We were slightly off mission today and got distracted by a "cheap" XJS that was advertised locally.

The owner said it ran but made a "ticking" noise....


Neither myself nor smgdata had heard this particular sound from a V12 before......

Unfortunately on closer inspection it appeared to have a broken timing chain tensioner. We could wiggle the timing chain about an inch with a screw driver through the oil filler cap.

Just wanted to get feedback if our diagnosis was correct ?

 

Sounds like a loose chain. That chattering sound is a typical loose chain sound.

I think best way to determine a broken tensioner would be to pull the front rubber bungs and stuff a little cheap endoscope camera in there.

 

Spot on.

The quietening on acceleration, and the clatter on overrun are the key.

Have fun.

 

In a 5.3l V12 engine, will the valves hit the pistons when the timing chain fails?
Rumor has it that this is how XK8 (AJ26) engines tend to die.

 

Ok, thank you team.

Pity..... The rest or the car was actually pretty good, but just too many things going on right now.

I know the AJ26 is an interference engine (valves collide with cylinders if timing is off)..... Good question about the V12........ anyone?

 

HE, I seriously doubt it.

The flat head PreHE, not sure, it would be tight.

 

Rumor? No... Real life. All AJ26 and AJ27 until August 2001 will die if not treated Done it about 19 times since last year!

 

That is weird, as technically then a new chain fitted wouldn't be that expensive compared to if the valves smash into the pistons. But I have read about valve damage on some V12s. Just not sure if HE or flat head...

Anyhow... I'll then drive like an old Volvo red block owner. Until the chain/belt snaps... And then simply fit a new one

 

The valve noise you are remembering is when the HE drops a valve seat from massive overheating. Generally mashes itself into a pulp, then the head of the valve parts company with the stem, and the piston becomes a very LO comp version.

The preHE did not have that problem that I have ever come across.

Drive it like ya stole it, the only way to keep a V12 running proper.

 

AH yeah that was it! Valve dropping.. Cheers Grant! Once I get my V12 running again, I'm out for a fun day hooning. I have been told the V12 likes to be held up in the upper third of the rev counter

The last drive I did in mine before taking it apart was to go to a tunnel and just toe it! 1st gear and wellies! Oooooh did that sound nice! There aren't many tunnels here, so I went to my nearest one late at night... Mmmmhm delicious!