MackTech

You said it only drops air when the lift axle is in the up position right? If so it very likely will be on the lift bag portion of the lift axle setup.

2 minutes ago, Joey Mack said:

are the "Down" bags over stretched and leaking?  they look wrong... What do you see here MarkT?

I'm thinking since the air bled out the axle dropped and no air was put into the ride bags.  I've seen that at the plant. Now if air was in there if question it.

I'm thinking there is a leak at the ride bag quick release, the solenoid, or it's one of the lines between the solenoid and the quick release or between the quick release and the lift bags.

18 minutes ago, Joey Mack said:

some one plumbed the axle to the primary, it needs to be on the secondary. The main supply out of the secondary tank needs a "Pressure Protection Valve" installed at the tank. so that if a failure occurs on the tag axle it wont drain most of the air needed to "Stop"!

Prior to Volvo dictating air piping Mack piped lift axles to the primary tank with a pressure protection valve.  I remembered when they changed it at the plant.

3 minutes ago, Dmurph2016 said:

Isn’t that the valve that I just replaced? Not on the tank though. I’m going to assume the way it is setup is the way the body manufacture set it up, not sure why you’d go messing with what’s on what system?

The valve in the pic you posted is one of the old style pressure protection valves.  It will close when the pressure gets to low to protect against too much air loss which could seriously affect controlled braking.  Once you lose too much air your yellow button will pop out and your spring brakes will lock up.

Did you replace the actual terminals in the connector or just the plastic part?  The female part of the terminal could be losing connection.  It's been too long ago since I worked on wiring to remember what circuit to look at, but if grounds are good, check the terminals.

I'm not sure when it changed but when a truck is made at the factory they put the net weight of the truck which is the weight of the truck without a driver, without a body, with minimal fuel (maybe 17 gallons).

Removing the lift axles will reduce weight, but you need to check where they will be used that there aren't axle weight limits you may be affecting with removing the lift axles.  At the plant we refer to the lift axles in front of the first drive axle as a pusher axle, and the lift axle behind the last drive axle as a tag axle.

On 4/3/2021 at 12:20 PM, jackdk said:

I am getting ready to replace my front brake chambers on my 1985 Superliner. My question is the rubber hose size. Not sure if mine are 1/2" or 3/8" hose, but are about 18" long. 

What doesn't make sense to me is, why do they both go through a 3/8 fitting. What is the advantage of 3/8" fitting to 1/2" hose to 3/8" fitting over a 3/8" fitting 3/8" hose 3/8" fitting. No matter what size hose you use, it still narrows down to 3/8"

I want to make sure I put the correct ones on. All my drop-down hose are so old, that all the markings and sizes on them are long gone.

There are federal regulations on brake timing. (Time that brakes apply and another regulation for when they release)

Timing is done when there are changes made at the factory to make sure that the brakes apply and release within a certain amount of time.  If you make any changes to the air system, from how it was built at the factory you could change the timing.

Little changes from changing from a straight or 45⁰ fitting to a 90⁰ fitting could even change your timing.  So putting a smaller house on that was originally on there can possibly affect your timing.

I work in Macungie and have worked a bit on the air system.

On 3/31/2021 at 4:42 PM, Dmurph2016 said:

So I only had a few min today to use the soap and water before the weather turned to rain, but here’s what I got done. 
stsrted the truck and let it air up until the governor shutoff. Shut the truck off. Could hear some air leaking from the front of the truck, o opened the hood and started spraying airlines. Not exactly sure what this thing is or does but it was bubbling at the red part. Secondly I confirmed that when I flip the switch to drop the lift axle, the green needle dropped. So it seems that there’s a leak somewhere in that system and when it loses pressure, the axle drops. It’s a start. Hopefully when the rain stops o can lift the bed up and start checking under there. As well as the brake cans as I have a feeling that could also be a culprit 

The green needle is for primary air. The red is for secondary.  The lift axle should be operating off of a solenoid.  When I'm the up position the solenoid will provide air to the lift bags and when in the ride position the air will go to the ride bags.

Now if you have a loss of air when I'm the up position, you'll want to check the ride bags. Then check the solenoid. Check the supply line for the solenoid which is very likely coming from a "red hat" pressure protection valve like you have in your picture.  I am pretty sure the CL pooping is different than the current generation trucks as the newer trucks have an air\elec solenoid pack near the right side front of bogey cross-member.  

Not sure where your solenoid is as the lift axle is very likely an add after the truck was built.

If the lift axle was put on in the mod center at the factory, I don't remember how they did them on CLs.

Maybe this might help.

On 3/4/2012 at 2:31 AM, nfreema5 said:

There was a very similar truck in Diesel Power a few issues back, but with a lot of performance upgrades done to it and a pinstripe delete on the paint. I believe I remember reading the owner also lives in Ohio.

As far as my truck goes, I got lucky finding this one. I had been wanting an older diesel pickup since high school since the newer trucks are so outrageously priced. I'm not crazy about Dodge trucks but on the other hand, I like the pre-'94 models and the Cummins 12-valve appealed to me more than the Navistar 7.3. After searching Craigslist for months, I found my truck and learned it was only about an hour away from where I live, so I snatched it up. Came with the custom side-pipe exhaust that you can see in the pic, but otherwise unmolested as I wanted it. With the new paint it definitely turns heads cruising around in the summertime. My only regret is that the truck has a 4 speed slushbox, but otherwise I'm very happy with it.

Now if only Mack would make a light duty truck again, all my problems would be solved, but that'll be a cold day in hell.

Anyway, thanks again for all the kind words and information everyone

-Nick

Nick, Mack is now making a light duty truck at the RVO plant in Virginia.

I know that occasionally the coolant level sensor will go bad, if it's not the harness that Mackpro suggested, I'd try the sensor.

When the yellow button is pressed in, it puts air into the spring brake side of the brake chamber and releases the auxiliary brake. When the brake pedal is pushed in, it supplies air to the service side of the spring brake chamber and applies the service brake.

I'm thinking the ch likely has either and sr7 spring brake inversion valve (bendix) or the ir2 (Wabco). (Unless you have a bridge formula semi, which only had a spring brake qrv)

Ron what is yours doing wrong?

The Customer Adaptation Center is still in operation, but they do farm out some mod work to Trans Edge.

No problem at all!

If it's an electrical issue you sure have a lot of hunting to do, I'd check all your grounds, both chassis and engine grounds as well. Make sure there is no corrosion and you have good contact with the terminals.

Best way to remove it is to unscrew the four t27 torx screws from the cover and pop it out by hand.

The only truck that can come out of North America now is the LR, cabover.

If you have rollover stability in the truck I would suggest you have it checked out.

11 hours ago, white_HULK said:

@MackTech how does rollover affect the idle? Mine did that this evening when parking the truck and idling. Mines a 2013 pinnacle. 

The computers in the truck are tied into acceleration when there is stability in the vehicle. 

39 minutes ago, white_HULK said:

What is the pie plate?

Sorry, the triangular plate on the middle top of the dash.

There could also be an issue with the spring brake inversion valve.

Just saw this post.  The 5th wheel solenoid is run through the VECU. You could switch the plug behind the switch with the neutral control, but you'd have to switch the wiring in the connector coming from the solenoid to the connector in the mono harness. I don't know where you'd have to repin it to though.

Neutral control does not go through the VECU and is a standard connector on the cab harness.

I'm pretty sure that a horsepower change is locked out for just anyone to change it.

There should be a folded up piece of paper under the pie plate. The radio first would be under there. The plastic pouch may have fallen off the underside of the pie plate and may be laying inside.

Is there rollover stability on the truck?

On 11/1/2019 at 7:14 AM, mrsmackpaul said:

They were built that way because t he R 800 wasnt around yet and that was as good as Australia could do with what it had I would think

Also worth remembering that all R model and no doubt all other Macks built in Australia are based on LHD  and converted to RHD in Australian factory

Paul 

The trucks are built currently at the Australian plant as RHD. Awhile back there were 5 RHD cabs for GUs sent to the Mod Center in Macungie to have the trucks converted to RHD.

The GUs were built online as LHD, then completely converted in the Mod Center using a combination of Australian and fabricated parts.

The last truck in Macungie that came off the assembly line was an RB.