Both drive belts just fell off

Both drive belts just fell off and I wasn’t even going anywhere on a 2011 Gen 3.

Is this a Jimny thing? I have never had a problem with a drive belt on any car in 35 years of motoring it’s bizarre.

Okay here is what happened, I was fitting a home made box so I can get front and rear cameras through one input, put it in reverse, you get the rear camera, take it out of reverse and you get the front camera for about 6 seconds, plus there is a switch on the dash. To fit it meant the head unit was out and powered for some of the time, with the ignition on, but engine not running. I was probably about 2 hours max.

The head unit tends to hang near the 2w, 4w and low range switches and when the ignition was on the drive did change a couple of times and the air con button got turned on.

Near to the end of testing, the low battery voltage warning came on so I started the engine, but it didn’t go off. Thinking I might have a wiring fault I shut everything down, pulled the head unit and all was okay. I started it up again, the low battery voltage was on and my volt meter only read 11.3v. Raving the engine a little made no difference, voltage went down slightly.

I then heard a clunk and the engine stalled. On checking both drive belts had come off.

I am guessing that the belts will need replacing, if they were just slack and had increased load from the 4w drive buttons been pressed and AC on without the engine running, then starting up could that have caused it? Or is there a guide keeps the belt in place?

I am assuming there is a guide somewhere on changing the belts?

Ta

That's unlucky.
Don't think it's a Jimny thing, but you can get wobble on the crank pulley due to the rubber insert failing, this normally snaps belts.
I've just changed both of mine, easy enough but I was surprised just how tight they are with the correct preload.
I recall watching a video or two on YouTube to get the general idea and went for it. Did it with the radiator installed, a little tight but Ok in my opinion.
Mike

Edit
Here's one

Thanks Mike,

It looks straight forward, I think I will try the old ones back on tomorrow and my local parts store has Dayco belts in stock, so will swap them over, if the old ones stay on and nothing else is wrong, like a seized water pump or AC compressor.

I am working from home tomorrow so should be back up and running quickly.

At least there is no damage, just a mystery how the belts came off in the first place.

Yes it's strange, can't explain why they both came off without damage.
It's possible they were just on the loose side, but you usually hear them squeal with lights on or PAS movement.
The only common point for both is the crank pulley, so have a good look at this to make sure it's ok. Pulley should run true, wobble indicates possible issue with the rubber bonding.
Hope the fix all goes well.

Definitely check the condition of the crank pulley.

Took me about 3 hours to put both belts back on, the alternator wouldn’t move and then the AC/PAS belt was so fiddly I couldn’t get enough slack on the tensioner, but it all went back and tensioned.

Before I even started the engine I could see the problem, the crank pulley was lopsided, actually it is loose so the rubber Cush drive has definitely gone. As it was about 7:30 pm by now I decided I had nothing to loose so started the engine, both belts jumped off straight away.

Still at least I know what is wrong (thanks for the pulley suggestion guys) and replacing the belts will be much faster next time.

The belts I took off look okay, but they are getting replaced with the crank pulley rubber, just to be on the safe side.

I will try and post a picture of the pulley, but it doesn’t always work from my iPad.

Pictures of the crank pulley, hopefully.



You can see how it is very lopsided.

Just wanted to say thanks to everyone, this is a great site for practical help, it gives me confidence to tackle jobs without a workshop manual.

Cheers

Robin

As they say "there's your problem"
Thanks for picture, have never seen a failed pulley, only been told they exist.
Good call on the new belts, prior to jumping off the pulley would have been giving them hell, usually the belts just snap.
Good work.

My new pulley arrived, 3 days late, it should have been here on Friday, but I eventually got it late Monday afternoon. Unfortunately with the additional trips back and forth to the delivery depot it is damaged.



Since I had to get the car going again, I contacted the supplier, said I was going to dress them with a file and then sort it out later. Unfortunately, they didn't dress very well, the metal which was folded over just cracked and I had to file away more material than I wanted. The new pulley is on and working, but it will have to be replaced for another one in a few days time.

Still I have now got the hang of this job, I borrowed an idea from another post on here to get the pulley off, a metal bar bolted to the pulley with two M8 bolts and then jammed to the side of the car with a block of wood. Actually my drive slopes, so with the car in 5th and let the hand brake off slightly the car's weight pushed the bar in to the wood, then with the car in gear, the pulley was very solid and the nut came off with a breaker bar.



To release the pulley from the shaft the same bar was used this time just tighten the two M8 nuts with it pressing against the flange of the pulley nut, this pops the pulley off the shaft really nicely.

Then to put the new pulley on, just reverse the wood, this time there was no need to put the car in gear.

Nice one Doc. Special tools, Bah. Some of these tricks were taught once upon a time. Chris

Thanks Chris,

The wood came off an old fence I have just replaced, definately keeping this bit now.

If you like home made tools and jigs, what about this belt tension gauge, it is made from two pieces of aluminium bolted together so they can slide. The is a notch for the belt and a [rough] scale at the other.

Just use two hands to move the belt up and down, keeping one part steady and see how much the gauge moves.