'm sure I read in HJ's column somewhere that I should leave my diesel engine running after a long run before switching off. Why is this necessary and why don't manufacturers warn buyers about it?
My engine is a 2.5 TDI (102 bhp). Congratulations by the way on this site. I had a very quick and helpful responce to my previous queries....Bob
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I think I received a letter from you about this today. Some turbos are water cooled. But if the turbo is no more than oil cooled it is cooled by the engine oil and engine oil also circulates in its bearing to lubricate them. If you switch off a turbocharged engine when the turbo is red hot, the oil in the turbo bearings carbonises. This shortens the life of the turbo oil seals and also, of course, adds additional bits of carbon to the oil circulating in the engine. So the advice is to simmer a red hot turbo for at least five minutes, circulating oil through it while it cools down. A turbo is likely to get red hot after driving the vehicle hard or a long motorway run or a long ascent. If you have merely been pootling round the suburbs at minimal revs the turbo won't get hot enough to worry about, so no need to simmer it. For different lengths of journeys, simmer for between 30 seconds and 5 minutes. It used to be possible to buy a 'simmer switch' for SAAB turbos so the engine stayed running for a few minutes after you locked and left the car, but this is now illegal.
HJ
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Illegal or not you can get a simmer switch from demon tweeks www.demon-tweeks.co.uk
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"It used to be possible to buy a 'simmer switch' for SAAB turbos so the engine stayed running for a few minutes after you locked and left the car, but this is now illegal."
Not illegal off the road, and always ( past 30yrs) was. Or am I missing something.
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HJ - for most of us, a motorway run is followed by a mile or two of 'pootling' before we get home and switch off. Does this count against 'tickover time' for cooling down the turbo?
Derek
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Do you know of any modern cars whose turbos are water cooled and therefore will not overheat if switched off without simmering. The oil variety may put off some non aware car owners who do no want to be bothered to be careful
Thanks
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It is to keep an oil supply going to the turbo bearings whilst they cool down,
especially when the engine has been worked hard, for example coming off a motorway into a service area.
If oil is left to dry out on hot bearings it carbonises and can lead to bearing failure.
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I remember reading about a device where a small electric pump operated through a timer kept the oil pressure up for a time till the turbo had spooled down and cooled. I think it was in Diesel Car Mag but quite some time ago.
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seem to remember my old 306dt's handbook said that after a long run to let the engine idle for approx 30 secs.
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On the old Renault 19TD the turbo was water cooled and there was an electric pump that worked from a timer after the ign was turned off. Runs for up to 15 minutes.
Can be the answer to a battery that drains quickly on these cars. Failure of the relay/timer (about £50 from Renault only) will leave it running for ever.
David
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some of the higher spec after market alarms (Toad?) have modules to allow the engine to keep running for a variable amount of time, to cool the turbo.
Andrew
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Beg to differ about calling Toad a higher spec alarm. As far as I am aware they are made by Radio Shack which is Tandy. Might be wrong though.
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Many of my Japanese turbos have 'turbo timers'fitted that you can program to run the engine for between 15 secs and 5 mins,sadly the SVA say they must be removed.
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Illegal to leave the engine of any vehicle idling while parked on the road or a public place unattended. An AA man with the vehicle while attending to a breakdown is okay. The AA had a problem of their rescue trucks being nicked in these circumstances, so came up with a gizmo that prevents the truck being driven away while it's idling to provide a charge for someone else's flat battery.
HJ
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I seem to remember a mate telling me that he got nicked for leaving his car and posting a letter. Apparently he said that he got 1 point but (a) do not know if this is tru and (b) whether it is possible to only get one point.
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In answer to Derek, yes. But use your common sense if you can find it (I mean the turbo, not your common sense). If the turbo is still red hot when you get home, it still needs to be simmered.
HJ
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AGRIEMACH,S Turbo Guard. [01342 713743] ensures turbocharger bearings are lubricated even when the engine has been turned off. Price in July 2000 was £164.50. I have no experience of this product I just remember reading about it.
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I had a diesel Discovery which needed the turbo reconditioning due to lack of oil, which the garage told me was caused by leaving the turbo spinning without the engine running (ie. switching off to soon). I was also told that you could get a kit which consisted of a t-piece, valve and reservoir bottle which attached to the oil pipe just in front of the turbo and if the turbo was still spinning when the engine was off then it would draw oil from the bottle and then refill the bottle when the engine was running again. I can't remember the make of the kit but at around £200 I thought it was a bit pricey considering the recon of the turbo was only £300 and it had lasted 6 years and 80,000 miles before going.
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The product I was talking about is it www.agriemach.com and is called Turbo Guard
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Advert in the local press:
Could be useful to some of you.
Turboproject
* Peace of mind - lubricates and cools turbo automatically for 2-3 minutes after shutdown
*Almost instantly lubricates Turbo at start-up
Hydraulically operated, not electronic
email to turbof@global.co.za
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