Hi Everyone,

I had put my Focus into a car wash yesterday and upon trying to come out the engine wouldnt start, working perfectly fine prior to this. I thought it could be electrical so ran a test and found the codes:

P0365 - Camshaft B Circuit / P0340 Camshaft Sensor Malfunction

I removed these sensors to swap around but found when turning the engine the camshafts and timing belt dont move, I can see the pistons going up and down (once spark plugs removed) and the crank pulley moving the aux belts but the timing belt isnt moving at all. Timing belt was replaced in March with new tensioner. How can this just happen in the space of a car wash?

Hopefully someone could shed some light 😪

Thanks

Josh

1 minute ago, joshuafalls said:

How can this just happen in the space of a car wash?

Did you not pay extra for a 'spin' cycle 🤣

The crank pulley isn't keyed on these.  My guess is that the crank bolt came loose because it wasn't fully tightened before.  Final straw would be an engine start.  Seems like a random coincidence that it happened just after a car wash.

Edit - Just seen that the aux belt still moves.  So this seems less likely now.  Potentially stripped teeth around the pulley instead.

4 minutes ago, joshuafalls said:

Timing belt was replaced in March with new tensioner.

Think you need to speak with the garage who replaced the timing belt and tensioner.

3 minutes ago, TomsFocus said:

The crank pulley isn't keyed on these.  My guess is that the crank bolt came loose because it wasn't fully tightened before.  Final straw would be an engine start.  Seems like a random coincidence that it happened just after a car wash.

Yeah thats what I thought, total coincidence it was just there and then. I think the crank pulley and crank sprocket are sort of bolted & squished together arent they? Will get onto the garage!

Would this of caused top end damage? 😨

9 minutes ago, joshuafalls said:

Yeah thats what I thought, total coincidence it was just there and then. I think the crank pulley and crank sprocket are sort of bolted & squished together arent they? Will get onto the garage!

Would this of caused top end damage? 😨

Edit again - As the pistons spin freely then there is likely to be valve damage in this case. 

1 minute ago, TomsFocus said:

Difficult to say with damage on this one.  If the engine just locked solid when it was cranked at  ~200rpm on the starter then it's probably fine.

If this had happened at 3000rpm on the motorway then there would definitely be valve damage.

I did edit that post though.  I missed the part about the aux belt moving.  I'm now less convinced about it being a loose bolt.

Okay so maybe some good news that the top end isnt gone, it was switched off, in car wash and then tried starting it. So fingers crossed.

Thank you for adding the belt pulley bit, we wont know until its stripped down with everything removed. I just wanted to get some advise before getting the garage involved 👌

Just now, joshuafalls said:

Okay so maybe some good news that the top end isnt gone, it was switched off, in car wash and then tried starting it. So fingers crossed.

Thank you for adding the belt pulley bit, we wont know until its stripped down with everything removed. I just wanted to get some advise before getting the garage involved 👌

Sorry, I had to edit that one as well.

As the bottom end now spins freely, that means there probably is some valve damage.  

(I'm now off to give my eyes a wash before reading any more posts!  )

19 minutes ago, TomsFocus said:

Sorry, I had to edit that one as well.

As the bottom end now spins freely, that means there probably is some valve damage.  

(I'm now off to give my eyes a wash before reading any more posts!  )

Ah okay, looks like my luck is over now! It just had a replacement engine in March as the old one had 235k and a hole in the piston, so this engine was a 60k replacement and its now gone. Oh dear 🙃

2 hours ago, joshuafalls said:

It just had a replacement engine in March

March must have been a busy time 🤔

3 hours ago, joshuafalls said:

Timing belt was replaced in March with new tensioner

So are you saying that the engine that was fitted in March, had a new timing belt and tensioner before it was fitted ?

This would suggest that either they reused the crank pulley bolt, which is a massive failure !! Or they didn't follow the correct torque procedure when tightening the bolt. Either way the fault is with whoever did the work.

On 5/8/2025 at 11:17 AM, TomsFocus said:

Sorry, I had to edit that one as well.

As the bottom end now spins freely, that means there probably is some valve damage.  

(I'm now off to give my eyes a wash before reading any more posts!  )

Hey Tom, I found the issue... crankshaft bolt had snapped which would keep tension on both the pulley & sprocket. I managed to retrieve the old threads with a screwdriver. Im just concerned now for any damage on the engine, so first steps will be to check the timing on the engine, compression test and see if we have any failure. My luck is 👎

Well, that's definitely the issue!

I wonder if the garage reused the same bolt?  The parts catalogue has warnings about doing so.  The garage would be liable for repair costs if so.

What was you originally using to turn the engine if the crankshaft bolt has sheared, or was you trying to force the crankshaft round whilst the pistons were hitting the valves.

2 hours ago, TomsFocus said:

Well, that's definitely the issue!

I wonder if the garage reused the same bolt?  The parts catalogue has warnings about doing so.  The garage would be liable for repair costs if so.

Cant believe it at all, it looks to be the same bolt due to the wear on the head of it. Im sure by now the pistons and valves have got to know each other better but ill do some further checks.

17 hours ago, joshuafalls said:

Cant believe it at all, it looks to be the same bolt due to the wear on the head of it. Im sure by now the pistons and valves have got to know each other better but ill do some further checks.

Garage should of used a new bolt as Tom mentioned. Hope you get sorted. 👍