slowly. We are still at a loss. Dont hear any major leaks, something that would make them bleed off so fast. Only thing i can think of is that the air tanks for the trailer arent holding air, or supplying to brakes. View attachment 80300239.pdf
Some things don't add up here. If the ABS is not active then turning the truck off and on should not effect the condition of the brakes. Does connecting and disconnecting the electrical connector have the same effect? It is easy enough to check if the tanks have air, just open the drains. If the tanks have air and the brakes are not on then check the line between 7 and 9 on the drawing you supplied. It should have air. If it has air and the chambers do not then it has to be the combo ABS/relay valve #9