What's this noise - can anyone help?

[cgm]

Hi All, I've got this really annoying noise that I can't pin down.

It's a high ringing sort of noise, like it is making the guard around the exhaust manifold vibrate or something similar, but I just can't quite work it out. There are a few specifics:

• Only there between 1000-1250 rpm
• Seems to only be there after the vehicle comes up to temp
• Have heard recently a couple of times as it was being started, but then not again until warm
• With aircon on it sits idling at about 1000 rpm and catches the noise, for example at the lights

It is a 4800 Petrol, GU, 2001.

Seems there is something causing it to "resonate" just at those revs. So the noise might not even be coming from the source of the problem (e.g. a bearing might be a bit knackered and that vibration is causing something like the guard around the exhaust manifold to vibrate).

Had a few friends and also mechanics look at it. Hard to even tell exactly which area the noise is coming from. One guy was trying to convince me it was a stone rattling in guard around the exhaust, but it's not that.

Had a thorough look with another mechanic. He had a nice commercial "stethoscope" with a long rod on it. Stuffing around touching everything you could find I was convinced with him that there was a bearing type noise coming from the power steering pump. He had it out and sent to someone - they "cleaned it", but reckoned there was nothing wrong with it. We thought it was still coming from there and that they were hopeless. Off to the wreckers and got another one (a whole other cross-cultural experience that is here - I don't belong down there and can't avoid the "white man" tax!!). We put it in and the noise exactly the same. So, there was nothing wrong with the power steering pump!!

So, in the end all the belts came off (including to water pump). So no belts on at all and noise is still there, so that rules out alternator, aircon compressor, etc.

We had a long discussion and he took it to some other contacts to discuss things like timing chain. Everyone reckoned timing chain related issues should be there throughout the rev range (maybe to different noise levels, but at least detectable). In the end he gave up and went back to being a Land Rover mechanic. LOL

Above and below those rev ranges the engine is smooth. At normal idle it is smooth. The car is still driving and running fine. The noise is getting louder though - I think in my head!!! It's really starting to do my head in that we can't easily work out what it is.

Maybe it's just something loose somewhere and nothing more.

Any ideas anyone? Anyone come across something similar?

I've tried to record it, but it's hard to get a good recording with all the background noise. I tried to tweak it a bit to lower the background frequencies. In the recording it's idling without noise. Then I put the aircon back on and rev it slightly to the get the idle to sit back at 1000 rpm. About half way through the recording you can hear the noise come in.

Hopefully someone is going to steer me in the right direction.

Thanks,
Cameron.

[Col.T]

Cameron,
only had diesels. Loved the record, sounds just beautiful, almost like grinding metal.
Your mate with the stethoscope or just plain shoving a bar or similar against absolutely every part should show something up. Shouldn't it?.
Sure it IS in the engine bay?
Haven't made any mods lately?
Sorry I can't be of more assistance,
good luck
Col

[cgm]

Thank Col for taking the time to reply. It's definitely in the engine bay. I reckon it is probably related to the guard around the exhaust manifold. The recording is really hard to get across the noise compared to hearing it in person. I was kind of hoping that just one person might hear it and have had a similar thing in the past. Let's see. Our discussion will give it a bump and someone else might recognise something.

[Bigcol]

cgm, that recording, were you stationary? or moving?
if it is happening when stationary, as well as when moving, you can cross off wheel bearings and loose stones in the brakes

my thoughts would lean towards something in or around the Flywheel area........????

get yourself a LONG long long handled screwdriver (or a stethoscope) and do what your LR mech was doing, just place it on the casing or outside of anything and stick the handle bit in your ear
around the front of the motor - for timing chain
around the back of the motor for noises from clutch / auto trans

anywhere that has moving parts - BE CARE FULL where you put your hands and the screw driver

but you WILL hear it eventually.

I hope you find it is an easy problem to sort.

cheers

[Bigcol]

also, does it have coil packs or a distributor?

[threedogs]

Not exhaust leaking from the block, just throwing stuff out there.

[Col.T]

Cam
I like Bigcol's post. Obviously we're genetically related
If it IS that guard I'd certainly expect pressing really hard against it from several different directions whilst running would HAVE to make a discernable difference to the noise.
Hang in there,
Col

[cgm]

cgm, that recording, were you stationary? or moving?
if it is happening when stationary, as well as when moving, you can cross off wheel bearings and loose stones in the brakes

my thoughts would lean towards something in or around the Flywheel area........????

get yourself a LONG long long handled screwdriver (or a stethoscope) and do what your LR mech was doing, just place it on the casing or outside of anything and stick the handle bit in your ear
around the front of the motor - for timing chain
around the back of the motor for noises from clutch / auto trans

anywhere that has moving parts - BE CARE FULL where you put your hands and the screw driver

but you WILL hear it eventually.

I hope you find it is an easy problem to sort.

cheers

Bit busy today, didn't get back to it. Will close these out before I head to bed.

Yeah, haven't really focused on the flywheel area, other than to push the clutch in and out to make sure that doesn't affect anything (which it doesn't).

It's definitely nothing to do with moving and there when stationary. But that also means I can get under as well to have a good listen to things from the bottom, just to see if it sounds different from down there!! The stethoscope/screwdriver approach I was expecting to help, but I was so convinced when we had it on the power steering pump and that was definitely a red herring. It's a manual and I assume it doesn't have a distributor, not 100% sure, funny that how things you thought you know when asked directly ... It won't have a distributor.

I haven't been back to a methodical approach the last couple of weeks. This weekend I'll have to start afresh and try and listen all areas again. Definitely work coming from the bottom and including the flywheel area.

I also think Col. T's other suggestion warrants a bit more effort on my part - the pushing around on the guard. Initially I had mostly been asking others to do the listening, suggesting, prodding, etc. The guy I was working with was good to the point of getting the belts off, etc. and ruling out all those moving bits. I've been a bit hesitant/lazy in that it is only there when it gets up to temp and poking around in there while it is hot inside and out isn't pleasant, but if I want to solve it.

Coz I'm still suspicious of that guard I will have to harden up and get something to poke around and put a good bit of pressure on that to see if I can affect it. I've got a good, very mechanically minded friend from Croatia I chase him up before he goes on vacation at the end of the week and try and have another round with all the latest suggestions.

TD I think the exhaust leak is a very valid point, especially around that guard area. Originally that is what I thought it was as it also had a leaky manifold noise and I thought they started about the same time. I'm getting a bit old now and details in the memory department are not all what I dream they used to be (probably never were, but anyway). Both the exhaust manifolds were replaced and the noise is still there. Also would have thought that was when the guard would have been tightened, etc. I don't think that is an issue as when that noise is not there there is no other noise at all - really smooth at lower idle and above that range.

Thanks guys for taking the effort to post, if nothing else it gives me a bit of motivation to go back and try again.

[cgm]

Bit busy today, didn't get back to it. Will close these out before I head to bed.

Yeah, haven't really focused on the flywheel area, other than to push the clutch in and out to make sure that doesn't affect anything (which it doesn't).

It's definitely nothing to do with moving and there when stationary. But that also means I can get under as well to have a good listen to things from the bottom, just to see if it sounds different from down there!! Haven't done that yet. The stethoscope/screwdriver approach I was expecting to help, but I was so convinced when we had it on the power steering pump and that was definitely a red herring. It's a manual and I assume it doesn't have a distributor, not 100% sure, funny that how things you thought you know when asked directly ... It won't have a distributor.

I haven't been back to a methodical approach the last couple of weeks. This weekend I'll have to start afresh and try and listen all areas again. Definitely worth coming from the bottom and including the flywheel area.

I also think Col. T's other suggestion warrants a bit more effort on my part - the pushing around on the guard. Initially I had mostly been asking others to do the listening, suggesting, prodding, etc. The guy I was working with was good to the point of getting the belts off, etc. and ruling out all those moving bits. I've been a bit hesitant/lazy in that it is only there when it gets up to temp and poking around in there while it is hot inside and out isn't pleasant, but if I want to solve it. One of his mates who was supposedly a "Patrol" man was focused on cleaning up the butterfly valve and air intake after the MAF. Not sure why that was. The day I picked it up it almost seemed like he had it coming in at a lower rev range, but now I'm not sure if that was really happening ... ha ha These mechanics I've been working with here are mostly Filipino guys, but I think some of them have some good experience. There are a lot of Patrols on the ground here (although small as a % of Land Cruisers).

Coz I'm still suspicious of that guard I will have to harden up and get something to poke around and put a good bit of pressure on that to see if I can affect it. I've got a good, very mechanically minded friend from Croatia, I need to chase him up before he goes on vacation at the end of the week and try and have another round with all the latest suggestions.

TD I think the exhaust leak is a very valid point, especially around that guard area. Originally that is what I thought it was as it also had a leaky manifold noise and I thought they started about the same time. I'm getting a bit old now and details in the memory department are not all what I dream they used to be (probably never were, but anyway). Both the exhaust manifolds were replaced and the noise is still there. Also would have thought that was when the guard would have been tightened, etc. I don't think that is an issue as when that noise is not there there is no other noise at all - really smooth at lower idle and above that range.

Thanks guys for taking the effort to post, if nothing else it gives me a bit of motivation to go back and try again. I'll update later in the week.

[Col.T]

Cam,
the good thing is that you're not alone with the blanks spaces in the memory dept. thing. The really bad news with that though is when you think you've remembered to do/test everything in a totally logical order, after running the full test programme you can't quite remember if you did, or didn't do it all in order or even actually what the full programme was .
Bummer!
Be strong, hang in there
Col