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MG Midget and Sprite Technical - 1500 Oiling Plugs: In Norway,Diagnose from UK?

Apologies, I hoped to be concise, but hopefully the detaild post is fairly complete for my situation.

I hope I can get some good advice about my brothers 77 1500 midget which is oiling up the plugs.

The car is in Norway. A used engine was fited a several years ago, allegedly 70k miles. I drove the car 600 miles from Stolkholm and engine behaved OK. Can't remember any excessive 'blue smoke'

Car has done less than 4k miles since then, all very short journeys. lead additive has been used with unleaded fuel.

Diagnosis from Norwegian mechanic via my un-technical brother "It is continually oiling up one plug and to a lesser extent another plug" - I do not know which plugs and I will not get any further diagnosis before my visit to the car in 2 weeks.

Whether it needs it or not I have arranged for a properly reconditioned head converted to use with unleaded to be shipped to Norway. Inc new valves, seats and guides - on the basis that if the head does not fix the problem then it will be good to have the head for a future engine rebuild.

I know that the oiling up issue could be associated with the existing head or could be oil control rings.

I will not be removing engine or pistons on this trip (maybe in the future) but want best advice to see if it is possible to make the engine work without oiling up the plugs. The car will do less than 2k per year, so some 'non permanent' fix will suffice for now.

Before I ask my specific questions,a little of my background to help you structure any answers appropriately.

I qualified as a mechanic and auto-electrician in the 70's but been out of the trade for 30 years. I practised as an Auto Spark, but on a personal level have done a little of every task on BL / MG cars from complete body rebuild, welding and painting to engine overahul (inc pistons rings, bearings etc), but not often enough to be the most efficient at diagnosis or repair.

The car has not driven for 2 years.
When I arrive in Norway I intend to get the car started with clean plugs and do as much diagnosis before removing the head.

I will have a compression tester with me.

Without me wasting your time further, telling you what I think I need to do I will ask.

My questions:
What is your best guestimate in percentage as to what is causing the issue:
1. Anything to do with the head.
2. The oil control rings or anything to do with the pistons / bore.
3. Something else

What steps should I take to diagnose the oiling up of the plugs (with existing head still in place)? ie how accurately can I diagnose a head or oil control ring issue?

If this diagnosios is not 100% certain what diagnosis can I do with the head off (either on the old head, or more relevantly on the block and pistons).

Assuming I am left with any possibility of an oil control ring problem (or any other issue regarding the pistons and block) is there any modern additive / compound that I can 'pour' around the pistons to improve compressions (if necessary) and more importantly reduce excess oil getting to the plugs. I am completely out of touch with modern 'repair liquids'.

Can you recommend equipment I will need apart from:
AF Socket set - with long bar
AF combination spanners
Compression tester
Torque wrench
Feeler guage
Plastic / rubber pipe to retune carbs.

Can you recommend any parts I should organise apart from:
A complete cylinder head kit with all relevant gaskets.
New oil and filter.

Can you direct me to useful web pages / videos which will help with the procedure.

If and when it comes to (as a minimum) replacing the oil control rings, (not on this trip)what thoughts do you have in doing this 'in place' with a sump and head removal (replacing bearings and thrust bearings at the same time) vs engine out - bearing in mind I will have to beg steal or borrow equipemnt / facilities.

Thanks in anticipation Colin

C Kinsella

I would start by checking that all 4 plugs are in fact firing. One could be oiling if it is not firing, in which case it could be as simple as replacing the plugs or leads. Check for spark at each plug. Check that engine revs drop by the same amount as each plug lead is disconnected in turn. If you have one of those laser-spot temperature guns check the temp of each cylinder is the same when it is warmed up and running.

Check that all 4 plugs are the same grade. You may just have a "rogue" lower temp plug fitted.

If its not plugs, then I would do a wet and a dry compression test. This would identify poor ring seal or poor valve seal. At least this might eliminate the possibility of broken rings.

Thus far, you shouldn't have got your hands oily, but I think beyond that you need to start a strip down. It could be that the valve stem seals have dried out and are leaking oil into the cylinder, in which case your new head will sort that one anyway.
Guy W

Guy Thanks for your input.

I know the car had new, correct plugs and good HT leads / spark about 3k mil
es ago, but thanks for suggesting some steps I might have missed.

I am aware of the possible seals issue which will be resolved by the new head.

Someone suggested that oil control rings could be a problem but compression rings OK.

Not sure how likely this is and assume a wet compression test will not identify faulty control rings.

C Kinsella

If anyone has any further input on my question I would appreciate it.

Thanks Colin
C Kinsella

If someone could look over my tools list in post 1 to see if I have missed anything important. At home I can just go to the local motor factors to buy whatever I need. Not so easy close to the Arctic circle in Norway.
C Kinsella

Hi Colin,
My apologies if I was focusing on the basic steps to check first, when you are almost certainly well aware of those points. I am an eternal optimist which generally means I assume that most problems are very easily fixed and I always start with the simplest of things like a loose plug lead or similar. I then gradually become increasingly disillusioned as all of the obvious and simple causes dry up and I am faced with expensive or complex solutions. Thankfully things often then go full circle after all and a simple cause that I had missed comes to the surface just in time!

I would have thought that the significant thing with this engine is that it was OK when you drove it over there, so it isn't going to be something wrongly assembled. - I say this because as far as I can recall the discussion not so long ago about oil control rings related to sets being wrongly fitted. If this engine didn't smoke when you had it then that seems unlikely.

Ruling out the simple things I would say that you are left with either a problem with valve seals / valve guides - which will be fixed by fitting the new head. Or a broken piston ring which will probably show up with a compression test. If the latter, then your selected tool list would enable you to fix it with the engine still in the car. But you would need to have replacement rings or piston and of course know the sizes, so as you say, you wouldn't intend going that far on this trip.

Oiling one plug and partial oiling of a second one does sound more like a symptom of the valve seals having gone hard through lack of use. Which would be an easy fix. If it isn't this and you just want a temporary resolution then you could just try changing the plugs to the next hotter grade. The problem though is that this isn't addressing the cause, just the symptom. And if the cause were a broken ring then continuing to run it would seriously damage the bores!

As to tools, if you remove the head you may then need some extras like new jubilee clips/ coolant hoses/ coolant/ radweld.
Plug spanner. Although the timing shouldn't be effected , you may also want to check the ignition so a strobe would be handy

Not sure why no one else is joining in with ideas - you would normally expect to get over-run with suggestions. And not all of them either polite or relevant! ;-)
Guy W

And you may well need a replacement by-pass hose. The short coolant hose that connects between head and block.

And fit a new thermostat and cork gasket whilst you are at it?

oil change & filter?
Guy W

This thread was discussed between 26/04/2014 and 04/05/2014

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