[xj40] Knocking noise

I have a knocking noise from the engine area even while the car is
idling and not in motion. It happens about twice per second on idle
and speeds up a little when the accelerator is depressed. I seem to
be able to feel this if I keep my foot on the brake pedal whilst
stopped. Any ideas on this one please.–
bassbandit
St Austell / Cornwall, United Kingdom
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In reply to a message from bassbandit sent Sat 1 May 2004:

What year / model of car?

Be more specific - the engine area is pretty large! Can you isolate
it to a more precise area - even using a mechanics stethoscope (or
a long screwdriver pressed to your ear and t’other end placed on
the suspect area)–
The original message included these comments:

I have a knocking noise from the engine area even while the car is
idling and not in motion. It happens about twice per second on idle
and speeds up a little when the accelerator is depressed. I seem to
be able to feel this if I keep my foot on the brake pedal whilst
stopped. Any ideas on this one please.


Bryan N ('91 Sovereign 4.0 L)
Cambridge, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–

Visit the Jag Lovers homepage at http://www.jag-lovers.org for exciting services and resources including Photo Albums, Event Diary / Calendar, On Line Books and more !

Hey mate, did you ever figure out what the issue was with the knocking? I’ve just purchased an XJ40 and it’s got the exact same issue.

(sorry for bumping a 16 year old topic)

Cheers

It might be the return fuel check valve. It makes a tock tock tock sound and is easily fixed.

Thanks Graeme, I’ll check that one out.

Also known as the helicopter noise :slight_smile:

Ah, I saw that in my googling but didn’t think mine sounded like a helicopter. That’s good to know thanks Robin.

Gentlemen …

As Bryan, our beloved Godfather of all things XJ40, sagely stated … “Be more specific - the engine area is pretty large!”.

Please take Bryan’s advice and use a mechanics stethoscope to track down the noise. If you own an XJ40 and you don’t own a $10 (for a really good one) stethoscope you are relieving yourself into a brisk breeze.

1 Like

Unless I’m mistaken the ‘helicopter’ noise is due to.a faulty damper in the fuel feed hose ahead of the fuel pressure regulator, not the non-return valve.

No worries Grooveman, I’ll pick one up tomorrow. In the meantime, here’s a video of the noise if anyone has any ideas. You can’t really hear the knocking sound in the video, don’t think the phone picked it up. But the noise occurs at the same rate that tube is pulsing (the tube with -/- visible from 3 seconds). That tube is connected to the silver girling unit. At about 23 seconds it sounds like the noise is coming from up the front. Dad’s got a hoist and all the gear so we’ll check it out a bit better over the next week or so.

https://youtu.be/z8u3LV4lgPY