idle revs knocking noise

[jonathant]

Trev is going back in anyways but I'm after ideas....

[b]Just[/b] got Trev back from a service, everythings great and running fine except we've now gained a new relatively quiet knocking noise.

Only seems to occur when the engine is warmed up and only when idling or near idling. Doesn't matter if in gear or not, and clutch in or out.

thoughts?

[mark atherton]

My Griff 500 is doing something similar, but intermittently. Been in to the garage but they couldn't decide what it was. Will keep running it until gets worse, perhaps then they will be able to tell.

[jonathant]

hopefully before something important falls off! shame really, it's sounding great, until I pull up and get some gremlin banging on a bit of wood!

>> Edited by jonathant on Wednesday 21st September 10:33

[jonathant]

Well I had three mechanics under and around my car today listening out for the elusive knocking sound. It only happens when idling and there's no load on the engine - even the cooling fans being on will stop the knocking.

They suggest it may be "camshaft slap", something to do with the camshaft being allowed to float front to back. There's a fix which fits a modified bracket to stop the camshaft from moving around but involves removing the front of the engine.

Thoughts?

[HarryW]

jonathant said:

....They suggest it may be "camshaft slap", something to do with the camshaft being allowed to float front to back. There's a fix which fits a modified bracket to stop the camshaft from moving around but involves removing the front of the engine. Thoughts?

Agree, I understood that the float was removed on the later cars by an additional step on the cam shaft shoulder and clamp gizmo on the front of the block. However as a 99 car I would have thought yours would have been fitted from new .
I'm sure someone will be able to say what date/engine serial number it was 'standard fitting' from the factory.

Harry

[GreenV8S]

Is it defo coming from inside the engine and not just the exhaust knocking on something? It does get quite close to the engine and chassis in some places.

[parrot of doom]

Engine mounts?

[jonathant]

FWIW the guys had their heads in the engine bay and the car on a ramp for a good quarter of an hour. They also had their high tech stethoscope and a bit of pipe out.

I presume this rules out the exhaust knocking? I'll ask about the engine mounts.

[Frogeye3]

I have a intermittent knocking on my TVR Chim when my engine is at 90 deg and is idling as soon as i rev it up a tad it goes off the oil pressure is normal at tick over and at 3000 rpm engine the engine came out about 3months ago to release a seized bolt on the E manafold i have tried the clutch in and out still the same
the cam sound fine when running over idling speed I notice a slight misfire under load and when cold ( under 70 Deg ) the rev counter jumps around
I have 2 Mech locally look at it and the jury is still out !

Any ideas

[Belle427]

What size is the engine?

[Frogeye3]

4 ltr

[Belle427]

Blowing gaskets can mislead and sometimes sound like a hydraulic lifter knock, worth checking these first.

[Frogeye3]

only makes the knocking noise at tick over and only now and again as soon as i rev up it doesnt do it

[Belle427]

Difficult to guess at really without hearing but maybe a lazy hydraulic lifter?