isolating annoying vibration/bellowing noise

[Knucklehead]

Hoping somebody can give me some idea how to narrow down a loud bellowing sound that my 80 is getting.

Hard to explain the noise in text.
I can't figure if it is a vibration as it is more a loud bellowing sound that I first thought was exhaust or maybe manifold stuffed as seems to come from around the engine bay.

Problem is it only happens at 1100rpm with engine under load (just about the point the green turbo light shows).
There is no noise below/above that rev and can hear nothing with the 80 rev'd at standstill.

I've had a good look over and can see nowt. Exhaust is sound, no loose panels, Ujs feel good...

Apart from strapping myself to the chasis as the misses drives, I am struggling to figure out how to sort this racket.

Any thoughts appreciated.

Dave.

 

[Shayne]

Leak in the intake sounds very likely had me thinking the manifold heat shield i had recently replaced was catching air and vibrating to make a noise similar to a wine glass resonating .

 

[clivehorridge]

Could be the flexi-pipe on the exhaust (if the HDJ has one that is).

On my HZ in the early stages of failure, the flexi section only made a row at certain revs, until it dropped off altogether.

 

[Knucklehead]

Cheers fellas. I'm starting to think engine related as the exhaust including the flex is in good nick.
Pain in the ass to isolate as only happens at 1100rpm under load, not above or below it.

Did notice white powdery type deposit on one of the rubber water pipes that run near the manifold heat shield.
Can feel no hot gas near it but maybe with the engine under load it all could change.

Think a minor strip down is in order.

Dave.

 

[Shayne]

Same as mine no noise until the turbo came into play , it was sucking air in rather than blowing .

 

[Knucklehead]

Yeah Shane, sounds similar. What was your fix in the end?

 

[Julian T]

I had a exhaust rubber mounting fail midway down the exhaust and that had a similar effect to what you are describing.

I doubt that you have a mechanical failure of the engine and suggest rather checking the air inlet, exaust and related systems.

If it is a sound that is always present them I would suspect engine or mechanical fault.

 

[Knucklehead]

Thats true Julian. Guess if mechanical as you mention it would show up more than that at 1100rpm as the turbo is still kicking above that and there is no noise. Even though sounds like coming from engine bay, a vibration could travel.

Will give the mounts a good look over again.

Cheers again guys.
Dave.

 

[Shayne]

Mines a 90 remember but after refitting all the intercooler and airbox pipes , while on the way to Romania , i eventually worked out in Germany somewhere on the return trip that my pcv pipe had split where it vents into the intake . I had cured the noise but not the problem while fiddling with pipes at my first service station investigation .

 

[Knucklehead]

No worries Shane. Appreciate the pointers.

Dave.

 

[Shayne]

I could boost past the ... howl for want of a better word

 

[StarCruiser]

Have you put a K&N air filter in it by any chance? I put one in and couldn't stand the noise so took it out. Plus it made my vibration worse.

 

[clivehorridge]

Dave, can you record the sound?

It would be interesting to hear it.

A short video (with sound) would do, and you could pull faces at us as you go...

 

[Knucklehead]

No, all standard in the engine bay. Will start with the simple stuff like exhaust and go up from there.
Maybe if I could find a company with a rolling road then could get the rev with the engine under some sort of load and hear were it is.

Wish whatever it is would drop off/break and then I would know for sure!

Cheers
Dave.

 

[Knucklehead]

yeah Clive, good idea. If nothing obvious shows up when look again at weekend then I will capture it. Not hard as bloody loud enough.

 

[StarCruiser]

Wish whatever it is would drop off/break and then I would know for sure!

Now if it were a Land Rover I'm sure it would oblige you of that within a week or two. Seeing as it's a cruiser, nah, it'll carry on through like the Black Knight in Monty Python's Holy Grail!

 

[Knucklehead]

Yeah they are tough old goats. Over engineering seemed to be thought of the day when they designed them.
Have to wonder at well over 200k miles, when will it stop being a reliable daily driver.

Then again, it might outlast me....

 

[Dave2000]

I had two vibes now down to one, the first was from the junction on the bulkhead where the heater 'T's off for the rear heater. The pipes had been disconnected prior to my ownership, no noise during revving but under load one was just touching the bulkhead and drove me nuts.

The second is one of the thin bars that operate the lower tailgate locks, I will sort that very soon!


regards

Dave

 

[frank rabbets]

Could be intake resonance. That happens at about 1100 rpm on the 24 valve at least. If something has come undone on the air box or inlet air tract it could be making it sound a lot worse.

Also you could open the throttle on the throttle linkage with bonnet open to try and pin it down.

 

[Knucklehead]

Thanks for ideas fellas.
Its all work and no play at minute so had no time to try out suggestions.

Will have a good look around the firewall/air box/inlet as could well be something like that.
Pain in the ass only happens when engine under load, head stuck in the bay revving engine and nowt, silence(apart from the normal precision 12v tractor engine sounds)

Cheers,
Dave.