B61T air compressor install tips needed

[GearUpJammer]

After troubleshooting all the common problems (no leaks,new governor,degunking unloader valves),I’ve decided to swap out my Tu Flo 500 for a rebuild.I’ve had the truck for a year and have been slowly going through it to get it roadworthy and make it a “rolling restoration “.The most air pressure it ever built was 10 psi and now it won’t even read on the gauge.I’ve made up my mind to just swap the compressor out and looking for tips and advice on the best way to do it without dropping 50 pounds on my chest.Thanks and have a great day!

[mechohaulic]

did you take off the discharge line from compressor check for any air being discharged ? keep in mine the air temp from compressor is extremely warm (hot), place a rag/ wear gloves . air coming from compressor yet no build up also consider the discharge line which should be steel/ copper has the short section of flex braided line that is known for collapsing internally. if end  result is removal ;no easy way. remember the compressor may hold just enough oil to make a mess when tipping it out from frame. don't want someone under it assisting removal.

[mowerman]

I would try to borrow an engine hoist .. but as Mecho mentioned it’s probably a small issue good luck… bob

[HarryS]

I did that job a couple of years ago and as Bob mentioned used my trusty engine hoist. My old air compressor would build air but also passed a lot of oil into the system. It is also a good idea to trouble shoot the system as Mecho recommends before just replacing the compressor.

[GearUpJammer]

3 hours ago, mechohaulic said:

did you take off the discharge line from compressor check for any air being discharged ? keep in mine the air temp from compressor is extremely warm (hot), place a rag/ wear gloves . air coming from compressor yet no build up also consider the discharge line which should be steel/ copper has the short section of flex braided line that is known for collapsing internally. if end  result is removal ;no easy way. remember the compressor may hold just enough oil to make a mess when tipping it out from frame. don't want someone under it assisting removal.

I had the line off at the wet tank,there was some air coming out.I wasn’t aware of the braided line,I’ll check that.Thank you.

[GearUpJammer]

Probably hard to tell how many PSI without a gauge but here’s a short video clip

[mowerman]

Wow from that short video clip it looks like it’s blowing out of there pretty hard. Good luck don’t forget to check your check valve. Also that may be all it is good luck.

[mowerman]

Did you say the compressor was blowing oil out of it?

[GearUpJammer]

4 hours ago, mowerman said:

Did you say the compressor was blowing oil out of it?

Thanks,I will check it out.Didn’t notice much oil coming out.

[mowerman]

Excellent you might not have to touch it

[T-Mack1]

Reminder,  you might also check for significant air leaks.    When our Areo-Quip line to the brake treadle went (internal lining cracked),  we couldn't build pressure.    Replaced it and now we build pressure quick.  Still have some kind of leak as it bleeds down if a few hours.  

[skydawg]

I thought pressure always bleeds down after a few hours.

[Brocky]

13 minutes ago, skydawg said:

I thought pressure always bleeds down after a few hours.

A good tight system should hold air for several days...

[Geoff Weeks]

I have trucks that will hold some pressure overnight Like 25 psi left. 

The real test of a system is how many minutes it will go between compressor cycles while going down the road. Best truck I had, truck and trailer on air ride, air wipers, would go 45 minutes between cycles of the air drier.  Anything less the 15 minutes and you have work to do.   

I haven't seen an air system that will hold for several days on the main system. 

My air start would hold enough air to start for 4 weeks, but the main system will be empty. 

[T-Mack1]

On 11/26/2025 at 8:29 PM, Geoff Weeks said:

..........................  I haven't seen an air system that will hold for several days on the main system. .............

 

On 11/26/2025 at 8:10 PM, skydawg said:

I thought pressure always bleeds down after a few hours.

I guess I was spoiled. Up until January '25, I worked at the Mack factory.  If a truck bleed down over night it was looked at with a fine tooth comb.   Actually an electronic  air leak down tester, and sometimes a sniffer which is actually a extremely directional microphone and a headset. 

  I forget the spec, but 0.3 psig in five minutes sounds familiar as the limit.  And that would be with air brakes applied (bracket thing holding pedal down).  Many pass with no leaks at the test.     Note: a 0.3psig leak would take approx 36 hours to go from 130 psi (average compressor cutoff on new trucks) to zero psig.   Although the PPV (pressure protection valve) shuts off the accessories at 90psig, so it may take longer.

[Geoff Weeks]

Yep, everything is all new only once. The leak-off rate while going down the road (measured by time between compressor cycles) is a fairly good indication of system health. The rest can be diagnosed by applying the item is question and seeing how much air is "used". I bet 85-90% of trucks couldn't go 45 min between cycles while running down the road. 60% couldn't make 30 min.

[mowerman]

lol I know all about it triple trailer hook ups a lot of times I would get down the road and it would start pissing air. You could watch the gauges going down of course it would not do that before I left the yard. It would wait till I got 30-40 miles out. Then start leaking. But yeah, you’re right as well. Lots of things that could be draining it. 

[Geoff Weeks]

Lots of connection points on multiple or modular trailers. More tanks and valves to leak. Then there are a air snubbers on the pintle hitch, the valve to control them etc. I towed some jeep, trailer stinger set-ups, they had less valving then triple wiggle wagons with converter dollies.

[mowerman]

Well, towards the end, it was mainly airbags leaking, but I don’t know why the hell they would wait until I got out of the yard  sitting there with the rig turned off 10 to 15 minutes absolutely no noises lol what do they say? Luck  of the draw?

[mechohaulic]

On 12/1/2025 at 10:00 PM, T-Mack1 said:

 

I guess I was spoiled. Up until January '25, I worked at the Mack factory.  If a truck bleed down over night it was looked at with a fine tooth comb.   Actually an electronic  air leak down tester, and sometimes a sniffer which is actually a extremely directional microphone and a headset. 

  I forget the spec, but 0.3 psig in five minutes sounds familiar as the limit.  And that would be with air brakes applied (bracket thing holding pedal down).  Many pass with no leaks at the test.     Note: a 0.3psig leak would take approx 36 hours to go from 130 psi (average compressor cutoff on new trucks) to zero psig.   Although the PPV (pressure protection valve) shuts off the accessories at 90psig, so it may take longer.

I  used the "sniffer" yrs back ; actually owned one. had a brand new Mack firetruck which didn't   pass the leak down test. new truck paperwork one sheet; new firetruck -4=5 pages  to fill out. used the sniffer to go over ALL the air system. found the culprit leaks. sniffer could pick up leaks soapy water couldn't.

[Geoff Weeks]

Never used or saw one, but most shops will not have one, just use the time/pressure drop method, but that only tells you there is a leak somewhere. I have a sniffer for both refrigerant and combustible gases, spend your money where the tool will do the most work.

I would walk around a truckstop parking lot (taking my dog for a walk) and I would see how many trucks I would "down" just from visual and listening to them while the dog did his thing. It was a large percent every time.

One time there was a guy beating on the dunnage under a load of pipe. I asked why? "I'm 1500 over on my trailer axles" Ok, but moving the dunnage isn't going to change that! He almost threw the sledge at me, told me I didn't know jack! Rory and I walked on, he was still beating on that dunnage an hour later!

[mowerman]

In the Freight business a lot of times I was able to run  up to  about 20 miles an hour and slam on the brakes I’ve moved a couple of thousand pounds that way off the heavy axle either forward or reverse I don’t think I would try it with pipes

[Brocky]

2 hours ago, mowerman said:

In the Freight business a lot of times I was able to run  up to  about 20 miles an hour and slam on the brakes I’ve moved a couple of thousand pounds that way off the heavy axle either forward or reverse I don’t think I would try it with pipes

I have done the same with bulk pneumatic loads.. Sometimes with the blower sending some air up thru the bottom of the product..