Random thudding - one time only so far

[rgallant]

This one is very weird, I was doing a alternator load test and oil pressure check, my battery has dropping voltage. The alternator is fine.

• Everything was going along fine excellent oil pressure 30-25 psi hot idle (no drive).
  As I was starting up accessories and checking my multimeter, I noticed a "thud/thump" as I got out of the cab. It is hard to describe but did not sound metallic, and seem to come for everywhere at the same volume
  Brought the engine rpm up, no real change in speed or sound
  Shut down
  Did some research on liner and rod knocks - none sounded right
  Fired the Disco back up to record the noise - nothing just my little exhaust leak and some rocker chatter
  Re-did the testing thinking I could duplicate the noise nothing - the rover gods laughed and laughed

The sound was like 2 solid objects sounded sort of like an axe hitting damp wood kind of thud

Any suggestions or ideas, engine temp was at about 183 F runs fine no codes at least so far. So far in 2 restarts running up to temp nothing

[landcrabmechanic]

Sounds maybe like detonation? Or backfire?

[rgallant]

@landcrabmechanic I had not thought about detonation being off, I would have thought I would have seen a stutter and CEL with code. But I wonder if it could have been exhaust/cat related.

[rgallant]

@landcrabmechanic thanks for that comment. I found a description of the sound on another forum and seems to be exhaust/fuel related. Now I know where to start looking, it may have been a one time issue but at least I can check cats and long term fuel trims and plugs if required.

[landcrabmechanic]

Could also be caused by your exhaust leak. Allowing extra oxygen into the exhaust system and wreak havoc.
I would suggest repairing all pre cat exhaust leaks and try again. Will more than likely solve this problem.

Sent from my BBB100-1 using Tapatalk

[rgallant]

@landcrabmechanic yup exhaust is the plan for tomorrow, it also occurred to me I had been hitting all the bolts and nuts with WD40 as prep so I may have introduced some into the exhaust system.

[rgallant]

Small update

So I undid and re torqued the right side y pipe connection, the driver's side need more penetrating oil they are locked up solid.

Checked everything and fired her up the

Videos below is what she sounds like, there is a concrete 1/2 wall to the left so a bit of sound reflection, also there was a almost rattle sound for about 4 minutes until she completed heated up - I have not tightened the intake or exhaust manifolds yet :

Cold start



Up to 150-160 deg just before heading out



After the drive 188 - 186



As far as I can tell other than a bit of tick at idle she is running fine

[rgallant]

Small update

So did the old shop vac in the tailpipe test the drivers & passenger side Y pipe connections are leaking.The driver side is almost 50% of the way around, and significant air the passenger side less so.

Using exhaust system paste externally to seal it up and see if the tick disappears or lessens as a start, it will need a proper repair.

This also likely explains the thud, I hit that area with a lot of wd40, which likely got into the system via the opening and ignited when the temp got hi enough which is why it never re-occurred, That would have also further damaged the y pipe gasket

[rgallant]

Final update no more rapid tick, there is is still a tiny bit noise but it nothing like it was, I am taking this as win.

I did do a oil pressure test just in case as the paste needed the engine to run for 10 minutes to set up

Idle at 720 dropping to 660 once warm
52 psi at cold start
36 psi at 172F
30 psi at 183F to 186F
52 at 2000 rpm 181F
returning to 30 once rpm drops to idle

Note these are cold to warm numbers I need to to take the Disco for a run and expect a 10-15 psi drop at idle

[ANDYD]

Hey Richard,

Congrats for finding and curing the V8 "tick", you will be able to give it a test good run on the weekend :bounce:

After owning a clattery-rattley LR diesel for a few years, all V8's seem extremely quiet, even with a few ticks and thuds :wink:

cheers
Andy