Compressor lack of compression

[julianf]

Following on from my issue with junk getting stuck in the non return valve on my compressor, i think ive got reduced compression.

Motor seems to run for longer to get to pressure.

This, coupled with, what i found in the nrv (it happened twice in total) -

The first time seemed to be just black rubbish, but the second time was either a flake of epoxy primer overspray buildup, or, worse, white metal. It was only small and i couldnt really tell.


The compressor is an old "airmaster" (clarke) thing. Google images actually came back to a thread here ( https://www.mig-welding.co.uk/forum/threads/airmaster-compressor-help-required.11336/ ) but the pump on mine is very slightly different.

I think my pump looks more like this one -

...but there are so very many small variants of the same thing. It has a plate on it, so ill see if anything sensible is written.


Anyway, the question -

You can see the expected age on the local forum post i linked to above. Is it likly that parts would be availible, and should i even bother? I mean i dont know what a gasket set will cost, but if its £20 + vat + delivery im probably to £35 to even look inside, and a whole new pump is about £150 and then i know it will "just work" (or at least that would be the hope!)

 

[addjunkie]

Loss of compression, faulty suction valve, or rings worn….if its the rings youll feel it out the oil filler. Gaskets just make your own….head gasket if its a copper ring just anneal it.

 

[graffian]

Looks like it will have simple blade valves, only time I have had a failure of a valve it had no compression at all on that cylinder.

 

[dobbslc]

but if its £20 + vat + delivery im probably to £35 to even look inside, and a whole new pump is about £150 and then i know it will "just work" (or at least that would be the hope!)

It won't cost you anything to take it apart and have a look.
If it's worth fixing then buy the bits needed.

 

[fizzy]

If you do need a new pump check out the returns section in some of the bigger Machine Marts. They often have new and unused air pumps etc with good savings off retail.

 

[julianf]

It won't cost you anything to take it apart and have a look.
If it's worth fixing then buy the bits needed.

Its not really possible to do it like that. I need to commit, as best as I can, prior.

The unit still works, just in a diminished way. The moment I undo a screw then I'm on the clock.

I'd want to have enough to hand to get it working again to it's existing capacity before stopping it working entirely.

In that it will cost me a gasket set to have a look. But if the gasket is just a diy cut then that's acceptable of course.

 

[julianf]

It won't cost you anything to take it apart and have a look.
If it's worth fixing then buy the bits needed.

I guess that's also what I'm asking though...

Are these things fixable? They're just reed valves at the top, right? All on a pre cut sheet (which I guess may still be obtainable or may not be) but other than the valves?

What I'm trying to work out is, assuming X is the issue, how many possible Xs are actually going to be repairable?

 

[dave h 2]

So, as addjunkie asked does it blow out of the oil filler? That includes oil as well. If it does and time is so vital to you buy a new comp like you should have in the first place.

 

[julianf]

So, as addjunkie asked does it blow out of the oil filler? That includes oil as well. If it does and time is so vital to you buy a new comp like you should have in the first place.

It does not blow out the oil, so far as I recall.

When you say "in the first place" could you clarify what you mean, please?

 

[voipio]

Based on post #6, it might be useful to at least have a backup compressor, of some sort. It doesn't have to be new, just a working one.

 

[julianf]

Based on post #6, it might be useful to at least have a backup compressor, of some sort. It doesn't have to be new, just a working one.

Probably. I gave my spare away to my brothers son... Nice little belt drive v twin thing. He was looking longingly at it and talking about saving up for a Chinese direct drive unit...

Anyway -

I have two units here but I used them both simultaneously. I've been eyeing up hydrovane units but it's unlikely that will happen tomorrow.

 

[keithski122]

A couple of times on my compressor the piston ring slots would all line up with a slight reduction in compression, it also would pressurise the lower end.It was just a case of moving them and utting back together didn't even bother with new gaskets so no cost.

 

[Fazerruss]

Before you go throwing money at it, first check the drive belt is not slipping. I also have an airmaster and its been a great little machine. Recently though I noticed it was running slow and taking longer to reach Full pressure. I thought it was the motor but the belt was slipping because the motor pulley is slightly worn.
Tightened it Up and job's a good un.
Also the head gasket is very simple in design. Mine blew around 15 years ago so I made a new one from gasket paper and it's been fine since.

 

[dave h 2]

It does not blow out the oil, so far as I recall.

When you say "in the first place" could you clarify what you mean, please?

Fixing the NRV twice now and the comp is still 'wrong'

"The moment I undo a screw then I'm on the clock.

I'd want to have enough to hand to get it working again to it's existing capacity before stopping it working entirely.

When spending the time is too expensive and you can't be without, just buy new to start with.

 

[Bsmith]

You can make your own reed valves from thin spring steel, like a paint etc scraper from a £1 shop. Cut them out with small disc on angle grinder.

 

[Smallfry]

A compressor will not have any compression as such, as it is effectively a two stroke thing with one valve open on the downward stroke, and then the other open on the upward stroke. The reed type valves on modern compressors are ****e really. The only thing stopping it working will be the reeds bent or the seats faulty, and they MUST be perfect to function correctly.
The rings do not really wear, unless run with no oil, or run with no, or useless air cleaner, and a lump of foam or wire is NOT a good filter for the conditions most compressors run in. Most likely the reeds are distorted or bent, and do not lie properly flat on their seats. If not available, can be easily made from shim steel, provided the seats are good.
As said gaskets can be reused or made.

 

[julianf]

A compressor will not have any compression as such, as it is effectively a two stroke thing with one valve open on the downward stroke, and then the other open on the upward stroke. The reed type valves on modern compressors are ****e really. The only thing stopping it working will be the reeds bent or the seats faulty, and they MUST be perfect to function correctly.
The rings do not really wear, unless run with no oil, or run with no, or useless air cleaner, and a lump of foam or wire is NOT a good filter for the conditions most compressors run in. Most likely the reeds are distorted or bent, and do not lie properly flat on their seats. If not available, can be easily made from shim steel, provided the seats are good.
As said gaskets can be reused or made.

I investigated and it seems there is no air filter at all. The screw on plastic block has no element in it, but is, I think, just some sort of labyrinth device to act as a slight silencer.