Ingersoll Rand SS-5 Air Compressor Belt Slipping

Published Categorized as Air Compressor Troubleshooting, Ingersoll Rand 19 Comments on Ingersoll Rand SS-5 Air Compressor Belt Slipping

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My compressor is an Ingersoll Rand SS-5 a 5 hp Electric. The problem I am encountering is that it pumps up to 90 PSI and then the belt begins to slip until it locks up totally. Then if I let it bleed down it repeats itself. I have replaced the head gaskets, and it got worse. Any ideas? Howard.

Ingersoll Rand SS5 air compressor
Ingersoll Rand SS5 air compressor


Does the motor lug down or keep spinning, Howard? Belt tension low if it’s spinning. Check the check valve as well says Doug from


I also am experiencing a very similar problem with mine. It starts out great and gets to about 65 psi and in an instant the rpms drop and the belt starts squealing. I usually run and turn it off but if left it will bog the motor down to nothing and after about 20 seconds it goes back up to somewhat normal operation. I need help also! Thanks in advance for any tips, Ryan Renko.


Did anyone figure out the problem, mine is doing the same. It will pump up to about 50 psi then the belt starts squealing and the compressor starts to lock up, this from Jacob.


Doug from says to Jacob, if you need help it’s very important to answer questions asked to provide the information to help us help you.

Still, if you’re lucky, you may just have a bad check valve at the tank. More likely, and if that isn’t it, your second stage intake valve is broken. Unless it’s something else which we can’t figure out for lack of information from you. Good luck and let us know what’s what.


That the compressor “locks up” as the pressure builds suggests that it’s a pressure related problem, and the first thing to check is the tank check valve to ensure that it’s not blocked from opening as the pressure builds. I doubt this is the issue.

That the change in gaskets made the problem worse confirms, to me at least, that it’s the pressure creating the problem.

If it’s not the tank check valve, then I believe it’s likely to be the pressure valve that’s reacting to back pressure from the tank line as the tank gets higher pressure, and it’s time to tear down the pump and check the valves, but also the entire compression chain if the valves appear fine.

By compression train I mean the piston apparatus, the piston seals, as well as the valves.

If all are good, then the focus must turn to the motor, but I don’t think it’s a motor issue dues to the “locking up”. That’s typically pressure related. Please do the checks and let us know as a comment in this thread as to what you found.

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Recently, my 12 year-old SS-5 compressor started knocking. After checking the oil (which was fine) I removed the head. There are two machine screws (M1 X 0.7) that hold down the banks of four exhaust valves per cylinder. On one cylinder, there were no nuts holding the reeds and “keeper?” (I don’t know what it’s called – it’s the heavier piece shaped like the reeds that bolts on with them.). and they were just lying there – completely off the screws. I found no evidence of the nuts anywhere. Over the years, the screws themselves had worked their way down,… Read more »

I’m not real clear on what you’re saying…or which valve, intake or exhaust.
But generally, they should be flat against the valve plate.
Do you have pix?

I’m attaching a manual which may be of what you have. The drawings are not the clearest, unfortunately.

Last edited 2 years ago by Doug in

Doug, Many thanks! We are talking about exhaust valves and the part I called a “keeper” is #29 in the exploded diagram of compressor internals on the eighth page of the manual It’s called a “Stop, Discharge”. I know the valves should be flat against the plate, as you say, but either my “Discharge stops” are bent or there are clearly two ways of installing them. I installed them with the “fingers” in a lifted position so as to maximize room for the valves themselves to lift, but maybe I was wrong. I’ll have it apart again this afternoon and… Read more »

Here are two pix. The first shows the fingers of the discharge stops pointing up, as I installed them at first. The second picture shows the discharge stop flipped over so the fingers point down. That can’t be right – but is it? Both photos show gasket damage – looks like I got careless while installing it. That’s possibly my whole problem right there!

Oh, OK, yeah, for sure the stops should allow some movement
Also, yes, the gaskets absolutely could be the whole problem.
OTOH, did you disassemble the valve plate or just remove the head?
It sounds like possibly the intake valve(s) are not closing. You can remove the intake filter and put your hand over it – it should suck in twice per rev. and never push out – not much anyway with no load on the output..
Good luck…

Thanks again Doug. Yes I’ve had the plate off – that’s how I discovered the heads of the screws securing the exhaust valves were loose and fouling on one of the pistons. The first time I reassembled it, I relied on a torque wrench from Horrible Fright. When I removed the head the 2nd time, the bolts turned much too easily – there’s no way the torque could have been more than about 20#. I’ve read somewhere that they’re supposed to be 75# – but that seems awfully tight to me. 2nd time I used my old torque wrench. ‘… Read more »

The only spec I have for an IR pump says 75 ft/lbs.
But elsewhere some say ( for various pumps ) 30.
Are any of your headbolts marked for grade? If so, they should probably be around half that or less, whatever it is.
FWIW I have an HFT click torque that seems to be ballpark accurate as measured with a bathroom scale.

Today I made a new gasket. And I discovered where I got the 75# torque specification: it was here on an Ingersoll Rand YouTube video. The recommendation was clearly stated: 75 foot-pounds of torque on the head-bolts. There can be no doubt about that recommendation. I had tightened the bolts in stages: 50#, 60# and finally 70-75#. Having reached 60# on all, against my own better judgement, I started going to 70-75#. Sure enough, following the manufacturer’s advice, I snapped a head-bolt. No surprise, no recourse, it just sucks! Even so, I ran it and it filled right up to… Read more »

Last edited 2 years ago by Allen Bachelder

Shoot. Seized? As in you can’t turn it by hand at all?
Was the bolt one of the originals? What grade is the sheared one and the rest?
How much air do you need for how long? Can you maybe rent one or just buy a new pump?

Doug, I really appreciate your hanging in there with me on this one. Once it cools down the pump will run normally. I have a theory: after my new head-gasket blew I made one to fit – which it did – but it is only about half the thickness of the original. Would that increase the compression ratio enough to make it seize? I have another gasket coming and I’ll try it before giving up on this pump. Regarding the sheered head-bolt, I see no markings on the head that mean anything to me. It is an original bolt –… Read more »

Maybe it was a bad bolt – 10,9 is similar to Grade 8 -you can google it. Hopefully it screws right out…or left out. ?

Gasket thin? I dunno. Doesn’t seem likely, but ya never know…

Now, the pressure switch thing.
Probably normal-ish. This machine has a check valve between the tank and pump, it’s stuck open/leaking. Or, as the troubleshooting section mentions, the seat is blown out. Probably why the reset trips, too.

Hey Doug, you haven’t heard from me in weeks. I regret that does not mean the problem was solved. I got a new head gasket for it; not a correct original as I thought I had ordered, but a crumby repro – a lot thinner. I left my home-made gasket in place and added this one. I tried one too many times to get the pump running when it was at least partially seized; the motor burned up. Literally: it caught fire and flames were shooting out the vent holes. Quite spectacular, really! Long story short: finally got new motor… Read more »

Did you verify the check valve?

No. ‘ Just found it in the owner’s manual. What’s the procedure for verifying it? Given all I’ve done so far, it sure seems likely. If faulty, does that mean all the pressure in the tank backs up to the pump? That would explain everything.

Thanks again, Doug. You’re the best (and only) resource available!


Yes, at least some of it. When it stops, as in you turn the switch off, does it hold pressure, or does it leak off (under the pressure switch)? If it leaks, the check valve is messed up.

Yup, that’s a productive answer. The leak starts when the switch is turned off. It stops when you turn it back on, but you can’t leave it that way for fear of burning up another electric motor…

Last edited 2 years ago by Allen Bachelder

About the motor – it’s the same RPM as the old one?
Good luck with the check valve.

Doug, ‘ Sorry this is so late. I lost the link to this site, but accidentally came across it again tonight. Indeed the check valve was the final culprit. I could see the problem in the old one when I took it out. ‘ Put the new one in, put it together and I’ve been using it for nearly three weeks now. It runs sweeter than ever and I am totally happy! I hope people do have the courtesy to thank you occasionally for the good work that you do. If I had figured this out sooner, I might have… Read more »

(running foot around on the floor)
Aww shucks. T’warn’t nothin’. Thanks.

Best wishes to you, too.