I just drive carefully for the first few miles... As a general rule I allow the water to get up to temperature, and then about the same length of time again.

As for cooling, IMHO, running the engine with no air being forced over it will only increase temperatures in the engine bay. If I've been driving enthusiastically then I ease off a few miles before I finish my journey and then give the engine 10-15 seconds to allow the turbo to stop whilst it still has an oil supply, then I switch off.

Most of my cars have been turbo charged, some have been high mileage (200k+) and I've never had any turbo problems... Touch wood!

Even if you don't think the turbo is a fragile unit, it's good practice to allow any engine to warm up and cool down IMHO.

Given that modern multigrades run more or less constant centistokes across the temperature range, why should you need to warm the engine up (unless it's sounding slightly tappetty, in which case it won't delive full power anyway)?

Also, since we're talking TDs, they start boosting at about 1500rpm or so. It's probably impossible to avoid revving above that unless you don't exceed 45mph!

I've always been careful to warm up engines before thrashing after my days working on 2-strokes. Ready to be shot down in flames but I believe it has to do with the thermal expansion of the metals in the block. As the piston has less mass than the engine block it expands quicker than the surrounding cylinder resulting in scoring of the liner or even total siezure.

I have also been told by an engineer about water cooling to combat oil burning in the turbo, negating the need for turbo timers etc. Does anybody know if VAG engines employ water cooling for the turbo, specifically the Octy2 VRS?

Just give it a serious blast at the weekend mate

Gave her a polish and wax today looking lovely, the 205 is getting alot of driving at the moment though. It's just waaay too much fun!

I've always been careful to warm up engines before thrashing after my days working on 2-strokes. Ready to be shot down in flames but I believe it has to do with the thermal expansion of the metals in the block. As the piston has less mass than the engine block it expands quicker than the surrounding cylinder resulting in scoring of the liner or even total siezure.

That's certainly true of an air-cooled 2-smoke; less so of 4-strokes.

OK, had a few thoughts on this whilst DIY-ing this weekend and came to the following conclusion:

Presumably the energy that causes the body of the turbo to get hot is mostly due to the adiabiatic (for the sake of argument) compression of the inlet air combined with the fact that the exhaust gases undergoing adiabatic (FTSOA) expansion on the other side of the turbo are already hot. Therefore the inlet air gets getting hot, and there's less of a cooling effect from the expansion of the exhaust gases since they're already hot.

Therefore, while there might be a case to run on for a while to protect the bearing, I'm guessing this does nothing about the increase in temperature caused by the turbo compressing the inlet air??? Never really got any further with my train of thought, other than to think that the amount of heat supplied by friction in the bearing is presumably much less than the amount supplied from compressing the inlet air, in which case is leaving the car running to supply cool oil to the bearing a case of fiddling while Rome burns???

It would be interesting for someone with a infra-red thermometer to measure the temp of their turbo after a good run and measure it again after 2 minutes of idle just to see if there is any real difference at all.

If you rule out this whole oil supply and lubrication thing because the turbo continues to spin, which we know it doesn't, the only real reason to allow the turbo to cool would be to prevent the oil from burning on the turbo shaft. But if the drop in temperature is insignificant i really cannot see a reason for doing it.

I'm not saying the turbo runs on anymore - I'm happy to accept that it doesn't. What I'm saying is that the turbo compressing the inlet air would appear to put a lot more heat into the system than the friction in the bearing, and so the localised cooling provided by the oil system does little to remove the massive amounts of heat stored in the system overall...

I would agree with that!

I just drive carefully for the first few miles... As a general rule I allow the water to get up to temperature, and then about the same length of time again.

That's interesting. One assumes that when the water is at peak operating temperature, so is the engine, but I notice that the car feels much 'perkier' after several more miles of driving.

That's interesting. One assumes that when the water is at peak operating temperature, so is the engine, but I notice that the car feels much 'perkier' after several more miles of driving.

I've noticed that water is up to temp well before the oil is, but never really noticed exactly how long.

I used to drive one of works diesel dis-astra's and that didn't have any temp gauges at all... So straight to the red line from cold..

i usually try and allow the engine till the water is up to temp at least and providing im not in a rush ill allow a bit longer and at the end of journeys i have 2 stretchs of road near me which are about 1-2 miles long so i usally just take it easy along these stretches to cool things off and usually let the engine tick over whilst i turn off blue tooth head set etc, id say the heating process is more important that the cooling.

Think about the viscosity of water vrs oil.

Water will get "up to temp" alot quicker than oil

As a rule of thumb I generally wait 10+ minutes after settings off before going anywhere near 3k+.

The turbo's on our company's fleet of Dennis refuse trucks are worked a hell of a lot in a day and as soon as your off the power the turbo gauge drops to minimum.

After a day of our abuse they get switched off pretty much straight away and "touch wood" we haven't had one let go yet.

Mind you we have had the turbo pipes split or blow off:eek:

I'm not saying the turbo runs on anymore - I'm happy to accept that it doesn't. What I'm saying is that the turbo compressing the inlet air would appear to put a lot more heat into the system than the friction in the bearing, and so the localised cooling provided by the oil system does little to remove the massive amounts of heat stored in the system overall...

Plus of course, half the turbo sits in the exhaust system. The problem isn't the turbo spinning, it's that the oil left in the turbo can get cooked onto the bearing surfaces.

Think about the viscosity of water vrs oil.

Water will get "up to temp" alot quicker than oil

As a rule of thumb I generally wait 10+ minutes after settings off before going anywhere near 3k+.

That's got nothing to do with it (I think you're thinking specific heat capacity!), but nevertheless, you need to remember that the oil is INSIDE the engine, whereas the coolant is OUTSIDE. Therefore it is much closer to the heat source (the cylinders).

Plus, your temperature gauge will only start to rise once the thermostat has opened, as it sits on the radiator side of the circuit. The thermostat won't open until the coolant on the engine side of the circuit has got up to 100 degC or so anyway, which will mean that the rest of the engine (and by extension, the oil) will be at this kind of temperature also...

Plus, your temperature gauge will only start to rise once the thermostat has opened, as it sits on the radiator side of the circuit. The thermostat won't open until the coolant on the engine side of the circuit has got up to 100 degC or so anyway, which will mean that the rest of the engine (and by extension, the oil) will be at this kind of temperature also...

I did not know that.

Plus, your temperature gauge will only start to rise once the thermostat has opened, as it sits on the radiator side of the circuit. The thermostat won't open until the coolant on the engine side of the circuit has got up to 100 degC or so anyway, which will mean that the rest of the engine (and by extension, the oil) will be at this kind of temperature also...

Are you sure about that :confused:

If your right and the thermostat ever failed in the closed position then the engine could get fried to a crisp with the coolant temp gauge showing stone cold

Surely Skoda aint that silly

I'm pretty sure the owners manual advises leaving the car for 2 minutes after hard driving. Personally, I've always let the engine warm up and, after a long hard blat, cool down.

On the recent Euro trip all of us would often leave the cars running whilst we stopped for a few minutes for pics and a break. Also, after a very long and/or hard drive I tend to open the bonnet to aid in cooling the engine and also have a quick check to make sure everything looks ok.

I must be fortunate because I live surrounded by 30 MPH limits, so it gives the engine

plenty of time to warm up, and cool down after a blast

Are you sure about that :confused:

If your right and the thermostat ever failed in the closed position then the engine could get fried to a crisp with the coolant temp gauge showing stone cold

Surely Skoda aint that silly

I may be making a sweeping generalisation ( ), but it's certainly the case on the MPi in my wife's car - I will reveal all in my forthcoming thermostat housing replacement TG!

In the meantime, you may take some comfort in the fact that the thermostat closes against a spring, which means that if the plunger breaks, the spring forces it open, and you always get coolant flow though the radiator. It means your car takes forever to warm up, but at least it won't overheat!

Now Summer's definitely over, the downside is that it takes absolute ages to get heat into the cabin, so the 'stat is getting replaced in time for the colder weather. Also, because the engine's always running cold, it overfuels a little which doesn't help fuel consumption - although 32mpg out of a car that seldom beats 34mpg is hardly a massive drop...

I may be making a sweeping generalisation ( ), but it's certainly the case on the MPi in my wife's car - I will reveal all in my forthcoming thermostat housing replacement TG!

Well, the only generalisation I'd make (and I didn't check the position on the 1.9D last night) is that, on anything I've worked on, the coolant temp sensor was on the block, even if the position on the block varied.

Incidentally, if the water is up to temperature, I'd expect the oil to be as well, simply because the oil has a lower specific heat capacity, as anyone who did heat treatment of metalwork projects at school, or physics, should know!

Well, I know it's in a different location on the PD lump in mine (and remote from the 'stat as it goes), however my observations as regards its operation are the same: e.g. the temperature gauge goes fairly rapidly from all the way to the left to straight up at the same time as heat comes into the cabin.

It takes longer on my diesel car than on my wife's petrol one for reasons discussed elsewhere on here (current 'stat failure excepted), but the fact the gauge doesn't rise until heat comes into the cabin suggests that the sensor is on the radiator side of thermostat since obviously hot coolant doesn't go into the cabin heater matrix until the 'stat opens... :ne_nau:

I'm surprised no-one has mentioned systems like clifford intellistart, which interfaces with clifford alarms. Allows you to remote start the car to warm it up (including turning on air con or heater if winter or summer), it lets you leave the car for a short time with the engine running (to drop into a shop) and also to run on for a specified time after the key is removed. Does all this while ensuring no-one can drive off and the car is secure etc. You'd think I was their sales man but I'm not honestly (am sure there's equally good other systems I don't know of).

I think it is actually illegal to leave a car unattended with the engine running though?

I'm surprised no-one has mentioned systems like clifford intellistart, which interfaces with clifford alarms. Allows you to remote start the car to warm it up (including turning on air con or heater if winter or summer), it lets you leave the car for a short time with the engine running (to drop into a shop) and also to run on for a specified time after the key is removed. Does all this while ensuring no-one can drive off and the car is secure etc. You'd think I was their sales man but I'm not honestly (am sure there's equally good other systems I don't know of).

I think it is actually illegal to leave a car unattended with the engine running though?

But don't such systems will require that the factory fitted immobilizer is disabled something that might not be popular with insurance companies no matter how good the aftermarket item is.

Yes I think they would affect insurance, although most are still secure. I think some systems involve a spare key being kept in a box behind the dash near the ignition barrel, and this is somehow switched on and off to allow the key to bypass the immobiliser when remote start is needed, but otherwise anyone without the key would be unable to start the car.

But overall yes think it would unfortunately, no idea by how much though.