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Discussion Starter #1
Hi All,

98 4.6 v8 Petrol 85k

I have an issue that started the other day. Loud noise like a lambretta when driving along, revs above 2k gets loud the harder the engine works, follows the rev's more that road speed.

See attached video:

Recent work done, cats swapped, UJ's greased. No issue initially. Problem only started when started towing.

Cats swapped back to original and problem still present.

I've checked for play in the UJ's and all ok. No knocking.

There is a knocking noise when engine is idling but when rev'ing but can't get it constant and its certainly not as loud as when driving along.

Having a look around then engine bay today I looked at the V Fan and water pump and noticed a fair amount of play in the v fan coupling and possibly the water pump. Both are only 2 months old.


So just wondering if anyone has any views or opinions on what could be causing this issue? Car still performs as normal. No overheating etc..

Cheers
Al
 

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I'd be popping off the inspection plate on the bell housing and checking the flex plate first. Might not be that - but if it is and it lets go, then you won't be going anywhere in a hurry!

If that checks out, then it could be something in the gearbox/transfer case - especially if it changes with revs, not road speed.

I am sure someone with more experience will come along and have some other ideas on things to check though.

Marty
 

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Discussion Starter #4
Ok great thanks, will have a look today.

Is there a particular way to test this? or is it just a visual inspection? hand cranking the engine?
 

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1 st video sound internally may be the fan blower its noise increases with the rev up because there is electrical problem as the serpentine belt lost the required drive torque to the alternator and this water pump gone already should be replaced the reason for all of this in my thought you have wrong size belt (shorter)
 

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Never heard a shot flexi plate (and hope I don't) so can't comment. It does sound remarkably like a 2 stroke exhaust 2 stroking though!
You've had cats off, on, back off and back on again, so have you checked for obvious exhaust leaks or perhaps a damaged/ missing/ loose lambda sensor underneath?
As for the viscous clutch and play in water pump, I've just done mine and had no play in either. Yours are clearly not right and with that amount of play could even be hitting something (shroud or internally in pump which runs with tight clearance between impeller and timing cover). The cause? May be wrong belt as quoted above, but thought you'd have spotted that when fitting, as with a decent bar on the tensioner it's an easy one handed job to slip it on. Could be a defective new pump. Either way, it won't last long with that amount of play and I wouldn't use it until resolved. Apparently when those fans let go, they make a right old mess.
Good luck.
BTW, if you put a more specific location in your signature there might even be someone on here local to you who can help
 

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Discussion Starter #7 (Edited)
Thanks for advice, checked exhaust and sensors and all ok. No loose or blowing parts.

I have removed the bell housing access covers and found something worrying..


No other obvious issues in there.. few photos in link below. Plus another video showing little bit of play in part of the flywheel assembly..

http://s1295.photobucket.com/user/lazylabs78/library/RR%20p38

I
'm in Lincoln, UK is anyone is local who fancies a butchers...all help welcomed...:)
 

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Nothing to worry about with that bit of play but there is one thing that concerns me slightly. The bolts you have concentrated on aren't the important ones, they just hold the ring gear on, the important ones are the 4 that are set inside the hole as these are the ones that transmit the power from the engine to the torque converter. Only one picture really shows it (this one http://s1295.photobucket.com/user/lazylabs78/media/RR p38/538177D3-D852-4EB0-8552-AE4CC186C4EC_zpsbzta4xkk.jpg.html?sort=3&o=4) and I don't like the look of the rusty coloured stain which suggests to me that it may be loose. They are done up to 37 ft/lb but should have Loctite on them too. From the video it looks like something has been laying in the bellhousing at some time and has marked the torque converter.
 

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Discussion Starter #9
Ah yes I tried to get some pictures of those but only had my phone at the time and it refused to focus on them. Will get my endoscope out tomorrow and have a proper look at those ones.

Yes the markings on the torque converter may well be old. Again hopefully I can get my scope in and have better look around. Also going to drop the sump as well to have a better look. Its due an oil change anyway.

If the bolts are loose can I just tighten them up? or better still could I remove them one at a time and loctite them and torque up correctly?
 

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If you look from underneath, through the round inspection hole, you can see the edge of the flex plate and those 4 bolts attaching it to the torque converter. If they have been loose, chances are the flex plate will have cracked unfortunately.
 

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Discussion Starter #11
Well managed to view the flex plate. Can't see any cracks and certainly not missing any pieces. Few photos here.

http://s1295.photobucket.com/user/lazylabs78/library/RR p38 flex p

Was able to press the flex plate and it was ok. No movement.

Water pump is off and definitely knackered.

Will fit new pump and v fan clutch. Then test. If no good after that will the drop sump and test those bolts. As can't get torque wrench in.
 

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Discussion Starter #12
Ok new v fan clutch and water pump fitted. That's cures the wobble but the knocking noise is still the same.

Stethoscope on the car today and found noise is coming from passenger side of the engine. Can hear it in the plenum chamber and little bit in the rocker cover and also on the heads just by the exhaust manifold.

Oh what can it be.
 

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I've had another listen to the noise and it still sounds "exhausty" to me. I'm guessing you used a contact type stethoscope for your search? Have you tried using the ancient "hose in the ear" technique and working around the manifold under the heat shield? My current thought is exhaust hitting tin!
I'll have a punt on manifold gasket or cracked manifold :)
Happy hunting
 

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Discussion Starter #14
I've had another listen to the noise and it still sounds "exhausty" to me. I'm guessing you used a contact type stethoscope for your search? Have you tried using the ancient "hose in the ear" technique and working around the manifold under the heat shield? My current thought is exhaust hitting tin!
I'll have a punt on manifold gasket or cracked manifold :)
Happy hunting
Well had another poke about tonight, couldn't see any problems with the manifold. No leaks or blowing. I don't have the heat shields any more. Gaskets look good.

Not tried the hose and ear technique before, tried it with a bit of plastic tube but not sure it was quite right. Presume garden hose would be ok?

Contact Stethoscope definitely picks up the sound on passenger side of the engine. However I'm not sure its the same sound as the one when driving along. Need to try and record the sound at idle.

Also noticed something else, when removing the oil filler cap after engine has warmed up they is the slightest bit of smoke coming out, plus same out of the oil dip stick tube.
 

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Probably best to hope that some P38 specialists jump back in here. You've used the same kit that I'd have used to chase down the problem. Garden hose will work OK (watch out for earwigs) but if you've already ditched the heat sinks there's probably nothing left to explore acoustically as opposed to by contact. I'd be deep into P38 paranoia by now, looking at rocker shafts for a start. Except I wouldn't because it doesn't sound like that. Let's see if anyone else kicks in...
 

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Smoke is probably irrelevant but could well be down to a clogged breather or oil trap in the RH rocker cover (as seen from the drivers seat). There's a breather hose from there to the plenum chamber and set inside the rocker cover is a plastic oil trap. If it gets pushed in too far it hits the inside of a splash plate and that blocks the breather.

The noise isn't regular which is the weird thing but if it's coming from one side of the engine then maybe it is something in the valve train? I'm thinking rocker or rocker shaft maybe?
 

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Discussion Starter #17
Right had more of a dig around trying to investigate this noise I'm getting when rev'ing the engine. Not sure if this is the same noise I'm getting when driving at 2krevs and above as per first video. Stethoscope on top of the plenum chamber shows the noise at it loudest, rev the engine and gets louder. Unfortunately haven't been able to record it as yet.

So I whipped the plenum chamber off thinking maybe something loose inside, nothing very exciting in there but I did notice one of the ram pipes is loose..


Not sure if this is enough to chase the stationary revving noise never mind the driving noise but there is movement in the ram pipe and all the others are rock solid.

Also took the passenger side rocker cover off, nothing obvious to me anyway, did another little video of this. Bit of movement in the end rocker.

https://youtu.be/MtsaRhHZPa0

But can't see anything broken of obviously rattling about.

As for the driving along noise I have been around the exhaust again tonight with rubber mallet and there is bit of a noise when hitting around the centre silencer box but can't quite pin point it. Guess only way is to take it off and see if anything loose etc.. that's for another day..

Popping it down to local LR specialist tomorrow to get there view if they have one hopefully.

any other view very much welcome...
 

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Discussion Starter #18

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Dollop of Loctite will sort the ram pipe, they are only a push fit, but I very much doubt that would cause the noise. Definitely a weird one.
 

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as gilbertd mention the noise is weird i suggest to lift the car with free running wheels and somebody get inside accelerate and try to inspect from under the car the source of the noise.

thanks for your good presentation.
 
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