Very metallic clatter from engine >1700 rpm

[pmansson]

Here?s a hard one:
completely rebuilt engine with a few hundred miles on it. A
very audible, by engine bay, and inside when driving,
clattering noise which I cannot detect the origin of. I
have used a stetoscope and listened to the servo pump,
generator, water pump, exhaust system, and cam covers plus
the valley of the cyl head. All tests above 1700 when the
clattering kicks in. A very metallic sound. And when
listening with the head inside the engine bay, one can hear
it on both sides and towards the front. Probably
reverberating from the source of origin, where the noise
just wanders around.
Has anyone come across this before? One nearby Jaguar
workshop had not, and could give little clue besides
removing the fan belt to try and eliminate generator and
water pump. I have not done this yet.

[abowie]

It's hard to diagnose engine noises based on descriptions.
I'd do what the mechanics suggest and see if you can eliminate it that way.
I'd also re-tighten the top timing chain.

[christopher storey]

As Andrew says - also could it be a loose silencer baffle ? or even a downpipe touching part of the frame ?

[Moeregaard]

As Christopher says, check for culprits outside the engine first. If the rear engine stabiliser is pulled up too tightly, it's possible for the downpipes to rattle against the torsion bar, particularly if the engine mounts are past their prime. I really don't want to suggest anything internal without hearing it firsthand, but I suggest going around the engine with a stethoscope.

[paulsco]

Could it be coming from the timing chains?

I've been looking into the replacement hydraulic tensioners that are currently available and it appears they can be prone to failure.

Paul

[abowie]

If the rear engine stabiliser is pulled up too tightly, it's possible for the downpipes to rattle against the torsion bar

I have had this experience. The noise was so awful I was convinced something had let go inside my newly rebuilt gearbox.
To check this remove the nyloc nut and slacken the adjuster off until the stabiliser is completely loose.

[Robert Hiland]

Before opting for major surgery, check the following externals:

-carb overflow pipe hitting air filter canister or frame rails
-exhaust pipes and heat deflectors
-mud shields and stone guards
-loose air canister

One last thing. If it sounds like a monkey rattling a can of bolts, remove the monkey.

Bob

[malcolm]

leave the monkey alone; just take his can of bolts!

[pmansson]

I raised the question on the JagLovers forum as well, under XK engine, and the most likely source seems to be the timing chains, where a damper could have come off. More specifically, one guy suggested one of the upper chain?s dampers, as the cyl head has recently been overhauled, whereas the bottom end of this 45k mile engine looked too good to touch.
The car, a Mk9, is going back to CMC shortly, and I will share the outcome on the boards. It could be another case of modern, poorly manufactured parts.....
Peder

[james-t]

Hello pmanson, when i first saw your post i thought another devastated jag owner who like myself had my 4.2 e-type engine rebuilt only to discover what i refer to as a cam train chatter which comes in at 2200rpm and remains through the rev range. Interestingly,t the engine is quiet on initial start up but within say a couple of minutes the chatter comes in. Like you i have checked all the items suggested by the contributors and despite having the cams out on three occasions and checked all the components including replacing the cam followers with slightly longer ones the chatter continues.Today i spoke with VSE and was informed that the cause of the chatter was worn tappet guides and even replacing new tappets would not prevent the chatter. The solution is for the head to come off and the guides machined and oversize followers to be inserted . I mention this in case when you have adjusted the cam chain your problem persists it could possibly be worn tappet guides. Best of luck James