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MG Midget and Sprite Technical - Smoking only when started/idle?

We are slowly in the process of restoring our MG midget to the condition it deserves.

We have some work to do to get it through the MOT, but what is a problem is the smoke we are getting when it is started coming out of the exhaust.

When running the car is fine, but if started sationary, it is pumping out a lot of smoke (oil smoke).

No seapage round the gasket, oil and filter recently changed, and not over filled (20/50 oil used). The car is fitted with an oil cooler.

Is it worth getting a gsket kit, assuming oil is getting through?

We do have to take the head off at some point, as the car is still leaded, it only has 19,000 miles from new, but was lest for years to rot, since then the last two owners have done a lot of work, sadly some of it not great, but functioning.

All suggestions greatfully received.

Regards

Dave and Kez
D A Amos

Just to clairfy, when driving no smoke at all, when started/stationary very very smokey

Dave and Kez
D A Amos

could this be an oil control ring that is not sealing properly at idle (when the engine loads are low), but at higher RPMs the increased load / chamber pressure forces the ring outwards, to seal?

or, it could be that the oil consumption is constant, but the higher air flow at more RPMs dilutes it so the smoke is not visible?

When dealing with an unfamiliar engine, it is not a bad idea to do a compression test to see how each of the cylinders are sealing (valves, rings), and re-doing the test with a bit of oil down the lowest cylinder helps to show if a low pressure cylinder is due to bore wear.

Another simple test is to see what happens when coasting down a hill with the throttle closed (crankcase pressure on the "overrun" tends to make worn cylinders/rings smoke more).

It could be oil consumption due to excessive wear (engine needs a whole rebuild), or it could be due to improperly seated rings (fresh rebuild but improper run-in).


The three places where oil can get into the cylinders is: from the crank case (the rings, as per above), or from the valve seals (which tend to leak while the engine is off, and smoke on start up), or from the oil passageway to the head (which tends to leak "out", all over the side of the engine, rather than "in" to the cylinders.

One more way that oil can get in, is through the intake. A failed PCV will allow it to suck oil right out of the crank case. This is, reportedly (according to Horler), why BMC switched from a PCV valve, to the clever "wye" inlet to the carburetor throats in '71, due to field failures of the diaphragm in the PCvalves available at that time.

A PCV failure would show up at idle (when the throttle plates are closed is when the manifold vacuum is the greatest, and the vacuum is the lowest when at wide open throttle).

Norm
Norm Kerr

Just a couple ideas

adding to norms thinking. With the engine fairly new at 19xxx miles... could it be cly glazing ? How did you break in the rings that 1st 500 - 1000 miles did you baby the engine and treat it gently and what oil did you use

Not sure which engine...but if its the 1275...MAYBE the gause in The oil seperator is overly clogged up or missing and the oil mist is not being captured cooled and drained back ...so the oil mist is getting sucked into the carbs ....theres more carb restriction at idle then full thottle so more oil mist is being sucked into the carbs
Prop

My guess is that with your low mileage it is unlikely to be either worn rings or valves. I would suspect valve stem seals. Particularly wirh the engine having stood for a while when the rubber seals may have dried out and cracked. Smoking at tick over and when starting is typical of oil seeping down the valve stems.
Guy

I would echo the thought about the PCV breather valve on the manifold. Block it off from the inlet manifold and see what happens.
Robert (Bob) Midget Turbo

Great call guy....

I thought that but then side stepped it becuse i just assumed the head was rebuilt when the engine was rebuilt....but that would make scence if only the lower end was rebuilt....another thought would be the re-builder may have just re-used the old seals
Prop

Prop,
I was busy typing my answer on the smartphone (slow!) when you were posting yours. But it could also be the breather.
I understood this engine to have only 19,000 from new (i.e.not from a re-build)So things shouldn't be worn, but rubber items like the stem seals - or like the breather hoses - do tend to break up if left to dry out for too long on an unused engine.
Guy

Cars that sit a lot or are driven gingerly for short distances frequently have sticky rings. These clear up after a couple hundred miles vigorous exercise. I had a VW pickup used for parts chasing in town that used a qt/100 miles. A 300 mile each way hard run used 3 qts going and none coming back, and fuel mileage and power went up 50%. I bought a Rover 2000TC (43,000mi) that had dawdled around and sat for a year or so, with no maintenance. I drove it hard 350 miles and used 3 qts, I then drove home on 1 qt. Changed the oil & filter again and drove 5000 miles cross country on a half pint. The car never used any oil after that in the next 100,000 miles.

And there is no need to worry about "unleaded head"; most people never have a problem, and if you do, it gets fixed when it needs it.

FRM
FR Millmore

Sorry... i mis read..... i thought this was a new engine.... but is actually orginal....yeah that certianly makes things interesting.


Yeah ive become vary dependent on my smartphone also...mainly because the laptop is on its last leg of life....im thinking ill replace it with a tablet instead..might make computing much easir with a 10 inch screen. Vs 4.3 inch..what would be cool would be a tablet with a 18 inch screen.... maybe someday
Prop

DAve, Kez, hi,

sounds like a car crying out for a bit of regular use and a full and proper servicing

You may know lots about mechanics but (and perhaps even) I think my usual advice applies especialy if preparing for an MOT

Buy an owners Handbook as it tells you so much you need to know as to own, drive, service and maintain your car - http://www.mgocshop.co.uk/catalog/Online_Catalogue_Handbooks_5.html

Always have the battery in good condition and all battery connections and leads clean, secure and protected, same for all electrical wiring and connections

As soon as possible do a full and proper 36,000 miles service only miss out items that you have 100% proof have already been done very recently, including;
g/box and back axle oils
brake and clutch fluids
coolant
dissy cap, rotor arm and leads (buy good quality ones) - http://www.distributordoctor.com/rotor_arms.html
fan belt

Be aware that brand new parts can sometimes be faulty, especially electrical bits (see just above) so don’t discount them when problem solving just because they are new, buy good quality parts

Change rubber coolant hoses to silicone when you get the chance - http://www.classicsiliconehoses.com/

Check the age of your tyres if they are 6 years old or more replace ASAP regardless of tread depth, this will improve, the braking, steering, ride, handling and possibly noise, of the car greatly

Use the car regularly - to get used to it, sort out any wrinkles and prevent the problems that occur with lack of use, and to enjoy it

Every few weeks check your horn, wipers and all switches work and heater valve turns on and off (all no problem if you use the car regularly)

Follow regular checks, servicing and maintenance as per owners Handbook

Drive in all weathers, the Midget hood should be very watertight if fitted correctly and the heater is more than adequate, if working correctly, for the small cabin

Do not do any cosmetic or improvement work for at least 12 months of regular use, unless you need to replace parts or components, as you may need to use the money elsewhere on the car

Also very useful, you can get suppliers catalogues for free to get you started to see where things go but in my personal opinion they’re not as good as a paper copy like - http://www.mgocshop.co.uk/catalog/Online_Catalogue_Parts_Lists_3.html

Cheers, enjoy your car
Nigel Atkins

This thread was discussed between 30/04/2011 and 01/05/2011

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