Air compressor question e7

[mcratchet1]

There’s a one inch off that runs off side of air compressor feeding drivers side air intake. Is this for extra boost? The hose broke a week later after replacement? 

[Geoff Weeks]

You got it backwards, the compressor intake is being boosted from the engine.  

[Mark T]

That setup requires more than a hose and a couple clamps. Weren't they made of Aeroquip with JIC fittings ?  That looks like a  piece of silicone heater hose on it. That can't put up with 30+ pounds of manifold pressure.

[Joey Mack]

A braided line would be better. Much stronger, and lives longer. Clamps are ok with braided line. But like MarkT says, aeroquip and JIC will work.

[mcratchet1]

Ah ok thanks a lot !!

[Geoff Weeks]

Heater hose can only be used if the intake of the compressor is connected to the trucks air cleaner (non pressurized). For those connected to the intake (pressurized on a turbo engine) a hose rated for pressure and temp needs to be used. 

I had some thick multi braid hose that "looked" like heater hose at a glance that worked well. rated for 300 psi and high temp.

Where it has to go around the head, tubing with short connector hose would be best. Steel or aluminum tube bent to fit with a bead to hold the hose at each end. That way, no chance of "kinking" the hose.

[mcratchet1]

Ok I called Mack and got a breakdown and that’s all they use is silicone heater hose. But a new one broke apart after a months use. I see a little oil coming out of air tank. So I guess it’s time to change compressor. Could the compressor be cresting back pressure if it’s leaking oil? I just want to make sure I don’t have another problem before changing compressor.

[Geoff Weeks]

Not exactly, What they show is a tube that is butted up at each end, then a short piece of hose that seals the two together The amount of exposed hose to the pressure is minimal, not the same as your pictures where there is a long section of hose. 

Still I would use silicone Radiator hose (rigid hose) to make the joint. 

You also have a clearance issue with another hose which will rub through the heater hose.

 New piping, new correct hose.

 Any compressor will pass oil if its duty cycle is high. A brand new one (not rebuilt) will. So 1st assess the condition of the air system before looking at replacing the compressor. There have been people on this board who have replaced compressors more than once with no gain, because the compressor is always loaded.

 Time your compressor cycles going down the highway, if the compressor doesn't go 15 min between cycles, you have work to do.

Edited 2 hours ago by Geoff Weeks

[mcratchet1]

Ok, no it’s popping off every 3-4 mins. So I need to look for leaks to main tank and governor?

 

 

[Geoff Weeks]

You need to look at the whole truck. Ready to roll (brakes off) engine at speed. I bet that 2-3 min drops to less than a min at 1800 rpm.

[mcratchet1]

Ok is the reason leaks? Which would make it cycle more often

[Geoff Weeks]

Ahh, that is what you are going to have to find. My best truck, air ride truck, air ride trailer, air wipers, air start, fully loaded on the interstate would go 45 min between blow off of the air drier. My worse truck was around 15-20 min. The differance between the two most likely had to do with the best used nylon air tubing and the other used airquip hose. 

Every hose, every fitting and valve are potential leaks. Not a fun job tracing them all down.

Bendix says 25% duty cycle, meaning the compressor is compressing 25% of the time MAX. (high use is 25% low use is 15% between those two is normal) That is you time the when the compressor starts compressing till when it stops, then time to when it starts again.  Put the 1st number of minutes over the 2nd and the result should be less than 0.2.

 Stop and go driving is going to use more air, but if you compressor is already struggling to keep the system up, it will be running continuously in stop and go traffic.

You'll notice that intake pipe is clamped to the rear head to keep it tight to the fittings at each end.  Your pictures don't show a tube/pipe anywhere near the head.

Edited 1 hour ago by Geoff Weeks
duty cycle correction

[Geoff Weeks]

Bendix's method of timing the time the compressor is compressing vs off time is the most accurate. It is hard to tell when the compressor starts compressing esp sitting in the driver seat. Timing the time between drier blow-off rolling down the road at a constant highway speed is a good approximation, and easy to hear from the drivers seat on most trucks. 

You can also watch the pressure gauges. If the go to cut-out pressure and never move, but the drier keeps cycling, the leak is between the compressor and wet tank (inclusive). If one gauge drops to cut-in while the other stays higher, then look at that side of the duel line system. If both drop, (esp if towing a trailer) it could be the trailer that is leaking. All trailers  are "single line" brake system that can be fed from either the primary or secondary side of the tractor brakes.