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V8 inconsistent clatter


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hello all,

there is an issue for the collective knowledge of this forum to handle

my truck is an M reg Disco I 300 V8 i 3.9 auto with 137K kms on the clock

for quite a while now (around five months) and ever since the first oil change since it ended up in my loving hands, I have noticed something peculiar. At first the block gave and inconsistent, ie non-rythmic, metallic clattery noise that has been increasing in frequency, though not really in loudness.

It is rather hard to locate and quite unlike rocker-lifter noise, that is more high-pitched in comparison.

The most interesting thing is that it does not appear to be doing it when cold (although I can clarly hear lifter clatter from time to time, that stops immmediately). The non-rythmic symptom starts after a full run of the motor and after I park it running, it starts after a little while.

Other than that the engine runs fine, it revs nicely, no other funky noises, no smoke, MOT'd succesfully recently and passed with flying colours. I have also been treating it with more than regular 10w/40 changes, plugs and lead are new and recently tried a shorter MAN oil filter just in case...no joy.

The interesting thing about that is it's inconsistency, it clatters non-rythmically and only when hot and my mech proposes that we do nothing about it, since it is probably not worth opening the block for something inconsistent and hard to locate (I might tend to agree with him as I fear that when we open it up we will end up having to change a cartload of stuff).

PS why would it non-rythmically clatter only when hot? Could it be a peripheral and if so?


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  • 4 weeks later...

10/40 is towards the thin end, I put some super synthetic 5W/?? in the 109 once and ended up with zero oil pressure at a play day after stalling on a hill :( remember it thins out when hot.

20/50 is recommended (£1/litre from the local motor factors) but 15/40 seems to work just as happily and is more readily available from places like halfrauds.

Does it not do it under load or is it just that you can't hear it while moving due to road noise?

Ideas / thoughts:

Viscous fan / water pump bearings or other engine-mounted ancillary - my water pump made a horrible grinding noise for about 6 months before giving up. If the viscous is kicking in when hot and putting extra strain on the water pump nose that could cause it?

Dodgy tappet - try engine flush & new oil

I've heard of cracked rocker shafts before now, rocker covers are faily easy to remove even if the gaskets are a PITFA to get back on straight...

I'd start by looking at as many small / cheap / obvious things as possible. At the end of teh day, V8's are cheap to come across (even 3.9's these days), or if you're intent on keeping the vehicle a rebuild by a reputable engine builder (EG Turners) could pay dividends.

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  • 1 month later...

Mine has been doing this for at least the last two years and about 7,000 miles. Have changed tappets etc but no fix. However I did find a service note re the rockers being faulty and once replaced the increase in power was noticeable.

Also removed the cats but same noise. In the middle of all this the head gasket went and I thought that’s it. Fitted new head gasket and guess what same noise.

I just live with it.


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Use Duckhams Classic 20/50W oil (I get mine from ARE motor factors)

Before you shove this in, get a tin (or 2) of FORTE engine ckleaner and shove into the engine,run / drive it about for 20-30 minutes then drain, this will remove muck from the engien - ir carbon = sticky tappet etc etc

Then refill with 20/50 and Use either a genuine filter or a F good brand :o

Have antifreeze at 50%, less and it will equally run hot - hot = odd noises often

Other than the above :

Do you have an oil pressure gauge ?...if so what is the Press at Tickover / 2000 rpm ?




Take one rocker cover off, and take a picture and post here, THIS will tell me / us a lot about the internal condition - more than you can possibly ever imagine

Looking forward to the piccy :

Nige (Again) :o)

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