sjr202 · Apr 17, 2024

Hi
I’ve a 1992, 3.9 V8 auto RR classic, it had its head/cams etc rebuilt a couple of years ago, I brought it out of winter storage last week and it seems to have a tapping noise under load which increases intensity with loaded engine speed. It’s smooth and silent when idling, also when cruising at any speed, this is only when under moderate to heavy throttle, eg acceleration or going up a hill etc.
Could it be injectors? Oil feed issues or the fact it’s sat for a few months? Had a good 100 mile round trip and it didn’t change, has fresh tank of super unleaded.

Thoughts appreciated.
Simon

AllanWorms · Apr 18, 2024

Check for an exhaust manifold leak. They are loud under higher loads, but can be competely quiet at idle.

I use a stethoscope, with a long stainless tube on it, and can hear the leaks plain as day.

sjr202 · Apr 18, 2024

AllanWorms said:
Check for an exhaust manifold leak. They are loud under higher loads, but can be competely quiet at idle.

I use a stethoscope, with a long stainless tube on it, and can hear the leaks plain as day.

Thank you @AllanWorms I’d not considered that. I’ll investigate

kermit_rr · Apr 18, 2024

A loose plug can tap, but I'd expect that all the time

sjr202 · Apr 22, 2024

Sent a video to the chap who normally fixes my LR's and he thinks manifold or manifold/downpipe gasket. Thanks again guys for the help

Ratae · Apr 23, 2024

As it's only under 'moderate to heavy' acceleration or under heavy load another issue could be ignition timing - too advanced - & that's what you're hearing.
Be interested to know the result.

kermit_rr · Apr 23, 2024

Ratae said:
As it's only under 'moderate to heavy' acceleration or under heavy load another issue could be ignition timing - too advanced - & that's what you're hearing.
Be interested to know the result.

Depends on what is meant by tapping.. it's a very generic word! A link to the video would help

sjr202 · Apr 24, 2024

kermit_rr said:
Depends on what is meant by tapping.. it's a very generic word! A link to the video would help

I tried to upload the video but seems it needs a link not an attachment. Happy to with any suggestions of how/where?

marjon · Apr 24, 2024

sjr202 said:
I tried to upload the video but seems it needs a link not an attachment. Happy to with any suggestions of how/where?

Doing it via U tube works.

J

norseman · Apr 24, 2024

Referring back to the original post, the first question I would ask is did the car travel any distance prior to the 'tapping' or was it from first start-up after storage?
Always assuming it doesn't turn out to be non-mechanical (ie gasket blow/timing etc.) is the sound commensurate with crankshaft or camshaft speed?

nb: with any engine faults I always ask .. was it running ok prior to the problem(?) as the answer can rule in/out many possibilities.

sjr202

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AllanWorms

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sjr202

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kermit_rr

Very

sjr202

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Ratae

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kermit_rr

Very

sjr202

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marjon

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norseman

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