Oil Leaks

[David Morris]

Hi All,

If there’s one thing about owning a Javelin or Jupiter, one that's uppermost in your mind when you open the bonnet, is ‘are there any oil leaks since I last looked’? The abiding habit of the engines in both vehicles to leak oil. Compare this with my, now venerable, Vauxhall Astra, you change the oil, drive 10,000 miles, and take the same oil out. Check it occasionally, but there’s no need to add any. The Javelin/Jupiter owner, on the other hand, has a spare can in the boot!
Now, Javelin/Jupiter engines do burn oil, 200 miles to the pint is considered good going. But, they also leak oil, cam shaft covers, rear main crankshaft seals etc. etc. But the one spot the driver homes-in on like a magnet, are the twin valleys on the top of the engine. These are the worst, and most troublesome areas. In themselves, they don't leak. Oil here means trouble elsewhere! It could be coming from the notorious gasket between the rear timing cover (RTC) and the block, and that is forefront in most worried owner’s minds. It involves some dismantling and a new gasket, at least. However, biting the bullet and fitting a new aluminium gasket with ‘O’ seals will make things much better here, in the long term.
But there is another reason for oil leaks appearing at the gasket interface, and looking identical to a failing gasket. This involves the small adapter that feeds the oil pressure gauge, or oil switch, that is also here. The tapped hole in the aluminium casting on the rear timing cover is right down near the gasket interface and not easily seen. The tapping in the hole is tapered. The wall thickness between the bottom of the tapped hole and the edge of the RTC is only a few mm, and this often develops cracks, allowing oil to leak here and look like a failing gasket. Jowett’s must have realised this was a weak point and I have seen at least five different versions of the RTC, with different wall thicknesses here, but the same part number!
So, if faced with valleys brimming with oil, and you fear the worst about the gasket, you will probably be taking off the RTC to cure the problem. However, before deciding what to do, have a good close look at the aluminium wall between the tapped oil way and the bottom of the RTC. There might well be a hairline crack here! The best solution is probably a better RTC from JCS!

On the subject of RTC’s, the very worst thing you can do, if faced with a gasket leak, is to attempt to tighten down the two set screws holding the RTC to the block. You will distort the mating faces of the RTC and probably strip the tapped holes on the block. Please do not attempt this! The whole design of the RTC, in my view, was a disaster for Gerald Palmer and a definite ‘Friday Afternoon’ job! A bit more thought could have made the mating faces flat to the block and avoided the problems caused by having angled faces, and hence oval oil ways.

Hope this helps? All the best,
David