Air Compressor - not quite shop related

C

Cushing H.

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I have a HF 1/3 hp air compressor that I use in my garage to manage my car tire pressures (actually bought it for a cool mist system .... but it was woefully insufficient for that purpose) that after a couple years is now not reaching its shutoff pressure of 120psi. It runs, slowly, slowly, slowly increases tank pressure up to about 60psi, then goes no higher. technically I can use that to inflate car tires to about 34 psi or so .... but I am sure it can not be good/safe to keep the thing running so long.

this is an "oil-less" compressor. Does anyone know if there is a maintenance item or repair that might be done to this pump .... or with an oil less pump, if it fails in this manner is it just toast?????
 
If it's still running and not building pressure I'd guess the compressor end is toast, if it's shutting off at 60 then it would be an air switch. Since it's a harbor freight model I'd just replace it. Saw a 6 gallon pancake at Lowe's for $100 today.
 
BlindMouse2of3 said:
If it's still running and not building pressure I'd guess the compressor end is toast, if it's shutting off at 60 then it would be an air switch. Since it's a harbor freight model I'd just replace it. Saw a 6 gallon pancake at Lowe's for $100 today.
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Yeah, its running, but not building pressure, soi guess it is indeed toast (where on earth did that saying cone from?)

I was at home depot yesterday eyeing probably the same pancake compressor…
 
It could be as simple as a relief valve or buildup on the intake valves not allowing it to fully seal but depending on how mechanically inclined you are and what your time is worth I'd just replace it. It doesn't sound like an expensive unit. Some people will strip them down and plumb the tank into the new system for extra capacity. But really if it's just tires probably best to move on.

If any of the local schools have auto shops you might be able to donate it for educational purposes.
 
I'd bet a cracked reed valve under the head. seen it before. struggling to make higher pressure because the air the piston pushes through the valve makes it's way backwards through the cracks and refills the cylinder. the air is just kinda going back and forth.

easy to pull the head and inspect. i have no idea if replacement parts are available
 
Backyard said:
I'd bet a cracked reed valve under the head. seen it before. struggling to make higher pressure because the air the piston pushes through the valve makes it's way backwards through the cracks and refills the cylinder. the air is just kinda going back and forth.

easy to pull the head and inspect. i have no idea if replacement parts are available
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good point - ill try to take a look.

I guess I did not make clear that I have looked/listened for leaks both on the unit and on any attached hose .... but do not find any.
 
A picture of the unit and a model number wouldn't hurt either. About how old is the unit? If you have no audible leaks then Backyard is most likely correct.
 
BlindMouse2of3 said:
A picture of the unit and a model number wouldn't hurt either. About how old is the unit? If you have no audible leaks then Backyard is most likely correct.
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No picture .... I was being lazy - actually thinking I was asking a general question about oilless compressors in general (I have never taken one apart, so do not know how they are constructed.). Now that I know that there is a reed valve in there, I can at least go in search of that - who knows, maybe I can find a replacement (at a reasonable cost....)
 
ok ... this is weird. Maybe someone else knows more about how these compressors are configured. Below is a photo of the compressor, red tank on the bottom. On the left is the piston (round grey thing) with one reed valce on its bottom. Not shown is the "head" with the cooling vanes, with another reed valve in it (when the piston goes down, air enters into the round chamber through the lower reed valve. when the valve goes up, air leaves the piston and goes into the rubber tube through the reed valve in the header for the piston.

I am **presuming* that air entering into the rubber hose has a straight shot into the storage tank. BUT, when I blow into the rubber tube (while simultaneously either opening the drain valve in the bottom of the tank, or holding open the dump valve below the pressure gauge at the outlet to the tank, ***there is no air flow****. Is there another valve of some sort between the mouth of the hose and the tank (it does not look like it to me)???? can anyone think of why I am seeing this behavior????? (I am hard pressed to think that the rubber tube/inlet tube to the tank is just totally occluded.... ?????)
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so slight update. I did go in and probe that rubber tube with a thin piece of metal .... and sure enough there is another check valve at the base of the hose where it connects to the tank. it was a little stuck ... and probing at it I got it to open and apparently then function as it is supposed to. My *real* find is that I think I found the source of the problem: it looks like one or both of the clamps on either side of the hose are not tight enough .... and there is leakage from the end(s) of the hose when the pump is running. I need to go out and get replacement screw-tightening clamps and get those properly tightened. Hopefully in the next day or so I will be able to do that and test....
 
that second check valve is there to keep the tank pressure off the piston when it has to restart. really hard for the motor to start under load.

also it's very unusual unless it's l low pressure compressor to use a rubber hose on the compressor output. most are aluminum or copper to deal with the heat generated from compression. might want to look at changing it out
 
Yeah - the new hose clamps solved the problem .... and the unit is coming up to its rated pressure of 100psi and shutting off.

Backyard - thanks for the advise re. the rubber hose. This is a really inexpensive HF unit, and probably not really worth any significant upgrades if I continue to use it for only inflating car tires. It really is a pretty wimpy unit .... it takes something like four or more minutes to come up to pressure (if I ever get a cool mist system, I will definitely need to get a compressor with more HP....

Thank you to all of you who helped out in this.
 
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