Is my New Dewalt Compressor Defective?

Just bought a new Dewalt 200PSI 15 gal compressor (5.4 CFM @ 90PSI) to replace my older Husky 8 gal 125PSI (3.7 CFM @ 90PSI) because the older one would not undo many tightened lug nuts. Even with a high torque (580) wrench the new one does not do any better than the older one. Might the new one be somehow defective, or am I expecting too much from the Dewalt? If the Dewalt doesn't do any better than the Husky, then I probably should take it back.

 

Welcome to the forums!

Are you operating the impact on the new compressor at the same or a higher psi?

90psi is the same no matter what compressor is used. The bigger compressor will hold a given pressure [cfm] for a longer period than the smaller one.

 

Both compressors are set to 90PSI.

If I understand your answer, the higher stated CFM of the Dewalt really only makes a difference re the delivered torque after a few seconds of use. But doesn't this imply that even compressors delivering 10-15 CFM won't deliver any more torque, but only means that they will deliver max torque for a longer period of time?

 

Yes, the bigger compressor will give that amount of pressure for a longer period before losing pressure. Have you tried using a higher psi setting?

 

I have tried a higher PSI, but most of the tools have warnings about using PSIs higher than the rated 90PSI. But even at 110PSI the wrench still cannot loosen many of the lug nuts. Do you suggest that I try even a higher PSI? Of course I can do the initial loosening by hand, but that sort of minimizes the usefulness of the HD compressor.

I have never seen a garage mechanic have problems with his impact wrench. What are they doing different or what capability do they have which I do not. All the wrenches that I have seen in catalogs are rated at 90PSI, achieving rated torque at 90PSI and about 5+ CFM. Sears does have a wrench that I believe has a rated torque at 1200 for $500 (far more than I would ever spend). Is that what the mechanics are using?

Regardless of compressor long term capacity, the nuts should come loose in a couple of seconds if the wrench is going to loosen them at all.

But after all the above we get back to the original question whether the Dewalt is really delivering the amount of air (5.4 CFM) at the dialed in pressure of 90+ PSI. At 15 gallons at 200PSI it clearly has more long term capacity than my 8 gal at 125PSI, but does it really deliver the peak 5.4CFM at 90PSI as it claims and which I seemingly really need?

 

"At 15 gallons at 200PSI"

are you sure? that sounds like a lot of psi for a small compressor

I think the 90 psi rating is just a standard pressure for rating the cfm. I usually set my regulator at 120psi when using most automotive air tools. I have a cheap impact that is rated about 250 lbs of torque, occasionally I'll have to use a breaker bar first.

I'm sure the impacts used by most pro mechanics is a lot stouter than the average diy type impact. I know the tire store I deal with most uses a lot of pressure [maybe 150 psi] as I've had trouble loosening lugs after getting tires from them.

Your new compressor should hold 90 psi longer than your old one.

 

Two things come to mind. The first is that consumer-grade air impact wrenches are notoriously over-rated and the second thing is that you need 90 psi AT THE TOOL INLET to ever hope to come close to the tool's rating.

How much air hose are you using and what is the internal diameter of that hose? Most air tools specify nothing less than 3/8 I.D. hose and in most cases that is at a maximum length of 25 feet. Quick couplers add significant resistance to air flow and if you have them on each end of the air hose (which is common) You are going to have even less length of hose before you simply "run out of air" at the tool inlet.

A third and fourth reason could be the pressure regulator and the water/oil trap on the compressor. Both of these can impart serious restrictions to air flow.

 

The hose ID is 3/8", but it is probably 50', and uses quick connectors at both ends. Based on advice I received here, plus some from elsewhere, I cranked the PSI up in steps to 160PSI. Using my high torque (580) wrench, some of the problem lug nuts came loose before I reached 160PSI, but some even resisted that high pressure, in essence confirming that the tire mechanics had use very very high pressure in re-installing the wheels. Those nuts will have to be busted loose manually. I need to do this since I would never be able to change a flat tire on the road as tight as the toughest nuts are.

I finally decided that since I would have to do the lug nuts manually since they were beyond the capability of the compressor, I might as well take the compressor back and, for the moment at least, rely on my lower power compressor which has handled all my compressor work except for the lug nuts. It is possible that the Dewalt is not running as it should since it did not sound completely OK to me, and could not break loose the tightest nuts, but I was never able to confirm this. But for near $400 it needed to everything I threw at it, which it could not do.

Right now I am looking for a large (30 gal is the largest that my garage can handle) cheap used compressor locally on Craigs List, but I am in no hurry. The local Home Depot has a highly rated reconditioned 30 gal Husky Pro Oil Lube for about $300, but its max PSI is only 135 which, given my recent experiences, seems to me to not be adequate. Your thoughts on this?

I want to thank you guys for your input which I found very informative.

 

More important than a giant compressor or impact gun..is a torque wrench for tightening the lugs to correct specs. And a good size T style lug wrench in the trunk. I'll lay odds most people WAY overtighten lugs when they do it by hand w/o a torque wrench.

I've always felt that unless you have a hard plumbed compressor setup or a shop with hoses on reels permanently hooked up...it takes longer to pull everything out and hook it up than it does to break the lugs loose by hand and either spin the nuts off with the T wrench..or use a cordless drill with a socket. I have a socket and adapter that just sits in the top of my toolbox for my lugs and my cordless tools are on shelves right beside the toolbox.

Heck...even an electric gun would prob be cheaper and easier than a pneumatic if you have a extension cord on a retractable reel in the garage.

 

The only reason you would do so is to compensate for an inadequate air tool or an undersized air line.
If you are dealing with a compressor that you plug in the most you will get out of a 120 volt 15 amp cct is a compressor that develops a true 6 cfm@ 100 psi.
Any more than this you would have to go with a 220 volt unit.
Also, you need to concentrate more on actual compressor output than how many gallons it is.
Gallons is an ideal unit of measure for a hot water tank, not air compressors.
CFM @ 100 psi is all you really need to concern yourself with.

Many who are stuck on this measurement do so to make up for a lack of cfm but you will only get a very small amount of extra impact time with a larger tank.
In the "old days" the size of the tank was directly related to the output of the compressor to prevent it from short cycling but because tanks are so cheap they are now a marketing tool.

GG has the right idea.
Even though I have all kinds of air and tools my favorite wheel removal combo is a can of WD-40, a breaker bar/socket and an 18 volt battery powered impact to do the easy spinning.

 

Virtually all the overtighting of lug nuts is done by the tire mechanics and not by the vehicle's owner. While I have yet to tackle my current set of overtightened lugs, in the past I literally had to use a 4 foot extension on my standard socket setup to get some of the lugs loose.

As to your other points, my Dewalt seemed to essentiall meet your criteria -- 15 gal, max 200PSI and 5.4 cfm @ 90PSI. But it did not do the job.

I have used the breaker bar/battery HD drill to remove sockets, but with the location of things my airtool does it a bit faster and easier, that is, when it works.

 

John...I wasn't criticizing...just expressing an opinion.

I've asked at both the places that have done any tire work for me..and they both use torque adapters of some sort for putting on lugnuts...I even saw them at the smaller place. That's why I said a homeowner who doesn't use a torque wrench is more likely to over tighten, no one has calibrated hands....lol. You said "virtually all", I think most repair/tire shops are aware of the problems with over-torquing (broken/stripped studs, warped rotors, etc) and take steps to avoid that. At least I qualified my statement with a "I'll lay odds...".

Spend $500 on a compressor and $300 on a gun to do something that I MAY do once a year.....I don't think so. If you have a lift in your garage and do it a lot..then of course it may be worth it.

 

I was not interpreting it as any criticism. And I agree with you re $800 for use only a few times per year. However my high torque wrench was a used one off of ebay for $60 incl shipping. I am now looking for a used or reconditioned compressor for no more than $300 and hopefully less than $200.

Besides puttering around my vehicles, I have some major patio/deck repair/replace work to do this summer which will involve removing and reinstalling a large number of big lag screws/bolts. I think a HD compressor will be very helpful in that endeavor.

I wished our locals would use torque wrenches, but I have seen none of them do so. All these lug nuts that I have been having problems with were mounted by our local (Wash DC area) professionals.