2010 XK.

Has anyone heard a noise like this and know what's making it?
Any informed advice will be welcome.

It only occurs for a minute after a hot start, like after a refuel and goes away as soon as revs exceed 1000. It also just goes away after a minute of idling or soon after pulling away.

There's no tapping sound after a cold start. If I let it sit idling the tapping will start after several minutes as the engine warms and then after a few more minutes the sound fades away.

At it's loudest it's audible from the cabin.
With the bonnet/ hood open It seems equally loud from above, below and either side.

The tapping doesn't alter (except it speeds up) with engine load and ceases as the engine reaches 1000 rpm.
If you blip the throttle the tapping goes, but returns as the engine slows back down.

I couldn't pinpoint it with a stethoscope, tapping sounded the same on both cylinder heads. I couldn't get beneath on that occasion to listen to fuel pumps.

The attached recording was taken from above the engine whilst tapping was at it's peak.

The tapping is consistently at half engine speed (300 taps/min at idle).

An oil change made no difference.

On most days the tapping never occurs but I want to understand it's cause and whether to worry.

Thanks and regards to all Forum members

 

That sounds perfectly normal to me. DI engines are noisy but there's nothing concerning I can hear there.

 

That’s definitely more “rod knocky” vs my 2010 xkr. Maybe use a thicker oil

 

Glad you've posted this - I recently acquired an XKR and discovered the same noise on warm starts when idling. I'd assumed it was chain/tensioners, and had bought it at a price where I was comfortable paying for some work to be done. Currently on 72k miles but seems to run smoothly otherwise, keen to see what others think of it.

 

I'm pretty sure it's not timing chain slap, it's not there on cold starts and it sounds too regular and independent of engine speed, (upto 1000rpm). Also new tensioners and chain inspected a year ago.
vvt or fuel pump?

 

Interesting - I'd been looking in to it and it sounds similar to the noises in this video - which seems to be solved by tensioner replacement with the same symptoms (warm starts).

 

Very similar 🤔

 

You spurred me on to do some digging - looks like there are some potential answers here?

https://www.jaguarforums.com/forum/x...-197461/page3/

 

Yes, a lot of ideas there.
It seems very common, accepted even!

I used an app to slow down my recording so I could accurately count the taps per minute at 300.

Its definitely not a fuel pump cam noise as these are driven at crankshaft speed.

I'm wondering if a vvt unit might rock back and forth creating the noise. That theory would be fairly easy to test by activating the vvt solenoid on each cam shaft to hear if the taps cease as the unit moves from its base setting.
(I'm sure this will also illuminate the ECU lamp and create cam timing correlation codes.)
Does anyone know what the 2W loom connector to solonoid is called and where to obtain one?

 

Link:
Repair and Diagnosis — 2010 Jaguar XK (X150) V8-5.0L Service Manual | Operation CHARM

Diagrams/Electrical Diagrams/Fig04.11 - pick your connector #
Diagrams/connectors - pick your connector #

You might back probe the pins of choice and apply power.

There is also a diagnostic that will report the VVT position that may be useful.

 

Here’s what mine sounds like at idle. Drove around for 30 minutes, got up to temp, and then shut down/started up.

2010 xkr with 108k miles. Burns about 1qt every 1k miles. Using 5w-30 restore and protect oil.

 

Thanks for the ideas,
I found the connector shell part number YPC908800 plus two terminal pins YPL500360. I will try and find a source, preferably pre-wired.

During a period of tapping I would want to unplug the connection to ECU at one vvt solonoid at a time and plug in the test connector to activate it for a short while and listen for changes.
Access is tricky so may need to remove the intake tubes. Definitely too hard for me to make a good quick connection to a solenoid with anything other than a proper connector.

The vvt position diagnostic I tried provides derived average figures rather than live. They are all read good, but don't throw any light on the tapping cause.
The idea did lead me to think maybe I could monitor oil pressure and see if there's a connection.

What puzzles me most is that there is no tapping with a hot engine until you turn it off and restart.

 

To the final part - there was a theory in the other thread around hot oil being less viscous and draining quickly, needing time to get back up to pressure.

 

If you are 5W30, try 15W40 synthetic oil for high mileage cars. I have known a number of Ford V8s that run with low oil pressure, flickering engine warning lights, and perpetual detonation.

 

I'm using Texaco Havolin 5w20.
There's no oil pressure sensor, just a switch. AI reckons it's in an awkward position obscured by the alternator. Maybe T'ing in a guage is not worth the trouble.

 

I found the connector shell part number YPC908800 plus two terminal pins YPL500360. I will try and find a source, preferably pre-wired.

A good photo of the connector and Google lens indicates that the same connector is used for the brake pad wear sensors. C2D2976 and similar. Hoorah for Google!