Was heading out yesterday in the 944 to get new tires and alignment. Got on the highway felt a little vibration a few minutes later a loud bang from something hitting the bottom of the car. I drive a few miles up the road get off my exit and have a slight vibration I feel in the shifter. Turn at the light car struggles to run and it dies. Open the hood and notice the power steering pulley loose. The crank bolt fell out. Towed the car home took it apart and it seems I got very lucky so far. I have a new crank bolt on the way and pulleys lined up in case anything is warped. Still dont know how this happened. I had a torque wrench on that bolt and a 3' piece of pipe to torque that bolt down.
Looks like I need a new crank bolt. The keyway needs to be replaced and the balance shaft pulley . Maybe the power steering pulley too if it doesnt sit flat.
So this happened.. Couldve been way worse
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Tom
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Wow, sorry about that. Normally the get tighter as the motor runs, not looser. Hopefully, you didn't lose oil pressure while driving. Spec is 155 ft lbs if memory serves, which should be doable with relative easy using a 3 foot pipe. Did you check the end of the crank to make sure the head of the bolt didn't just snap off?seiplej wrote: Tue Dec 23, 2025 2:46 pm Was heading out yesterday in the 944 to get new tires and alignment. Got on the highway felt a little vibration a few minutes later a loud bang from something hitting the bottom of the car. I drive a few miles up the road get off my exit and have a slight vibration I feel in the shifter. Turn at the light car struggles to run and it dies. Open the hood and notice the power steering pulley loose. The crank bolt fell out. Towed the car home took it apart and it seems I got very lucky so far. I have a new crank bolt on the way and pulleys lined up in case anything is warped. Still dont know how this happened. I had a torque wrench on that bolt and a 3' piece of pipe to torque that bolt down.
Looks like I need a new crank bolt. The keyway needs to be replaced and the balance shaft pulley . Maybe the power steering pulley too if it doesnt sit flat.
Luckily the car died so fast I didnt lose oil pressure. I was never more more thankful I left a ¯\_(ツ)_/¯ battery in a car and hadnt bought a new one yet..
I did have the car at a local Porsche indy shop to check timing belt tension for me. That was the last person doing anything to it. I called them not to put blame but let them know what happened and feel them out for their process. They offered to supply me with the parts to fix it. They are a reputable shop with a great following.
I did have the car at a local Porsche indy shop to check timing belt tension for me. That was the last person doing anything to it. I called them not to put blame but let them know what happened and feel them out for their process. They offered to supply me with the parts to fix it. They are a reputable shop with a great following.
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dr bob
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Edit: The 16V 944 doesn't have the same harmonic balancer setup as the 928 does, so you can safely ignore the [mis-] guidance on the balancer I shared.
My original post:
Were it mine...
I would take a very hard look at the vibration damper/harmonic balancer. These work by having the mass of the outer ring bonded to the hub by a rubber layer. Like all the other rubber things in the car, these deteriorate over time, particularly from heat and exposure to petro products, from ozone smog, and more. As the rubber hardens, it starts to loose the isolation, and will eventually crack. At 40-ish years for most of us, it's an easily solvable midlife crisis. Just get a new balancer. Avoid NOS and used ones if you can.
I don't own a 944, but... On the 928, the crank nose bolt depends on a thick washer with relief on one face to put the clamping pressure on the damper and pulleys when it's tight. In some cases, we've seen damage as you describe when the washer is installed with that relief groove facing forward. The bolt still tightens, but the clamping is applied to the face of crank nose. The damper and pulleys are allowed to move axially very slightly on the nose, rotation restrained by the Woodruff key. Telltales are wear on the key, slight galling on the crank nose, and wear in the bore of the balancer hub too. I'm sorry I don't have any handy pictures of the washer. In almost 30 years of offering repair clinics, I've only seen two instances out of a few dozen owners replacing timing belts in my workbays.
928 and 944 Master Greg Brown has adapter hubs for the 928 that allows use of an ATI balancer. It's a heat-to-fit piece that has threaded holes for removal with bolts, vs. the zero-zero fit of the factory damper hub. I don't know the other 944-specific pieces that might work, just want to share that tidbit. For sure it's worth the consideration and inspection. And another consideration when you have that bolt out for anything. I have a 50% chance of getting it right the first time, and a 100% chance of getting it wrong if I'm not paying close attention. It's a personal thing...
My original post:
Were it mine...
I would take a very hard look at the vibration damper/harmonic balancer. These work by having the mass of the outer ring bonded to the hub by a rubber layer. Like all the other rubber things in the car, these deteriorate over time, particularly from heat and exposure to petro products, from ozone smog, and more. As the rubber hardens, it starts to loose the isolation, and will eventually crack. At 40-ish years for most of us, it's an easily solvable midlife crisis. Just get a new balancer. Avoid NOS and used ones if you can.
I don't own a 944, but... On the 928, the crank nose bolt depends on a thick washer with relief on one face to put the clamping pressure on the damper and pulleys when it's tight. In some cases, we've seen damage as you describe when the washer is installed with that relief groove facing forward. The bolt still tightens, but the clamping is applied to the face of crank nose. The damper and pulleys are allowed to move axially very slightly on the nose, rotation restrained by the Woodruff key. Telltales are wear on the key, slight galling on the crank nose, and wear in the bore of the balancer hub too. I'm sorry I don't have any handy pictures of the washer. In almost 30 years of offering repair clinics, I've only seen two instances out of a few dozen owners replacing timing belts in my workbays.
928 and 944 Master Greg Brown has adapter hubs for the 928 that allows use of an ATI balancer. It's a heat-to-fit piece that has threaded holes for removal with bolts, vs. the zero-zero fit of the factory damper hub. I don't know the other 944-specific pieces that might work, just want to share that tidbit. For sure it's worth the consideration and inspection. And another consideration when you have that bolt out for anything. I have a 50% chance of getting it right the first time, and a 100% chance of getting it wrong if I'm not paying close attention. It's a personal thing...
dr bob
1989 928 S4, black with cashmere/black inside
SoCal 928 Group Cofounder
928 Owner's Club Charter Member
Former Ex Bend Yacht Club Commodore Emeritus
Free Advice and Commentary. Use At Your Own Risk!
1989 928 S4, black with cashmere/black inside
SoCal 928 Group Cofounder
928 Owner's Club Charter Member
Former Ex Bend Yacht Club Commodore Emeritus
Free Advice and Commentary. Use At Your Own Risk!
944 engines, except for the 16 valve variants, do not have harmonic damping / vibration isolation devices on the crankshaft. The most likely cause of a crankshaft bolt coming loose is from the power steering pulley not being positioned correctly prior to tightening. There is a shallow centering hub on the pulley that can easily be mis-aligned during assembly. Since you still have the pulley, look for deformation of the hub.
This is most likely what occurred. The pulley I have is now damaged from it spinning free. I would not trust trying to flatten it out and reusing it.barnwerks wrote: Fri Dec 26, 2025 9:52 am 944 engines, except for the 16 valve variants, do not have harmonic damping / vibration isolation devices on the crankshaft. The most likely cause of a crankshaft bolt coming loose is from the power steering pulley not being positioned correctly prior to tightening. There is a shallow centering hub on the pulley that can easily be mis-aligned during assembly. Since you still have the pulley, look for deformation of the hub.
Make sure the PS pulley isn't damaged, getting it off the snout and tightening the crank bolt is a problem. Even with my years of experience I did that on a car, ironically the nicest one I've ever worked on. 
Porsche 944S2 5MT '91
BMW E39 540iT 6MT '00
Mercedes-Benz W201 190E 2.6 5MT '89
IG: @stitch2k1
BMW E39 540iT 6MT '00
Mercedes-Benz W201 190E 2.6 5MT '89
IG: @stitch2k1
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Thom
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This is also what I thought as the damper is listed in PET for the 944 S but I have never seen or heard anyone with an S confirm their car had the damper.barnwerks wrote: Fri Dec 26, 2025 9:52 am 944 engines, except for the 16 valve variants, do not have harmonic damping / vibration isolation devices on the crankshaft.
'90 944 turbo