P38A tapping/knocking noise

kermit_rr · Sep 27, 2020

Hi all, I've mentioned this elsewhere but it's now getting worse and think it deserves its own thread.
I originally thought it was coming from a tappet or rocker, but seems louder underneath, I've not been under with a listening stick but at a guess, I'm wondering if it's not engine noise at all, but traveling from elsewhere.
What does a dead/dying flexplate sound like and could that be temperature dependent? Is there anything else, gearbox related that could tap/knock?
I've looked round YouTube and hear all sorts of noises, from tapping like mine, to rattling!
Cheers

Marshall8hp · Sep 27, 2020

Mine had that, once warmed up. You thought the engine was going to fall out. Turned out to be the LHS cat's innards falling apart. The rattle was transmitted up the pipe so it sounded like it was coming from the cylinder head area of the LH bank.

Henry_b · Sep 28, 2020

drop the inspection plate off the bottom of the bell housing and shine a torch in, a broke flexplate is easy to spot.

Tappets and/or rockers/shafts are the usual culprits

A video would help.

Grrrrrr · Sep 28, 2020

Heatshield under the driver's seat?

kermit_rr · Sep 28, 2020

It's too mechanical for a great shield or other rattly bit. If o get chance today I'll do a new video

Karlos the jackal · Sep 29, 2020

kermit_rr said:
It's too mechanical for a great shield or other rattly bit. If o get chance today I'll do a new video

is yours petrol or diesel

RangeRoller dt · Sep 29, 2020

Never seen either

He always runs it on LPG

DanClarke · Sep 29, 2020

RangeRoller dt said:
Never seen either
He always runs it on LPG

Ahhhhh.... dropped liner then ;-)

kermit_rr · Sep 29, 2020

I've not run it on lpg in years! And not since the replacement engine

falconho · Sep 30, 2020

kermit_rr said:
I've not run it on lpg in years! And not since the replacement engine

Hi had similar last year was head gasket blowing externally on drivers side, thought it was manifold initially no such luck lol, hopefully yours is something more simple

kermit_rr · Oct 4, 2020

Henry_b said:
drop the inspection plate off the bottom of the bell housing and shine a torch in, a broke flexplate is easy to spot.

Tappets and/or rockers/shafts are the usual culprits

A video would help.

Finally got to make a video from underneath! Taken a while because it doesn't always do it. Only ever when it's hot and more often when it's in gear, but sometimes when it's in neutral or park

Henry_b · Oct 4, 2020

Christ..

Do it subside if the revs are raised?

kermit_rr · Oct 4, 2020

Henry_b said:
Christ..

Do it subside if the revs are raised?

Yes it does, sometimes you can hear it at 1500 revs, other times it goes completely. Sometimes a quick blip of the throttle gets rid completely at idle.
When i was trying to get a recording, took me ages, I'd stop, no noise, in gear no noise! Drive a bit further and eventually started again

Henry_b · Oct 4, 2020

kermit_rr said:
Yes it does, sometimes you can hear it at 1500 revs, other times it goes completely. Sometimes a quick blip of the throttle gets rid completely at idle.
When i was trying to get a recording, took me ages, I'd stop, no noise, in gear no noise! Drive a bit further and eventually started again

Sounds like a dry follower to me..

What oil you running in it?

Henry_b · Oct 4, 2020

kermit_rr · Oct 4, 2020

Valvoline vr1

Henry_b · Oct 4, 2020

kermit_rr said:
Valvoline vr1

You have good oil in it..

Oil pressure check or a strip down will usually highlight any issues!

When it starts to sound like this is when you have issues.

kermit_rr · Oct 4, 2020

It's only a single tap, my logic says if i had low or no oil pressure, I'd hear all the lifters tapping? So more likely a single dead lifter?
I initially thought it was a lifter all those weeks ago but didn't want to strip down, new cam, lifters etc if it was something else

Henry_b · Oct 4, 2020

kermit_rr said:
It's only a single tap, my logic says if i had low or no oil pressure, I'd hear all the lifters tapping? So more likely a single dead lifter?
I initially thought it was a lifter all those weeks ago but didn't want to strip down, new cam, lifters etc if it was something else

Yep I do an oil pressure check as a precautionary measure, rather easy with the kit..

A strip down and inspection of the rockers/shafts tappets and cam would highlight any issues.

kermit_rr · Oct 4, 2020

I did try to put an oil gauge on but there was no chance of taking the oil pressure switch out without major upheaval!!

P38A tapping/knocking noise

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