Any thoughts on a compressor problem?

[davidsuffolk]

I have a SIP 50 litre V twin 3hp direct drive compressor which is not working properly.

In truth it has given me more than my fair share of problems so I have put it on eBay as a non runner though it does work, just not correctly.

What happens is this. It starts fine and pressure builds but as the pressure climbs air starts to leak from the oil filler (there is a pin hole in the dip stick) until when it gets to about 80psi it is really strong and starting to lift the whole dipstick. If turned off tank pressure holds and the leak stops.

I have replaced both head gaskets and the reed valves seem OK but it seems that somehow the crankcase is getting pressurised.

Any knowledgeable members any thoughts on where the problem might be?

 

[pedrobedro]

It sounds like the unloader or check valve is faulty letting the tank pressure back into the cylinder.

 

[rtbcomp]

The unloader won't let pressure into the crank case, do you get a hiss when you turn it off at the pressure switch? Does it restart OK?

The check valve will be OK as the tank pressure holds.

Sounds more like rings to me.

 

[Browser]

Seconded, from my limited experience sounds like pressure getting past the piston and pressurising the crankcase. Lid off, check piston rings.

 

[Julian_P]

Seconded, from my limited experience sounds like pressure getting past the piston and pressurising the crankcase. Lid off, check piston rings.

Agreed, piston rings/bores bsollocked. It's (essentially) breathing heavily like an old Ford Kent engine and needs a rebore

Julian

 

[davidsuffolk]

Thanks for all the replies.

I had a look on the SIP spares pages and many parts for this machine are no longer available and, if like a car it still needs a rebore, that would be more than it is worth. I think in truth it has had it's day and better that someone gets use of the good parts.

 

[keithski122]

I had a very similar problem with my sip compressor though the dipstick would fly out occasionally.I thought it would be the rings so dismantled it and found nothing wrong.Put it back together, drilled the hole in the dipstick slightly bigger and all was ok.
I think the problem might have been the ring gaps lining up which I forgot to check when taking apart but made sure they were in different positions when I put it back together.

 

[Browser]

Agreed, piston rings/bores bsollocked. It's (essentially) breathing heavily like an old Ford Kent engine and needs a rebore

Julian

Funny you saying that, that's the exact engine I was thinking of for blow-by when I read this post! A mate had a kent-powered class 2 grasstrack car and the engine was about knacked when he bought it, evidenced by a pressurised crankcase

 

[normspanners]

Definitely Rings worn I my opinion allowing blow-by unlikely to be rings in line just probably worn if it is not rattling you may get away with the piston and bore just get it honed and a new set of rings.