Hi All,

I'm a bit stumped as to why this sound has started. Suggestions on a Facebook group think that it could be the piston touching the valve. I'll give some history and explain exactly what I did.

2008 TD4, 175k km on the clock. No evidence of the timing belt having been done but other than that the car has had an easy life. It ran and sounded perfect when I drove it home. I ordered a timing belt & water pump kit and bought the three locking tools as a set online.

I lined up the timing hole on the cam pulley and made sure the pin was in fully. Removed the starter then lined up the flywheel and pushed the pin all the way in through the timing port.

I have a feeling that I didn't fully engage the flywheel locking tool between the teeth on the flywheel when I undid the crank pulley bolt, but there was no movement of the crank. I fought to get that bolt out but eventually got it loose. Both timing pins were still in place.

Old timing belt, tensioner and idler pulley out, new ones in. I missed a step here, removed the pin from the tensioner and just set the tensioner so that the pointer was in line with the notch instead of tightening it past the notch then turning over the engine 10 times by hand. Put the crank pulley back on and torqued up to the recommended specs as per the manual (70 NM + 82 deg).

I removed the flywheel locking tool, and both timing pins this was the first time I turned the engine over by hand and heard this metallic click just a few degrees past the point where the cam pulley timing hole is.

I redid everything yesterday and started from the beginning and did the tensioners exactly how the book describes it but still no change in that sound.

Could this be a valve stuck open which is contacting the piston? Any ideas why this would happen. Could it have something to do with the hydraulic pressure of the lifters not moving the valve fully? Here's a link to the youtube video of that sound: https://youtube.com/shorts/HKJxQFdVcXI?feature=share

Sounds like it's not in the engine as such

Can you have someone turn the pully while you check the action out from above. Put your finger on the tensioner bolt feel for the click.

Adding what make of belt kit did you purchase

It seems to happen every few revolutions of the crank and always at the same angle when it does. If it was the tensioner surely it happen more frequently and on each revolution? If I had to describe where the sound comes from it sounds like it's right in front of me and not up towards the left where the tensioner is.

It's the Dayco timing belt kit with the Airtex water pump.

Take everything off and check the reluctor wheel. Go back to basics with the timing.

I took everything off again yesterday, belt, tensioner and idler pulley and started again. Re tensioned the tensioner and still got the click

The reluctor ring can only go on one way over the key right? I double checked by watching one of the videos on YouTube that seems to be quite popular and my reluctor ring went on the same way.

Don't want to clutch at straws and waste your time but if it were me just as a test I would strip everything back and re fit all of the old gubbins back on. All you have to lose is time.

Sorry can't remember how the reluctor goes back on

Can you guess the place from where the sound comes?
Inside motor, outside, top, bottom?
Inside motor there are a few things that could cause "a" click...
The two balance shafts, the chain and sprocket from the oil pump, the camshafts chain and its tensioner....

FWIW
As an extra check I mark two points on the old belt teeth and on the camshaft and crankshaft pulleys, then after locking the flywheel and camshaft I transfer those marks to the new belt by lying the old one along side the new or counting the teeth.
Obviously not on the tensioner side of the belt run. Jules

Just seen the OP's name.
Could it be coming from that nut that fell inside the bellhousing or did you get it out ? Jules

@jules yes it's me and my troubles again haha!

I dropped that nut through the starter motor hole when redoing everything from scratch for the second time (salt in my wounds ). That dropped nut hasn't added any extra sounds. I've just ordered a scope camera and will get it out the way you showed me.

I did the tippex marks on the belt as an extra security measure to make sure that I had the correct number of teeth between cogs when fitting the new belt. Both times I got the same number

I'm considering just bolting it all back together (once I remove the dropped nut from the torque converter bell housing) and seeing if it starts. Surely if the flywheel pin and cam pins line up and the tensioner is set correctly then what could possibly be out of timing?

@alex - It sounds like its coming from just behind the crank pulley inside the engine. Maybe about 1/3rd of the way up and slightly towards the left. I can feel a tiny vibration through ratchet when I hear that click.

Definitely not coming from either of the pulleys, I held my finger on their bolts and got my partner to turn the engine over and felt nothing from them.

After doing some more reading up and getting ideas from other members, this is what I think could be going on.

If there's a valve sticking open, either due to being bent by a swirl flap or just sticking in its glide because of lack of regular oil changes for example, then maybe what could be happening is when the piston touches that valve the spring quickly closes that valve which could be causing that ping. Maybe when the engine is running/warm that valve gets moving without any contact with the piston.

The only thing is I can't definitely say for sure is wether the sound was or wasn't present when lining up the timing pins the first time round. It's possible it was there and I just didn't pay attention to it because I was focussed on getting the timing pins in place.

Looks like the next step is going to be to remove the valve cover and turn the engine over by hand and listen/feel for any pings. If it's a valve then the head is coming off next and we'll just have to see what's going on under there.

This might take me some time to get round to. I'll send some updates as I go. Thank you to everyone for your help so far, I really appreciate it

On my previous cylinder head, I had an exhaust valve sticking open for a about 5 minutes after starting from cold.
Once warm enough, this valve would suddenly start sealing randomly for a few seconds than it would start close normally for the rest of the running cycle.
The was no evidence of valve contact with the piston in my case as the valve only stuck open a few mm, but it was enough for it to run on 3 cylinders for those few minutes.


The only issue with your idea is you can't remove the valve cover and still turn the engine, as the valve cover is also the cam retainer.

This is what you see when the top cover is removed.

Click image to enlarge

Just wondering if you have someone turn the engine, take the oil filler cap off and closely listen at the oil filler hole can you hear anything

@chips - I’ll ask someone to turn it over this weekend so that I can listen through the oil hole.

@nodge - that’s very interesting! Did you end up rebuilding the head or did you have to replace it? Thanks for the advice about not being able to turn it over with the cover off. Looks like I’ll only know which one is the problem once the head is off