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MG MGB Technical - Massive oil discharge.

Hi All,

I thought that I would document a recent oil failure on a journey to rolling road tuners 17 miles from home. I had made the usual fluid checks before leaving and I guess my average speed on the journey was 45-50 mph.

On arrival at the tuners, after reversing the B on to the rollers, the tuner pointed out that I was dropping oil on the floor. Having recently replaced the rear tappet cover gaskets I assumed that this was the source of the leak. On opening the bonnet I was staggered to see that the RHS of the engine bay was awash with oil. Oil was covering the electrics, fuse box, the oil filter, the coil, the washer bottle, the starter, the distributor and, after inspection, most of the RHS underside. In fact, oil was dripping from the rear of the real wheel arches, the rear springs and the cross member!

As you can imagine I was horrified as the rolling road company had much Italian exotica parked around their workshops. On inspection, the oil level on the dipstick was just touching the bottom of stick, so wherever the oil was leaking from it had discharged almost all of the engine oil, ~6 pints, over the 17 mile trip.

We restarted the engine and immediately the oil leak was traced to the flexible oil pipe connecting the engine block to the oil pressure gauge. The engine was switched off and an initial clean-up ensued.
For the tune-up we capped off the oil pressure gauge supply at the block, replaced the oil, performed 6 power runs up to 5-6000 rpm with no ill effect and no engine destruction from bearings potentially being run dry.

My point is that the flexible hose was purchased from MOSS UK, fitted in 2009, and had only covered ~3000 miles. My journey was 17 miles and in that time this failure had deposited all the oil onto the road without any warning. Oil pressure was indicating within normal tolerances. Had I driven further I believe that my engine would have been destroyed.

I have purchased a new oil hose from MOSS, and in the process I explained my experience asking if they had changed their supplier. They stated that they had changed supplier in the lasts 6 month so I’ve now fitted this new part. It is different in many respects. The spanner size for the nuts is different and the diameter of the union and bore is different.

I would warn anyone who has purchased this part from MOSS in or around 2009 to check its condition. This part, costing < £10, failed with so little active servic, would have resulted in a failed engine costing 200x the price of new hose.

This raises several questions:
1) Can you run an engine with such low oil levels with no apparent damage, for a short time? And if not, what damage might occur?
2) How can an owner monitor a rapidly reducing oil Level? Oil pressure switches only tell you that there is an issue when it is too late.
3) Any suggestions about the life expectancy of my engine?
4) Where can I get better parts that may cost more but do not fail like this?
5) Do I now need to check my oil every 17 miles? !

I am particularly keen to hear ideas on how to detect dropping oil levels so that a light or alarm can be set up to alert the driver should there be a loss of oil prior to there being a total loss of oil pressure with the catastrophe that it would involve. If I can devise a detection solution I’ll publish it here.

Over the weekend I have cleaned the complete underside and restored the car to clean status. I attach a picture.

Any comments welcome.


Richard Thompson

I would be interested to hear replies as I had a similar event - but mine was a burst oil filter canister. It was lucky that I heard a strange "squidging" sound and stopped to investigate. Very messy mop-up job. Checking the filter afterwards, I think it was a previous owner who had tried to get the filter off with some chain tool and failed. The real nark is that I was on my way to buy service items, including new filter as I had just bought the car.
Graham Moore


Since you say you never lost oil pressure and you were driving slowly, I doubt you hurt the engine at all. Had you lost oil pressure, damage would have followed shortly after. Had you been driving hard you might have overheated the remaining oil and possibly done damage. As you describe it, I would not be concerned.

It is common for expensive engines to be set up with a high temp & low oil pressure light / alarm / and automatic shut down system. Then there is an override button on the dash that you can hold to avoid shut down if safety concerns mean you need to risk damage to the engine in order to get off the road.

I think the systems I remember on semi trucks were made by Kaiser Cadillac. I am sure other companies make them as well. Also, it is common to have a very large low oil pressure light on competition cars. I mean large like the size of a marker light on a trailer. I've never installed one, but my guess is that you just need to put a tee in the pressure line system and add an electric sender and a light.

That must have been high detergent oil because the underside of your car sure looks nice.

C R Huff

if you really think the engine might have been damaged why did you and the tuners continue with the 6 power runs at 5-6,000 revs and drive the car home – you’ve answered your own question there

it is a little frightening that in around 5 years you've only done 3,000 miles, had you done more you might well have been more aware of the p*ss poor quality low priced modern made parts, I’m glad you see you see the sense in paying more for better quality but most classics owners don’t they want cheap parts, it doesn’t matter much to them as they so rarely use their vehicles, so because of their tight fistedness we all suffer from these p*ss poorly made modern parts

your engine and other components and parts will probably last longer if you use the car more and regularly carry out full and proper servicing and maintenance and repair, basing the servicing on time intervals rather than mileage, with such low mileage in fact you’ll need more servicing not less on such low mileage

if the part you have fitted now is well made then you can statistically forget about this ever happening again so not worry about it

there are places that sell better quality parts and components and these are not necessarily from the main suppliers but it all depends what part you want and some parts were so p*ss poorly made that even tight-fisted classic owners could no longer put up with them so the quality improved – some suppliers have owners or employees that are honest enough to tell you about the quality if you ask them but obviously they wouldn’t want to risk their jobs if they work for the like of Toss with their ‘ers’ management
Nigel Atkins

ETA: sorry to sound so moany again but is it my monitor or have you two different tyres on the back - such low mileage won't help with the tyre sidewalls getting hard and old
Nigel Atkins

4-Lots in the archives about poor quality hoses. Try Stevson Motors 0121 472 1702.
2-Mini spares do/did a 20 psi oil pressure sensor.

Trying to tee off from the join between the braided and solid pipe on the firewall has proved difficult. I had a fitting made and am not very happy with the result. It may be easier to tee off from the block end of the braided pipe.

The plan was to replace the redundant dimmer control with a large yellow "oil pressure- oh sh1t" light.
Michael Beswick

The later export cars had a connector union for the top of the footwell/bulkhead with an extra female thread specifically made for a low pressure warning light. It's a very neat sollution to get one of these parts.

If you're really scared, why not have a warning light circuit also operate a relay (normally closed) to cut power to the coil in a low pressure situation. Surely with the engine cutting out and a warning light illuminating you'd have the presence of mind to shove the car in neutral and coast safely to the curb to avoid mechanical revving of the engine. Would probably save your engine but, of course, could result in a massive crash if it happened at an inopportune time, such as overtaking. Id rather lose my engine than my life, but it's always an idea ;)

"The later export cars had a connector union for the top of the footwell/bulkhead with an extra female thread specifically made for a low pressure warning light"

The fitting was for a switch that was part of the North American anti-runon system, not a low-pressure warning light. NLA for years, unfortunately.

The gauge hose on mine came with the car 25 years ago, and it's staying till it busts!

I've recounted this before but many years ago I watched a Scimitar GTE roar off the line at Prescott Hill Climb, wondering what the big orange light on top of the dash - a Mini indicator light unit - signified. Only to see a large and spreading pool of oil on the ground. He must have travelled several hundred yards at full chat before he realised. He rolled back, fitted a new oil filter, and on his next run posted FTD.

I've just replaced the bottom hose as part of some other work, the one that was on there also came with the car 25 years ago, and I pondered refitting it. The only saving grace of the 'new' one is that I bought it as a spare about 20 years ago, and it does seem to have the same construction as the 'old' one.
Paul Hunt

Ahh yes, you're correct. I should have said " oil pressure switch which could be linked to a low...". They're NLA but MG breakers should probably have a few for the right price.

Many thanks for all your comments. All indications since last Friday look good and there seems to be no detectable change in the engine, so I guess I have been very lucky.

I like the idea to insert a “T” union on the bulkhead to drive an oil switch and indicator. I see the logic in having an ignition interlock but it would probably cause other problems. I guess for a racing engine it is valuable however on most circuits there are good grassy run-offs to take the car onto in the event of an oil failure and an automatically shut down engine, sadly UK motorways are not so well equipped.

Nigel, prior to the power runs we replenished the oil and it was ticking over for about 30 mins when timing, linkages, balance and mixture were adjusted so we were optimistic. I have identical tyres on the back and they are in line for replacement once I have completed the current tasks sealing up oil leaks.

Charley, thanks for the complement, I did a re-shell and having it all painted it is not too difficult to keep clean, except when there is a tidal wave of oil!. The whole clean up took about 6 hours.

Michael, Thanks for the link to Stevson Motors. I’ll call them and ask if they supply Moss. If they can supply a better one I’ll buy it. Maybe the name of the light should be “Oh slick“

In looking for a solution I have searched around and there are oil level sensors made for today’s cars but most are designed to be located in the sump with a link cables out of the sump.

Ideally I would want a solution that could be fitted without removing the engine so I have been thinking of a design using a perforated tube with a float in it that inserts down the dipstick that would actuate a contact/hall effect device or similar, but such a lash up may be unreliable at best given the small bore of the dipstick, engine and oil temperatures.

Thanks for the advice and comments. This BBS is a superb asset for all MG owners.


Richard Thompson

Hi Richard,
just the monitor and my poor eyes then about the tyres, they looked like they were slightly different

I was trying to allay your fears on the engine by suggesting the tuners wouldn't have put it on the rollers or let you drive home in it if they thought there was any real damage to the engine

obviously because this sudden loss of oil it's now a concern of yours but what are the chances of it happening again (subject to quality of new part), perhaps if you have one of the oil cooler hoses rubbing through to a hole but you'll check they're all secure and not chaffing not I've mentioned it

but I can understand if it makes you feel better you might want to fit a warning (how is it tested to make sure it's working?)

some owners once had problems like a fuel pump playing up so they carry a spare fuel pump or fully dissy and leads or loads of other parts - I can't understand this as my philosophy is to fit a good quality part and then to make sure it works well and test it, record when the part was fitted, date and mileage and consider its replacement by review before it goes ceases to function well and certainly well before it's likely too fail - but for some parts and components this could many years hence

the only time I've been really let down on this with my current Midget was when the work was done by 'specialist experts'

oh and the newish accelerator inner cable that snapped, I done a roadside repair, with I loathe, lucking in warm sunny weather, and made it home easily, I'm putting that one down to a combination of poor quality cable and my over tightening the clamp on it
Nigel Atkins

Have a read of this.

How lucky was I and how tolerant is the "B " series engine to low oil pressure. If you catch it nearly enough you will survive. I know that my problem is not yours, just an example of how hardy this engine is to catastrophic oil feed failure. The only reason I stopped was because I noticed in the rear view mirror that something was following me down the road. It was the oil filter!!!!!

ex MGB owner
Tony Oliver

"a design using a perforated tube ... that inserts down the dipstick"

It's a very small hole, I tried to get a 1/4" tube down there and it would only go so far. There is also oil slosh to consider. I would have said a pressure failure switch was the best option, if you can find a suitable Tee. A pal (who had gauge hose failure) and I spent some time trying to reproduce the original arrangement with parts available today, but getting the right combination of gender, seats and thread proved impossible while our patience lasted.

Testing a dipstick device is easy - simply lift it up with the ignition on, just the same as a brake fluid level sensor.
Paul Hunt

Mk3 Escorts used a dipstick with a level sensor...
D O'Neill

I have a low oil pressure switch (40 psi) and large warning light in the cabin of my MGA (modified 18GB 1960 cc engine with HRG head) - not the most aesthetic setup but gives me comfort that lube system is working okay!

Mike Ellsmore

Out of interest where did you get the tee from?

Did you mean a 4 psi switch? 40 psi is pretty high, and above a hot idle on a hot day for me.
Paul Hunt

This is mine. Believed to be the US-spec one.

D O'Neill

These T-pieces used to be readily available at auto spares shops.
D O'Neill

Great !

I was searching for such an item this morning.

Many thanks.

Richard Thompson

Paul, yes it is set at 40 psi. No problem with town/country Oz driving with trips around 150 kms and regularly getting a flogging in motorkhanas and hill climbs. The only time it has flicked on momentarily was coming back to the pits at idle after a couple of 6 lap sprint sessions around Mallala circuit a couple of years ago. Engine has since been rebuilt (broken cam follower/damaged cam) so I am interested to see how it stands up to a couple of sprints meetings coming up this month. Engine has an oil cooler, uprated oil pump and electric fan and runs at 62 psi - idle is normally around 45-50 psi.
Not sure where the T piece was sourced from as installation was done by MG Workshops prior to my ownership of the car. I would imagine it would be easy enough to sliver solder together a hybrid tee from available fittings if one cannot be sourced.
Mike Ellsmore

Hi All,

Many thanks for all your contributions, they are much appreciated.

Yesterday I took the MG for a run down the M4 to Newbury at typical motorway speeds and all seems fine, apart from the oil pressure being approximately 5-10 psi lower than it was prior to this oil loss in the rev range up to 2500. Above this rev range the pressure rises up to just shy of an indicated 60 psi, which was the case before. At idle the pressure is as it was before indicating 20 psi. I have 15w40 oil in the engine which we put in prior to the rolling road runs. I normally use 20w50 which I am going to switch back to later this week. I am hoping that this will restore the pressure behaviour. Should I be optimistic ?

Best wishes,

Richard Thompson

Drive it and enjoy it with an occasional glance at the oil pressure gauge! If you become paranoid about dropping oil pressure add a bright warning light - otherwise strip the engine down and check your bearing clearances.
Mike Ellsmore

yes you should be optimistic, the different make and model of oil as well as the different grade could make all the difference to the readings

no doubt you have an oil cooler fitted that is difficult to or you don't drain so running the present oil as a type of cleaning/flushing oil is a good idea

the important thing about an oil change is to be thorough - have the oil in the engine as warm as possible at draining and leave it to drain for as long as possible to get as much of the existing oil and muck out as you can

don't forget to change the filter and have a new sump plug washer if required

if you have an oil cooler then you'll help the oil by also having a oil thermostat fitted otherwise at many times you'll be over cooling the oil
Nigel Atkins

That Tee is no good unless you have the appropriate fittings on the end of your flex hose and oil pipe, which as standard they don't, or you can get suitable adapters, which I haven't been able to find.

The fittings for the original Tee and straight-through connector are conical, that tee uses flat fittings.

15W/40 can give lower pressure readings than 20W/50, but it is one of the recommended grades for our climate.

I've only ever changed a sump washer on one occasion in nearly 50 years, and I've never had a leak from the sump plug. The one instance was on the ZS the first time I changed the oil. The washer fitted had a rubber insert, which I hadn't seen before, instead of being plain alloy as it apparently should be. So I fitted a plain alloy seven years ago, and no leaks on that either.
Paul Hunt

Paul I should have put if the sump plug washer is one of those squash types - unless you know differently

I keep meaning to get a solid copper sump plug washer and jut turn it each time but I never remember

I've seen spw with rubber or nylon looking insets as well as alloy looking ones and of course copper, solid and squash
Nigel Atkins

Rather than fitting the Tee between the oil pipe and the flexi hose, it can be fitted directly to the block.
D O'Neill

"Rather than fitting the Tee between the oil pipe and the flexi hose, it can be fitted directly to the block."

Pictures? There's not much room there, and with tapered threads the Tee would have to be screwed in far enough to bring the switch hole to somewhere accessible. It may be possible to screw the hose into the side and the switch into the end, but that would put a bend in the hose and reduce the free length for engine rock.
Paul Hunt

I had the same thing happen to me on a lovely Sunday afternoon drive a few years ago. I happened to glance over at the oil pressure gauge just in time to see it falling like a rock! I killed the engine with the pressure reading about 20 psi. and coasted into a parking lot. When I opened the hood, everything was covered with a fine layer of oil. It took me a couple of minutes to find the source of the leak. Fortunately, the oil pressure gauge hose is small and the leak was minor compared to what might have happened if it had been an oil cooler line that had burst. I still had about two quarts of oil left in the sump, but couldn't locate a place that had a Woodruf fitting to block off the hose. I cost me $229 to have the car flatbedded home. No damage occurred, but it did scare the hell out of me. This was the first time that the car had left me stranded in over forty years of service. It later turned out that a large number of faulty hoses had flooded the market and it took quite a while before the the distributors could clear their inventories of them. The best advice that I get is to take your old line to a local hose manufacturer and have them make up a new hose using the fittings from your old hose. RAY
rjm RAY

" but getting the right combination of gender, seats and thread proved impossible while our patience lasted.""

wont fit!

The 2 end fittings need to be male with a concave internal seal. The pressure switch to be female.
Michael Beswick

This thread was discussed between 26/05/2014 and 04/06/2014

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