Starting problem

[Thelittlesthobo]

Hello
I bought a volvo v50 2.0 diesel SE back in march. I must say its a really nice car and my wife and I love it to bits. However.....I left it running for about 10 minutes last Thursday morning to defrost, and when I got in it, there was a strange burning smell coming through the vents which stopped a few moments later. It hasn't done it since until today when I was arriving at the inlaws the smell came back. So I popped the bonnet and had a quick look, when looking a few wisps of smoke were rising out of the electric fan cowling at the radiator (it wasn't the starter). Anyway, the smoke stopped so I thought I wouild have a look at it Monday, however when I went back to the car it was very flat, and the AA had to slave start it for me, after running it to work and checking it, it is charging at approx 14.5 volts, the battery has tested healthy, and it draws less than an amp when all switched off. I suspect a fault with the electric fan because I couldn't see any other electricals in the area. Does anyone know of any issues with the fans and also what the 3 electric wires to the fan do? Pos, neg and signal? If so what voltage is the signal, or is it a data signal?
Any help would be much appreciated.
Best regards
Robin

[Guru]

Hi, you didn't specify the MY you have but nevertheless, recall "R/2009/024 possible engine bay fire" may be of interest to you.
Look it up on the VOSA page HERE. Let starting date be> 04.2004

But that doesn't explain that flat battery, are you sure it's not the alternator that is smoking? all to common if it's a 120A alternator.

I must add, that you shouldn't heat a diesel engine by letting it idle, that's for petrols. Your 2.0D needs to be started and driven within 2 minutes or so, but driven gently, with rpms in the 1500 +-200 range, after it reaches optimal operational temperature, feel free to drive as you please.

[maleercan]

Originally Posted by Guru

I must add, that you shouldn't heat a diesel engine by letting it idle, that's for petrols. Your 2.0D needs to be started and driven within 2 minutes or so, but driven gently, with rpms in the 1500 +-200 range, after it reaches optimal operational temperature, feel free to drive as you please.

Dear Mr Guru (!)

Your last comment intrigued me - I've never heard that before.... is this because diesels need a bit more of a load on them to get them warm?

[faffi]

No engine should be heated at idle. It leads to increased wear and pollution and will cause unburned fuel to mix with the engine oil. You need to use a bit more rpm when the engine is cold so that you don't lug it. If you read the manual, it says to start driving immediately after starting up. I have to climbe an 8% hill after driving only 200 yards and I let the engine climb it at around 2400 rpm i 2nd gear.

As a sidenote, my son's Mercedes Vito diesel (non-turbo) recently blew a head gasket after 130,000 miles. This 2-ton van has only 88 hp to move it, which means it has lived most of its life with the pedal to the metal and high rpm. Even cold you don't get anywhere without lots of throttle and rpm. Still, there was still clearly visible hone marks in the cylinders and the combustion chambers and piston crowns came spotless clean with just a swipe of the rag. Proof positive that modern oils as well as materials in engines are increadibly good and that there is little cause for concern regarding extended pampering of the engine from cold.

[Guru]

Dear Mr Maleercan (!)

In addition to what faffi said, a cold idling diesel engine does not provide sufficient lubrication to the higher engine parts, i.e. to those furthest from the oil pan, which will lead to premature wear of those components, this is due to lower oil pressure when cold... the parts that suffer the most are the valves and rocker arms /they'll start making a clapping noise/ and the catalytic converter will over time start clogging up too due to reasons mentioned already by faffi.

Regardless of oil viscosity used, freezing cold engine oil is more viscous and thus harder to draw and "move around" so after it is propelled by the oil pump, at idle it loses kinetic energy quickly which causes a drop in oil pressure.

Aiding the oil circulation and thus the whole lubricating process by driving the car at reasonable rpm figures when still cold will help prevent excessive wear by improving lubrication through raising oil pressure.

I know this applies to modern forced induction diesel engines using synthetic or semi-syn engine oil, whether it also applies to naturally-aspirated engines, or engines using thick mineral oil... I do not know.

[faffi]

The interesting aspect of oil lubrication is that the pressure itself has no relevance other than circulating the oil. More pressure can move more oil at any time. Which is very good when you want oil from the pan and up to the relatively dry camshaft etc. in the top end, which last most of its oil supply as it drained down to the pan after shutting off the engine.

But what actually keeps the metals from touching other metals is an effect that I do not know what is called in English, but it is an effect that grows stronger with rpm (until a certain point where friction cause so much heat that the oil film breaks down again). This effect means that the cam lobes and crank bearings and other gliding parts that rely heavily on the oil film for protection typically have the most problem at low rpm. During idling, you risk that the parts aren't moving fast enough to build up the required protective film. This is even worse when the oil is cold and thick. So what happens is that the oil film breaks up and you get metal-to-metal contact with the resulting increase in wear.

As mentioned, this film only needs oil in order to form, the pressure itself is irrelevant other than making sure there is always oil present to renew the protective layer of oil.

[Thelittlesthobo]

Originally Posted by Guru

Hi, you didn't specify the MY you have but nevertheless, recall "R/2009/024 possible engine bay fire" may be of interest to you.
Look it up on the VOSA page HERE. Let starting date be> 04.2004

But that doesn't explain that flat battery, are you sure it's not the alternator that is smoking? all to common if it's a 120A alternator.

I must add, that you shouldn't heat a diesel engine by letting it idle, that's for petrols. Your 2.0D needs to be started and driven within 2 minutes or so, but driven gently, with rpms in the 1500 +-200 range, after it reaches optimal operational temperature, feel free to drive as you please.

Thanks for your help
I noticed that the alternator was too hot to touch, and my wife had mentioned a whining noise aswell. After testing the alternator it turned out to be faulty, which was (a) draining the battery and (b) making the whining noise and smoke). I've replaced the alternator and its good as gold again. Thanks for your help and thanks to the Techy at Kings volvo Southampton for the advice. My alternator was a 150a by the way.
BR
Robin