audi40

Came home from work tonite and pulled into garage - as soon as I got out of the car and shut if off, I was hit with the smell of coolant and the sound of the engine cooling fan running. Had just driven 20 miles from work with temp < 15 degrees, so no reason I could think of why fan would be on - engine temp was normal and no indicator lights on. I popped the hood and nothing seemed to be amiss. Fan stayed on for at least 5 minutes so started it up and backed out of garage to see if any signs of coolant leak - there were none so I pulled back in, shut if off and fan also went off. Went out to dinner shortly thereafter - got to restaurant, shut down and no cooling fan on. Went home from dinner an hour+ later, pull into garage, shut engine off and cooling fan is running again - stayed on for at least 7 minutes, before shutting off automatically. Don't think this is normal for fan to be running after car is shut down in these temps - anyone else experience this or have thoughts? Maybe something specific to TDI??

Mike_L

Its cooling the turbo to prevent oil coking. I think all current forced induction vehicles do that. My CTS-V and X5M did the same thing. Built in turbo timer.

Brooklyn

On my B8 S4, that was a precursor to my thermostat dying.

in2dwww

That's the DPF regeneration, where it heats the exhaust filter up to burn off the soot. It will run when the car is on and can last 5-15 minutes. If you park the car during regen, it will shut off but your exhaust temps are 1472 F, so the cooling fan remains on. This is normal for all TDI models. It happens roughly every 700 miles, but it really depends on driving style and city/highway use.

audi40

Thanks, after a quick search I found the following which describes it exactly:

http://georgetownvw.wordpress.com/20...he-engine-off/

Street

I had a 5000 Turbo Quattro and the turbo had an electric pump to cool the turbo after shut down. According to service manager, if you hear the cooling pump on a C7, you've got a big problem. Pumps are now silent.

I too thought the fan was for the turbo, but this forum set me straight.

Sickler

I don't have the TDI but my cooling fans never came on until a couple weeks ago after a quick trip to the store (mellow drive). As Brooklyn said, the next day I spiked my temp gauge and the thermostat needed replacing. In 100C water it opened only 4mm instead of the typical 8 (if I remember the number correctly). This was at 31,000 miles.

dbbyleo

Thanks for this post. It has put my mind at ease!

dbbyleo

And thanks for the link to the article. Although I'm curious what mechanism heats up the DPF? Electrical heating element?

Audidi

Extra diesel is injected at exhaust stroke, causing high exhaust gas temperature.