Oil and Fluid Leaks on the MG T-Series: What Is Dripping, and From Where

A T-Type carries seven or eight separate fluids and most of them can find their way onto the garage floor. This is how to work out which one you are looking at, where it came from, and whether it matters.

There is a patch under the car. It was not there last week, or it was there last week and now it is bigger, or it has always been there and you have finally decided to find out what it is.

This is the most common question in T-Type ownership and it is usually answered with a shrug and the old line about an XPAG with no oil in it. That line is true as far as it goes, and it is not much help when you are lying on a cold garage floor with a torch trying to work out whether you have a characterful old car or a real fault.

The engine is only part of it. A T-Type carries engine oil, gearbox oil, a completely different axle oil, brake fluid, coolant, petrol, damper fluid and a couple of dozen grease points, and most of those can arrive on the floor. Working out which one you are looking at is the first job, because the answer determines whether you top it up and carry on or stop driving the car.

Start here: what is it, and where is it

Find the highest wet point rather than the lowest. Oil travels a long way along a casting or a chassis rail before it drops, so the position of the puddle tells you less than people expect. What follows assumes you have wiped the underside clean, run the car, and looked again while the trail is fresh.

Telling the fluids apart

Take a smear on a clean finger or a piece of white card.

Engine oil. Black on any engine that has been run since its last change, thin, and it smells of hot engine. Blackness is not a fault. Combustion products get past the rings into the sump on every engine and turn the oil dark, which is one reason a leak on a T-Type shows up so clearly on a light floor.

Gearbox oil. On these cars the gearbox takes a plain, non-EP oil, so it looks and smells much like engine oil and is usually cleaner and lighter in colour. Position is what separates them.

Axle oil. Unmistakable once you have met it. Hypoid EP oil carries sulphur and phosphorus additives, and the smell is sharp, sulphurous and unlike anything else on the car. Thicker than engine oil, and usually a dark honey colour. If you can smell it from arm's length, it is axle oil.

Brake fluid. Nearly clear when new, straw to brown when old, thinner than any of the oils and slightly slippery rather than greasy. Conventional fluid strips paint on contact, which is both how it announces itself and why it must never be left on a wing. Any loss of brake fluid takes the car off the road until it is found and fixed, because the fluid has nowhere to go except out of a system that needs all of it.

Coolant. The recommendation for these cars is a traditional inorganic antifreeze, which is blue or green. It is faintly sticky between the fingers, dries to a crust, and has a sweetish smell. It is also toxic to animals, which matters if the garage doors get left open.

Petrol. Announces itself. Evaporates from the card in a minute or two and leaves nothing behind. Any fuel leak is a stop-now fault.

Grease. Will not run and will not soak in. A dark, tacky deposit under a joint is almost always surplus purged from a grease nipple, which is what is supposed to happen when the joint has been properly filled.

Damper fluid. A thin oil, usually clean-looking, appearing high up near a damper body rather than dripping from anywhere obvious.

What your car actually has

Not every T-Type presents the same set of leak paths, and the differences matter when you are trying to identify a source. Where a cell says not established, that is a real gap rather than an omission.

Three things follow from that table.

The TA is a different engine, and almost nothing written about XPAG oil leaks applies to it directly. This archive does not publish MPJG workshop data, because no named source for it has been confirmed, and the same caution applies here.

The TC and earlier cars have a steering box rather than a rack, which is a sealed unit of a different kind with a different set of failure modes from the TD and TF rack with its rubber gaiters.

The axle differs. The hypoid axle arrived with the TD, alongside independent front suspension, rack and pinion steering and twin-leading-shoe front brakes. Earlier cars are not the same unit, so blanket statements about the T-Series axle should be treated with care.

The engine, which is where most of it comes from

The XPAG and XPEG leak by design, and the reason is straightforward. They were laid out before synthetic lip seals existed. The front of the crankshaft is sealed by rope, in two halves, which cannot make a complete seal. The rear is not sealed at all in the modern sense: it carries a scroll machined into the crankshaft that pumps oil back towards the sump while the engine turns, and does nothing whatever once you switch off.

That is covered in full in Keeping the Oil In: The XPAG Rear Seal, including the scroll, the four-piece sump gasket that is so often blamed on the seal, and the conversion kits. What follows is the rest of the engine, and the pressure that drives oil out of all of it.

Breathing, which decides everything else

Whether an XPAG weeps or drips is decided less by its seals than by the pressure behind them.

Combustion gas gets past the piston rings into the crankcase on every engine, and more of it as bores and rings wear. It has to get out. If it cannot, the crankcase pressurises and pushes oil through every joint available. Paul Ireland, writing in *Totally T-Type 2*, gives the most useful sense of scale: a pressure difference of only one pound per square inch across the sump is equivalent to a heavy adult standing on the side of that large aluminium casting. Very little pressure is needed to defeat a rope seal or a scroll.

As built, the engine breathes through a draught tube, a large bore pipe running down the left side and turned to face the airflow at its lower end, so that a car in motion draws its own crankcase gases out. Fresh air enters through a connection between the rocker cover and the air filter.

Two things commonly stop that working, and both are cheap to check before anyone starts thinking about seals.

A blocked breather. Eric Worpe, in the same publication, describes congealed oil closing the breather pipe off entirely. A blocked breather turns an ordinary amount of blow-by into a pressurised crankcase, and the oil leaves by whatever route it can find.

A tappet cover gasket obstructing the breather. Ireland describes cork gaskets distorting in service, the thinner early ones particularly, and a distorted gasket cutting the gas flow enough to raise sump pressure. Worpe describes the related case of the gasket covering the breather hole outright, noting that raised nodules on the cover are meant to prevent exactly that. Ireland's fix is to use a thin steel gasket, which cannot distort, with cork only at the edges, and he names John James as a source for steel side gaskets.

Worpe also gives a symptom worth knowing. On a worn engine, blow-by can be heavy enough to push visible fumes and oil out of the rocker box at idle with the car standing still. If you can see that, the engine is telling you about its bores rather than its gaskets.

Where else the engine lets go

Front to back, and ordered roughly by how easily each is dealt with.

• Rocker cover. The most frequently misread, because oil from here runs down the block and arrives at the bottom looking like something worse. Usually the gasket, sometimes a cover distorted by over-tightening.
• Oil filler cap. Worth a look on a car with heavy blow-by, since it is a relief path of last resort.
• Tappet chest covers. Their gaskets matter twice: as seals, and as the thing that can obstruct the engine's breathing.
• Front cover and rope seal. Some loss is inherent. On assembly the oil thrower disc behind the seal must be fitted with its dished face towards the front of the engine; the wrong way round turns a seep into something much worse.
• Sump joints and drain plug. The four-piece gasket is dealt with in the rear seal article. The drain plug washer is a consumable and is meant to be renewed at every change, as set out in Changing the Engine Oil & Filter.
• Oil filter housing. The joint faces and seal, and on converted cars the spin-on adaptor.
• Oil pressure gauge pipe. A small bore line under full pressure running to the bulkhead, with a union at each end. A weep here often shows up inside the car rather than underneath it.
• Rear main and scroll. Its own article. Worpe adds one cause worth naming: oil thrown from the main bearings themselves once running clearances have opened up with wear.

The rest of the car

Gearbox

Oil arriving at the bell housing from the gearbox end looks exactly like oil arriving from the engine end. The rear seal article makes the point that a bad rear sump joint drips down inside the bell housing precisely where you would expect rear main oil, and the gearbox front end adds a third candidate in the same place.

The one thing that must not go wrong is what you put back. The gearbox contains bronze components, and the extreme pressure additives in hypoid axle oil attack yellow metals. Gearbox and axle take different oils and the difference is not a preference, it is the difference between a working gearbox and a damaged one. Gearbox oil and rear axle oil set out both.

Rear axle

The axle leaks in three places: the pinion seal at the front, the hub and half-shaft seals at the ends, and the plugs. Two of those matter more than the mess.

Oil from a hub or half-shaft seal finds its way onto the rear brake shoes, glazing them and causing grabbing, judder or a pull to one side. Oil on a rear backplate is a brake fault, not a housekeeping problem, and cleaning it without curing the seal simply wastes a set of shoes.

Before condemning a seal, check two much simpler things. An overfilled axle will push oil past the pinion seal, which is why the level plug rather than a stated capacity is the correct way to fill it. A blocked axle breather does the same job that a blocked crankcase breather does at the other end of the car, raising internal pressure until the oil finds a way out. Both are covered in The Rear Axle & Differential.

Dampers

Every T-Type left Abingdon with hydraulic lever arm dampers at both ends, and on a TD or TF the front damper doubles as the top wishbone, so a worn or empty one is a suspension geometry problem as well as a damping one.

They leak from the shaft seal behind the arm, which perishes with age. A damper that is weeping slightly but still damping cleanly can be topped up and resealed; one that has lost its damping wants a rebuild or a reconditioned replacement. The bounce test is the quick check: press a corner down firmly and let go, and the car should return to level in a single movement rather than continuing to oscillate.

What this archive cannot yet tell you is what to put in them. No factory fluid specification has been confirmed from a named source. Terrance Van Parys, writing for the T-ABC club on rebuilding these dampers, uses a twenty weight motorcycle fork oil, with a thirty weight for a firmer ride, and reckons about a quart to fill all four. That is a practitioner's choice rather than a factory figure and is offered as such.

Steering

On a TD or TF the rack is filled with oil rather than grease, and it is retained by rubber gaiters at each end. A split gaiter lets the oil out and grit in, and the grit does far more damage than the loss of oil. Check the gaiters rather than waiting for a puddle.

On the TA, TB and TC the steering box is a different arrangement and this archive has not established either its correct lubricant or a documented leak pattern.

Grease

A dark tacky deposit under a suspension or propshaft joint is usually not a fault at all. The correct greasing method is to pump until fresh grease just appears at the joint, so a small surplus is the evidence of a job done properly. Wipe it off, because grease left in place collects road grit. Chassis Lubrication and Grease Points covers the points and the method.

What is normal, and what is not

No published figure exists for an acceptable rate of oil loss on these engines. The only written threshold anybody has produced is the MOT one, discussed in the rear seal article. Everything else, this page included, is judgement.

What is worth watching is change rather than quantity. A car that has left the same modest patch in the same place for years is behaving as it always has.

Investigate when:

• the patch is growing, or has appeared somewhere new
• oil consumption is rising while the visible leak looks unchanged
• oil pressure is falling or fluctuating, which is a separate matter covered in Oil Pressure on the XPAG and XPEG
• the clutch has begun to slip or judder, which points at oil reaching the friction plate
• there are visible fumes from the rocker box at idle
• there is oil on a rear backplate or inside a drum

Stop driving when:

• you are losing brake fluid
• you can smell or see petrol
• the oil pressure gauge has changed its habits

One pattern is genuinely reassuring rather than otherwise. A car that stays dry on a run and marks the floor overnight is doing exactly what the design predicts, because the scroll at the back of the crankshaft only pumps while the engine turns and the draught tube only draws while the car moves. A leak that appears only at rest is the design showing, not a fault developing.

The garage floor

Three approaches, and they suit different people.

Catch it at the car. A shallow tray fitted beneath the bell housing collects the oil where it falls rather than after it has spread. David Pelham described making one in aluminium for *Totally T-Type 2*, holding about a quarter of a litre, with a threaded plug so it can be drained without removing it. Nothing has to be slid about under the car, and the cost is that it needs emptying and remembering.

Catch it at the floor. An absorbent mat, a shallow tray, or plain cardboard. Cardboard is worth a mention on its own, because it shows exactly where each drip lands and how the pattern changes, which makes it a diagnostic instrument as well as a floor protector. Change it often enough that it does not become a fire risk.

Seal the floor. Bare concrete absorbs oil permanently, a sealed or painted floor does not. That is a decision to take before the staining rather than after.

On lay-up, the relevant point is the oil rather than the leak. Used oil is acidic and is better out of the engine before a long stand, which is set out in Winter Storage and Storing Your MG T-Series. A car stored with fresh oil will still mark the floor. It will be doing itself less harm while it does.

Fixing it, cheapest first

Work down this list in order. The first four cost almost nothing, and between them they cure a great many leaks that owners assume need the engine out.

1. Check the oil level is not too high. An overfilled sump raises the oil level towards joints that are normally above it, and it gives the crankshaft more oil to throw about. Fill to the dipstick rather than to a stated capacity, every time.

2. Clear the breather. Congealed oil closing off the breather pipe turns an ordinary amount of blow-by into a pressurised crankcase, and pressure is what pushes oil through joints that would otherwise only weep. This is free, it takes minutes, and it is the single most likely explanation for a leak that has worsened without anything else changing.

3. Look at the tappet chest cover gaskets. They seal, and they can also obstruct the breathing. A distorted cork gasket restricts the gas flow; one that has crept over the breather hole blocks it altogether. Ireland's remedy is a thin steel gasket, which cannot distort, with cork used only at the edges.

4. Renew the cheap consumables. The sump drain plug washer is meant to be replaced at every oil change. The rocker cover gasket is a few pounds. Neither is worth leaving.

5. Check you are running the right oil. Too thin an oil leaks more readily and protects the camshaft less. The grade question is set out in Fuel, Oil & Additives.

6. Do not over-tighten anything. A rocker cover or tappet cover pulled down hard distorts, and a distorted cover leaks worse than a slightly loose one. These are thin pressings and they want even, moderate pressure.

Once those are done and the leak persists, you are into work that means dismantling.

Front cover and rope seal. Accessible without removing the engine, and the one detail that catches people out is the oil thrower disc, which must go back with its dished face towards the front of the engine.

Sump gasket. A four-piece set with joins that are themselves the leak path. This is the job most often done in the belief that the rear seal is at fault, which is why the rear seal article tells you to rule it out first.

The rear main. Engine out, and covered in full in its own article, including an honest look at the conversion kits.

Reducing the engine leaks, and what the cures cost

Beyond clear breathing and sound gaskets, the substantial answer is to stop the crankcase pressurising, by fitting positive crankcase ventilation in place of the draught tube. The published accounts are unusually honest about the compromises, which is why they are worth reading before committing.

Ireland tested a PCV installation on his TC and varied the size of the fresh air inlet. A small inlet produced a crankcase depression of roughly one and three quarters to two pounds per square inch and stopped the front and rear seals leaking, at the cost of pushing oil out of the dipstick and the centre of the sump at large throttle openings. A larger inlet gave around one pound per square inch, reduced the front and rear losses, and left seepage along the centreline. No setting produced a dry engine.

There is a carburation consequence that owners are rarely warned about. A system returning the gases to the inlet manifold draws unmetered air into the inlet and weakens the mixture, which is a real change on a car whose carburettors have been set up properly.

Ray White took a different route in the same publication, rejecting a conventional valve as unsuitable for his supercharged engine and adapting an aircraft-style scavenger in the exhaust to draw the crankcase down, aiming for a depression in the region of three inches of mercury. The installation was still untested when the article was published, so it stands as an approach described rather than proven.

What is not established

• No published figure for a normal or acceptable rate of oil loss, outside the MOT threshold.
• The damper fluid specification. No factory figure has been confirmed. The fork oil recommendation above is a practitioner's, not a manufacturer's.
• The steering box lubricant for the TA, TB and TC, and the correct oil for the TD and TF rack.
• The rear axle type fitted to the TA and the TB.
• The location and servicing of the axle breather, which is repeatedly cited as a cause of axle leaks without anybody saying where it is.
• The breathing arrangements model by model. Ireland's testing was on a TC, and the differences between TC, TD and TF have not been verified here.
• No clearance figure for the rear scroll appears in the workshop data this archive has been able to source.
• Ray White's exhaust scavenger was unproven at publication and no follow-up has been located.

If you can answer any of these, particularly the damper fluid and the axle breather, it will be published here credited to you by name.

Sources

• Paul Ireland, "Keeping Oil in an XPAG", *Totally T-Type 2*, MG T Society, 1 November 2020
• Paul Ireland, "Keeping oil in an XPAG: Positive Crankcase Ventilation", *Totally T-Type 2*, Issue 68, October 2021
• Eric Worpe, "Double trouble, oil and dribble (the XPAG rear seal)", *Totally T-Type 2*, Issue 72, June 2022
• Ray White, "Crankcase pressure evacuation", *Totally T-Type 2*, Issue 64, February 2021
• David Pelham, "Help at hand for Incontinence", *Totally T-Type 2*, Issue 13, August 2012
• Terrance J. Van Parys, "Replacing Rubber Seals on the Luvax/Girling Dampers", T-ABC

Read next

• Keeping the Oil In: The XPAG Rear Seal
• Oil Pressure on the XPAG and XPEG
• The Rear Axle & Differential
• Running Gear Health
• Chassis Lubrication and Grease Points
• Changing the Engine Oil & Filter