Smokey on start up - XJ40 1993
Discussion
If it's blue smoke on start up then perished or worn valve stem seals are the most likley cause. Lack of oil changes cause these to become brittle and then they start to wear.
Might be worth changing the engine oil - old mineral oil looses it's hot viscosity index number as the addative package breaks down and the effect of this is a 10W 40 slowly becomes a 10W 30 and so on. That means the oil when hot is much thinner than it should be and that will allow it to drain down past a slightly worn seal much more easily then it would if it had retained it's original hot viscosity. A good clean out of the engine breather system may help too.
Apart from that there's not much else you can do apart from a strip and rebuild of the head.
Might be worth changing the engine oil - old mineral oil looses it's hot viscosity index number as the addative package breaks down and the effect of this is a 10W 40 slowly becomes a 10W 30 and so on. That means the oil when hot is much thinner than it should be and that will allow it to drain down past a slightly worn seal much more easily then it would if it had retained it's original hot viscosity. A good clean out of the engine breather system may help too.
Apart from that there's not much else you can do apart from a strip and rebuild of the head.
Most, maybe almost all XJ40s smoke a little at start up due to valve stem seal wear; whether it is a problem is I guess, a question of degree. If your car just produces a puff of smoke from the pipes when first started and nothing more, then I don’t think it is a problem and rebuilding the cylinder head shouldn’t be necessary for quite some time.
I haven’t tried it myself, but I have heard of several people who have managed to reduce start up smoke or even prevent it by using 15w 40 Castrol High mileage oil. This has a seal conditioner in it which can improve the stem seals if they are only marginally deteriorated.
I haven’t tried it myself, but I have heard of several people who have managed to reduce start up smoke or even prevent it by using 15w 40 Castrol High mileage oil. This has a seal conditioner in it which can improve the stem seals if they are only marginally deteriorated.
fast cars said:
Steve, thanks again for your advice, are you a jaguar specialist? If so where do you work from?
Cheers
Danny
No not a specalist, I'm an ex multi franchise mechanic from the days of points and carburettors - who's wasted quite a bit of my life and quite a bit of my money running and repairing older Jaguars Cheers
Danny
Worn valve stem seals can cause this but sometimes an oil change can sort the smoking out, tired old oil can get thin and make it's way into combustion.
If it's a higher mileage engine I'd recommend a thicker oil than 10W40, a 20W50 would cut down smoke and give stronger oil pressure.
If it's a higher mileage engine I'd recommend a thicker oil than 10W40, a 20W50 would cut down smoke and give stronger oil pressure.
Gassing Station | Jaguar | Top of Page | What's New | My Stuff