Oil leak again!!!!

[al2006]

A while ago I posted on here about a massive oil leak I had, from the rear of the sump-ish- which only seems to happen on long journeys i.e. about 8 litres of oil in 300 miles.

It doesn't leak or consume/burn oil during my day to day driving, or when standing (mostly short journeys), and there is never any smoke.
Its only on motorway journeys when its a problem, even though I keep it below 60.
It was recently in the garage for a week to fix the problem.
The engine was removed and the oil seals were replaced. The sump was removed and resealed (incase of leak here), and everything was thoroughly checked.
I don't believe the engine was overheating as there were no warning lights (apart from the oil light!), and no smoke.
The inside of the engine is clean and all seems fine. There are no cracks and all seems struturally sound.
There is no smoke or pressure when I remove the oil cap, so not worn rings/bore problems.
I also had the clutch replaced as it was drenched in oil.

I have now done the dreaded 300 mile journey again, took it easy, and have got through 6 litres of oil, and my new clutch was slipping badly.

So, the garage didn't solve the problem and now I'm back to square one with the leak and I need another clutch.



Any ideas?

[MoggyTech]

This has to be over pressurisation of the sump due to blow back gases and or incorrect crankcase ventilation. Or excessive oil pressure causing the oil to be forced past the scroll seal at the rear of the crankshaft. A gallon of oil in 300 miles without leaving a smoke trail, means it has to leaking or getting forced into the clutch bellhousing.

I would remove the engine, replace the oil pump and check the pump cover on the backplate is sound. Replace the rear engine plate gaskets, and fit a new oil pressure relief valve.

[bigginger]

I'd be checking/clearing the breathing system before taking the engine out, on he grounds that it might stop it, and be an awful lot less hassle

[bmcecosse]

It's either insufficient crankcase breathing - or badly worn main bearings allowing excessive oil to flood out of the bearing - more than the scroll seal can cope with. You can try adjusting the top half of the seal - so it sits closer to the crankshaft. Best to connect one of the breathers either to the carb - or directly into the inlet manifold via a 1/8" diameter restrictor hole. That fixed a troublesome Mini engine for me a while back!
But perhaps the best bet is to just hire a car for that long trip - and keep the Minor for the local day to day stuff!

[DaveC]

If you are mainly doing only short journeys, then it is quite possible that the breather pipes have become clogged with mayonnaise, thus bocking the crankcase ventilation pipe (from the side of the crankcase) as folks have said above. This happened to me last winter, and once I had rectified the fault (as suggested by folks here) the problem went away as if by magic . Depends on the age of your vehicle, and especially if it employs carb vacuum pipe type of ventilation**: this pipe must be kept clear.
Hope you get it sorted
(**oil condenser the size of a brasso tin on the side of the crankcase)

[downsey]

How come the crankcase breather isn't fed into the manifold rather than the air filter. I could be wrong but isnt there much more vacuum in the manifold, i.e past the throttle butterlfy? I think theres always vacuum in the manifold except maybe at full throttle.

[DaveC]

I originally thought this, but in fact the pipe from the air filter (or the vented oil cap) is the inlet. The outlet that should be connected to the carbourettor (manifold side) is on the RHF side of the block as you look at the engine. I believe that later cars only have a breather pipe venting to atmosphere from this point.

[IslipMinor]

al2006,

Which engine and breather set up do you have? Also which oil filler cap?

There were a number of different designs fitted to the Minor over the years, some were more hope than effective. The later one, with the PCV, would work, so long as everything was in good condition.

Venting directly into the inlet manifold is not a good idea, unless there is a controlled restriction, such as the PCV offers. Have never tried the idea of a fixed restriction, such as the 1/8" hole suggested; does it work well?

[Kevin]

Which engine and breather set up do you have? Also which oil filler cap?

As richard has said, and the others it does sound like crankcase pressure, you dont by chance have a 1275cc fitted by chance with the original 1098cc timing chain case fitted do you.

[al2006]

Its a 1966 morris 1000, with the original 1098cc engine, and a 1275 head from, I believe, a metro (though someone suggested it could have been a midget).
The timing chain has been replaced, I'm not sure if its original spec.
It also has an aftermarket carb (K&N), and larger exhaust.

I'll go and take some photos....

[al2006]

The oil cap says GFE 6007, thats all I know about it. I did notice a bit of oil in the grooves on the top of the engine, but I think this is most likely spillage from the many times I had to stop and top up.
What would be the significance of using a 1098 timing chain with a 1275?





One question about the carb... There is a pipe coming from the back with a bung+surclip on. Should this be connected to anything?[/img]

[Orkney]

Whats the one behind with nothing on?

[bmcecosse]

Fairy sure the blocked pipe is the inlet for the oil breather/ Simple test - take the pipe off and run the engine - is there suction at that point ? You really MUST get some suction going on the block.
And yes - I had a 1340 Mini engine that was troublesome with oil leaks - connected breather to inlet manifold via unused servo fitting - but hole restricted to 1/8". It upset the idle slightly - but was fine when running and cured all the oil leaks - and no horrible smells in the car either!

[aupickup]

the pipe nearest the manifold should be connected to the breather, the middle one can be blocked off and the other is obviously fuel feed

[Kevin]

Whats the one behind with nothing on?

Thats a fuel breather and should be left like that.

There is a pipe coming from the back with a bung+surclip on. Should this be connected to anything?

That is a crancase breather and is blanked off when not connected.
You have an MG metro rocker cover which does not have a breather but your original 1098 one might have had one hence extra crankcase pressure.

What would be the significance of using a 1098 timing chain cover with a 1275?

It would pressurise the crankcase as the 1275cc one is fitted with a breather pipe.
Is there any chance of a photo of the other side of the engine as the water valve looks straight whereas on a 1275cc head it would be at an angle.
Also is there a breather from the tappet cover below the manifold position.

[bmcecosse]

The wee bit of thermostat cover showing does look to be at the angle for a 940 head. The heater tap looks like a special!

[DaveC]

FWIW
This is my setup. Various bits may be different, but it may help
Oil condenser:

Vent pipes. (The one that goes from the air filter to the rocker is the inlet. The one from the oil condenser to the carb is the outlet):

Carb connection:


Until I got some vacuum in the crankcase as MT/BG/BMC say, I was losing loads of oil! With this set up I hardly lose a drip

[Matt]

Agreed...

The exhaust/inlet manifold is either a metro one or an ital one (both 1275).

I have seen quite a few heater taps like that on minis.


Agreed on the crankcase pressure though. Either put a vented rocker cover on it and attach it too the carb, or do the same with a tappet chest breather

[IslipMinor]

al2006,

The picture from DaveC shows the requirements for crankcase breathing. The rocker cover does not need to be connected to the airfilter, and the oil filler cap must be the vented type, which the MG metro one you have should be.

What is the design of the removable side tappet covers on your engine? Is there an oil separator fitted, as DaveC, or is there just an open tube?

Does the timing chain cover have an oil separator (1275 type)?

If you do not have either of these, one of them will need to be fitted. The open pipe from the tappet chest cover should not be connected to the breather, as without the oil separatot, you will just suck the oil into the engine, along with the fumes! The same applies to connecting the carb breather directly to the rocker cover; there is no separator.

Whichever you fit, you also need to make sure the the vented oil filler cap is clear of gunge.

[alex_holden]

Whats the one behind with nothing on?

Thats a fuel breather and should be left like that.

On one of the carbs I have here there's a little plastic filter on there to stop dirt getting into the float chamber.