Oil from breather pipe

[Classiccars]

Recently had the 1275 engine refurbed.Noticed oli is coming out of the breather under pressure as some hit the fire wall.Is there some way of returning the oil to the engine via a fitting so that the oil is not wasted.Cannot see any reason why the oil would come out .Wonder if the gauze in the cylinder has been left out and that may let the oil out.Will find that out in the mean time.

[svenedin]

Has your engine got a “chimney” type oil catcher on the side of the tappet chest? If so, that should have a metal wool in it. I used a stainless steel pot scourer (type with a fairly open curly mesh). As I understand it that wire wool is designed to help the hot oil fumes condense back into liquid. Does the breather pipe connect to a PCV valve or the carburettor? Could the pipe be blocked? There shouldn’t be that much crankcase pressure. It strikes me as odd but let’s hear from the engine experts. Maybe the chimney is blocked but not quite sure where it is leaking oil from exactly?

Stephen

[Classiccars]

I have the cannister to the rhs of the engine front but the breather goes to fresh air

[svenedin]

It should not go to fresh air. There should be a pipe connecting the canister to either a breather type carburettor or a PCV valve on the inlet manifold. The whole point is that the breather system is connected to some engine vacuum. Oily fumes (blow-by gasses) are sucked into the engine and burnt. Fresh air enters via a breather type rocker oil filler cap. That is the set-up your engine should have but there are earlier variants that have a rocker cover with a breather tube connected to the air filter instead (and a draft tube inlet, non breather oil filler). Having an effective breather system reduces the propensity of the engine to leak oil especially the rear crankshaft scroll. Can you post a picture of your engine?

[Classiccars]

Rocker case and cannister at rhs frontbench engine

20230513_134407.jpg (1.48 MiB) Viewed 3194 times

[svenedin]

Thank you. I confess I am quite confused by your arrangement which is not at all standard Minor. Is there a pipe between the rocker cover and the inlet manifold there? If oil is coming out of the chimney your system is not working properly.

A possible fix might be to put the system back as it should be. That would mean fitting a non-breather pipe rocker cover with a vented oil cap and connecting the canister to the inlet manifold. Another possible fix is to leave it as it is but add a pipe from the canister to the inlet manifold. I remember old Roy (BMCEcosse) suggesting this for my engine but I never did it.

[mowogg]

The canister ouitlet pipe on thr timing chain cover should either be connected to thr carb side inlet assuming it's a su. Given its a 1275 it's possibly a hif44?

An alternative is to put connect it to thr inlet manifold via a pcv valve

[philthehill]

The carbs are twin SU carbs.
There is no connection between the rocker cover and air filter.
The twin carb manifold is suitable for drilling and tapping for a PCV valve.
The oil separator should be connected to the PCV valve and not exit the engine to fresh air..
With the PCV valve fitted the breathing system them becomes a near standard 1275cc Midget/Sprite breathing system.

[svenedin]

Phill,

I thought this was a connection to the rocker cover. Is it just a blanking off pipe?

20230513_134407.jpg (692.89 KiB) Viewed 3175 times

[kevin s]

The theory is the oil vapour should become a liquid as it expands and slows down through the breather can then drain back into the engine, originally the hose would have gone into the back of the air cleaner on a minor or to a pcv valve on the 1275.I'm guessing you may have pancakes on the twin su's though. Re-routing the hose up higher may help or you could take it to a remote catch can. As others have said I would be inclined to fit a pcv valve and connect it to the blanked connection on the inlet manifold, you will need some sort of vent in the rocker cover as well though. (I'd drill and tap it for a hose fitting and fit one of the little air cleaners used on Rover V8 rocker covers for the same purpose)

[mowogg]

The pipe as shown above looks like it should be thr point a pcv valve intake would be. Not clear why it has been blanked off, but it was probably connected at one point

As Phil suggested above making this connection will return the engine breathing system to a near stick set up with the use of a pcv valve.

[svenedin]

If the OP reinstates the PCV valve I’d suggest he sources an original Smiths valve. I had a repro on my car for a while and it did not work properly. The diaphragms for the later Smiths valves are still available.

[philthehill]

The pipe marked with the red arrow above is blanked off with a rubber cap. It is not connected to the rocker cover.
The other pipe connected to the manifold fitting is the servo vacuum pipe.
The usual rocker cover vent outlet is on top just forward of the oil filler. The rocker cover has the boss but undrilled .
If a PCV valve is fitted and the oil filler cap already used is not vented you can either fit a standard vented oil cap or fit a small breather as suggested above.

[svenedin]

It’s actually quite an interesting subject engine breathing if you’re quite dull like I am! The first internal combustion engines just leaked oil as a matter of course and nobody seemed too concerned as there were so few of them. Then there was the idea to provide some weak negative pressure on the engine crankcase to try to reduce leaking. That’s the draft tube idea. That system was very vulnerable to the car going through even shallow water and only worked when the car was travelling at some speed (the open tube was low down near the road and used the Venturi effect). Then the closed breathing circuit was developed with no open tube except some means to allow fresh air (filtered) into the engine, usually a vented oil filler cap with a gauze filter inside it. Later the the PCV (positive crankcase ventilation) valve was developed and some late Minors used an ingeniously designed PCV made by Smiths. A really clever piece of kit that varies the vacuum in the breather system. Many cars (including mine) have ditched the PCV for a carburettor with a breather pipe connection because the operation of the PCV was not understood by many and not set up properly with too weak a vacuum.

The most important things is, whatever breather set-up is used, is that it actually works as intended. Signs that suggest the system is not working include oil leaks, especially the rear crankshaft scroll and "cottage cheese" oil/water emulsion in the rocker cover. The rear crankshaft scroll oil thrower is overwhelmed when the crankcase pressure is too high and leaks can be significantly reduced or even completely eliminated by a working breather system.

[kevin s]

I've bought the bits to experiment with a modern (well 25 year old !) Mx5 pcv valve. On the mx5 the valve pushes into a grommet in the cam cover then connects to the inlet manifold, my plan is to replace the top of the breather can with an alloy plug as others have done so it can be cleaned out but have the mx5 valve push in the top of the plug and a hose going to the inlet manifold. If it works it will be a simple unobtrusive set up.

[philthehill]

Kevin
Are these the MX5 valves you are referring to?
https://www.ebay.co.uk/itm/284967939953 ... R77m_JaDYg

https://www.ebay.co.uk/itm/403306899250 ... 8017019342

[kevin s]

Its the bottom one, my wife has a mk1 mx5 so borrowed the one off that to rough out the idea, I've subsequently ordered a secondhand valve and new grommet now it looks like it could work. (I'll test the valve works ok on the mazda first).

[philthehill]

Please let us know how you get on as those original Smiths valves appear to be no longer available.
I paid over £70 for a NOS Smiths PCV valve for my Ser 3 Landrover.
Phil

[Classiccars]

Thanks all for the info.I am advised that the cannister will need emptying and new wire wool put in.May solve the issue.Is this something I could do on the 1275 engine.I know the rad will need to be removed but as the cannister is joined to the front of the engine what else will I need to remove.Would it be the water pump and if doeable what gaskets will need to be renewed .Is this a job I can do with basic tools please.

[mowogg]

You will need to remove the timing chain cover to access the gauze. This is relatively straightforwards and I would suggest you look at the workshop manual.

I don't think this alone will fix it. You still need tienit up to the inlet via a pcv for it to work. I would be tempted to do this 1st as you may find it will start working ok