Oil leak

[al2006]

My car drinks oil on long journeys (or spews it out), after about a solid hour of driving- anything less than this and its fine.
I did a 300 mile round trip at the weekend, and got through ~8 litres of oil!

I've been told its leaky seals, as everything seems structurally sound.
Are these a nightmare to change myself- I'm reasonably confident and willing to ledarn, but I don't really have the equipment to remove the engine?
Should I attempt this or take it to the garage?
Any advice/bodges?
Ta.

[alex_holden]

Can you tell which seal it's leaking from?

[Rob_Jennings]

8 litres in 300 miles?

does it drop any when standing? (running or not) it not then you are burning it. I would have thought most oil leaks (out of engine) still drip when the engine is stopped, and at least would show if you turn it over and stand in one place for a time.

replacing piston rings is one oif the bigger jobs, and probably means looking at things like bearing etc at the same time.

[al2006]

I think its the rear of the sump/gearbox kind of area.
There may be a few drops occasionally under the car, but usually only when its been running.

[rayofleamington]

First things worth checking:
1) Clean the engine thoroughly and have a good look for any oil leaks. Anything from the rocker cover downwards could be your leak and unless you know where to start, then don't start trying to fix it.
2) is your water pump / radiator / thermostat working correctly?
Overheating can dramatically increase oil consumption.
(my pickup used 4 litres of oil on the 300 mile journey home as it was overheating badly. After sorting that out it used 2 litres on the Le-Ork 1600 miles...)
3) is your breather / breathers ok? If there is any resistance then crank case pressure will accellerate your leakage rates.

[MoggyTech]

That's one huge oil consumption. To burn that much in 300 miles, if it was worn bores/pistons, you would be lucky to be able to see out of the rear window, and would most likely get pulled over by Mr Plod.

I'm guessing this is going to be the oil pump seal on the backplate that is leaking, it's an engine out job to repair.

Have you checked compressions? Checked for blue smoke fumes from the oil filler cap with the engine running? Are the plugs dry or oily?

[al2006]

There was no smoke, so is it safe to assume its leaking and not burning?
Firstly how would I check if the radiator/water pump is working correctly (I haven't noticed any problems with this- I've topped it up maybe twice in 6 months)?
And also, how does one go about checking compression?

One other thing I did notice was that towards the end of the journey (hot engine), when the oil was getting quite low (nearing the minimum mark) the engine seemed to be over-revving when I pressed the accelerator, without giving any more forward thrust (particularly when going up hills). Is this compression related?

[alex_holden]

the engine seemed to be over-revving when I pressed the accelerator, without giving any more forward thrust (particularly when going up hills).

That sounds like the clutch was slipping, possibly due to oil leaking out of the rear seal, splashing around inside the bell housing and soaking the friction plate.

You test the compression with a special pressure gauge that screws into the spark plug holes.

The best way to keep an eye on the cooling system is to fit a temperature gauge.

[MoggyTech]

The over reving with no increase in momentum means the clutch is covered in oil, which confirms it's a rear plate leak into the clutch bellhousing. Most probably the oil pump rear cover sealing joint, which is simply soldered onto the engine backplate.

So the engine has to come out to check for the problem. The good news is your engine could still be in otherwise good health.

The rear oil seal for the crankshaft is of the scroll type, so do not fail, however it is possible, a previous owner has fitted the modification that fits a proper oil seal to the rear of the crank. These require precise machining of the engine backplate to fit, and if not done correctly, fail in spectacular fashion.

[IslipMinor]

What engine is it?

Worth checking that the crankcase ventilation is working properly before taking the engine out. It does sound like the oil is getting into the clutch housing, but this can happen if the crankcase is being pressurised in any way.

If you take the oil filler cap off when it's warm what happens? There should be no smoke or pressure at all. If either exist, it might be more down to rings/bore problems?

Could also be the oil pump gasket, need to do a few checks to see if the cause can be identfied.

[rayofleamington]

Firstly how would I check if the radiator/water pump is working correctly

As Alex says - the easy way is with a temperature gauge. Otherwise it's a bit more guesswork depending if it 'smells' hot, whether the water leaving the radiator is cooled properly etc...

But yes - a slipping clutch does indicate an oily clutch (or maybe just a worn out clutch)

[bmcecosse]

That oil consumption is crazy - the underside of the car must be slick with oil! First check - are you overfilling the sump ? Maybe the dipstick is not correct for that engine - to check you would need to darin off all the oil - and see how much you get! With that consumption you don't need an oil change - you've done that twice in the journey. Test for engine pressure by removing the oil filler while the engine is idling and hot - if there is a plume of smoke/fume - then there's the problem - it will blow oil out the rear crank seal. Your clutch is now wet with oil - so likely it will need changing - but a temporary cure can be made by connecting one of the breather pipes directly to the carb, or to the inlet manifold via a 1/8" diameter restrictor - this forces the engine to breathe it's own fumes and can keep a failing engine going for a wee while longer - while you look for a better replacement. It won't be the oil pump - there shouldn't be any substantial oil there anyway.