Another Air Leak Thread ....

[G&K]

Ahh. Trick question. You fix the marker right now because it will get you a ticket at the scale.

 

You make sure your air loss rates are equal to or less than the table below.

 

There is no real judgement required. You are not allowed to drive with much of a leak and the test is simple.

 

Geo

 

The Official Air Brake Handbook

 

Drivers must be alert for air brake system leaks and pressure loss in the air tanks when brakes are not being used. These conditions indicate air loss in the air brake system. For safety, drivers should test the air-loss rate of the vehicles brake system.

 

To test the air-loss rate of the brake system, release the spring brakes, establish normal air pressure and shut off the engine. Hold the brake pedal in the fully applied position and observe the air-pressure readings for one minute.

 

The pressure will drop noticeably when the brakes are first applied, but must not continue to drop at a rate greater than specified in the chart below. The amount of pressure drop that takes place when brakes are first applied is not considered when performing the air- loss rate test. The air brake system is defective when air loss exceeds the specified values.

 

Step-by-step procedure

 

Properly secure the vehicle and release the spring brakes.

Ensure that the air brake system is within its normal operating pressure range. Shut off the engine.

Press and hold the brake pedal in the fully applied position.

Note the pressure indicated on the primary and secondary air tank gauges.

Note the change in pressure over one minute.

Pass

 

The vehicle passes the test when the drop in pressure is equal to or less than the value specified for the vehicle.

 

Fail

The vehicle fails the test when the drop in pressure exceeds the value specified for the vehicle.

 

Important: The Ontario Highway Traffic Act and regulations prohibit operation of a vehicle with an excessive air loss rate.

 

Air Loss Rates

Type of vehicle

Maximum allowable air loss

 

Straight truck, tractor or bus

21 kPa (3 psi) per minute

 

Tractor and trailer

28 kPa (4 psi) per minute

 

Tractor and two or more trailers

41 kPa (6 psi) per minute

[Jack Mayer]

 

I know I will be shot down again on this one or even "Deleted".

 

Disagreement will not get you deleted or other action taken. Personal attacks of any kind will. There is plenty of room here to disagree on topics as long as it is civil. In this particular case the "challenge" being given is good....it will make people think.

[G&K]

Yes. It's great that there are clear, standardized guidelines on what is acceptable.

 

Geo

 

So you can have leaks with in certain tolerances??

[Guest THE TRAILERKING]

OK, move along Boys.....................Nothing to see here!

[G&K]

On the contrary. It was a good thread to stir some thought about a common, important issue. Thanks!!

 

OK, move along Boys.....................Nothing to see here!

[Dollytrolley]

Get out the flame throwers......I'll get my Nomex undies on........

 

In the days when trucks would get bit by T-Rex dinosaures ........Grumps would say........"Ok Einstine, how much better will the air leak the farther you drive??..........ANSWER: likely the leak most often gets worse ( exception.....frozen valves need to be "thawed" to be "fixed"..........

 

If we focus out and leave the lawyers in the sleazy bars........consider that "modern" trucks are a fairly large collection of "tolerated leaks" with cheap plastic valves and "push-leak-fittings".........cheap......not better.....

 

Back in the Stone Age......airlines that really mattered were stainless-braided with metal to metal fittings.......did the leak......ya, Very little.....did the metal valves leak.......ya, very little........not cheap but better in the long run........

 

Air leaks these days seem to be the norm.......the question seems ...........just how much of a leak is ok and if ok how much time do we have before the leak is not ok??? We tend to trouble shoot air leaks with the truck stopped but trucks leak more when moving down the road......

 

In the Stone Age leaks were fairly rare, but when you had a leak, it was mostly not OK..........it tended to be a real leak that needed attention.......with cheap plastics air systems today it is more complex since leaks are just a growing problem that takes a eagle eye to keep on top of........

 

Drive on.........(Leak.......little)

[HERO Maker]

TK - Air leaks happen. If it passes the brake test, don't worry about it and when you have time, spend it looking for the never ending leaks.

 

So back to my quote - YOU WILL HAVE LEAKS! Fail the brake test - get it fixed. For all those other leaks (minor) have fun tracing them down. And as our friend Dolley says - Drive On.

[HERO Maker]

I don't go back to the stone age - although I feel like it - but did those trucks lock up your brakes if the air loss was great? (today's safety factor)

[RickW]

Wow! Had no idea this thread would take off the way it did overnight.

 

TK rest assured if the truck was unsafe I would not even consider using it or possible even moving the truck until the problem was resolved. Like most here I tend to be anal about maintenance and fixing things. In the past 20 years have only been stuck twice due to a issue. In both cases routine checks prior to the failure did not indicate even a hint of any potential issues.

 

This leak is very minor and slow. The fitting, which was replaced yesterday, was a much larger issue and still passed a brake leak down test with flying colors. Honestly the leak I asked about I doubt would be found, at least easily, in a truck stop, rest area or on the side of the road while being looked over by one of Phil's peers. When I found the leak it was quiet enough that I could hear the hum of my bear fridge and the squirrel throwing oak acorns out of the tree 50 yards away. It was deafly quiet.

 

After fixing the fitting, backing the truck out and parking it, I could only hear the leak with the hood closed by leaning in to the hood with my ear almost touching it. Several hours later (4 or 5) I could not hear the leak as I went by but I still had air in all 3 of my tanks. Greatly depleted, but still enough that when I pulled the lantern air was released.

 

Based on everything, I will make this weekends 600 mile trip but keeping a close eye on the problem to see if the status changes. If I have a change in status, while not idea, I will fix the problem while on the road if necessary. I know I will not have time to fix it next week prior to the rally, but if the condition changes any I will make sure it is resolved prior to departing on the 9th. But right now I am pretty confident that I will not have any issues waiting until after I return and can repair it at my leisure.

[Dollytrolley]

I don't go back to the stone age - although I feel like it - but did those trucks lock up your brakes if the air loss was great? (today's safety factor)

Yes Hero even back in the Stone Age the trucks had spring brakes that would "shot-gun" with loss of air.......not much has "improved" in air brakes since ......,,air was invented......exceptions is better air dryers and maybe auto-adjust-slack adjusters............disk brakes maybe.....

 

In fact many old trucks had a low-tech air-loss flag arm that drooped down from above the drivers windshield that said "hey dummy your about to have the spring brake to shot-gun then you are walking............"

 

Drive on.........(not shot gunning......)

[rdickinson]

Yes. It's great that there are clear, standardized guidelines on what is acceptable.

 

Geo

 

It looks like the Ontario and BC leakdown standards are the same. Have a look at the link I posted. I'd hope the leak started slow and would increase over a period of time giving you adequate opportunity to have it fixed. My rig had a leak in the airbags line. Berkes in Alberni did some hunting and found the plastic fittings that come with the Trailsaver were leaking so they were switched out with brass. In their search they found the air manifold on the dash leaked pretty badly. The mechanic said it would fail inspection. I had it replaced as individual parts were not available.

 

So I was driving a leaky truck, discovered a problem and got it fixed at the earliest opportunity. Don't know how long it had been leaking. But now doing the Pretrip, it would have been discovered sooner as are several other problems.

 

Same with the harness replaced last month. Had it not been replaced at a cost, the problems it would have caused would have been far more costly.

 

Can't do more than that. I figure I have exercised my due diligence.

[rickeieio]

My 1959 International has air brakes, but no spring brake. It has a long black handle sticking up through the floor that's really difficult to pull when you're trying to swerve through a red light without hitting crossing traffic.

 

Maybe that's why I retired it?

 

Newer trucks are better.

[rdickinson]

I think that was a driveshaft clamp, it may have had the top part of the handle to tighten or loosen the adjustment.

 

Stan can say for sure.

[Guest THE TRAILERKING]

My old '45 REO had band/drum brake on the rear of the tranny. With only air service brakes. I took the hand lever park brake off and equipped it with maxi/spring brakes.....Like modern day.

[skp51443]

My 1959 International has air brakes, but no spring brake. It has a long black handle sticking up through the floor that's really difficult to pull when you're trying to swerve through a red light without hitting crossing traffic.

 

Yep, that is a drum brake on the driveline and can be a pain, think they are still using them on hydraulic braked trucks. There are two adjustments, a fine one on the stick and a coarse one under the truck on the drum assembly.

 

We found that if we set the fine adjustment to where it would hold the truck and fiver on flat ground it was much easier to set the brake. We'd just spin the fine adjustment down further if we found ourselves on a hill but that made for some good arm exercise that we wanted to avoid as much as possible. We also made an extension out of PVC pipe that slipped over the handle, we cut it as long as we could but short enough to miss banging on the dash, the extra length gave Trudy (short arms) a lot more leverage.

[Broncohauler]

IMO as a commercial driver fix the air leak. At the very least make sure you have the part and any tools needed along with you for the trip.

 

Using the analogy of a tire leaking slowly let it go .

Absolutely not the tire could decide to blow on you at any time causing massive damage and leaving you stranded.

 

I've driven a truck that had catastrophic air failure causing the brakes to lock up and trust me it was not fun.

Not saying that's going to happen to you. I'm sure you're going to be completely fine I just don't recommend running something like that when you know it's broken.?

[Scrap]

Rick, be sure to pull the DEL lines off first to be sure that the treadle isn't just exhausting somebody else's leak. You are also allowed to fan it a good few times to be sure the valve didn't just take a bad set when you were checking it. Suppose I should clarify that is in the valve mfgrs TIB and not a CVSA thing.

 

All the consternation over a treadle valve is valid though. If it rolls an o-ring you are not going to have any application in that circuit and you aren't going to have any emergency springs for a good few seconds until it exhausts to that level. On top of that you won't have the ability to modulate your springs since it is the treadle that messed up. So you land wherever you are destined to land. But where is that going to be? When you apply hardest on a downhill corner - even though you shouldn't drive that way but it happens. And since you can't modulate your way out of it you are going to end up in a jacknifed wad just past the apex of the corner. So yea it is something you want to keep up with. Rear relays are a close #2.

 

And yes they still build trucks with wire braided and even FC air lines. You just have to buy the option. Sans ESP I don't think they've changed relay valves since the early 80s. Treadle valves pretty much as well. The E8-P in y'alls trucks just have a different external spring to give it the same feel as the ol E6 that hasn't changed since 121 air systems were born.

[rdickinson]

Wouldn't pulling the trailer brake lever or pulling the red knob help prevent jackknifing before air leaked down enough to release tractor brakes?

[Broncohauler]

Rick, be sure to pull the DEL lines off first to be sure that the treadle isn't just exhausting somebody else's leak. You are also allowed to fan it a good few times to be sure the valve didn't just take a bad set when you were checking it. Suppose I should clarify that is in the valve mfgrs TIB and not a CVSA thing.

 

All the consternation over a treadle valve is valid though. If it rolls an o-ring you are not going to have any application in that circuit and you aren't going to have any emergency springs for a good few seconds until it exhausts to that level. On top of that you won't have the ability to modulate your springs since it is the treadle that messed up. So you land wherever you are destined to land. But where is that going to be? When you apply hardest on a downhill corner - even though you shouldn't drive that way but it happens. And since you can't modulate your way out of it you are going to end up in a jacknifed wad just past the apex of the corner. So yea it is something you want to keep up with. Rear relays are a close #2.

 

And yes they still build trucks with wire braided and even FC air lines. You just have to buy the option. Sans ESP I don't think they've changed relay valves since the early 80s. Treadle valves pretty much as well. The E8-P in y'alls trucks just have a different external spring to give it the same feel as the ol E6 that hasn't changed since 121 air systems were born.

Scrap, Thank you? Most people on this form will take it a lot more to heart coming from you.

I know that we truck drivers may over push safety sometimes. But then again I don't think you can be to safe when it comes to brakes.

Charlie

[Guest THE TRAILERKING]

Scrap, Thank you Most people on this form will take it a lot more to heart coming from you.

 

Well I guess that's good..................Someone with some Authority.

[Broncohauler]

Well I guess that's good..................Someone with some Authority.

I wouldn't call it authority. Just my opinion but I call it respect.

[Big5er]

I wouldn't call it authority. Just my opinion but I call it respect.

X2

[noteven]

I'm with Scrap and broncohauler and others.... Don't leave home or camp with a known leak showing up when you operate the treadle valve or other parts of the brake system. A little hissing from other systems like suspensions, seat air, fan drive could be put off till convenient but not the binders...

 

Has everyone taken their trucks on the road and activated the emergency brakes in a safe place to do so to see what happens?

[Jack Mayer]

Has everyone taken their trucks on the road and activated the emergency brakes in a safe place to do so to see what happens?

Scrap probably experiences that often enough messing around with things

 

Years ago when I was driving a nice longnose Pete my neighbor and I were taking a load into NYC when we popped the valve just inside the city. Believe me, it was ugly. You don't want to do it.

 

BTW, using a longnose truck inside NYC is just plain stupid....but you do what you have to do.....in this case it was backing a 48' trailer down an alley into the back of a hospital to access the docks. With an entire 6" of clearance on each side of the mirrors. I never did that back.... he did it.... To make the cut into the alley you had to use the entire street and the sidewalk....the cops loved us. Of course you could only go in between 10pm and 4am.

[G&K]

X3.

 

Bear in mind we are haggling over a very slight leak and we all have very different points of reference. I think about mostly how this discussion applies to offroad service, with the unit being out of the shop for sometimes a month at a time. RV service or most other types of service are going to be a bit different. And we're are talking about a leak that is so slight you probably wouldn't have picked it up in a normal pre-trip. I wouldn't have, most of my field pre-trips have a lot of engine noise in the backgroud.

 

Reality for me is whether any leak or combination of leaks are enough to fail the brake application leak-down or any of the other air system pre-trip checks. Rough use, pre-trips when its very very cold, and lots of connections to cause trouble. So we've got some guidelines as to what is acceptable that don't just depend on you being able to hear a hiss or not.

 

Think about this only being allowed to drop 6 psi per minute. And you're doing the inspection at -20*F. In the dark, with the wind blowing.

 

 

And this one is only allowed 3 psi per minute. All the air operated valves don't get you an extra allowance, its still only 3 psi per minute.

 

 

So I don't think there is really any fundamental disagreement here. If something is broken, fix it.

 

I find the legal guidelines helpful as they clearly establish when the unit has to be downchecked, regardless of the source of the problem...

 

Geo