What mileage is okay to drive with a broken fan belt?

I drove my 911/965 turbo from Guildford to Uxbridge on M25/M40, a distance of around 18 miles, with no fan belt it snapped at junction 10 .I was under the assumption that engine relied on ram effect with fan cutting in when in traffic or stationary. Was I lucky or do you think I have damaged engine. I am intending to drive car to garage to have new belt fitted. Should I not or will it be ok.

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: 911 Fan Belt and Pulley Replacement

[Wayne 962]

Zero miles is what you should drive on a broken fan belt. You're not correct on the ram air function - this is bad advice that you got from somewhere. The cylinders of the engine are cooled by air and nothing else. If your fan belt breaks, then your engine will overheat even if it's just idling. No miles are okay to drive with a broken fan belt - I personally cooked an engine when I didn't realize the lights were on, on the dash. When I pulled over to a gas station and popped the hood, the oil was sizzling in the engine like one of those old Valvoline commercials. 50 miles later I had about 7 pulled head studs and a completely destroyed engine.

- Wayne

[paulgtr]

none

[Geronimo '74]

Don't drive the car, install the new belt yourself. Shouldn't be too hard.

[Wil Ferch]

Seems like its a story of asking questions too late....

[porschenut]

If you started with a stone cold engine, you could probably make it 1 or 2 miles before it got above operating temp. Starting warm, 0 miles I would think.

[kanadary]

i cooked an old 356 motor with no fan belt. drove maybe 3 miles.

[scoe911]

It happened to me but my AC belt broke first...flapping around it then broke my fan belt. I first thought I had run over something and it was stuck in a rear tire. I drove a few blocks before I saw the alternator light...I'm still here...:-) replaced both belts myself... this was back in Aug 07... I have driven many miles since...

[herr_oberst]

How many miles can you drive your 911 without a fan belt?

The same number of miles you can drive without oil.

[Quicksilver]

The fan is forcing an incredible quantity of air through the engine and an aircooled eingine doesn't have a large mass of water to use as a heat sync that might allow you wiggle room.

If you really drove it 18 miles the next step is to disassemble the engine to see how much can be saved. Frankly a used motor will almost certainly be the least expensive choice in this situation.

[Ned, NYNA11]

I remember reading a post a few years ago about a 911 that was driven for a while without a belt. Mobil 1 was in the engine at the time and it somehow kept the engine lubed and there was no damage.
Please post the inspection results

[304065]

Long enough to pull over, shut the motor off and call the flatbed.

[RSTarga]

Thats why the factory tool kit comes with a spare and the tools to change it.

[quattrorunner]

Omg!

[rnln]

Hey guys, since some of us had this problem with fan belt and many have the famous cracking and fan housing problem. I am thinking that it's should be easy to install a plastic electronic fan there (even keep the stock fan housing in place), the normal radiator fan. What is/are the disadvantage\s?
Just a thought.
Thanks.

[DaddyGlenn]

Originally Posted by rnln

Hey guys, since some of us had this problem with fan belt and many have the famous cracking and fan housing problem. I am thinking that it's should be easy to install a plastic electronic fan there (even keep the stock fan housing in place), the normal radiator fan. What is/are the disadvantage\s?
Just a thought.
Thanks.

Good luck finding an electric fan that can move that kind of volume.

[Traveller]

Originally Posted by RSTarga

Thats why the factory tool kit comes with a spare and the tools to change it.

He should check to make sure that the appropriate sized belt is on board as well as the correct tools to change it. My 993 tool kit did not come with the 10 mm triple square, 24 mm box end wrench or the 5 mm hex key needed for a belt change. It does now.

Also, he should try this at home and get some practice before actually needing to do it.

[DRACO A5OG]

I think there is no electric fan that can meet the CFM (air flow) requirements.

[quattrorunner]

Again, OMG!

[Tsunamiboy]

Our host sells fan belts for something like $6. There is no excuse to not have a spare and the few tools to fix something like this on the side of the road.