MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Oil Change

I haven't changed the engine or gearbox oil for a couple of years so need to do it now. Car has not been started for many months and I read somewhere that oil can get milky. Do I drain cold or is it OK to warm the engine up first
/
Rod Merrall

I've never heard of oil getting milky without a problem letting water in, and if you think that's what's happened then drain it cold. I might then use a flushing oil, drained hot, before filling with decent stuff. Change the filter twice, before each of the refils? Not a huge expense.
paulh4

Rod,
unless the oil is milky then hot.

Check the oil filler cap, dipstick, take the rocker cover off if you want, but if you don't see any milkiness don't worry about it.

Can you get milkiness from very bad storage condensation I don't know, it's usually from a head gasket failure or the like.

If you don't have milkiness then get the engine and gearbox oil as hot as you can for draining and leave it draining for as long as is sensible that way you'll get the most old oil and muck out.

Follow the instruction in the Driver's Handbook for engine and particularly gearbox if it has overdrive.

If (in addition to those in the Driver's Handbook, WSMs) you want some basic, clear, easy instruction on oil changing for engine, gearbox (and rear axle) I've done some just email me and I'll send by email return (Word.docx or PDF attachment whichever you prefer).
Nigel Atkins

How often does the gearbox oil need to be changed - is it as soon as every two years?
Peter Allen

Every 24,000 miles, drain, clean O/D filters if fitted and refill.
Chris at Octarine Services

Peter,
WSM (and I'd imagine Driver's Handbook but can't remember) has every 24k-miles or two years whichever is the sooner of course this was in the days of the owners actually using the cars regularly but even so as we know most things deteriorate with age (and lack of use of the whole car has many detrimental effects).

Below is just an example page someone sent me, from a Driver's Handbook.



Nigel Atkins

Thanks for that I'll change hot. I noticed oil seepage from the sump gasket, not too bad, but I might change the gasket. At the front of the sump 3 bolts seem very hard to get at being under the cross member; any tips to deal with them?
Rod Merrall

You may need to lift the engine to access them, maybe enough 'stretch' on the mounts. This can be done by jacking under the sump but you MUST spread the load with a stout piece of timber or board.

However John Twist has said that MGB sump gaskets never leak. Brave claim, but it could be from the crank pulley seal or the front cover gasket even if drips are further back, or the tappet chest covers which are prone to leaking, rocker cover, and oil filler cap.

Ideally start at the top fixing leaks, not the bottom.

If you do replace the sump gasket only use a smear of non-setting sealant - not gobbets or sillycone, or it can split the gasket when tightening. Don't over-tighten - 6ft lb only, and check the flange is straight. Over-tightening in an attempt to fix a leak causes the flange to bulge down and leak worse. Same for the front cover except that the 5/16" bolts are 14ft lb.
paulh4

I'm with Paul, with leaks allow for gravity start at the top, and that where the leak is and where the oil drops could be a via a convoluted path tracking round and over components, parts and body bits.

Oil filler cap also makes me think of the breathering, if you have a bling chrome oil filler cap they're not as good for breathing as the standard plastic with filter and larger breathing holes (see photo).

There's a John Twist video on checking the breathing, very easy.

IIRC John Twist says to use the later thicker tappet cover cork gaskets even on the earlier engines.

If you want to find the leak sometimes if you clean everything so no oil is around and then use the car to see the leaks are, or some use stuff like flour? talc? to highlight the wet areas.



Nigel Atkins

As well as the two types of cork gasket there are rubber, and whether to use the rubber or not depends on what type of cover you have. When changing them bear in mind that what is fitted now might not be correct, and the cover may not even be original to the car.

To complicate matters further I found the rubber was slightly too small for the groove in the cover and wouldn't stay in, unless I clamped it in position on the bench overnight then got it on before it could pop out again.

Also important are the rubber crush washers on the bolts. http://www.mgb-stuff.org.uk/enginetext.htm#tappetcover

As far as the rocker cover gaskets go it's easy to crush the cover through over-tightening which results in leaks, and there are rubber sealing doughnuts under the cup washers (maybe not on early cars) which also go hard. They are supposed to be a service item but not mentioned in the usual places, as I recall. http://www.mgb-stuff.org.uk/enginetext.htm#rockercover

paulh4

Thanks I'll delve deeper. I intended when changing the oil to use castrol gtx. I've not used it before and not clear whether the modern stuff is a mineral oil. Advice welcome.
Rod Merrall

Concerning the topic of oil changes, I have had to remove the oil pan on three different British vintage cars for various reasons and each time have found a “jelly sludge” substance 1/2” thick in the bottom of the pan. These were on cars that had oil changes every “few years”. My question is could/should this be flushed out by squirting a cleaner up the drain plug to avoid pulling the pan.
L Frisch

Rod,
which Castrol GTX or do you mean Castrol Classic XL 20w-50 distributed by MGOC?

Either way don't worry about the oil not being mineral it will be mineral regardless of the sales and marketing description unless you're buying a lot higher price product.

Paul and I are on opposite sites of the oil belief he, I suspect like yourself, is into the old tradition (must be mineral) oils, which will be a different and better formula than back in the day anyway, whereas I'm into oils that call themselves 'synthetic' or actually are really synthetic.

A good oil is a good oil regardless of its make up and sales and marketing description and name.

Duckhams Q is back (with a new modern better formula) and still a mineral oil.

If you don't use your B much in winter (or at all) then for your piece of mind stick with the oils that have 20w-50 on there labels (20 is a range and so is 50, 20w-50 oils vary but don't worry about that as a good oil is a good oil).



Nigel Atkins

My car is on stands at the moment and I don't fancy taking it for a run and having to jack it up again. I was contemplating running it in gear on the stands; is this safe?
Rod Merrall

L Frisch (Terry?),
I can't see that squirting a cleaner up the drain plug would doing any good. Do you have the oil flushing, er, oil that you get in small cans that you can add to the existing old cruddy oil and run up the engine up to temperature before emptying out (hot) before changing to the fresh new oil?

Better still would be to use a full flushing oil (or cleaning agent of some sort) and have the car run with that for a while to do a more thorough clean.

If there's crud/muck/jelly in the sump what's in the rest of the engine.

The jelly is probably from lack of use of the car let alone proper use of the car and/or lack of proper maintenance of the car as the oil could be years (to decades?) old. Otherwise it must be contamination from other substances added or leaked.

Personally I'd make sure the owner saw and got some of the evidence on his fingers and realised why there was extra work involved and extra labour and materials costs.

Have a look at this - https://www.youtube.com/watch?v=Y2XEpK5HpXQ
Nigel Atkins

Rod,
not just the safety but I think IIRC it's not a good idea anyway for the mechanics of the car, I forget the details. If you have a rolling road it'd be ok.

Got any ramps?
Nigel Atkins

There should be no sludge in the pan of an engine changed hot annually at least, or 6k intervals if that comes sooner. Cleaned out once it should then stay clean.

The only 'cleaner' I would put in an engine is something like Forte engine flush, in the oil filler of a hot engine, and run for a few minutes, to be drained out with the oil. Squirt some cleaning agent in the drain plug hole then it could well still be there when you start the engine and it starts drawing up oil.

Modern oils with a later API designation contain less ZDDP which is needed to protect the tappets and cam. Lower viscosities will probably find more places to leak from.

The gearbox can be drained cold as the oil there should remain clean, unlike the engine which builds up contaminants from the combustion process. Both mine have been after many tens of thousands of miles. I hear people say they drained theirs and it came out black, which doesn't sound like good news to me.
paulh4

As you're adding to the existing oil level with the add-in flushes (like Forte) you need to check that the oil level isn't already full or over full. Surprisingly those that don't change the oil can tend to overfill to save looking at the dipstick (no not the one in the mirror but engine) for another fews years.

The gearbox oil will drain better hot and will probably get more muck and old oil(s) being hot, it may well also reduce the significant amount of reside old oils and muck left in the gearbox, and engine.

I tip a small amount of warmed fresh oil in the gearbox towards the end of the drain and let it drain to act as a flash flush.

Nigel Atkins

Back to the “sludge in pan” issue for a moment. One car had been sitting for years and years without changing oil and I had to scrape it out. So my advice with this situation is to drop pan and clean it. The other car was a fresh rebuild but very little use for a few years. That jelly was explained by my “garage expert friends” as assembly lubrications that migrated to the bottom of the pan. In that situation, as mentioned elsewhere above, we changed oil, ran motor to temperature and flushed a few times.
L Frisch

Terry,
I see the points you're making and agree with using judgement to the situation.

Presumably if you don't know the history of the car at oil drain you look at what's drained into the container and judge whether it's worth putting a probe through the drain hole to get out a sample of what's sitting on the bottom of the sump. Or if what's sitting in the drain bowl is that bad the sump will need to come off for cleaning and further investigation of the bottom of the engine.

Not knowing the history of the car is where I particularly recommend carrying out a full 36k-mile service and check (staged between using and enjoying the car if possible). Including hot thorough oil changing of the gearbox and back axle as well as engine as looking at what comes out can tell you a lot sometimes and by doing this you also know the exact time when the oils were changed and that fresh, new, good quality oils were used and a thorough job was done.

If required further flushing and cleaning.

This should also apply to the cooling/heating system.

I think you want to start your ownership of the car with the systems as clear and clean as possible so that you get better reliability and can, if you want to, explore the fuller potential of the car.

If you want to be like some owners and only go out for a few miles on a sunny Sunday afternoon to a local show once or twice a year then it probably doesn't matter but if you want to drive the car, and anywhere near the manner it was designed to be driven, then it needs to be in reasonable driving condition.


Nigel Atkins

Nigel, yes we are on the same advice page here, make sure you have clean oil running through the veins of your motor.
L Frisch

Certainly change all fluids if the car has been sitting.

I am rebuilding an engine that I changed out of the B. I bought a rebuilt engine and installed that so I have lots of time to rebuild the one that came in the car.

When I pulled the oil pan off last weekend, I discovered a pile of gunk in the bottom of the pan just below the oil strainer. There was a ring around this mound that was oil resistant, almost if it was water-based mud.

The engine had obviously been rebuilt by the DPO. The lock tab straps on the connecting rods had not been locked and one of the rod bolts was all but finger tight.

Time for a rebuild but I am still wondering about that pile of gunk.
Glenn Mallory

This thread was discussed between 15/06/2020 and 20/06/2020

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.