trailking brakes question

[daubrey]

Need help with a trailking 3 axle 50 ton air ride trailer. The brakes seem to have a 5-10 second delay after releasing the brake pedal. I have replaced the sealco valve part #110200 on the trailer and it didnt help at all. All 6 chambers release at the same speed so I dont think 1 axle is holding up. it seems that the air is not releasing fast enough to allow the springs to back off quickly. talked to trailking, they mentioned the valve, but to no avail. tractor works fine with other trailers. any suggestions would be greatly appreciated.

 

[Jeff D.]

Hello Daubrey,I'm not familiar with the Trailking trailer,but I've had the same problem that you're describing with other trailers,and it has always been a valve in the trailer brake system that was the problem.

I pull different trailers every day,and each seems too have different valves in the brake systems,some with many valves.Does your system only have one vavle,the one you've replaced?I had the same problem on Tuesday with a trailer,very slow releasing.It was so irritating that I stopped and kept pumping the brakes thinking I'd loosen the valve that was the problem.It didn't help.I called the mechanic,and he explained where the valve was that would cause the problem.(the particular trailer only had one "master" valve,that controlled all braking,including the anti-lock portion.)I pulled the glad hands off,and poured alcohol in the air lines,the re-connected them,pumped that through the trailer brake system,and then they were fine.There must have been some ice in the valve.

Since your located in a warmer part of the country,I'd guess it's not an ice problem,but I'd still suspect its a sticky brake valve problem.I'd check to see if there isn't another valve under there that couldn't be the problem.Good Luck!!

 

[Jeff D.]

I thought of another area of your trailer brakes that could cause a similiar type of problem,but usually it's accompanied by the fact that your trailer brakes "come-on" very fast and are much more aggressive than normal.(in addition to the slow releasing)

If you had an air leak on the portion of your brake system that releases your brakes,i.e. the air that is supplied to your canisters that overcomes the springs for parking.If there was a leak on that side of the system,of if you were to have a small hole in one of the diaphrams that are internal to the canisters,your pressure on that side would be low.When you push on the pedal,full air is supplied to the service brake side,and they come on real fast,as there isn't the normal pressure on the opposing side(overcoming the springs)

I've had that type of problem also,and it usually seems to take longer for the parking brakes to release,plus the fact if you just breath on the pedal it's throwing you into the windshield.Never fun if it's slippery out,or if your trailer is unloaded!!

If that describes how it's acting,and since you've already replaced the suspect valve,I'd check that part of the system.Good luck!!

 

[daubrey]

should have mentioned

I should have mentioned all 6 of the brakes are single chambers, not the locking type. thanks

 

[Ford LT-9000]

The trailer has no spring brakes what so ever ?

Some one has messed with the brake pots all the Trailking trailers I worked on have piggy back pots on all 4 wheels.

The trailking trailers with spring brakes don't have a quick release valve so the air on the trailer has to bleed through the trailer brake button on the truck.

 

[daubrey]

It looks to be a factory set up. The single valve does exhaust air out the bottom, but not in a sudded burst. You can hear it slowly bleed off and watch all six slack adjusters ease off at the same slow rate. This plays havic when your traveling down the road.

 

[Jeff D.]

Daubrey,I'm also suprised that it doesn't have brake canisters with springs. Possibly a problem with the larger size of the canister,and interference.It must have some type of emergency brake system,in case the trailer were to come off the truck,the trailers brakes would set.

This is what I understand so far:

The truck doesn't have similiar problems with other trailers.(most likely eliminates the truck as the problem)

The trailer has only one valve,which was replaced with a new one.The problem didn't change.(could the valve have been plumbed wrong before,and you've duplicted the error on the new valve?)

You've six diaphram only brake cans,each with one hose.All release at the same rate.(Do the hoses connect to the valve individually,or do they go to a common connection,then to the valve?If a common connection,could there be a internal obstruction in that connection causing slow air bleed?)

The only other things I can think of are:

Could the supply line,between the glad hand and valve,be pinched or obstucted causing slow bleed off of pressure when you release the brake pedal?To the valve it would appear like your slowly backing off the brake pedal,therefore it would slowly decrease the pressure to the cans.(It would also cause the brake pressure to increase slowly as you brake.Might be a clue if it seems like it does do that.)

Unless the trailer is old,old,old it must have some provisions (by law) for emergency braking.Possibly an air tank that dumps air to the cans when the emergency(red)glad hand is removed.I would think this odd,but I can't think how else it could do it.There could be a problem in this area that would cause the service brake problem.

That brings up the question,is this trailer an antique?(pre 70's)If so,then that might also be an issue.They didn't have any standardization on brake systems in the early trailers,and I've heard of problems when mixing trucks and trailers of different brake design.They may have the same emergency/supply air line hook-ups,but the air flow transfer rates,brake chamber volume,etc,were sometimes very mismatched between truck and trailer,until the manufacturers were given guidelines on what they MUST be.

I hope you find the problem,and if you do please post what it was.I'm very curious now!

 

[daubrey]

the trailer is mid 90's, not sure the year. The valve I replaced receives air directly from the glad hands through a service port and an emergency port. In the middle of the valve is a port that feeds 2 air tanks. On the bottom of the valve are 4 ports, the front two go to each chamber on the front axle, the other two go to the inlet on the middle axle chambers and the rear axle is fed from lines tied directly to the middle axle chambers. No other valves apply to the braking system. From what I understand the brakes will come on if the emergency supply line comes loose, but brakes will only be supplied while air pressure remains in the trailer tanks. (is this legal?) Good idea on the supply line from the glad hand, I will check on that.

 

[Jeff D.]

Although different,I think that could be a legal system.It would provide braking in the event that the trailer breaks away from the truck.

Braking would be dependant on air stored in the tanks,but electric brakes on trailers will only have brakes until the battery goes dead once the break away switch is pulled,and they're legal.

The down side to a system like that is the diaphram life might be shorter,due to the constant pressure while parked,until the air all leaks out.Also you'de have no brakes while you were backing under the trailer,unless you hooked up the glad hands first,and pulled the johnny bar down,before completing the coupling.A unknowing person could end up chasing that trailer all around the parking lot while backing under it.(if it had empty air tanks)

Trailking must have felt that the compromise with this system was necessary for some reason.I imagine it's a low boy or drop deck and has too little of room around the axles for a different system.

 

[daubrey]

Found the problem! The service line was kinked right behind the glad hand.
thanks for the help!
D.

 

[truecountry]

i was going to say pinched air line but was beat to it .... the alcohol in air most time works for sure ......here lately my trucks are having problems with air dryer hissing air thur purge valve and some have been rebuilt ( bendix ) and they strated hissing again i began to notice the sicone grease that came with kits were hard and sticky to touch , i started useing air tool oil and never had a problem since ,,,,, the wabco air dryers i hate they hiss out the turbo valve beside the purge valve and sometimes truckers would call and give me wrong info ...i just work on them not drive them but i try my hardest to fix them right the first time and keep everyone safe on highways

 

[Kgmz]

Just add something for anyone else that ever has a problem like this.

We have a TrailMax TRD54 tri-axle and about a year or so ago I had a problem just like this, brakes slow to release. So I got under it and didn't really see anything wrong, but went and bought the same type of valve to be sure. When I took the hoses off of the old valve I saw the problem, I had bee's building a nest in the air lines and when I hooked up the air hoses it forced the bee's and all there crap up against the valve. So I blew the air lines out and replaced the valve anyway, cleaned the old one so I have a spare now.

So now to prevent future problems I now cap my glad hands with another set that is plugged off.

 

[Jammar7]

Yep, that'll do it, wouldn't let the air release on the service side. If that doesn't do it, check your tractor.