15 replies to this topic

[samohnz]

Hi there, We are worried about the oil loss,or consumption of our mini.It seems to be losing a substantial amount, but we are unsure where.The plugs are not oily,it is not blowing blus smoke out exhaust,and there are not puddles of oil lying all over our garage floor.Car accerates very well,and is a strong runner.The only thing that i can see was oil leakage coming from the crankcase breather pipe low down on the crankcase,which i remedied ,but the oil consumption still remains.Could the oil be forced through up through the breather, and out through the carb,which it connected to? can i try to connect a catch tank to see if this is the case?.Any thoughts much appreciated.cheers Samoh ps we seem to be having prob after prob !

[Blatherskite]

What is a "substantial amount"? How often (miles) do you refill a litre? If there's none on the outside of the engine, then it's being burned, but remember, these are old engines now and don't match a modern motor's low use.

[samohnz]

Hi, went for a 120km drive,used around 250ml of oil,I guess this wouldn't be classed as normal,but i can't see any evidence of the oil being burned.cheers 

[Cooperman]

That is about 170 miles per pint which is indeed a bit high. Check for piston blow-by by starting the engine and when warm let it tick-over and remove the oil filler cap. If it is 'puffing' smoke out of the oil filler cap then the bores/rings are suspect.

Alternatively do a 'leak-down' test on each cylinder which will check ring/bore seal.

 

Alternatively it could be valve stem oil seals.

[samohnz]

Thanks Cooperman,I have done a check of the oil cap when idling,and didn't see any smoke puffing out oil cap. Am i going down the wrong line thinking of crankcase pressure ?. Car is running 10 : 1 compression,with a single su carb and only one breather from the crankcase.Car was intially set up with twin su carbs and the single breather. I wonder if the twin carb set up would have aided in the release of crankcase pressure and maybe not force oil out that way ? Your thoughts ? 

Many thanks Samoh

[Cooperman]

Some engines do seem to burn a bit more oil than others. The original 1275 Cooper 's' was known to use a lot of oil, maybe 100 to 120 miles per pint from new.

It doesn't necessarily mean there is an engine issue. For example, engines used for competition are often bored slightly oversize by 1/2 1 thou or so and can burn a bit more oil as a result.

Are you using a top quality 20w50 mineral oil (Valvoline VR1 for example)? If not a thinner oil will be more likely to give a higher oil consumption.

Don't lose sleep over a bit of oil use  .

[samohnz]

Hi, We are using a mineral penrite classic mini oil 20w-50,I know the engine builder was using a mineral Valvoline formula 50,which I think may be a bit thicker,Maybe I am worrying a little,but i like to know where things are going ! 

Cheers 

[Cooperman]

If the engine is newly built it may just be the rings not yet fully 'bedded-in' in the bores. This can take up to 1000 miles to happen fully.

[samohnz]

Engine done about 4500 miles. cheers Samoh 

[carbon]

Samoh,

 

A bit more info about the engine would be helpful.

 

Is it a 1275 unit, and are there valve stem seals fitted to both inlet and exhaust valves?

[samohnz]

Carbon, yes it is a 1275 unit bored out to 1312,sorry more than i can tell you regards seals.(mechanically challenged )

 

Samoh.

[russo]

Assuming oil is being checked on a flat surface and cold before first start up. If being checked on a hot motor some oil can still be in oil galleries and not fully drained back into sump and when topped up can result in overfilled engine.

[samohnz]

Always checked cold and on flat surface

[samohnz]

Must add that i only have one breather from the crankcase up through to the carb,from reading other forums this may not be adequate,and could it therefore be causing our oil loss due to excessive pressure ? and will adding a breather from the rocker cover be suitable ? many thanks Samoh.

[ChopperHarris]

You mention that you fixed oil coming from the existing breather....how did you do that?