Air brakes

When I got My class A Dl many years ago in MI. I took a air brake test. Not sure if it is the same now, But it should be. To be direct. You need to take or read about air brakes before someone gets hurt.
Please be safe.
Do the right thing.
Learn about air brakes from the proper source.

mpierce wrote:

My MH has what is called a retarder. I thought it was an exhaust brake with the Cummins engine same as my PU was. It's not, more like the trans acts as the exhaust brake with aggressive downshift patterns in no throttle situations. Curious how this works going down hill compared to a real exhaust brake.


Answer: On a retarder, when you use it turns the tranny into a hydraulic pump, and restricts that flow of oil. This makes the engine work hard, trying to pump that oil. This used power, thus restricting the engine, like an exhaust brake. You can get semis with BOTH a Jake, and a retarder. Guys that run mountains with heavy loads use both.
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In the early days of Allisons with retarders, the ATF was quickly overheated, ruining many transmissions. Watch your trans temp when you use it.

terryallen...yep, they still work that way. My reference to not `loosing the brakes` was to draw attention to the fact that they didn`t just quit qorking. They didn`t even fail...the driver either didn`t see what was happening and got rolling too fast to stop, or they didn`t do the `Brake Check` at the top of grade..slack adjusters out of whack.

I am supposing that RV`s that are so equipped, have auto-slack adjusters. It used to be, that to set them, one put the rig in reverse, got it rolling a bit, then braked hard. I have no idea what the methods are for RV`s.

Also..if someone is reading this and has air brakes...the air gauge that you watch when you are first starting the engine...tells you several things. The time that it takes to come up to 90 lbs..if it takes more than 5 minutes, something is wrong. You have a leak or a faulty compressor. Then, having attained full operating pressure of 120 lbs..and someone will correct me if I am wrong..it`s been a long long time since I tested...you make a full brake application, with Maxi off...if your air drops down below 60 lbs, I believe, that signifies that your slack adjuster need to be set up or you need new brakes.

You know when you are passing a large truck or bus and you hear that sound of air releasing phsssss...that is the dry tank, doing a regular timed release of air, to ensure that any moisture is removed. Wet air..no brakes. Look when you pass a large truck and you will see a set of tanks, laying down, often stacked on top of each other. They sorta look like oxygen tanks. There`s the air tanks. They each have a petcock, to bleed air manually if needed.

Dynamiting is when the vehicle`s compressor runs below a set lb of air pressure and the brakes come on. The air pressure keeps the brakes OFF..once pressure drops below a certain lb, the spring is no longer held away and the brakes are applied. Those heavy black tire marks you often see on a highway, might have been that. Those lines you see froma truck to trailer are the airlines. If one of those breaks, BANG..dynamite. RFN. All the air just spews out.

Same with an RV..if there is a rapid loss of air pressure, down below, I think 45 lbs..but again, I will be corrected if I am incorrect...BANG... Now..if you are going down a hill and you have heated up your brakes already...and you have been fanning your brake pedal and have taken your air down to that magic point, your brakes come on, only they can only be as effective as the braking surface provides. If they have been over heated and expanded, you are in for a hride.

Hopefully others will chime in and make any corrections and perhaps add a few more tid bits.


Gary Haupt

garyhaupt wrote:
I do not want to hijack this thread ...

You have heard the news reports of the truck that lost it's brakes...it didn't 'loose' them, .....


This is a YouTube course using a simple presentation.


http://youtu.be/_gmoIkP8ywI


Gary Haupt

Good advice - lots of good tutorials & info on the "net".

Surprised the dealer turned you 'loose' without some basic info ... 'cause you don't ever want to 'lose' your brakes..:W

~

Slownsy wrote:
The air keeps the brakes from engaging and when air pressure is release or disappears brakes activates.

Only half true at best. Air keeps the "PARKING BRAKES" from engaging. You also use air to operate the service brakes. They are two separate systems that only use the same air supply

et2

The url for the Manitoba air brake course follows:

http://digitalcollection.gov.mb.ca/awweb/pdfopener?smd=1&did=20528&md=1

Not requiring an air brake endorsement in MI may be a problem in other states or provinces. It is unlikely that an air brake endorsement not being required in MI will mean that the endorsement is not required elsewhere. I doubt there is reciprocity. In any event your safety and that of others on the road is at stake. Nuf said!

My MH has what is called a retarder. I thought it was an exhaust brake with the Cummins engine same as my PU was. It's not, more like the trans acts as the exhaust brake with aggressive downshift patterns in no throttle situations. Curious how this works going down hill compared to a real exhaust brake.


Answer: On a retarder, when you use it turns the tranny into a hydraulic pump, and restricts that flow of oil. This makes the engine work hard, trying to pump that oil. This used power, thus restricting the engine, like an exhaust brake. You can get semis with BOTH a Jake, and a retarder. Guys that run mountains with heavy loads use both.

Just bought a 2013 Winnie Journey, 40U.
There is so much info given in a PDI.that a person would need to
record and tape it to get it all. I hat to say I don't know where the tanks are
or the air dryer. Will find out tho.

et2 - my vote - an air brake course would be very helpful so you understand the operation of the system.

A modern well maintained system will not collect a lot of moisture in the tanks but you want to know how to check.

et2 wrote:
We just purcased our new DP. Regarding the air brake system. Is there a air storage tank that needs to be drained for water.

2013 Fleetwood Expedition.

Some (probably all) 2013 Fleetwood Expeditions were built on a Freightliner chassis, so I am assuming that Freightliner manufactured your chassis. The link below has info about the chassis. Beginning on page 26 of the document, you will see a lot of info about the air system.

Freightliner Chassis Info

Another helpful link has additional info about the Freightliner Chassis at:

More Freightliner Chassis Info

I hope this helps.

Fred