tappety tap

May 04, 2006 7 Replies
G

oh oh...



My P38 is booked in to get the leaking valley & rocker gaskets replaced next week. Today I had to do a trip to Chichester, when I got there my engine was clacking like a very tappety thing. After 5 hours standing I started it and it was all quiet again, drove back to London no problem and when I pulled up it was tapping out loud again. Noise disappears or reduces above 1500-2000 rpm off load and is only there when its hot. Doesn't seem to be any worse under load. Sounds like a pronounced "clack" sound rather than a knock but it seemed to be coming from the business end rather than the top although I could easily be wrong. Its done 99k. Doesn't loose oil or water (apart from the valley & rocker gaskets), oil & filter changed every 3-4k miles. Any ideas from you V8 gurus as to what this may be, can something shagged in the bottom end make a sound like a tappet or this this most likely a stuck/knackered lifter?



Gazza


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B

What grade oil do you use? I use 20w/50 oil in my RR V8.

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G

10w/40 Castrol "high mileage engines" stuff in there at the moment.
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R

my 3.9 did the same last week. i thought it was a liner slipping but when i took it to a lr specialist they found the drivers side cat was buggered. it only does it when hot. Richard

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A

On or around Fri, 05 May 2006 08:00:52 +0100, Gazza enlightened us thusly:

way to thin for hot temperatures.

decent 20W50 if you can get it... failing that 15W50, it's the 50 part that's important.

API SG or higher (API SF is worse than SG which is worse than SH, etc.) is good too, less sludge-forming.

What's the word on Thor engines? ISTR different oil pump and stuff, does that mean they're happier on thin oil?

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B

10W40 or 15W40, due to the tighter production tolerances and different oil pump type, Austin. it's only the "serpentine" type engines that have the later pump, all earlier variants (with a distributor) have the old style pump and need the 10 or 15W50 oil, the exception being the late "interim" 3.9 engine which has a distributor, but also has the late pump and serpentine belt. Badger.
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G

I just rechecked the can, it's actually 15w/40. I don't see what difference the "for high mileage engines" bit is about, maybe special detergents added? RAVE says 15w/40 is ok 50c+. Opinion is the noise is definitely top end cam-knock/tappets related, being stripped down next week, I'll put my wallet on sedatives now.

Gazza

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A

On or around Fri, 05 May 2006 19:47:46 +0100, Gazza enlightened us thusly:

which engine, though? I'd still not fancy a W40 in any of the earlier ones in summer. Cold weather might be OK. The book, reflecting modern trends in oils, recommends thin stuff, but that doesn't alter the engine design...

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