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1996 4.6 P38 - knocking sound on idle


argonaut

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you have all the parts you need there i would replace the drive plate about £40ish from land rover that is the small plate the torque convertor bolts too as it is that cracks where it bolts to the centre boss

Excellent news, many thanks for your help and for the tip ref drive plate - I will get a new one as it makes sense to replace this item at the same time. I have now bought the eBay item, hopefully it'll help solve my current problem.

I'm still on a steep learning curve with my P38 - looking a little closer at the rear of the flywheel I think I can see that the timing holes/slots are actually machined into the flywheel itself - I was expecting this to be a sep. item.

Thanks again, I'll report back with progress.

Cheers

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Well chaps, I know I'm making a little heavy weather of this but I don't want to buy a pig in a poke and then have to spend more money buying something else. I've found a replacement flywheel on the the German eBay site for a reasonable price and it "appears" to be in reasonable nick. I just want to check to see what else I will need - reluctor ring I think and am I correct in assuming that this is available seperately? (I don't want to buy a cheap flywheel and then a brand new expensive one to go with it). Here's a front and a back view picture, thanks for your help

post-21022-127545591533_thumb.jpgpost-21022-127545592775_thumb.jpg

Well another update, the replacement eBy flywheel arrived today, looks to be in pretty good condition, I took it along to the repair mechanics so that they can get on with the job and they're not happy with it and claim it's not the correct item. This is all getting rather frustrating now - they tell me that the flywheel currently fitted to my car looks different to the replacement I got hold of and that it looks like this one: post-21022-127610383039_thumb.jpg

So, have I bought the wrong flywheel? Is it possible that the one I've bought is the correct one but the one on my car is a different one? Is the new one I've bought compatible in any way?

Sorry to be a nuisance with so many questions. Thanks for any help!

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you are correct the flywheel you have bought id for the thor not gens speak to the seller and demand a refund or a gems unit!

many of the breaking in the uk don't know the difference when breaking and just sumise it fits all! been in this position plenty of times with customers who source there own parts many know leave me to it

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you are correct the flywheel you have bought id for the thor not gens speak to the seller and demand a refund or a gems unit!

many of the breaking in the uk don't know the difference when breaking and just sumise it fits all! been in this position plenty of times with customers who source there own parts many know leave me to it

Oh bother (or similar) is what springs to mind. Ah well, I'll see about getting a refund, the listing did state suitable for 94 - 02 but clearly the seller wasn't aware of there being a difference.

Anyone want to buy a Thor flywheel ? ;-)

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  • 5 weeks later...

Oh bother (or similar) is what springs to mind. Ah well, I'll see about getting a refund, the listing did state suitable for 94 - 02 but clearly the seller wasn't aware of there being a difference.

Anyone want to buy a Thor flywheel ? ;-)

So, closure as they say.

Finally was able to collect the car yesterday, after almost 3 months it's finished. New flywheel, drive plate and crankshaft sensor plus miscellaneaous gaskets replaced, gearbox oil top-up and a complete engine oil & filter change. The car is now running sweetly again with no ominous knocking or rattling sounds.

Many thanks for all the help with diagnosis, saved me a lot of hassle as the garage refused to believe it was the flywheel until I was able to describe the symptoms properly and they then checked.

I still have quite a list of to-do's but many are cosmetic and not important.

Next up is an EAS check over as my EAS pump runs a lot, sometimes almost continously, I have a new seal kit and I will have a go at fitting that next.

Cheers

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P38A Noise.mp3Very interesting thread. My 4.6 HSE has developed the knocking sound. The garage diagnosed it as a faulty tappet but I have my doubts as it only happens when it has been hot. At first I thoought it was related to two water leaks that developed about the times when I was hearing the sound. After fixing the first leak it kind of went away but after fixing the second leak it lingered. I am attaching a sound file. I have never had thought the flywheel would be a possibility!

Is there an easy way to see if the flywheel is the culprit or does the transmission and engine need to be decoupled?

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P38A Noise.mp3Very interesting thread. My 4.6 HSE has developed the knocking sound. The garage diagnosed it as a faulty tappet but I have my doubts as it only happens when it has been hot. At first I thoought it was related to two water leaks that developed about the times when I was hearing the sound. After fixing the first leak it kind of went away but after fixing the second leak it lingered. I am attaching a sound file. I have never had thought the flywheel would be a possibility!

Is there an easy way to see if the flywheel is the culprit or does the transmission and engine need to be decoupled?

As it does it only when it hot and it appears to calm down a bit when revving, I would say that it is a slipped liner.

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P38A Noise.mp3Very interesting thread. My 4.6 HSE has developed the knocking sound. The garage diagnosed it as a faulty tappet but I have my doubts as it only happens when it has been hot. At first I thoought it was related to two water leaks that developed about the times when I was hearing the sound. After fixing the first leak it kind of went away but after fixing the second leak it lingered. I am attaching a sound file. I have never had thought the flywheel would be a possibility!

Is there an easy way to see if the flywheel is the culprit or does the transmission and engine need to be decoupled?

Hmm, that sounds a bit different to the sound my car was making - it seems to be related to engine speed whereas mine wasn't - only that the sound from my car was evident at idle speed and disappeared once the revs incresed. Your sound seems more likely to be coming from the engine itself. Nevertheless, I believe that the flywheel can be partly seen by removing the cover plate under the bell housing - bear in mind though that I'm a newbie to RR's, somebody more knowledgable than I might have a better idea. Note also that my car made the noise regardless of engine temperature.

Sorry I can't help you more.

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Yes, you can remove a plate from bottom/front of the bell housing to have a look at the flex plate, associated bolts, and torque convertor.

Have you checked your exhaust manifold gaskets for leaks? It doesn't sound like it, but audio recordings are very weird things, and can mask what a sound truly is like.

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The frequency of it does sound like a tappet actually, or something above the cam anyway (valves, followers etc).

Tappets and liners sound VERY similar. The main difference is that tappets are worse when the engine is cold and a liner when it is hot.

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I'm leaning towards P76 on this

If it is engine and not TC etc then here goes engine wise fom Moi :

I've heard a select of knocky noises over the years from V8s

and cam tapets sound more like a spoon being whacked on the rocker cover, Liners are a deeper lower knock

and rythmic to the engine RPM (as are tappets). This sounds more "Deep" and if not a liner (which it dop sound like)

then it big ends / main cam bearing noise, although having said that its not as loud and deep as a big end / mains,

and lower deeper than cam so I still lean with Mr p&^ M'lud

Nige

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Thanks for all the clues. if it is, as it seems to be, a liner, what is the fix for that? can I replace that liner? do all have to be replaced? what is the reason they get loose on the first place?

If it is a liner, basically find another block. This is usually cheaper that having top hat liners fitted. You will need to replace all the liners, maybe pistons as well.

There has been much debate over the years as to what causes a liner to start moving. It is probably evenly divided to poor machining when the motor was built to overheating. I lean more to poor machining as it seems to affect certain motors more than others.

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If it is a liner, basically find another block. This is usually cheaper that having top hat liners fitted. You will need to replace all the liners, maybe pistons as well.

There has been much debate over the years as to what causes a liner to start moving. It is probably evenly divided to poor machining when the motor was built to overheating. I lean more to poor machining as it seems to affect certain motors more than others.

Alternatively, if you plan to keep the Rangie for a while and the engine is otherwise good, it can be worth going the route of getting the block redone with top-hat liners. That way you'll know you're not going to have that problem again, whereas with a replacement block you could be looking at the same problem again in a few months/years and the cost of pulling the engine, rebuilding it and putting the new one back in isn't so far off a top-hat job.

If you do get a replacement block, you should try to look out for one with a dab of red paint in the valley - this was after Land Rover realised the problem and started cherry-picking the best castings for the 4.6. The problem was (or at least one theory on it is) that the block is pretty much on it's limit at 94mm bore diameter (cf. 89mm on the 3.5) so any block where the bores are cast slightly off-centre leads to very little metal between the water jacket and the liner, which combined with the crazy high coolant temperature Land Rover choose for the 4.6 (to lower emissions) led to the problems with coolant getting into the heads.

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How can I confirm if it is a liner? What happens if a slipped liner is left like that? Will the engine eventually fail?

The only way to confirm it is a liner is to pull the heads off. They are often not that noticeable and you have to look very closely. As long as the block is not cracked behind the sleeve, there is probably no reason that you could not keep on driving it for years. My Land Rover mechanic has bought a number of Land Rovers with slipped liners and has continued to drive them for many years. It is more the annoyance of the noise or if the block is also cracked and is letting in coolant. A disco I bought had 3 slipped liners and the only thing that stopped me driving it was the noise. It now has a brand new 4.6 block in it and I am very happy.

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Thanks, that is a relief. I don't think I have a cracked block since oil is very normal. By the way, I checked the oil level yesterday and there were 3 litters needed to top it off. Either on a very recent oil change they screwed up or something else is going on. I haven't seen any leaks. Once I topped it off the noise was somewhat attenuated.

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In my opinion that sounds too "slow and loud" to be a lifter... hell, there's 16 of the little buggers and i doubt just one would freak out and not any other.

I'd take the rockers off and rotate the engine to see if anything is loose / got play in it / doesn't look right.

Or... flex plate ?

If you were to get a stephoscope you might be able to have a poke around - but it's a bit of a pain in the butt to do !

G

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  • 3 weeks later...

If it is a liner, basically find another block. This is usually cheaper that having top hat liners fitted. You will need to replace all the liners, maybe pistons as well.

There has been much debate over the years as to what causes a liner to start moving. It is probably evenly divided to poor machining when the motor was built to overheating. I lean more to poor machining as it seems to affect certain motors more than others.

slipped linner deffo put money on it as for the statment above what a load of carp!

too of my customers recently had second hand engines fitted at garages for over 3k with engines i can bebuild and fit for less if most parts are good and can be reused and give a 12 month warranty too!!!!

there are very little good used blocks out there now

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slipped linner deffo put money on it as for the statment above what a load of carp!

too of my customers recently had second hand engines fitted at garages for over 3k with engines i can bebuild and fit for less if most parts are good and can be reused and give a 12 month warranty too!!!!

there are very little good used blocks out there now

I can buy a new block from Land Rover for half that money, so my statement stands.

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