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MG Midget and Sprite Technical - Where is all my oil going?

Good afternoon everyone, sorry for the long post.
I bought this standard 1972, 1275cc RWA about six months ago, structurally very sound and original.
The engine bay was a bit of a mess, oil & water leaks everywhere and the car had not covered more than 2k miles in twenty years. With the amount of oil under the bonnet and around the carbs, I suspected crankcase breather issues too.
Before my works, the car ran ok and did not smoke apart from a little on the over-run and at start-up.
The oil consumption has not changed and is still about 250 miles per pint, which I think is a lot.
Did the following:-
Full service of all fluids, filters etc.
New valves, guides, springs & seals (8), together with unleaded valve seats.
Full overhaul of the carbs, needles, jets, springs, float valves etc. ( the wrong needles were fitted together with one very stretched spring)
New water pump, new hoses, timing chain, sump gaskets & oil seals etc.
All oil & water leaks solved (apart from small drip from the back of the sump which appeared after I jacked the engine up to change the timing cover oil seal for the third time!)
No leak from the rear scroll, which is unusual.
While the head was off, the cylinders were inspected and appeared smooth and worn enough to match the 50k miles on the clock.
The cylinder head and tops of the pistons were badly coked up and the breather pipe from the timing cover oil separator was split.
Plugs are now a nice light brown colour, with no evidence of oil.
The car runs very well with no evidence of burning oil at all anywhere.
No oil being sucked up the breather tubes, just a nice negative crankcase pressure.
My compression tests were as follows:-
Hot/dry 1)165 2)164 3)165 4)165
Hot/wet 1)185 2)184 3)186 4)184
Would the 12% increase in compression be OK and commensurate with 50K miles?
Any ideas? my only thought was stuck piston rings.
Regards, Tony
Tony G

Well either it's burning it or it's dripping it.

So it's either coming out of the exhaust, the timing cover seal or the sump gasket or the scroll.

Your certain it isn't dripping, so that leaves burning it.

Drop the sump again, off with it's head and pull the pistons to view the rings.

If the bores are good, just re-ring and reassemble.

I'd chuck in Cords.

:)

Lawrence Slater

According to the Autocar 1971 report 1200 miles per pint of 10/40 was the norm.

Why don't manufacturers give oil consumption figures any more??

Ian


I Ball

I'm with Lawrence on this one...

If it ain't leaking out it must be going out the exhaust. The wet/dry difference suggests poor ring sealing and if the compression rings are having trouble the poor three part oil ring will be unable to cope

I've heard good things about Cords and I would probably go with these before splashing out on a full re-bore.

MGmike
M McAndrew

Hi and thanks for your posts.
If the head & sump need to be removed and new rings fitted, is it worth replacing the big end and main bearings at the same time? can these be removed with the engine in place? I have only done this with the engine out.

Thanks,
Tony
Tony G

Big ends you can do, mains not so, without taking the engine out.

You can pull the caps and look at the mains, but if it's making good pressure I'd leave it as it is. 50K is ok to leave them for quick job. I've done it and had no trouble at all. But it depends on what you see when you drop a cap off.

With the rod ends, I've even reused the same ones if in good condition, but they are cheap, so just look at the journals and use new shells.

Again if it's making good oil pressure, and the shells are still a nice smooth dull grey when you pull them, just put in new shells and bolt it up again.

This really all depends on what you want to spend money and time wise, and how often and agressively you are going to drive it.

At 50K, i'd say there's another 50k left in it without doing too much.
Lawrence Slater

Tony, Whilst it was apart, did you check the condition of the rocker shaft? They do wear quite quickly - on the underside particularly - and this will increase the oil flow rate out past the rockers. Even with new stem seals, excessive oil on top of the head can leak down the guides.
Guy

Hi Guy, yes a new rocker shaft was fitted. The engineer who fitted the guides and seats inspected the rockers and found they were OK to fit onto the new shaft.

The oil pressure I got prior to works (and am still getting) is 70+ at start-up, with 60 running when hot dropping to 40 at idle, these reasonable results, coupled with the smooth bores were the main reasons I did not want to mess with the inside of the engine at this stage.

Regards, Tony
Tony G

Tony,

Your engine sounds like a good one to me.

The previous carbon build up you described earlier, and the ongoing extra oil consumption, would encourage me to drop the sump, engine in the car and pull the pistons.

Given the good oil pressures, I really wouldn't do any more than that.

It's an easy enough job. Shame you have to waste a head gasket, but that's not so bad. If your sump gasket comes cleanly off you can reuse that, maybe with a bit of blue gasket sealant. I like Hylomar.

Anyway, just pull the caps off, pull the pistons and re-ring. I'm sure I don't need to tell you to keep the numbered caps and rods in order. --- with the shells too if they are re-useable :)

Some may say it's a false economy to only do the rings (and possibly the end shells if needed), and that whilst your doing this, you might as well pull the engine and do the lot.

To me though that would be to waste the many more miles left in what is only a part worn engine, that from your description is in pretty good nick.

Get the car up on ramps at the front, axles stands under the axle at the back, and you'll get plenty of room to work.

I'd clean the pistons myself rather than take them to be blasted or the like. Otherwise your getting into small ends and then, --- well why not new pistons?, and on it goes.

But this is just my thinking, it works for me and it's how I've kept my engines going for years.

Course it means you have to be able to do this stuff yourself, and I suppose enjoy doing it too. I do. :)
Lawrence Slater

Ian,
that was 1971, in my experience, if the (A-series) engine has been reconditioned then the car fully serviced and maintained I wouldn't normally expect to it use much oil at all until it's on its higher mileage

as an example with both my Spridgets I wouldn't expect the oil level to get anywhere near the min mark on the dip stick or even really to need to top up between 6 months/6,000 mile services at all

I used for previous Spridget for highish monthly mileage and my present midget recent done 1,300 hard driving miles on my tour of the Welsh mountains with negligable oil use and it has an oil drip ever since I had to replace the sump gasket (engine has about 25,000 miles on it since (believed) recon)
Nigel Atkins

Hi Lawrence, I do, I do, I do, my wife thinks it's a second childhood, I spend more time on the car than the house! Taking me back to my 1990's concours days.

My plan is: head off, new rings, measure/inspect cylinder/big end wear, bigs ends only if worn, reassemble.

That should solve the oil consumption, seal the sump gasket and give me an indication of time scale towards a full rebuild.

I have never used cords before, apart from cleaning, do the bores need any prep, honing etc. or special fitting?

From what I read, they cut their way into the cylinder walls and make a new seal, sounds rather extreme.

Regards, Tony

Tony G

If these Cord rings cut into the bore, don't they then just continue to prematurely wear out the cylinder walls? What tells them when to stop?
Guy

lol. I knew this would happen. I posted something about cords recently in another thread, and said at the time some people don't like them.

It's tea or coffee time again. :)

Tony. You clearly have a very wonderful and understanding wife. :)

You could, if the bores are nice, just re-ring with standard rings for the bore size.

The point about cords is that they are designed to deal with a worn engine. I seem to remember once reading somewhere that they were a rebore in a box, but it's not as extreme as that I think. They certainly don't go on and on reboring the cylinders indefinitely as far as I know.

I'm fairly certain I have a box in my loft containing a leaflet that came with the rings the last time I used them. I'll go up and have a look tomorrow.

How do they know when to stop?

My memory seems to suggest that the cutting edge of the ring eventually beds in and no longer cuts. But I first used cords something like 35 years ago, or more, and have since stopped worrying about how they work, since I know for sure they do work.

I must have used them at least a dozen times in various cars. Triumph 1500 TC saloon, Ford capri, my sprite, sisters mini, bedford beagle van, transit, brothers mk2 consul, late escourt, etc. A mechanic mate told me about them, and he was Rolls Royce apprenticed.

I've got a set in the 1275 that's in my Sprite now. When I last built it, it was smokey prior to the build. I took it apart expecting to do the works, but like your engine, the bores were very good and I decided to save time and money. That was at least 30/40 thousand miles ago.

In terms of fitting, very easy, no special fitting. They just have to be fitted according to the instructions but all rings have to be. The last lot I used contained cupped rings and you have to make sure they go in the right way up. But that's about it.

Personally I don't like to hone unless the bores are scratched, and if they have deep enough vertical scores, I rebore anyway. I only use cords on good but part worn bores. For "glaze busting" I just use a bit of very fine grit paper, and clean with petrol.

I read an interesting article once about glazing in bores being a bit of a misnomer. And that deglazing and or honing bores, was counter productive, since it made it more difficult for the rings to bed in. The story being that honing and abrasive deglazing, creates scratches that the rings can't remove. No doubt that will cause a debate too. :)

The best people to ask for all the tech are Cords themselves. You have to anyway, as they don't use dealers as far as I know.

www.cordsduaflex.com
info@cordsduaflex.com
01685 353240

They're in Wales. Not that that should count against them, lol. I should get a job with them, all this plugging from me, they should give me a free set at least. :)

Actually hepolite used to make a similar ring set I think. Maybe you could contact them too.

I'll look out the leaflet tomorrow and if it has anything useful, I'll scan and post it here.



Lawrence Slater

I'm still waiting for an answer from cords to my inquiry though.
Alex G Matla

Lawrence,
I am not against using them. Far from it, l am considering fitting some. I have been aware of them for years just now gathering information. The Cord website is particularly poor on detail .
Guy

Well my memory is failing. I thought I was out to 30 thou, but according to mt Cords box, it's only 20 thou.

The two sides of the leaflet are below (above depending on your view). Tells you how to install, but not how they do the job. So best to give 'em a ring.

Arie, did you read receipt them?






Lawrence Slater

Page one instruction leaflet.




Lawrence Slater

Page two leaflet.



Lawrence Slater

Thanks Lawrence. Interesting reading.
There is an implication that the ring sets are specified for the engine model on the assumption it has the original manufacturer's pistons fitted. When mine was last re-bored it was fitted with new pistons but I cannot now remember the manufacturer, I think it said TWG on the box. - or something similar. But it was a while ago now, 8 or so years. Might have to do a bit of detective work to find out what I have in there.
Guy

I think I remember telephoning them just prior to my last rebuild to ask about which rings to get.

I have the luxury of a spare engine, so the one I needed the rings for was out of the car, and I was able to ID the ring set I needed by talking to somebody there. I do have original type pistons in my current engine, so it was pretty easy.

As you say the website doesn't tell you much of anything, but I'm sure a call would get you through to someone useful. They must have a store of knowledge garnered since 1937. --- You would hope. :)
Lawrence Slater

Here's an interesting alternative to cords.

Gapless rings. These people do a ring that fits the 19320 cooper s piston. My spare engine has these I think, so I might check them out and see if they are suitable for re-rings.

http://www.performanceunlimited.co.uk/totalseal.html
Lawrence Slater

Good evening Lawrence, thank you for your posts and scans of Cords instructions, all grist to the mill.
Starting to strip the engine in the next few days, I will keep you posted with what I find.
regards Tony
Tony G

"Arie, did you read receipt them?"

Lawrence, I'm not Arie.... I know we dutch all look alike....

I took the engine apart, and the ring gap is 6mm !
Maybe a bit too much, even for cords.
Alex G Matla

Ha ha sorry Alex.

Usually it's all greek to me, I haven't made a mistake with the dutch up until now. lol . In my defense, I would say that 3 of my brain cells were busy, and the remaining small number were asleep. :)

Yup 6mm is a bit big for a ring gap. What's normal for a Volvo then?
Lawrence Slater

Something like 0,5mm.
Alex G Matla

Does the glaze have to be busted before using the Cord rings? I've got a brand new rebuilt engine that is letting oil into the 2 and 3 cylinders.

Thanks!

--Jack
JM Morris

How do you get from .5mm to 6mm ring gap? That's some amount of bore wear.

JM, cords advise glaze busting (see leaflet below), but I've only ever rubbed down with fine grit paper and washed with petrol to clean up, rather than use the tool they mention in the leaflet.

Did you just rebuild with cords then?
Lawrence Slater

Lawrence--no, did not rebuild with Cords. I have a fresh rebore (.020 over) new pistons, new rings. And the second ring is a gapless ring to boot. I've got way too much blowby. Engine was run for 20 minutes at 2500 rpm to bed in the cam. Then about 5 miles of a hard run to help bedding in the rings. To no avail, apparently. Looks like the next step is to replace all rings with Cords.

--Jack
JM Morris

Jack,
What miles on the engine now? It can take a couple of 1000 miles to bed in properly.

The other question I would ask is what oil did you use when first running the engine. Some of the lubricant qualities of modern oil work against the process and encourage bore glazing. You are better off running it on a basic cheap oil for the first 1000 miles whilst the rings are bedding in.
Guy

Jack
Give it a couple of hundred miles before you go that way!
The running so far is nothing.
Onno K

Lawrence, I don't know, bought the engine like that. But it looked ok...
Oh well, some win, some lose
Alex G Matla

Guy--only about 5 miles on the engine. I'm using Valvoline VR1 20w50. The reason I used that oil is that it contains high amounts of ZDDP. What's a recommended weight for break in?

Guy and Onno--you've given me hope. But I've got little pools of oil on top of 2 and 3 pistons. 1 and 4 are OK. Guess I'll hang in there a little longer.

--Thanks!
JM Morris

Jack
Sounds strange but that oil sound way to goodto be running in an engine!
Get some cheap mineral 15w40 for diesel engine's and drive for at least 500 miles.
Only then start thinking about good oils.
Their anti wear property's do not help bedding in the rings
Onno K

Oil pooling on top of the piston sounds more like valve guide or stem seal problem. But for now l would definitely use a basic oil and run it on this for 1000 miles. During this time the ring seal should gradually improove and your oil consumption reduce.

Then drain that oil (hot) to get rid of any running in debris , fit a new filter and refill with your premium oil.
Guy

I'm sure I'll be accused of going over the top now

when I ran my engine in with cheap 20/50 I changed oil and filter at 50, 200, 500, 1,000 and then normal service intervals of 6 months/6,000 miles

you can still get running-in oil

I built up my revs with the mileage band of 500 to 2,000 miles but varying within any rev range from when I got the car at a supposed/assumed 50 miles since engine recon

after about 10-12,000 miles you could think about fully synthetic oil
Nigel Atkins

Way over the top, Nigel. ;-)

Actually , l changed mine after 100 and then 1000.

By comparison, a new Astra diesel gets its first oil change at 30,000 miles with no bedding in process at all!
Guy

as the engine was new-to-me I thought better safe than sorry

and it didn't drop any oil until I had to change the sump gasket

I'd probably still do 50, 200 and 1,000 then normally 6 months/6,000 miles
Nigel Atkins

Jack,
You say this is happening to bores 2 and 3. That to me excludes the wrong oil.

Also, as its a new bore with only 5 miles on the clock, excludes glaze build up I would say.

So where is the oil coming from?

In no particular order

1) As Guy says, Stems/guides.
2) Past the rings.
3) HG failure to the oil passage ways.
4) being sucked up the breather. Unlikely as only bores 2/3.

So

1) Fresh rebuild on head with new guides valves and seals?

2) Did you build it? Confident about ring placement and non breakage?

3) Years ago, in my lazy ignorance, I broke a head stud re-torquing down the head after initial run. At the time I thought I was lucky to be able to remove the stud without taking the head off. I replaced the stud. 200 miles later I took the head off again, becuse I was consuming large amounts of oil. The hg failed on enough to allow oil in.

Personally, if it is pooling that much oil, I'd only run it for a few 10s of miles, before pulling the head again.

And as it's a new bore, I wouldn't use cords. I would pull those 2 pistons for a look see, if it's not the head.
Lawrence Slater

Started the engine
Bed in the cam for 20 minutes
Adjusted the timing and carbs
And went for a 300 mile night drive only stopping the engine for refueling.
Not labouring the engine and only moderate revs
Changed the oil
Then did 700 miles of normal daily driving (no trips shorter than 30 minutes)
Only moderate revs slightly increasing with distance
Changed the oil
Then figured it was fine and blasted the hell out of it!
Onno K

That's pretty much the routine I follow Onno, except not at night. Although it makes good sense as little or no traffic to get stuck and overheat in.

But not if I've got large amounts of oil pooling on a couple of the pistons.
Lawrence Slater

Lawrence: To answer your questions:
1)Head is freshly rebuilt. New everything.
2)Yes and no. I wasn't there when the rods, rings and pistons were fitted, so there could be some doubt there.
3)Head gasket (Payen) is brand new.

Further background: Car was first started about 1 month ago after fresh rebuild, run for 20 minutes at 2500 rpm to bed in the cam, then run hard for 4 miles to help bed in the rings. At that point, there were a number of minor issues and the car was not restarted again (1 week later)until the minor issues had been solved. Car was then run hard again for 4 miles. At that point, water was discovered in the oil. We decided the head gasket had been blown. When the gasket was pulled, oil was noted on top of the pistons as well. Another Payen head gasket has been installed plus all new studs. The water in oil problem has been solved but not the oil on pistons issue.

So I guess the next step is to check valve stem seals, refill with el cheapo oil and run it. Last resort (groan) is to pull the offending pistons. Is that how you see it?

Thanks!

--Jack

JM Morris

Jack
There are several that will disagree but clearly running hard has not worked.

Clean it all up and run in like I stated in the post above.
If it has not improved after a the first stages you might want to think about a new set of rings and slight hone....
And repeat the driving in procedure without the hard on approach
Onno K

I have just been reading the instruction leaflet that came with my pistons fitted 8 years and some 70,000 miles ago.

It says after fitting new rings, to take it on the road, and to accelerate hard form 30 to 60, and to repeat this 10 times over (oddly, the French translation says 12 times over!)using a mid-range gear to avoid the engine labouring. It then just says to vary the engine speed for the first 100 miles but avoid sustained high speed. It makes no mention of the 2500rpm for 20 minutes that is needed to bed in camlobes and followers.
Guy

No why would an instruction for piston rings say anything about breaking in a cam?

Only in our old pushrod engines is bedding in a cam critical because the rocker make the loads on the cam a lot higher than on a ohc cam engine.
Onno K

I agree Onno, I wouldn't really expect it to. But there is a potential there for contradicting advice on how to bed in the two sytsems
Guy

That is true.

But strangely that is why I never rely on only one source of information.
When all sources give simulair info there is no need to search further.
When sources contradict you can eventualy make your own slightly educated decision.
And by including comon sense cockups are usualy avoided.
;)
Onno K

Regarding break in, see a separate thread I've started--"engine break in theories"
JM Morris

Jack. Rebuilt, but how flat is your head?

seems to me you have to pull the head again anyway. whilst at it, check the head, and block for flat.

yup, apart from a sump gasket, pulling the pistons will only cost time. so I'd do it.

Then on rebuild, run it up, check torque.

Did it overheat at any stage in your previous run in?

If so, could have scuppered a ring or two.
Lawrence Slater

This thread was discussed between 25/11/2011 and 01/12/2011

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