air line question B85

[Mack58B42]

Hi,

I have a question that I'm hoping someone mechanical can answer.  I've attached a Word doc with a picture of my compressor (at least I THINK that's what it is!) and the main air line that comes off it.  I can't quite tell for sure where it goes, although I assume it's the air tank.  Anyway, if you look at the spot where the arrow is pointing, the copper line and the SS braided line have been rubbing together so long that it has created a leak in the braided line, and if the copper line isn't leaking, it appears to be rubbed almost all the way through.

This leak has been there for quite a while, but recently got a bit worse, so it was time to crawl around and find out where the issue was.  I was hoping it would just be a loose connection.  So much for that theory.  I do hold 100psi, although the compressor does run more to keep it there than it used to.  I can't afford to get it into the shop at the moment, but I do have a couple of places to bring it in the near future that are within 10 miles of home.

First, is it safe to assume that as long as I'm holding 100psi in the tank, that my brakes will work?  Does that SS braided line go right into the main tank?  And is that an original line?  Might anyone have the Mack part number for that so I can get the part on order, or see if I can find an equivalent?

I assume that if the line blows out, I'll know it, because the hiss would become a gush, and it would be obvious that I'd lost pressure.  If that happens, I'm also assuming that the Maxi-brake would kick in.  It would no doubt be an unpleasant stop, but I just want to make sure that that is also a correct assumption.

Just want to make sure that my assumptions aren't off base, and that I'm not completely crazy to keep driving it with the leak as it is....

 

Mike

air leak 071617.docx

[BC Mack]

I am going to help you, but not in the way you are expecting..

I am going to stop you from "assuming" anything, anymore, about your air brakes...

as the driver of an air braked vehicle on a car driver's licence you "should" be performing a pre-trip every time you operate the vehicle, and I know it isn't mandatory for a private or antique or motorhome in all US jurisdictions, but, it is sensible to know what is going on with the gauges, how to pre-trip inspect the system and when to drain your air tanks etc.

even though you can drive past a weigh scale, there is nothing to stop an LEO pulling you in if they see something, whether it is in your car, motorcycle or antique truck, they have the right to do so... an audible leaking air would be an automatic "park".

attached are some publications that will help, good bedtime reading, your local licencing centre should be able to provide you with some publications as if you were to take a CDL, in there will be some more helpful info and a pre-trip form you can use for the walk-around.

you don't have to be a mechanic to do this, very few truck drivers today have a clue what makes their truck work but they are required to know the air brake system.... 

your line about assuming the 'maxi will kick in' only works if the slacks are adjusted correctly... and you would have checked that in the pre-trip brake test, consequences of a runaway truck are 'pants soiling'.

please accept this as 'help' and not a lecture...!!!

BC Mack

 

tractor_air_brake_troubleshooting_guide[1].pdf

air brake problem finder.pdf

Bendix Air Brake Handbook[1].pdf

[j hancock]

Don't have a part #.  Even if you had a number, no one would know what to do with it these days.  There is special type of DOT teflon hose now so that it can take the heat of the compressed air.  Take the old one off and a new one can be made at a good quality truck shop.  Take a good look at the copper line also.  It may be a wise decision to replace it while you are there.  Last time I bought the teflon hose it was $9.00/ft.  

If everything is is in good shape, the Maxi's would stop the truck at the loss of air.

Stay in the driveway until it is repaired.  

 

[Mack58B42]

Thanks for the advice.

BC- as a former firefighter, I am well versed with doing a pre-trip inspection and walk-around, and I take the time to do it before every trip.  When I first heard the hiss, out of curiosity, I checked the maxi by not engaging it when I parked, and when the air drained to 75psi, it did kick in automatically, so I'm fairly comfortable that that works.  But air systems are not my specialty, and I will peruse the docs you attached to get more up on that.  I certainly don't want any surprises with my brake pedal!

J - was speaking with someone at work this morning who is a mechanic, and he agrees with you that a good high-temp hose should be fine, so he's going to take it off, and we'll have a new hose made up to the right length and pop it back on.  He's worked in fleet maintenance in the past, and it sounds like he thinks it's a pretty straightforward job...

 

Thanks again!

Mike

[Hobert62]

If I remember correctly from when I replaced my Teflon feed line.    Modern trucks use 5/8" line and my B was 3/4".     Everything was available just nobody local had on hand.   Bought the Teflon tubing with stainless braiding sleeve by the foot and reused my ends with new crush sleeves.   It goes together just like compression fittings on plastic airline.