Our 12H is making no air, When the outlet line is off the compressor there is no blowing or sucking at all, not even a tiny bit, which seems to suggest a major failure, not just a valve problem, it has about 2500hrs. Does anyone know of any common problems these have had?
I'm not close to my parts/service books, and it's been awhile since I've had compressor problems, but could it be that the compressor drive gear is slipping on the compressor crankshaft? Can't remember how the connection is made, whether it is keyed, tapered shaft, or what. Could be serious, but might not be as bad as you think. Good luck, I hope others will throw in their ideas. smoothoperator
Have to determine if compressor is turning as smoothoperator said.
I am thinking its not turning, will hopefully get it pulled apart in the next few days
I'm not sure what compressor that has but most of cats compressors have a plate on the bottom and/or back so you could check there first for pieces if you think there's been a major failure. Or turn the motor by hand while watching the compressor crank through the bottom cover.
If it's anything like the compressor on my truck check the unloader valve assembly. It's the mechanism which stops the compressor making air when the desired pressure has been reached. If it gets stuck like mine did, then you won't build any air pressure, the compressor will just freewheel with the inlet valve off its seat. I took mine apart and cleaned it up. It had enough corrosion on it to make it sticky but now works fine. It's a pain when it happens as the air brakes are just stuck on and you can't move the truck. AusDave
sounds like the input shaft had snapped, they will shear if there is a major failure of the compressor to prevent it breaking bad enough to send metal into the engine
I would suggest a diagnosis in 2 stages. 1. Is the compressor turning..? 2. If the answer to 1 is yes, look at the onloader valve and the system it controls. May need the head off the compressor to make sure the valves are OK.
The unloader/regulator is separate from the compressor, I have not looked at it yet, the only operator we have does more harm than good to our roads and the machine so I have not rushed to repair it.
Check for the presence of water in your air tanks. If the system has condensation it usually finds its way to the unloader and siezes it up. If you need a step-by-step disassembly guide for the unloader let me know. Don't forget to give at least the Serial Number prefix.
Thanks for the offer, it is the compressor that is faulty, it is making absolutley no air, with my finger over the outlet it does not blow or suck at all
Nige is right. Prolly been run to long with tanks full of water . what does water do ? seizes valves etc etc. check all your pipes filters ( blow them out ) valves etc. believe me those cat pumps can take a hiding. but if its been recirculating water and rubbish any thing is possible. And kick that Operator up the * DRAIN TANKS DAILY. especially up there in those very dusty environments. Yea I have worked up there. And no it wasn't me. cheers.:drinkup
Still have not had a chance to pull it off, . This unit has the intake from the air cleaner then an outlet from the compressor to the regulator, then it goes to the tanks, there is no way the water in the tanks has any way to get into the compressor. There are no relief or regulator valves on the compressor I know I have Qld in my info but I am in PNG and I wish we had more dust, it rains more often than not. we dont really have what i would call operators for any of our machines, we have a lot of men who drive them!!
I'm also in an area that I guess must be similar to PNG with 300+ days of rainfall/year combined with high ambient temps. One of our big bugbears is trying to keep (condensed) water from the high humidity environment out of air systems. I'm more thinking about the condensed water produced between the compressor and the tanks affecting the rest of the system, plus (IIRC) the signal line to the unloader being taken from the primary (aka "wet") air tank. The compression process heats the air a heck of a lot, That means whatever water vapour is in the air as it passes through the compressor is carried to the tanks, where it cools and condenses. Does the machine have an air dryer between the compressor and the first air tank..?
It has a filter? system on the regulator assy, but we have not had this machine long and i have not had anything to do with them before and no parts or service manual, so that combined with to much work to do and inexperienced local staff I have not bothered to much to work it out yet, add to that the driver is useles an as far as I am concerned the longer it sits the better until we get a decent operator:Banghead Ahhh lifes good
What's the Serial No..? I can check. If you need parts details for the air compressor PM me an e-mail address.
The unloader valve and the air govenor are two different things. When you say the unloader valve is seperate from the air compressor, I think you may be referring to the air govenor,,,, the unloader valve is operated from the small line from the external governor that goes to the side of the compressor (unloader valve)... is this possible your confusing terminology?
Always possible, But this compressor appears to have no pressure regulating of any kind on the compressor itself, it simply has a pipe in then flex hose out then the pressure is regulated.
Gramps, the compressor governor on the 12H is remote mounted away from the compressor. It's actually located on a bracket under the main air tank.
Unless they've change them drastically, there has to be a small line from the governor going back to air compressor to the cut out(unloader valve)?
Yes indeedy ..........it wouldn't work otherwise. My comment was more related to the fact I find it strange that the governor is mounted remotely from the compressor, usually it's bolted right to it.
That would be bottom hose 6, shows how close i have looked at it!!
The lower line of lines six feeds your unloader valve.
So after all my stalling to have a look at this, that thankfully gave grandpa enough time to come along and tell to open my eyes there will be another hose, which then made me think that there may well be something in the compressor that has failed instead of my first thought which was a major comp failure. I drained the coolant and pulled the top off the compressor. So you can see in the pic that the valve was stuck in this position which means air compressed by the piston simply goes back out the intake. This valve is operated by air coming back from the reg through the hole in the bottom rhs and pushes a little piston, with spring return, this piston spring etc was stuck, so it has air again, thanks to all for helping. Next question: It is leaking/relieving air continually out the bottom of the drier, is it supposed to do this??? And just so you know how good our operators and civil crews are, when i drove this today it has a shocking clunking noise, almost continually, its the ball pivot for the front axle, nobody has mentioned it to the workshop though!!
Good you found the problem with the compressor. Now to your 2nd dilemma - it should not leak air out of the bottom of the air dryer continually. The air dryer works in combination with the compressor governor so that when the system gets up to pressure and the signal is sent that opens the compressor unloader valve the same signal opens the drain valve at the bottom of the air dryer, thus expelling any water that has accumulated in the "cup". After "blowing down" the valve should then close. It'll need a disassembly & clean up to find out what is wrong, maybe the valve itself neds replacement. Also I would suggest in your climate that the dessicant cartridge for the air dryer should be changed on a regular basis and at more frequent intervals than whatever the Maintenance Guide suggests. Certainly is the case here with high humidity. Sounds like your front axle is going to be the subject of another thread............
I did not think it should bleed air continually but had to ask, the boys had the duel tank out to fix the starter a while ago and broke the plastic fitting on the bottom of the drier when they put it back in, so I have had that out one out and cleaned it up, will have to pull it all to bits, What hourly interval would you recommend for the cartridge change?
Also check the air line from the governor to the air dryer.... Cat lets say doesn't use the best hose IMO going under ther engine,,, these leaks can be a real bearcat to find but none the less can cause the problem you relate to, altho I agree whole heartedly with nige's diagnosis ( hi Nige :waving) and service the dryer also.
We change the dryer dessicant cartridges every 1000 hours instead of the 2000 hours the factory recommends, but remember we're working 24/7 so 1000 hours is only about 8 weeks operating. If the machine's not doing a lot of hours (50/week or less for example) change the cartridge at half the calendar interval recommended by the manual. IIRC 2000 Service Intervals are a yearly interval, so I would change the cartridge every 6 months. Also plan to put a service kit into the air dryer drain valve about every 4 dessicant cartridge changes. According to me the air dryer assembly is a 215-3005. The dessicant cartridge is a 203-2389, the purge valve kit (the valve at the bottom of the drier) is a 218-2971, and the cutoff valve kit is a 203-2390. Be prepared to replace all 3 initially, although if the photo of the compressor unloader valve is anything to go by a good cleaning of both the purge valve & the cutoff valve might be all you need to do. The air line from the governor to the drier is really short, only about 12" if the drawings I've seen are correct. The governor is mounted right next to the drier. First make sure that the line from the governor to the drier actually pressurizes when the governor cuts the compressor off. The possibility exists that you may have a problem caused by a blockage in the governor port that sends the signal to the drier to blow down. Try draining all the air from the air tank and then start the engine on idle. Watch the air pressure rise and when it reaches the cutoff pressure (about 120psi-ish) you should hear the compressor unload and a distinct "chuff" noise from the bottom of the air dryer accompanied by a slug of water out of the purge valve as it actuates. Your purge valve might have a hose attached to it to direct the water down through the machine frame to the ground.
the drier bleeds continuously. i will get it off and strip it, in the mean time i will order service parts. I will have to follow up with my account dept as we dont have an account for cat yet, first credit application I gave them did not get submitted I wonder if they sent it in this time:Banghead Will let you know how i go with the drier etc, thanks Again
If you have a parts book double check those numbers. I THINK they are correct for your machine but wouldn't swear to it 100%. Again thinking back to the state of the inside of the air compressor I would be tempted to disassemble and clean the compressor governor at the same time as you're disassembling the dryer. 9M-0402 is the repair kit (seals, etc) for the governor if you need one.
I am organizing service kits for the compressor, governor and drier as well as the cartridge, as coolant goes through the compressor i would like to put new gaskets in, put it back with the old ones and a bit of sealant to make sure it worked. My accounts dept has not done the account app so i still dont have an account for the dealer, have ordered through my Australian supplier, I just ordered by description and send in the photo of the id plate and pics of the drier etc. digital cameras make life easier, cheers
Just what exactly did we do before we had them ...??