A Special Builder's Notes


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07 May 2015

A Mystery.

A couple of weeks ago, The Great Collector set out in his 20/25 Rolls but got no further than the end of the drive; a curious noise from under the bonnet stopped him in his tracks. Opinion was sought and we all stood round with cups of tea, stroked imaginary beards and put in our ten cents. One thing was clear, the noise was coming from the timing case. Chain slap? Could be. Isn't it gears in there? Dunno. Anyone got a book? Fortunately, The Great Collector had a very useful book covering the smaller horsepower Rolls Royce engines which, as bedtime reading, allowed me to get to grips with the disassembly sequence.

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After removal of the radiator - an engine hoist job; it was heavy - the sump had to be supported whilst the front engine mount was removed. This would have been simple if I could have got a spanner to the nuts more easily. The top four bolts weren't a problem as the nuts faced downwards but the bottom four with the nuts on the upper side of the bracket were almost impossible to get at and so it wasn't until 5 hours later I could address the timing cover itself.

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The dynamo shaft brakes came out first, then oil pipes were disconnected and all the nuts and studs removed from the case. A couple of the studs were a reamed fit and have to go back in the right places.

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With the crankshaft pulley removed, the serrated nut behind the starter dog nut was loosened with my special Rolls Royce C-spanner and the cover then slipped off. The paper gasket had been put on with just a smear of grease so that was able to be preserved for reassembly. The serrated nut was then put back on as the front flange of the nut overlaps the starter dog nut. When this latter is loosened, it acts as a puller and the crankshaft vibration damper comes away from the crank leaving the Woodruff key in its slot.

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The worst thing about all this was that nothing had so far fallen out onto the floor and there was no sign of damage or anything broken to tell us where the noise came from. The idler gear had a bit of play in it so that was removed and new bearings will be fitted.

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The idler gear serrated nut was really tight and heat was needed to get it to move. The end of a baked bean can was cut off which allowed it to slip over the nut and act as a shield to contain the heat in the right area without setting the rest of the car on fire. With an extinguisher in one hand, I played the flame down the can for about 30 seconds and that did the trick.

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The RR C-spanner came in handy again and that was all I could do for the time being. There was a bit of end-float in the water pump gear which could account for the noise but I'm no more convinced than Counsel was when I suggested that the noise could be a crank web hitting the oil level gauge float (it's cork I was told a bit later but, not bad for lateral thinking?).

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So while the crankshaft vibration damper is being rebuilt (it's a bit loose but not the source of the noise) I'm off to France to take up my duties as plongeur in a little hotel just East of Biarritz and to ponder the problem of the noise.

Il est tout pour moi un mystère.


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