Scraping noise when accelerating

[jiri_j]

Hello guys,

first of all: Happy New Year to all of you :-)

Just returned back home from a Xmas trip and when climbing steep curvy roads up from the coast, I experienced a scraping/creaking noise most likely coming from the engine bay. The noise picks up when the engine is under a heavy load - this is when climbing a steep hill on 1st or 2nd gear or when quickly accelerating. I can duplicate the noise easily by accelerating and pushing the brake pedal the same time. I uploaded a short file onto the following link (you can play it in e.g. windows media player, please let me know if you have any difficulties with that): http://rapidshare.com/files/440526982/VOICE018.LGV
The noise I have in mind starts at 10.5 seconds of the recording.

It seams to me like metal to metal scraping noise (a worn bearing ??? or something similar).

I can hear the noise only inside the car. I tried accelerating with opened windows, or with opened hood and a person listening from outside, and there is no way to hear the scraping noise - this is most likely because it is masked by the engine noise. Noise is more frequent when the engine is warm. There is no noise when rewing the engine and the car is steady.

The truck in particular is D2 V8 manual with 165t km. I checked the engine bay, and except a slight head gasket coolant leak (the area around the PAS pump) I haven't found anything. I checked the exhaust manifolds for broken bolts, changed the Y-pipe gaskets, changed spark plugs, changed engine oil, greased propeller shafts, checked pulleys, wheels, nothing worked so far. Note that I have an engine oil pressure gauge, the oil pressure is perfect. Please could you help to identify what might be causing this noise?

Where to start?

Please help!

Thank you all,
regards
Jiri

[catch-22]

something to do with the water pump maybe?

[Discobaker]

Engine mounts?
Exhaust shield plates? The plates welded to the pipes to protect the cats came off one side on my V8, sounded horrible & expensive & it would occur only when the motor was under load.

[jiri_j]

Thank you all for your help!

Based on your tips guys I have done some further checks: I checked the engine mounts and transmission mounts - everything fine here. I went through all hoses and shields in the engine bay and checked exhaust shields, nothing here. I checked the fan for rubbing without success.

It seems to me more and more that the noise is more like 'a worn bearing' noise. As I said I checked all the pulleys, but since the noise comes at higher RPMs and when the engine is under load I am thinking about a further check.

Is there anything wrong if I take out the serpentine belt and try a quick accelaration on a side road without it, when the engine is still cold (like 40-50 'C)? I need 1 minute maximum to drive the truck to simulate the noise. This would confirm/eliminate a noisy pulley. Is this safe to do in terms of the engine temperature?

Thank you again! Hope someone will be able to help :-)

[catch-22]

Nothing wrong with doing that but boy will it be hard to steer :o

[jiri_j]

Nothing wrong with doing that but boy will it be hard to steer :o

Thanks mate, I will pick a straight side road. No need to use steering at all :-) I will report the results soon.

[Fluids]

Check your front tailshaft universal/DC join at the transfer case ...

[trev]

Sorry! sounds obvious I Know,but have you looked at your brake Pads?

Trev.

[jiri_j]

Thank you guys. Just a quick update: The noise is getting worse and more frequent. I have done further checks and found out that the noise is not related to the driveline and transmission. Will check the pulleys again even though it was the first thing I did. It is very confusing since the noise appears at a high engine load only.

[dutchviking]

Could well be your viscous fan on its way out. Or its bearing in the front cover.

[firstdisco]

Hi Jiri, I put up with a similar frustrating noise which took me almost a year to find. It sounded like a worn bearing. Mine came in at 2200 RPM (seems to be a bad range for TD5s).
My so called expert Land Rover dealer at the time assured me it was the flexible link in the exhaust, and it cost me over $600 to have it replaced. You guessed it, the annoying noise was still there, from the engine bay area.
I could never simulate it at standstill, only on the move, and going through 2200 RPM, after which it would go away.
I got a mate of mine to stand on the side of the road as I drove past, and he said it appeared to come from the wheel bay area.
Off with the wheel and presto, I find the disk protector plate was just touching the caliper. It would develop a harmonic vibration as it rubbed against the caliper, and that was the noise. A screwdriver under the plate to bend it slightly away from the caliper and it has been quite as a church mouse now for a couple of years.
I hope yours is that simple to fix.
Regards, FirstDisco

[jiri_j]

Thank you again for your help, guys. As I wrote already, the scraping/grinding noise comes at a high engine load only. After two weeks, when it appeared the first time, I can simulate the noise even without driving the car. Just apply brake and throttle (I have a manual transmission so it is a bit tricky :-) and after 2200 rpm it comes. A 'worn bearing' noise. So now I know that the noise is not related to the actual movement of the car and must come from the engine bay - most likely a pulley. I removed the fan and drove the car without it, noise still there. I checked all the pulleys, and there is a bit free play at the water pump. However, when turning the water pump pulley (even with some force), I didn't hear any noise. All other pulleys look solid.

Any advice what to do now? Just change the water pump and see if it cures the problem? Any other tests I could do?

What is the chance that the noise comes from the main shaft bearing? Is this a frequent thing? Any check I could do myself?

[dutchviking]

The belt tensioner is known to wear. Easy and cheap to replace.

[foss]

i have exactly the same issue...it is the same noise & symptoms, although the disc shield sounds worth checking...i just turn the radio up now :D

[jiri_j]

Update 2: today I changed the water pump, and the noise is still there!!! Now I am getting into troubles https://www.aulro.com/afvb/images/imported/2011/01/926.jpg

I drove the car without the belt for a few seconds and I could hear the noise! This means that it is not related to any pulley, and the noise comes definetelly from the engine. Note again, that the noise is still there when braking and accelerating, without the actual movement of the car (transmission and drive train can be excluded).

What could be wrong? Main bearing? Please help!!!

I also observed that the engine is twisting to the right (when sitting inside the car) when under load. If the engine rubber mounts get soft during time and hence the engine is twisted more then usual, do you think that this could result in this grinding noise?

[catch-22]

Have a read of this article before continuing.....sound like what you have

www.discovery2.co.uk / Crankshaft pulley* / TV damper replacement (http://www.discovery2.co.uk/CrankPulley.html)

[jiri_j]

Thanks catch-22. I checked the crankshaft pulley and it is rock solid. I think that for V8 it is of a different design than TD5.

I am also thinking, if such a noise could be caused by timing chain. I changed it 50t km back though. Any thoughts???

[Sully]

Sounds very frustrating mate.

You've mentioned you checked the manifold bolts, was this at engine level or where the manifolds meet the exhaust system pre-cat?

In either case, check that your manifold bolts are tight on the engine block, they can come loose, especially close to the firewall.
Get under the car and check that the nuts/bolts on the flange securing the exhuast system to the manifold are tight.
These often come loose and create all sorts of horrible noises that sounds a lot more expensive and scary that it actually is.
If they are loose, chances are that the gasket in the flange has blown out and needs replacement.
Be wary though, these nuts/bolts often freeze up and have a tendancy to snap off instead of being tightened or loosened. Replacements are cheap though, so it's not that big a deal.

[Blknight.aus]

if you want to find out if its a bearing change your oils and check the oil for metallic particles and shards of bearing. do the engine box and tcase, if the oil comes out nice and clean then its not an engine/box problem. Dont forget to open up the filters and have a look in them too.



Landies are very solid vehicles and noises radiate around them sounds that sound like they are coming from the engine can come from diffs and sounds that sound like they are coming from the back can be coming from the front...

(I cant get the sound file to download/play)

[jiri_j]

Thank you Dave. I will check the engine oil for metalic particles. I think the particles will be caught in the filter, will try to open it and have a look inside. The noise is not gearbox/t-case related, since I can simulate it when standing still and breaking/accelerating (creating pseudo high-engine load condition) without moving the car at all. This means that it comes somewhere between the crankshaft pulley and the clutch.

[Blknight.aus]

actually if thats the case it generally proves you have a harmonics related problem....

so it could be anything that hangs off of the engine or is connected to the chassis

if it was a bearing problem in the engine it would be most noticable at low engine rpm under higher loads like when you take off in first or second gear when the oil delivery pressure and flow is at its lowest. metals that come from crank bearings tend not to just wind up in the filter a lot of them simply fall out of suspension from the oil at the strainer and sit in the bottom of the pan.


I strongly suspect that we're not looking for something thats going to be fatal to the engine more likely something simple like a failed exhaust gasket, something fallen into the valley cover that you cant see, a shield thats weakend or a vac leak. a decent recording of it might reaveal it to be something that someone else has already experienced.

[Rudolf]

Torque vibration?

Can't download the sound file.

[jiri_j]

I uploaded two sound files onto the following links:

1. First I tried to accelerate and keep the engine at 2500-3000rpm and then started to brake. As a result of a high load condition, noise starts to pick up. The noise is like metal-to-metal 'worn bearing' noise. I can't hear anything at idle or when cruising, only when accelerating (higher engine load).

http://muj.optol.cz/janousek/LR/LR-D2-noise1.wav

2. The second recording is the same, but at low rpm of around 800-1000rpm. The noise is very obvious rather at the end of the recording (at 44seconds, low frequency rattling-like noise).

http://muj.optol.cz/janousek/LR/LR-D2-noise2.wav

Anyone has an idea what is going on??? Has anyone heard a similar noise? I tried to check everything in the engine bay area and found nothing. I have a very bad feeling that the noise comes from the engine. I ran the engine without the serpentine belt and noise is still there. Noise get worse when the engine is warm. Noise is RPM dependant. I checked engine oil for metalic particles, looks pretty clean, only a very few tiny metalic chips. I didn't try to open the filter though.

A few of you mentioned TV damper. My disco is V8 and to my knowledge there is no TV damper at the crankshaft pulley on V8. Checked the pulley and it looks to me very solid - no side movements. Any thoughts?

[Sully]

I've asked this before, but have you checked your manifold is tight on the block and have you checked the flange gaskets on the manifold where it joins to the exhaust pre-cat?

If the manifold to exhaust flange is buggered the car will make a hell of a noise when under load, but sound fine while idling. It will also get louder when warmed up as the exhaust joins expand more with heat.
Everything you're describing sounds similar to the exhaust flange(s) failing.

[Rudolf]

Sully's correct. Low pitch noise sounds like cylinder puffing past gasket.

Cam or valve system?

[jiri_j]

G'day Sully, sorry I forgot to reply you on this. Yes, I did checked all the bolts of the exhaust manifolds at both banks, even between the y-pipe and the manifold. I checked for a cracked manifold as well. Also was looking for any sign of carbon, found nothing. My wife was complaining that in the last couple of days I spent more time lying below the disco then her :wasntme:

But when I think about it now, mate, some time ago I have replaced the y-pipe gaskets (the old design, made of the high temperature material only) with new ones. The new design comes as two thin steel plates with the material in-between. In principle, the gasket could explode within the joint between the pipes and the plates could be making that noise. Good point. I will replace them tomorrow, still got the old ones. Thank you and I appreciate your help!

[Sully]

Nice one. It's all a process of elimination. I hope this is the problem as it's a relatively easy fix.

Let us know the outcome after replacing the pipes.

[Blknight.aus]

it sounds like its only on one pot so I strongly suspect that it is the exhaust manifold gasket on one side or the other.

make up a dummy spark plug on a strong aligator clamp and disconnect one cylinders lead at a time connect it to the dummy plug and then connect the dummy plug to a good earth point.

rotate the dummy plug to all 8 pots one at a time till you find the dud pot and then further diagnostics can commence.

[jiri_j]

Update: changed the y-pipe gaskets, didn't solve the problem. Measured compression in all cylinders, look very good 170+-5 psi all cylinders. Blown head gasket can be excluded. Will try the trick with the dummy spark plug. The idea here is to run engine on 7 cylinders only, and look for an exhaust manifold leak, correct?

Here I have one question: to make sure that there is no fuel dumped through the exhaust (which could burn the cats) should I remove the particular spark plug? Such that all the fuel goes inside the engine bay area, and not through exhaust?

Is it safe to run the engine without one cylinder by the way? Probably for a very quick drive this is fine, correct? Thank you all.

[jiri_j]

Bad news: checked for an exhaust manifold leak, found nothing!

I have found out that driving the car at idle speed and introducing an engine load (by braking) I can get the same noise at a low frequency. You can actually hear pretty loud banging :-(

I measured the frequency of the noise and it is exactly at half the frequency of the crankshaft. This means camshaft seems to be a problem.
Why camshaft??? I had an engine rebuild 1.5 years ago (45t km), which involved a camshaft replacement. The reason was a cracked timing cover, which allowed an oil pressure drop in the engine. As a result the camshaft was worn out and had to be replaced.

For this reason I put an oil pressure gauge and monitor the engine oil pressure. No problem at all here. So why a worn camshaft???

Or is there anything else that could make noise at half the frequency of crankshaft? worn hydraulic lifters? These were changed as well by the way. Looks to me I am facing a big and expensive job :-( Any thoughts how to test for a worn camshaft further???