[Lack of] oil in the engine

Kinky

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Doing my routine car check yesterday afternoon (tyres, lights, various levels, etc), I came to check the engine oil level.

Pulled the dipstick out, gave it a good clean, stuck it back in, pulled it out, and it was basically telling me that there was a tiny bit of oil on the stick, well below the minimum level.

Hummm, that's a bit odd I thought. Oil pressure is OK, the dash warning light comes on ok when I start it up. The engine sounds and runs fine - absolutely no problems at all.

So. I checked it again and again - still the same.

So I took the car out for a quick local run (taking it easy, just in case). All seems ok inside - no warnings or anything.

Came back. Left it 15 mins and checked the levels again. Still the same. No oil deposits on the driveway (I do regularly check).

So, fortunately I had some spare oil (10W 40) in the garage - same viscosity as that Purslows had used.

So I stuck 0.5 of a litre in (just to make sure I was not getting a duff reading and overfilling it). And sure enough it was 'registering' on the dipstick. So I stuck another litre in and it was showing about 2/3 up the minimum level.

I took it out for another run - and again - everything is as normal. It's not obvious that the top up has made any difference - still sounds and feels the same.

Fortunately the oil cap is nice and clean and oily, showing absolutely no signs of any mayo-gunky stylie crap on it. And the oil on the stick is nice and clean too.

I've parked on a level spot here at work today, and will check the level later - to see if there's any difference in the 25 miles I've done this morning at 80ish down the M3.

So 2 things are worrying me now.

1. There's no obvious signs of a leak anywhere - so could I assume the 'smokey' situations I've been having up/down the M40 recently are attributed to this (see seperate thread - cack pants on the M40).

2. Why is my dash light not flashing to warn me.

Bugger. More hassle.

Answers on a postcard to ....

And thanks in advance.
 
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pluggers

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could be valve stem seals,I think if the rings were knackered there would be smoke all the time.
 

andy_k

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my experience of "low oil level warning lights" is that they only ever come on when the level is beyond what any normal human being would class as reasonable - this isn't based on MB warning lights but those fitted to other marques - We used to have a Rover V8 which had a low oil warning that switched the fuel pump off to avoid engine damage, it didn't kick in until there was about a pint of oil left in the engine (we tried it during an oil change just to see if it actually worked).

Low oil is a worry, mainly because you need to know where it's leaking from - an engine will run fine with very little oil in the sump without suffering any damage - I read somewhere the figure is about half a pint for a warm engine it's when it's cold it needs a lot to get circulation.

Assuming you are losing no fluid from anywhere else then the smoke you are seeing is where the missing oil has gone. Does it smoke when you first start it? Get someone else to start it and watch for yourself. I agree with pluggers, it's starting to sound like the valve stem oil seals

Andy
 

Koolvin

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check your water, does it seem clean? no oily bits in water?
 
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Kinky

Kinky

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yeah - water colour was ok and clear of any obvious deposits. However I will go and re-check it.

There's no smoke on start-up (I do check). The only times I've ever seen it smoke is at high-speeds (motorway) and only after an hour or 2 of driving.

If it is the valve stems ... is it a costly/time consuming fix?

Also - would this be considered natural wear and tear - commensurate with a 10 year old car with 124k on the clock?
 

andy_k

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is it possible that something is causing the crankcase to pressurise? {blocked or restricted breather maybe) causing oil to be forced into the cylinders.

from what I know (but i'm willing to be corrected here) the system works a bit like this,

unburnt stuff (oil vapour, blow by gasses etc) is recycled through a filter into the inlet manifold and mixed with the fuel - supposedly to reduce pollution. Deceleration causes the gasses to be sucked from the crank case as the pressure in the manifold is higher (ie it's a vacuum) but acceleration forces them out due to higher crankcase pressure - your oil pressure guage is a good indicator of what's happening in te crankcase.

Check all the breather hoses for signs of damage or blockages - if the engine has been run with old oil in there may be a build up. Whilst you are there check the breather for the camshaft cover - they usually have a filter or "fire trap" on them as well which on other cars I have owned have blocked leading to raised pressure in the cam galley.

As it's not smoking on start up, the signs are that the crankcase is pressurising and the smoke you are seing is when the pressure is released under deceleration. so the logical place to start searching has got to be the ventilation system. If cleaning that out doesn't cure it I'd get a compression/leakdown test done to try and isolate the problems.

Is it commensurate with an engine thats done 124k? Well, that would depend on how that engine had been looked after and it's so hard to say yes or no. An engine thats been used for short runs, never getting up to full operating temperature and not being properly maintained, then yes, it's not only reasonable, i'd expect it. on a car that's done most of it's work in motorway mileage and that has been regularly maintained then no, it shouldn't be happening. You say your car is 10 years old, with 124k on the clock, I'd call that low to average mileage of around 250 miles a week - break that down further to 2 or 3 trips a day and you can see they are all short journeys where the car never really gets warmed up - I've always reckoned it takes 10 - 15 miles to get everything up to "operating temperature". That's school run/shopping/second car mileage with the car being run "cold" where most engine wear will occur so any maintenance you do should be based on that - get the engine thoroughly flushed and replace every filter you can find.


A point worth remembering is that a few years ago, a car with 100k on the clock was the exception - most had died long before that milestone.

Andy
 

Robbo

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Kinky,

How many miles have you done since the last service and noticing the oil level was low?

Robbo
 

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