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turbo diesels - warming up/cooling down


martc

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Folks,There is much nonesense spoken on the interweb. Advice is often contradictory.In particular I am interested in peoples views about warming up turbo diesels (and allowing them to wind down before switching off). Should these engines be allowed to warm up before setting off, or is general gentle driving until on temp. OK? As for switching off, I've read that the turbo should be alowed to spin down to idling before shutdown - if this is the case how long should it be allowed to wind down?Thanks in advance - and I'm sure none of the advice will be contradictory!

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The whole buisness about warming up / coling down is just to do with oil flow and supply to the turbot bearings - whilst cold supply is not great and so oil starvation and wear can potentially occour - ditto shutting an wngine off with the turbot spinning can also cause premature wear of the bearings - so the cooling down period id quite literally a few seconds to let the thing shut down and spin down - but how many of us shut it off after a balls out thrash straight away? Most of us will be pootling to our home / car park and not using the turbo at low speed pootledom.Not ragging the arse of any car untill warm is also a good idea to prolong head gasket life.

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For a high-performance car which is likely to be running OMG!!11 boost levels, you can get turbo timers which afaik allow oil to be pumped around the turbo after the engine has been turned off, to cool it off in a safe manner. Some do this with a seperate electric oil pump, some do it by running the engine on idle with the car secured for a set time. Posher ones can remote start with the doors locked to warm the engine through before you want to get in the car.For startup it's a good idea to wait until the oil temperature and pressure are in 'normal' range before booting it, to ensure a decent oil delivery to the turbo. If the oil is cold and thick, it won't be cooling or lubricating the turbo properly and you may well damage it. I once ruined a G-Lader supercharger on a Polo in this exact manner, took a guy out for a spin from work in my break and had too heavy a right foot with a cold engine. Result was a broken scroll and metal shards in the inlet.....For a normal TD car, or even a turbo petrol which hasn't been tuned, normally just laying off the high-speed driving as you arrive at your destination is enough. For most people living in a residential area, this is 'the norm' anyway. Similarly, a few minutes driving below 3000rpm say will have warmed the oil enough to provide all the lubrication it needs.

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I don't really know about diesel turbos but with petrol turbos I drive carefully off-boost until I'm happy the oil is warm (about 15 mins, more if it's freezing cold) and towards the end of my journey I'd try to use as little boost as possible. At the end I'd pull up and leave it idling for a couple of minutes and turn it off - you can get turbo timers for this as described, but I used it as an excuse to rewind my tapes, give the aircon a run, etc. Be particularly vigilant with the running down period if you've just come off the motorway, driven up a steep hill or been driving like a hooligan.My way is admittedly a tad overcautious, but in normal driving it didn't really make much difference to me as it's 30mph roads around here all round for a few miles anyway. Though if I was going on the motorway (5 mins away) from cold, I would always give it 15 minutes or so drive around the estate to get the oil nice and warm first.

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Driving elderly turbodiesels on a daily basis, personally I:- try not to exceed more than 2,000rpm (so the turbo is just spooling up rather than chomping huge amounts of steroids as it does in the 2,500-3,500 range) until the thermostat has opened, which usually takes 10-15 minutes;- leave it idling for at least a minute before shutting it down.The warmup part can be a bit of a drag as I have to make a right hand turn onto a 50mph A-road in the mornings, so it is traffic dependent; on the flipside, 2,000rpm in fifth equates to 50mph anyway, and the last mile or so of my journey is all downhill so I usually just coast onto my driveway to satisfy the cooling-down requirement.Both cars have >185k on the original turbos (as far as I can tell from the service history) and have the oil changed every 5k with decent-quality lube. Mind you, the engines I refer to don't have a reputation for turbo destruction, but are well-known for chomping head gaskets if the cooling system isn't kept in A1 condition.

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No oil pressure or oil temperature gauges in my cars either Fred - in fact I don't think I've ever owned a car with the latter (had a couple of Vauxhalls with the former, mind - eeh, the 6-dial dash on the high-end Mk2 Cavs were great, I tell thee).Could be worse though - some cars (such as the brand-new Zafira I hired last month - this is progress?) have no water temperature gauge. Not ideal, as once the idiot light comes on you're FUBAR'd.

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some cars (such as the brand-new Zafira I hired last month - this is progress?) have no water temperature gauge. Not ideal, as once the idiot light comes on you're FUBAR'd.

Most old Renaults have a light instead of a gauge. My gold R5 used to put the light on quite frequently in traffic as the radiator fan didn't kick in - I eventually ran a live to it straight from the battery if I thought there was a chance of heavy traffic. It never seemed to do any damage though, even when the light was on for several minutes. The BX estate was the same - the light came on dragging the old Renault Novaquatre up a long hill on the A3, but the engine didn't seem to suffer any ill effects. I think there's a little bit of warning built in before the engine goes pop. Mind you, I suspect a modern Ecotec might not be quite as robust as an old Renault Cléon.
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Something new MINI has in common with old Mini - no temperature gauge!My old 5 didn't have one either. Nor a light. Well, I never saw one...In fact, the H van didn't have one either.Worrying thing is - on a good 70% of the water cooled cars I've bought, I've had to change the 'stat almost immediately. How are you meant to know it isn't warming up without a gauge? (ok, so my BX 16v was purchased in winter - I could easily have told even without the gauge!)Not all bad with moderns though - the C5 has water AND oil temperature displays!Oh and for the record, while I'd run the engine at motorway services and the like, I wasn't that careful with my pld Pug 306. It'd regularly be spooling up with the engine still fairly cool (great living in a village at the bottom of several hills!). Did over 40k in that car with no issues - though I did change the coolant at least every 2 years to keep the HG happy.

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I always let ours idle a bit at startup and then again before shutting off. Force of habit I suppose; I drove a Ford tractor for a summer at 16 that had a TB Turbo conversion and a bloody great sticker on the dash warning of the dire consequences if you didn't do the above!

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That's crazy, regressing to the days of boggo Peugeot 205s without temp gauges - I can't think of a more modern car that does without

The GF has a Saxo Forte which does without a water temperature gauge, just the Lamp 'O' Death. That's a 51-reg car!
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Something new MINI has in common with old Mini - no temperature gauge!

Do none of the BINIs have a temperature gauge? Most of the real Minis had a temp gauge and oil pressure gauge either side of the speedo.
We've got the use of a Cooper Diseasel (newer bloated shape) and it certainly has not gauge. My wife's City E Mini (povo spec FTW!) only has a temperature gauge because someone has fitted (very wisely!) an aftermarket item.
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Thanks for the comments - much more useful than some I've read elsewhere! Basically take it easy when warming up and just before switching off.On the topic of lack-of-temp gauges, my wife's 2002 Daihatsu Charade (future sh*te ahoy!) is sans gauge, having only a light on the dash (as was a 2004 Honda Jazz I used to run). Being Japanese cars I suspect there is less chance of seeing the light of death than in some other cars.Incidently my first car was a bog standard 1970 Hillman Imp and I'm pretty sure that was without a gauge. This was a car that was certainly in need of one. In fact I do recall it having a bright orange, semi circular warning light which had a dual role in that it indicated that either the water temp was too high or the oil presure had failed - imagine my panic when that one lit up (which was quite frequently) - although the gently rising steam in the rear view mirror was a major clue as to which emergency was at hand!PS Neither my Beetle or 2CV had a gauge either :D

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PS Neither my Beetle or 2CV had a gauge either :D

I once helped a friend sell her type 4-engined bay-window panel van. Youngish lad comes to look at it with his older, fat friend who picks fault with everything. The final straw was when he took the oil filler cap off and proclaimed 'head gasket has gone mate, there's sludge all over this. Needs a new engine, i'll give you scrap value'. :shock::roll:
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