Too Much Oil

[Mac of Cygnet]

Stopped at Kirklees Upper Lock to change oil & filter. I use a flushing oil, so after sucking the old stuff out, put the former in and went to start to engine. A quarter turn, then a clunking bang and engine stopped dead. And again, sounding really expensive. Couldn't really believe my oil change could cause this, but checked and found I'd overfilled. Took some out to below the mark, tried again.Another couple of clunking bangs and dead stop, so it wasn't the oil, no?

 

Called out RCR, not daring to try again in case I did further damage. He came after an hour, tried the start. A cough, the engine ran, with LOTS AND LOTS of smoke (but temporary). Then perfectly OK. He did explain something about the pistons coming up and being stopped by excess oil, but I find this difficult to envisage. Apparently if RCR had told him I'd just changed the oil, he'd have diagnosed over the phone. The hour's wait after I'd taken the excess out had made the difference.

 

I know that you shouldn't overfill with oil, but didn't know it could cause such drastic symptoms. Can anyone tell me exactly what happened? And also (which I forgot to ask, being so grateful not to have an expensive repair), could the violent clunks and bangs have done any damage to valves, seals, or even pistons? It seemed perfectly OK on the subsequent half-hour run up to Brighouse.

[Chalky]

It's called hydraulic- ing and it's caused by oil getting into the cylinder. When the piston comes up it compresses the contents of the cylinder which is supposed to be air. Oil (or water) won't compress and it causes the whole lot to hydraulically lock up. (My lawn mower will do the same it I leave it tipped up for too long, I have to remove the spark plug and drain the oil before it will start.) The large amount of smoke is the excess oil in the lnlet, exhaust and cylinder being burned off (with the mower the whole garden disappears for about 10 minutes!).

 

Depending on when the oil / water gets into the cylinder can have different effects. With the engine stopped then it will stop it from starting - as you found out. If it's in say a car that then goes through a ford / flood and pulls in water then this will cause the rotating engine to stop fairly instantly. The effect can be to bend con rods, break pistons etc. In 1998 we had floods in the midland and I know at least one vehicle maufacturer that had con rods on back order for months

 

The interesting bit is how much you overfilled it by (suggests by quite a lot) and how worn the engine is. In one scenario the overfill doesn't cause the engine to hydraulic however it does allow the oil into the cylinder. The engine then burns this as fuel and this carries on till potentially the engine seizes - I've seen this in an engine on a test bed. Be careful with overfilling, especially with an older engine.

Edited June 2, 2013 by Chalky

[Mac of Cygnet]

Thank you Chalky, for a very full and quick reply. I put in what I thought was the correct amount of flushing oil, but of course I may not have got all the old oil out for some reason. When I checked, the oil was about 7mm above the top mark (the top & bottom marks are about 2cm apart). I couldn't believe that the awful clunks and bangs wouldn't have done any damage, but as I said, it ran for half an hour up the river afterwards with no apparent ill effects.

[Paul C]

Unlikely to be hydraulicing, since the oil doesn't have a direct path into the cylinder. More likely its the crankshaft which hits the pool of oil in the sump and thrashes it around - a lot. Its more of an issue on cars, where they are put through more dynamic loads than a narrowboat - a slight overfill meaning the crank is usually clear, but then some cornering which means its not, results in the crank going through the oil at high speed. Luckily for you, low speed (during starting) and not under power, you look like to have avoided any monetary damage.

 

More likely the smoke was due to a fraction of the oil getting into the cylinders via borewash - there being so much oil trashed around at the bottom of the cylinders, the walls got soaked and the rings were unable to keep it all separate from the combustion space within the cylinder.

[Mac of Cygnet]

Unlikely to be hydraulicing, since the oil doesn't have a direct path into the cylinder. More likely its the crankshaft which hits the pool of oil in the sump and thrashes it around - a lot.

 

Well, a disagreement here! I'm not technical enough to say who's right, but would a crankshaft hitting a pool of oil and thrashing it around cause a very loud dead stop after a quarter turn? Although I too can't see how the oil got into the cylinder(s), it's what the RCR engineer said happened, and what Chalky described.

[Paul C]

I dunno really because I've not seen/heard an engine overfilled with oil trying to start. I did once hydraulic a diesel Land Rover (with water) and it just clicked and wouldn't spin over on the starter motor or tow-started. Chalky is probably right, I've no idea how the oil would have got into the cylinders enough to hydraulic it and affect starting though. A little could have got in, and a little oil would produce a lot of smoke - but enough to hydraulic it - unsure?

[churchward]

Unlikely to be hydraulicing, since the oil doesn't have a direct path into the cylinder. More likely its the crankshaft which hits the pool of oil in the sump and thrashes it around - a lot. Its more of an issue on cars, where they are put through more dynamic loads than a narrowboat - a slight overfill meaning the crank is usually clear, but then some cornering which means its not, results in the crank going through the oil at high speed. Luckily for you, low speed (during starting) and not under power, you look like to have avoided any monetary damage.

 

More likely the smoke was due to a fraction of the oil getting into the cylinders via borewash - there being so much oil trashed around at the bottom of the cylinders, the walls got soaked and the rings were unable to keep it all separate from the combustion space within the cylinder.

I doubt it would be this as the majority of engines are designed to splash about in their sump oil. Many older engines certainly when they did not have a proper oil pump relied on this method alone of distributing oil by what is often known as the spit and catch method. Modern engines to a degree will splash the oil about in the sump at normal oil levels. This does not result in oil being drawn into the cylinder as it would have to get pass the oil control and compression rings first. The cylinder liners will be oil coated per up stroke by the slashing about and scraped off by the rings on the downward strokes.

[Paul C]

I doubt it would be this as the majority of engines are designed to splash about in their sump oil. Many older engines certainly when they did not have a proper oil pump relied on this method alone of distributing oil by what is often known as the spit and catch method. Modern engines to a degree will splash the oil about in the sump at normal oil levels. This does not result in oil being drawn into the cylinder as it would have to get pass the oil control and compression rings first. The cylinder liners will be oil coated per up stroke by the slashing about and scraped off by the rings on the downward strokes.

 

But that doesn't explain what occurs if an engine is overfilled with oil. What happens, I suspect, is too much splashing and some getting past, as well as making more work for the crank.

[bizzard]

I presume its an OHV or OHC engine. In which case oil could have ''seeped past worn valve guides and or their seals'' when pouring the oil into the valve cover oil filler as one tends to fill and flood this valve cover right up with oil by pouring too fast as it drains back down via the push rod holes or tubes ''OHV'' some might seep past past the valve guides as described above which would then go directly into the combustion chambers. But if that was the case I'd expect the engine to emit some blue oil smoke when running.

[steelaway]

But that doesn't explain what occurs if an engine is overfilled with oil. What happens, I suspect, is too much splashing and some getting past, as well as making more work for the crank.

 

Could it be that the lack of or blockage of the engine breather - pressurising the sump and blowing the oil past the rings into the cylinder head?

What engine is it and where is the breather?

 

Alex

[churchward]

But that doesn't explain what occurs if an engine is overfilled with oil. What happens, I suspect, is too much splashing and some getting past, as well as making more work for the crank.

Even over filled it is unlikely to get past the rings unless they are very warn. The sump is an unpressurised part of the engine and it is vented. If enough pressure forms the oil will be spat out of the vents before going up the cylinders. I have seen a diesel spay oil all around the engine bay from the sump because it was presurissed from a pressure blow past broken rings. It is much more likely that excess oil would be forced up into the valve cover and get down into the cylinders via the valves and valve guides. Once in the cylinders it doesn't take much to lock the engine up. Any amount of fluid will increase the compression ratio significantly and stop the engine faster than any drag on the crank swimming in a pool of oil.

[by'eck]

I presume its an OHV or OHC engine. In which case oil could have ''seeped past worn valve guides and or their seals'' when pouring the oil into the valve cover oil filler as one tends to fill and flood this valve cover right up with oil by pouring too fast as it drains back down via the push rod holes or tubes ''OHV'' some might seep past past the valve guides as described above which would then go directly into the combustion chambers. But if that was the case I'd expect the engine to emit some blue oil smoke when running.

 

Bizzard's suggestion seems by far the most likely explanation. Flushing oil being thinner than normal would increase likelihood of this happening.

[bizzard]

If you'd said you'd overfilled it by 10cm instead of 10mm then I'd say yes oil might have pushed up past the pistons but 10mm on an engine of narrow boat size, no. If it was a very small say motor bike engine that only held a pint or so of oil then 10mm overfill maybe I'd say yes.

[Timleech]

If you'd said you'd overfilled it by 10cm instead of 10mm then I'd say yes oil might have pushed up past the pistons but 10mm on an engine of narrow boat size, no. If it was a very small say motor bike engine that only held a pint or so of oil then 10mm overfill maybe I'd say yes.

I agree, filling too fast is much more likely the cause, than filling too much.

 

Tim

[n.b.Goldie]

I agree, filling too fast is much more likely the cause, than filling too much.Tim

I agree, my lister canalstar operators manual gives dire warning of filling too quickly with resulting hydraulic lock and potential damage. Something to do with the recirculatory crankcase breathing system of the canalstar.

 

I wonder what engine the op has.

 

Regards

 

Ditchdabbler

[bigste]

Another problem with overfilling, and not by a great amount, is it can blow oil seals. This is caused by too much pressure in the sump and crank case. Valve stem seals and crankshaft seals are often blown because the oil is half and inch or more above the max on the dipstick. Seen it many times.

[Mac of Cygnet]

I agree, my lister canalstar operators manual gives dire warning of filling too quickly with resulting hydraulic lock and potential damage. Something to do with the recirculatory crankcase breathing system of the canalstar.

 

I wonder what engine the op has.

 

Regards

 

Ditchdabbler

 

It's the smallest Vetus (Mitsubishi) 2 cylinder. I have absolutely no idea where the breather is, or if it has one. It doesn't normally smoke, blue or otherwise, but it is a wet exhaust, which makes it less obvious. The smoke which enveloped everyone as the engine finally started was of course white, but only lasted less than half a minute. Can I assume that since it ran as normal for a half-hour run up the river afterwards, that no permanent damage has been done?

[bigste]

Keep a check for oil level and leaks otherwise ok, it may have blown a seal.

[Radiomariner]

I agree. Filling too fast rather than too much. Especially with flushing oil which will have a much lower viscosity which like Heinekin reaches parts no other oil reaches!

[IDS]

If you have a rocker cover with a breather pipe like this, then filling the rocker cover to the level of the breather will pass oil directly to the inlet manifold and hence into the cylinder.