So while trouble shooting another issue on my air system (which is now fixed) I discovered my oil level on my air compressor was nearly empty. It was topped up last in September last year and done no more then 200miles since.

Any ideas/advise why this would be loosing oil when there no obvious leak, and how to resolve?
I haven't been able to check the contents of the air tank but this was also emptied and cleaned at the begining of October last year, but my guess is it has ended up in the tank.

The air compressor is still pumping strong and still holds pressure in the pipe between compressor and tank when stopped

Cheers in advanced!

My bus number (if any): RMF2771 (RCN701)

Two very knowledgeable guys to ask about this Matt and who are on your Facebook friends list are Martin Detheridge & Tim Barrington.

My bus number (if any): RM967 (Driver/Restoration consultant)

There are a number of reasons why a compressor loses oil the head gasket being one of the main places it can escape and the compressor will continue to function with this leak. Are you certain there is no oil loss under the head or under the compressor? You might not see oil on the comprsssor after a run, it can often get sprayed around in motion and with the belts running.

Some of our RT compressor lose oil and some never need topping up, although we check them daily when on a campaign.

Seems like you have a choice if it's functioning OK and you can top it up, you could leave well alone or take it off and get it checked over, there are people on this site who will do it for you.

My bus number (if any): RTL 960, RM 1585, RMC 1486 and several RTs

There are varying ways of filling and topping up.

Some items need to be filled, then operated, topped up, operated again and checked and topped up again.
This is to ensure air is not trapped in the filling process and that the oil/fluid is where it should be.

Other items have a bleed process and they have a normal course of procedure.

It may be it was not filled up correctly and has now settled.

Crucial for any fresh fill:

1. Note exactly how much oil or fluid you add.
2. Know the specified capacity.
3. Compare what you put in with what the specified capacity is.
4. Don't go by the dipstick or gauge alone until topping up.
5. Always factor in capacity of filters and pipelines not just the reservoir.
6, Always fill slowly and evenly.

No.5 can be confusing as some capacity specifications include filter and line capacity in the total and some just specify the actual reservoir capacity. Sometimes filters are listed with their own capacity.

So by taking a careful note of what goes in from dry, then running or operating and then making checks on the dipstick, gauge or level indicator you can top off to the mark.

This way you know that the correct amount is in.
Then check over the first few runs to see if it needs a slight top up.

Hope this helps.

Brian:
i will look into the oil on the outside when i go back to my bus in two weeks.
but the compressor looked clean and dry after having had it run for about 20mins while problem solving another issue (now resolved) and it still had some oil in it (but very little)


Mark:
I didn't measure it last time in September but it was a full 5 litre bottle when i filled it up and not used the oil bottle since till the other day when about half a litre was missing,

I did measure it in this time and about 290ml when in before over flowed and it was parked on flat and i am lead to believe it should have 400ml in it by the Maintenance Manual


What i think i will do is in 2 weeks I'll make sure its full then clean and
dry the compressor, and empty the tank, then, take her for a run, then see if the outside of the compressor is oil/level of oil/any oil in the tank!

regardless of this i think i might have the compressor of to check the gasket/seals. I don't think single run would be long enough to get any really meaningful answers so does anyone know if there are kits/spares for this and where i can get them? or willing to have a look at it for me if I remove it?

My bus number (if any): RMF2771 (RCN 701)

The RM compressor only takes about a pint or two of oil when empty, so I don't see how you can put 5 litres in it! Are you checking the right place?

The compressor is a right pig to get to to fill up as it's on the side of the gearbox and the filler is behind the main air pipes. You need arms like Twizzle to do the job and a bottle with a long bit of tube passed down through the floor with someone else inside the bus.

If you're looking at "the tank" are you looking at the brake oil reservoir on the side of the bus?

My bus number (if any): RML2532

Hi roythebus

i think i could have written that bit clearer sorry, i said "was a full 5 litre bottle when i filled it up" i meant the oil was coming out of a new previously unopened 5 litre bottle of oil, not that i used 5 litres

I did go on to say straight away "not used the oil bottle since, till the other day when about half a litre was missing," meaning i deduced the last time i put oil in i reckon i put in about 500ml in on that occasion.

I then went on to say "i did measure it in this time and about 290ml when (went) in"


yes i agree with the filler is a pain, which is why after the last time i made a extra long funnel from a bit of old (clean) white cable conduit. It has been heated up and bent to shape, so it fits around and goes in perfectly for a easy fill. It worked great and filling this time was easy!!

My bus number (if any): RMF2771 (RCN 701)

Thanks for clarifying that. The compressor will use a small bit of oil, so don't worry too much. Don't let it run out, they cost about £700 to rebuild these days!

Lack of use can be part of the problem.

My bus number (if any): RML2532

Trawling through the LT manual came across this, which might be a timely reminder:
Little trouble should be experienced with the compressor provided that the oil level is maintained without heavy toppings but attention is drawn to the need for efficient maintenance of the intake and unloader filters .

Capacity of Compressor 3/4 pint approx

The Air Intake filter is situated in the driver's cab beneath the seat. Its function is to clean the air entering the air pressure system, to prevent damage to the compressor and cause erratic valve operation due to foreign matter.
It is of the utmost importance that the felt filter should be kept clean otherwise slow build up of air pressure will occur together with shorter compressor life. The felt element must be replaced and/or dry cleaned at every rota. ie 4 weeks.

My bus number (if any): RTL 960, RM 1585, RMC 1486 and several RTs

Put the filter in the washing machine!

Or as a late friend once pointed out, with the air intake in a similar place in an RT, if the driver passed wind, you'd have compressed f@rt brakes!! :)

Peter Claughton R.I.P. thanks for those words of wisdom.

My bus number (if any): RML2532

this is all very interesting,

having looked at the price of getting it overhauled, it makes sense for me to replace it with a commercial grade 24v air compressor rated for heavy duty use.

These are around 1/4 the price, this would also mean no need for a unloader valve because they can be electric switched off at a high pressure and on at a low pressure. If the system is tight then it could be a good 30mins before it turns back on again!

Has anyone done this? Think of a reason why i shouldn't if any, when my compressor gives up the ghost!

If people can't see a reason why i shouldn't, then i might just look at doing it straight off the bat, and then offer my compressor (for a reasonable fee) to someone who wants to overhaul it as a spare for their own stock.

(i realise i would have to get a smaller belt to power the quill drive still)

My bus number (if any): RMF2771 (RCN 701)

And therein lies the problem!

My bus number (if any): RML2532

On another note,

Having waited a month for my order of 2 air filters for the compressor from Filtration Control Limited, they are now no longer able to supply them.

Their part number was FCL3257

My bus number (if any): RMF2771 (RCN 701)

A bit of sponge wrapped round the inner former should do the trick.

My bus number (if any): RML2532