V8 Engine Noise

[Robert Crooks]

I have a tapping noise. It isn't there on cold start, but arrives a minute of two after starting. It then disappears when the engine is at full temperature. It's there on acceleration, but disappears on a trailing throttle. It is at a constant speed, ie it doesn't increase as engine revolutions increase. Any thoughts?

[WEllison]

Is it proportional to road speed then? If not, then it has to be independentent of engine or wheel rotation. An electrical motor?

[Robert Crooks]

No it isn't proportional to road speed. Yes, I think it must be a constant speed electrical motor. Just weird that it isnt there immediately on start up and initial drive, it cuts in after a few minutes and then stops when car is fully warm.

[Günter]

is it for sure that it isn't related to 'rpm' ? ..as there would be a possibility of a slightly not tight steering pump, or water pump pulley/wheel !? ... or anything else that is in motion, and gets stressed by a expanding block/engine bay -or temperatures in general.

wheel-bearing , but that again would change on speed ? (road speed for that matter..)

loose exhaust/silence parts -who hit a driveshaft or something on the frame ?

Fit a digital-cam (pocket cam ) on your engine bay -go on a typical drive ..maybe that gives us more impression on what is actually happen with your car..

for verification -with 'trailing-throttle' ..does your engine jump around to much? , as for the change in position on 'pull' & 'trailing-throttle' ...maybe the engine hits something on the bulkheat plate ...watch out for the position of you two main radiator pipes going down on the engine front. ..

[WEllison]

I would have to guess the air injection pump, left rear.

[freshcut]

That would be my guess as well Wayne. It's really the only constant speed motor that comes to mind that is independent of engine speed. Can anyone verify if it comes on immediately after ignition, or if it doesn't kick on until the O2 sensors warm up? If it does wait for the O2's to heat, then that would put it right around a couple minutes after cold start.

[Günter]

does a 2001 GB car have air injection ?

[superdavelotus]

Hi Robert,

I need to hear it first but it could be a number of things depending on noise. I take it this is on a stationary car?

1. If it's a tapping 2-3 a second say the it could be exhaust/manifold blow due to studs snapping or gasket going.

2. If it's once every few seconds then it could be heat shields expanding if a fixing has broken or if it's cracked.

3. I doubt it's sticking tappets as this would increase with revs.

Hopefully I'll get to see you later this week, so I'll have a listen and see what it is.

David

[73JPS]

Hi Guys,

It sounds like I have the same issue as Robert. This is an "un-related-to-engine-RPM-or-road-speed-and-not- unpleasant-to-listen-to" tapping. It arrives like clockwork (just before I arrive at the 9th Line on my winter exercise-the-car route) and is gone within 2 minutes. The tapping tends to last for 5 or 6 seconds at a go, and in the two minutes it lasts I might have 4 to 8 episodes. In terms of its frequency I would say that it is in the 2-3 taps per second range. It has the sound of a loose tappet, but as David has pointed out, it is not: for all of the reasons already stated. It simply has that sort of sound to it.

This is season 2 for my sound, and to be honest, I can't remember if I get it as the ambient temperature warms up. I think I had it from time to time last summer, but not as consistently as I get it in the winter.

Edited March 5, 2010 by 73JPS