This isn't really a question, just a line of discussion.
A few years back I owned a Rover Maestro Clubman D (!!), the one with the old perkins diesel engine. It handled terrible, but I loved it. Anyway, it used to burn a bit of oil so needed regular top-ups, one morning when heading for a day out with some friends, I checked the oil and it needed another litre (which it did about once a month/3000 miles), so I mentioned it to my friend and went to get my stuff ready, came back and put a litre of oil in, little did I know my friend had already topped it up. So off we went down the M62, within a few miles smoke started plumming from the back. So I pulled over then we realised the mixup and that it was overfull with engine oil, so we decided to carry on, thinking the excess would burn off - wrong!!!
As we drove off down the road, the car accelerated - seriously fast for this car, took my foot off the accelerator and still we went faster, panic set in, I dipped the clutch to pull over and the engine just revved and reved, I took the keys out of the ignition and still it revved, with plumes of smoke comming out of the back. This is where logic kicked in, I realised that somehow the engine must be pulling the oil from the overfull sump (through a breather pipe, which is supposed to sit above the oil level I guess??). It was revving flat out-screamming, in a situation like that what are you supposed to do, the ignition was off (though in that car I think it just stops the diesel supply, but of course by now it was running of the engine oil), how can you stop it?
After about 10 mins of continuous revving, and almost shutting off the m62 due to the emmense smoke, it gave one last cough and died, timidly I checked the oil/water levels, the oil was about back to normal, it had used a fair bit of water, so I tried to start it, and it turned over and was fine. Infact it did another 100,000 without any major engine problems before it had to be scrapped due to the bodywork. Were my assumptions about the engine oil being sucked up right? does this kind of thing happen a lot? should I have tried to stall it?
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Heard somebody on the radio relating a similar tale about a hire car- following the recent Which report.
You were very lucky, usually ends with a bang and valves embedded in pistons?
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'Run-away' is a known hazard with diesel engines but I've never before heard of it happening to a Perkins Prima on the road. The sump must have been very over-full. Running with a very dirty air filter and/or at very steep engine inclinations can be other factors.
The only Perkins engine that I am aware of where run-away was a possibility, under extreme conditions, was modified to avoid this before it went into production. In your case, I would think that the events that led up to run-away were exactly as you described.
Run-away usually occurs with engines having closed-circuit breathers where sump oil reaches the bottom of the breather drain pipe and is then drawn up with the breather gases into the air intake manifold. It then feeds the engine just like fuel oil, only in an uncontrolled manner. It can happen with engines fitted in things like grass-cutting machinery or diggers that are taken to too much of an angle on a bank, or in situations where the machine or vehicle overturns.
Modern engines will almost certainly have some sort of device to prevent run-away, or at least to overcome it very quickly. Some engines have a mercury switch which shuts off the engine before it tilts enough for run-away to occur, but this will not prevent run-away caused by massive over-filling of the sump. A more favoured method is to incorporate a one-way fluid valve or other oil transfer controlling device in the breather system itself.
By the way, lifeboats powered by Perkins Prima engines had to be able to be launched into the sea at an angle of 30 degrees. Even then they didn't suffer from run-away and I can't remember any special breather system being fitted!
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The only Perkins engine that I am aware of where run-away was a possibility .... >>
I should have said "WAS aware of". I am now very aware that the Prima engine can go into run-away mode!
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Yes, but it was very overfull with oil, I'd reckon the litre I Guestimated in would have taken it to about a quarter of a litre over the max, and the litre my friend guestimated in (which may well have been more than a litre) would have taken it well over the designed limit. I always found when filling it that the the dipstick didn't report the new oil until the engine had ran for a bit then cooled (I assume it takes a while for the oil to make it round to the dipstick section), hence was always difficult to gauge, as you couldn't always see what you were adding.
I was surprised it worked ok after. I wonder if the best thing to do to keep the revs low would be to keep it in gear and carry on using the brake to keep the speed undercontrol. I am sure the police would have had something to say about it though, what with all the smoke and all. (I felt a lot safer in the ditch with hands over my head-waiting for the explosion!!)
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Couldn't you have stalled it, using the brakes and fifth gear?
Chris
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I suppose it should be possible to stall the car on the brakes, at least in theory. Remember though that the engine will almost certainly be running at a speed higher than its maximum governed speed, probably at valve bouncing speed, and the power it is producing is also likely to be higher than its normal maximum.
Also, run-away is likely to start very suddenly and is quite likely to have been initiated by oil surge as the car was going round a bend ... not the best place to slam on the anchors!
Run-away is not something for diesel car owners to worry about though. It is almost unheard of in road-going vehicles so I hope we don't see it sensationalised in the press.
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"the car was going round a bend " - motorway actually, but had just got on, and it started as the car got up to full tempreture (as the oil expanded and became more volatile)
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Easy to say after the event, once the revs were up there it would have probably smashed the clutch plate or mangled the gearbox. If I hadn't of dipped the clutch in the first place it might of been ok I guess to slow it down and stall it, but remember it was an old car and the brakes weren't that great, also the way it accelerated away was unreal, I was already doing 70 and it shot to 85 in seconds-throwing me back into my seat, so your first reponse is to dip the clutch. It is worth bearing in mind, that this was a very stupid accident in the first place and unless your really thick (er... like me!!) then it won't ever happen.
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Sounds very dramatic. I've heard of this happening with very high mileage diesel engines, but I guess you'd know what was coming for weeks in advance as the oil consumption went up.
Chris
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Dizzy,
Self dieseling was definitely a problem in the early marine Yanmar engines which were basically converted stationary engines for water pumps. Can't blame Perkins for that though.
The YSE engines were problematic when used as sailing auxiliaries as they were single cylinder horizontals. OK on a canal boat but would self destruct depending upon which tack you were on when motorsailing. Never a problem with the single vertical YSB IIRC.
Made for interesting conversations when driving back from an eventful weekend trip. (motoring link)
As for the slipway launched RNLI boats, for some reason I had them down as dry sumped installations. Obviously not, we all live and learn.
Cheers,
FiF
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FiF,
Thanks for the additional information - it all helps complete the picture.
The lifeboats I was talking about needed to be capable of launching at 30 degrees off a ship - Big splash! They were not dry-sumped but I think they did have specially shaped sumps with a deep centre well to keep the oil covering the pick-up inlet and away from the breather oil return connection.
It's a long time since I was involved with these marine engines, getting on for 20 years I should think. My job at that time was to obtain engine design approval from Lloyds, Det Norske Veritas, Bureau Veritas, RINA etc., in order for the ship or boat to be insurable.
The most difficult part with the Prima engines was convincing the marine approval authorities that deep-rolling the main and big end journal fillets increased the crankshaft fatigue strength by at least 50% (the crankshafts were SG iron, a 'first' for Perkins). It was difficult for them to understand how an 'undercut' could increase the strength at all, let alone improve it by 50%!
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