Crank pulley knocking

Hi, I have been chasing a mystery knocking noise coming from the front of my 2012 M13A jimny and have now got the rad and fan out. When I take the alternator belt off the knocking stops. Its a regular tap tap tap matching the engine speed. IF I spin the alternator by hand it feels smooth with no play, same for the water pump. The Crank pulley does have some play in it and if I gently wiggle it with a pry bar the knocking noise will change. So the question is do crank pulleys fail ? are they easy to change ? 

I think the design of the pulley allows the rubber to act as a form of damper. I have heard people gluing cracks to try and prolong the life of the pulley as the rubber can separate from the steel outer, allowing the belts to fly off.

In the end I reused my old one as it looked the better of the two I had.

Removing and refitting was easy for me, I'd already removed the air con condenser as it was holed and this allowed me to room to get a cordless impact wrench in. Used a shallow 17mm socket . Probably took 60 seconds of the gun rattling away before the bolt started moving. My donor engine whizzed straight out.

If you don't have access to an impact gun, you can put the car in gear and there's someone on you tube who uses a spanner wedged into the pulley slots and the chassis and uses a breaker bar.

I have a cheap pulley holding tool of eBay, but I think it would break before the bolt came loose.

Fully expect to have a serious fight to get the crank bolt out, they are done up ft and then the integrated flange rusts solid to the pulley. I have a 1000Nm impact wrench just for this job. Some people have to resort to death wheels on the angry grinder!

Your crank pulley needs replacing otherwise both belts will come off and you won’t get far without a water pump.

I took the radiator off my 2011 and made a tool to lock the pulley, it is drilled with M8 in two places, then used a 1m breaker bar and good fitting socket, it came out with a bit of force. I would suggest a new bolt as well, just in case you round the corners on the old one.

The only other issues were the new pulley arrived with a dent after the courier played football with the package, meaning I had to get a second one shipped and one of the alternator bolts was (still is) very tight, making the belt difficult to tension.

I look out my post on it.

If you don’t fancy doing the job yourself it’s quite an easy job for your small local garage/mechanic to do.

Robin

My experience

www.bigjimny.com/forum/6-jimny-chat/6684...ust-fell-off?start=6

Others have made similar tools.

I still have the special service tool in the garage, not sure if the new Gen 4 is the same size.

Robin

passy wrote:

 So the question is do crank pulleys fail ? 

More than a pulley, the part you're talking about is actually performing a critical function on your engine.  Google "harmonic balancer".  And yes, they do eventually fail.

I think a tidy, regular tapping noise is a little unusual for a failure mode, but if you are seeing play in the crank pulley, you must have found a problem and you need to swop that part immediately.