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Fan Failure?


Boosh
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Hi all,

A few weeks ago, my 1.8 tdci was in the garage for a fuel pipe leak and possible faulty injector. Upon getting the car back, I noticed a 'hot' smell coming from the engine, and put it down to possible chemical sprayed to clean up the leak. A couple of days ago, I noticed that the smell was still there, and that the the temperature gauge needle seemed to be going up and down according to speed: quickly down when at speed, quickly up (no more than half way, though) when slowing down. I checked engine coolant level: took one litre to bring to min. Coolant was circulating when engine was running. However, I couldn't find any sign of coolant leak under the car, in engine bay, didn't notice particular smoke, no gunk under oil filler cap. So I'm wondering whether some coolant loss was necessary for fuel leak repairs and just wasn't topped up, or whether I should be worried. I also noticed after my 7-mile commute, that the the fan still hadn't kicked in: could a faulty fan be responsible for yoyo temp needle (as cold air at speed cools engine, but idle and no air make it go hotter)? It spins freely when flicked by hand, so could my problem be caused by bad fan switch? Bad thermostat? Other?

Sorry to write down my life story, just trying to be as detailed as possible.

Thanks for your help,

Boosh.

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have you seen it running at all it could be the fan module or have you put a current direct to fan to see if it works as motor could have burnt out??or fuse blown these what i be looking 4 regards pete

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Can't say I have, but until now I had no reason to suspect anything was wrong. I'm not too savvy with electricals, but checking and/replacing fuses is within my ability. Any idea which one that'd be? Thanks for your help,

Boosh.

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Don't know on the Mk4, but on my Mk3 I've been through four fans in two years - the original one, two from a scrappie (one lasted a year, one lasted 3 months), and now on a 4th, universal fan which I bought new. Needed a little wiring/soldering work to connect it to the module, but it's good now, and better than paying for a new £150 fan from Fraud, that does the same job.

But I digress... In all cases it was the fan motor itself which had died. You can test it by hooking the fan direct to the battery (bypassing the control module too). I had two fans that didn't spin at all, and one that spun but made the most god-awful racket. I tested it by unplugging the fan, and getting a metre or so of 3-core, stripping off about eight inches of the outer sheath either end, and crimping spade connectors onto the wires. Plug one end onto the fan, and the other end to the battery. Would NOT recommend doing it for long as, depending on the grade of cable you're using, it can get very hot.

Another way you can test the fan is to stick a pair of multimeter probes into the fan terminals, and spin the fan by hand. The multimeter should register a voltage increase as the fan turns (or it'll show a negative value if you got the probes back to front), but either way you should see something happen. The voltage indicated should be fairly consistent with the fan turning at a fairly constant speed. If you get nothing, or fluctuations back to zero, the motor is probably shot. This method isn't exactly fool-proof, and I much prefer and recommend the battery method for a definitive answer.

Again, on the Mk3, the fan comes on straight away when you turn the air-con on. If the fan doesn't come on, the air-con compressor shuts off again, and it keeps going on and off every few seconds (most people think this is an air-con gas pressure issue, but mostly it's not - it's the fan).

Hope this helps.

As for the coolant level, now you've filled it to max (with coolant I assume - not water), I'd just keep a close eye on it to see what happens. I can't see a fuel problem causing coolant loss, unless they took the header tank off for better access to something, which would explain the litre or so that was missing. But then, any garage with any sort of reputation would have refilled it correctly.

Just monitor it for now (daily, for a week or so, when the engine is cold) - you could stick a bit of tape onto the side of the tank to mark the exact level and remove any doubt whether the level has fallen or not. If it goes down again, and assuming there isn't a puddle under the car, you can start to investigate further.

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Well, not being able to borrow a multimeter until next week makes it a bit difficult to establish whether fan motor is getting power or is cooked. However, I had a good look (albeit from above) and could not see any sign of leak, though level has gone down by about a pint in a week. Coolant temp sensor area was dry, so were the coolant bottle area and the bottom of the radiator... Following a tip from another post, I turned the air con on to see whether the fan would come on. It didn't. But I also noticed that the aircon compressor pulley didn't seem to engage, judging by the three nuts on the pulley not spinning with the auxiliary belt. I had a look at the aircon fuse on the side of the fuse box, seemed ok. Could an air con issue cause a loss of coolant? Or am I barking up the wrong tree? Thanks for your help,

Boosh.

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