Maverik Posted May 23, 2013 Share Posted May 23, 2013 Hi guys, I'm just writing a presentation and was wondering how much time one had from the oil pressure warning light coming on to engine damage, of course the sooner you can turn it off the better, but was just trying to quantify it as guidance... Talking Td5/TDci type engines... cheers Mav Quote Link to comment Share on other sites More sharing options...
Team Idris Posted May 23, 2013 Share Posted May 23, 2013 It's likely to be damaged before the light comes on, if the pressure was just above light-on for a while but working hard. Or a few seconds if it was making good pressure just before the light came on. And then it's what was keeping the oil light off; good clean oil or froth? And how good is the engine and Turbo before? And is it a tiny bit of damage, or the amount of damage before crank grind is a must? So all a bit tricky, which is why so many engines have the stop wired to the pressure switch. Quote Link to comment Share on other sites More sharing options...
qwakers Posted May 23, 2013 Share Posted May 23, 2013 in my experience the engine is stuffed long before the light comes on. Quote Link to comment Share on other sites More sharing options...
mmgemini Posted May 23, 2013 Share Posted May 23, 2013 in my experience the engine is stuffed long before the light comes on. I know you're wrong there. My 300Tdi Defender did 20 miles with no oil pressure. A big end shell change 4,000 miles ago and it's still running. Quote Link to comment Share on other sites More sharing options...
Tanuki Posted May 23, 2013 Share Posted May 23, 2013 Truth is, "It Depends". Decades back I was doing IT-consulting stuff for various clients, one of which included "Ricardo" down on the south-coast. on one of my visits, knowing my interest in things-automotive they invited me to witness a test-to-destruction of a Jaguar 4.2-litre petrol engine which was current fitment in a couple of UK-government scout-cars. The test was to see how long the engine would last in a simulated "hit-a-land-mine-but-must-get-back-to-safe-territory" scenario: both the radiator and the sump being catastrophically-ruptured. So, they warmed-up the engine on the test-dyno, loaded it up to around 75BHP and drained the oil and coolant. For the first five minutes, nothing untoward happened. Then it developed a slightly-harsher sound and smoke could be seen rising from the exterior of the block. Ten minutes into the test it began to audibly knock and lose power, so they opened the throttles further to maintain the test-specified output. The smoking from the outside of the engine got denser and bluer; after around fifteen minutes the poor thing was emitting jets of smoke from the block/head-gasket interface and the throttle was wide-open to try and maintain the power output. What finally brought the test to an end was when the cylinder-head warped to a point where one of the camshafts could no longer turn. On strip-down, the bottom-end was surprisingly healthy - they reckoned a 10-thou undersize machining on the crankshaft, a 20-thou overbore on the block and new pistons would have had it ready to go again. The head was mega-warped and several of the valve-guides had seized on the valve-stems to the point where the valves were only opening/closing because the guides were moving in the head-casting. The moral of this being - if you shut your engine down as soon as the oil-light comes on, you could easily be able to rebuild it! --Tanuki Quote Link to comment Share on other sites More sharing options...
qwakers Posted May 23, 2013 Share Posted May 23, 2013 the 3 engines ive had pumps go on or the one where the sump split and dumped all its oil all got switched off withing milliseconds of the oil light coming on and coasted to the side. still had scored bores, bugged cams and play in the crank.rip, scooby.... Quote Link to comment Share on other sites More sharing options...
pat_pending Posted May 23, 2013 Share Posted May 23, 2013 It realy depends on why the light's come on. An engine with minimum wear and good oil pressure that suffers a sudden failure of an oil cooler pipe or split sump, will fare better than one that's lost pressure because it's so worn. Quote Link to comment Share on other sites More sharing options...
Nigelw Posted May 23, 2013 Share Posted May 23, 2013 This throws up the old slick 50 commercial where they ran an engine without oil,they then tested an engine that had been run with slick 50 in it and drained it out to show the difference, just put slick 50 in the sump before running and drive on my son Quote Link to comment Share on other sites More sharing options...
JeffR Posted May 24, 2013 Share Posted May 24, 2013 My experience is that by the time the idiot lift comes on, the damage is done. Most oil warning lights are set at a stupidly low pressure (circa 7-10 PSI), that's why uprated oil pressure warning senders were SO popular in Minis and Escorts. Mind you I once saw a video of a Cadillac being driven across the Mohave desert with no oil or water - the Firestar engine in it "turned off " pairs of cylinders sequentially to keep the temp down. Quote Link to comment Share on other sites More sharing options...
Maverik Posted May 26, 2013 Author Share Posted May 26, 2013 Thanks for the feedback gents, much appreciated. Mav Quote Link to comment Share on other sites More sharing options...
Aragorn Posted May 28, 2013 Share Posted May 28, 2013 FWIW, my old A4 had a worn oil pump for about 40k of our ownership. At hot idle it would drop to 8psi and the lifters would start clattering if left idling for more than about a minute. The light never came on because the Audi dashboard IGNORES! the light below 1500rpm. I only discovered this issue after we'd had the car about 30k miles, when i fitted a pressure guage. At 195k i swapped the engine for another for various reasons, and stripped the worn engine down, and the insides were pretty much spotless. The crankshaft is now in my own car, and only needed a polish and runs on stock size bearings, the engine block itself only showed typical wear you'd expect to find on a 200k engine. My current car was bought with a siezed engine due to blocked pickup. The crank had welded itself to the rods on a couple of cylinders. I replaced the crank (with the one from the 200k engine above) fitted new bearings and a set of used pistons from another engine with some new rods (as they're a known weak point). The cylinder head and cams somehow survived and barring some odd marks on the bearing journals looked relatively unscathed. The engines done over 20k after being rebuilt. Quote Link to comment Share on other sites More sharing options...
o_teunico Posted May 28, 2013 Share Posted May 28, 2013 Found this at YouTube Quote Link to comment Share on other sites More sharing options...
Nigelw Posted May 28, 2013 Share Posted May 28, 2013 Whilst looking around the tube I found various videos of products that you add to the oil and Petron Plus was one which came up and I asked on another forum about it as we had had a discussion about Molyslip before and thought I would throw it up with them, but I have seen loads of videos and I can only say that what I have seen in them does not match what I have seen in real life!!! An oil pressure gauge and separate warning light would be your only guarantee of knowing what pressure is there and what is happening in the engine! Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 29, 2013 Share Posted May 29, 2013 Talking Td5/TDci type engines... Those two are quite a long way apart in many ways. There's so many variables with this it's impossible to give useful answers, although Tanuki's anecdote does give you a very good clue - namely, try phoning up Ricardo and speaking nicely to them as they do a hell of a lot of engine development for manufacturers. Their newsletter is usually quite a good read too. Quote Link to comment Share on other sites More sharing options...
Maverik Posted May 29, 2013 Author Share Posted May 29, 2013 I'm not looking for hard facts, more disscussion on the subject. i found some rather interesting youtube video's of hillybillys trying to destroy engines, I found a perticulalry good one, the engine type will come to me, but this thing just wouldn't die, you saw it burn off the water, then burn of the oil and it carried on going... Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 29, 2013 Share Posted May 29, 2013 I'm not looking for hard facts I'm not sure what sort of presentation or guidance you're working on where YouTube videos of rednecks is considered a better source of information than people whose job it is to know the answer. Why not just ask the nearest squirrel? Quote Link to comment Share on other sites More sharing options...
Maverik Posted May 29, 2013 Author Share Posted May 29, 2013 I'm not sure what sort of presentation or guidance you're working on where YouTube videos of rednecks is considered a better source of information than people whose job it is to know the answer. Why not just ask the nearest squirrel? Ouch wrong side of bed this morning... I've giving guidance on warning lights of the vehicles we "AMRT" operate. the guys that drive them aren't overly concerned about maintaining them and will carry on driving them if they don;t understand what red flashing lights mean... the guidance is more - if this light comes on, - you should stop the engine and we may have a chance of saving it or if this light comes on, its screwed anyways, keep driving and get as far as you can, type advice... Again I think of a lot of stuff all the time, but I'd not got around to spending some of my rather precious brain power thinking about the specific failure modes of a Td5 engine and whether or not it is at all comparable with a TDci.... Whether its a redneck blowing up an engine or Rools Royce fireing a frozen turkey into a Gas Turbine, I still find it rather interesting seeing what happens. I did ask the nearest beaver but they hadn't experince of common rail diesel engines so he refered me to LR4x4, where he thought I might get some grown up answers with constructive points... Quote Link to comment Share on other sites More sharing options...
Aragorn Posted May 29, 2013 Share Posted May 29, 2013 Its certainly interesting discussion. I've noticed some manufacturers starting to take a more proactive role, and removing the driver from the loop because they're bloody useless. A good example of this is TDCI landrovers (and i'd imagine other vehicles using the same engine/ECU setup?) will cut the power if the ECU detects the engine is overheating. On the one hand, its a good thing, as if the moron driver ignores the gauge/warning lights etc and keeps driving it as many of them do, you risk warped heads or other serious engine damage. Ofcourse the flipside is you then get drivers moaning because it "cut out on them and left them in a dangerous situation" or some other rubbish. Wether they'd use the same arguement when the headgasket blew because they'd ignored the guage pinned round into the red i'm not sure. I was slightly shocked when i got into my brothers E90 320d, and realised it doesnt have a temperature guage. After pondering it a while, i realised they'd almost certainly removed it because no-one actually looks at it or cares what it says. Presumably it has some audiable/flashy overheat warning, but otherwise you get no feedback on engine temperature at all. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 29, 2013 Share Posted May 29, 2013 Just confused, that's all... I'm not looking for hard facts I might get some grown up answers with constructive points... If you didn't need oil pressure then it wouldn't be there - the decision of whether to keep driving is surely down to whether stopping is better/safer than getting away. If you're being shot at, then an engine rebuild is lower down the list of problems. Quote Link to comment Share on other sites More sharing options...
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