The 40400 is a small, DIY type air compressor, and appears to be manufactured off-shore for Harbor Freight with a 2 HP motor positioned on the top of an 8 gallon tank, with pull handle and wheels under the tank for easier movement.
The 40400 is oil lubricated, and must be filled with compressor lubricating oil before being run for the first time. Check the oil level in the sump by looking at the sight glass located under the oil fill plug on one side of the pump. If filled to the correct level, oil will be visible in the sight glass, and level with the center of the dot in the middle of the sight glass. Do not overfill. If you do, use the drain plub below the sight glass to drain off excess oil.
With so many questions submitted about the operation of the model 40400, it has earned its own forum page here on www.about-air-compressors.com. If you are looking for help with your 40400 you will find it below.
Please do read the existing posts to see if your compressir issues has already been addressed. It's also a good idea to review the troubleshooting pages too to see if your question has already been answered there as there, are many common compressor problems have already been addressed on those pages.
If you can offer advice on another vistor's posting about their Central Pneumatic model 40400 air compressor, please do so by adding a comment on the existing question.
Download a copy of the manual for the Central Pneumatic #40400 air compressor, by clicking here.
As the numbers of comments added to this page grows, it may get harder for you to find the specific answer you are seeking so I've added a search box here for your use to help you find the information you need.
Having an issue with your Central Pneumatic Model 40400 air compressor?
Please see below. You may find a solution to your problem already posted. If not, add your own.
intermittent issue with shut-off
I run my compressor with the regulator set at about 100 pounds to supply air to a pneumatic framing nailer. The automatic shut-off will sometimes work …
Buying Parts for 40400
I over tightened the cylinder head bolt and cracked the head. I cannot find one anywhere. I am almost ready to buy another brand. Do you know where I can …
40400 Compressor Hums
My 40400 hums when turned on. I opened the shroud looking for the reset switch and could not find it. However, the fan blades will difficult to rotate. …
Air hose needs replaced
Air hose leaks
Unit will not pump air or show air pressure on gauges
Needing to know how to repair, unit will not pump air or show air pressure on gauges. The unit will turn on, but the tanks will not fill with air.
Stripped threads on oil fill plug - get a new one?
This issue is with the plastic oil fill plug on my Central Pneumatic air compressor model 40400. Where can I purchase a new one ?
What capacitor for a 40440?
What size needed to be compatible?
I'm trying to find the sizes of metric fittings to connect to check valve
To make a long story short, the two compression nuts that connect the copper tube that runs to the check valve on the model 40400 are cracked. I need …
I have a Model 40400 air compressor it runs but won't build air pressure. Central pneumatic harbor freight.
Need to replace pressure switch?
I have model 40400 with a leaking valve inside the switch. Two outlet on the bottom of the switch with a pull/push, on/off switch I need to replace …
40400 has big leak - all air leaks out
my compressor suddenly all air leaks out. model 40400 will not build pressure, big leak
40400 fills well but releases air when it reaches the set pressure limit .
My CP 40400 fills well but releases air when it reaches the set pressure limit . Do I need to replace the pressure switch? And where can I find …
Replace electric starter
Will not start, would like to replace starter
Unloader valve hose / tube for air compressor
Need to know what the part number is and where to buy it. Approx cost? This is the hose that goes from the tank to the regulator dials. The end connector …
Parts for a Central Pneumatic 40400 compressor
I can't find connector to fit the compressor. I have tried a 3/8 inch and it is too big and a 1/4 inch is too small.
Motor does not run on Central Pneumatic 40400 air compressor
while filling tires, the compressor started...s l o w l y...and then quit. Since then I have been unable to elicit any response whatsoever out of the unit? …
Central Pneumatic compressor overload protection has to be reset frequently
The overload protection button has to be reset frequently to build pressure. It will run for approximately 10 to 15 seconds and shutdown. I can reset and …
Central Pneumatic air compressor will not stay running
my compressor all of the sudden started to run for a few seconds then shut off then after a few seconds i hear a click and it starts back up and will do …
40400 runs in bursts then trips overload
I bought a Central Pneumatic #40400 two years ago, used it for a little while, then put it away and just began using it again. When I run it, the …
Check valve blew on 40400 compressor
I have a Central Pneumatic 2HP 8 Gal compressor (40400) about 2 or 3 years old. I use it only about once a month for a few minutes at most. It just …
Central Pneumatic model 40400 will not start
CENTRAL PNEUMATIC AIR COMPRESSOR 2 HP-8 GALLON 40400 I need to know what to do when the compressor doesn't start? ___________ Hello Don. Nice to hear …
My compressor just won't turn on.
I've read a few people say hit the reset button. I can't find a reset button on my unit anywhere. Can you point it out? I was a small engine mechanic …
What is causing oil leaking on model 40400
Central Pneumatic #40400 oil leaking at cylinder head and regulator valve? Also starts on its own, came on and it was running about an hour..room full …