Smoke from Exhaust after downhill run

Post by **David53** » Sun Sep 27, 2009 5:07 am

Near my house there is a very long and steep hill. When I come down it I am in top gear and have no accelerator at all but the car is still running at high revs at around 50 mph.

At the bottom of the hill is an intersection and I notice that when pulling away in first gear I get some white/blue smoke from the exhaust. This doesn't normally happen and is gone by the next intersection. Something about coming down that hill with no accelerator seems to be causing the smoke. Any ideas what it might be?

Post by **Peetee** » Sun Sep 27, 2009 9:41 am

It's probably oil being drawn in down the valve guides.

Post by **youngun** » Sun Sep 27, 2009 9:50 pm

Worn Valve guides, almost certain of it as father was moaning about it the other day and talked of exactly the same symptoms!

Post by **carlosramalho** » Sun Sep 27, 2009 10:40 pm

solutations for that?

Post by **bmcecosse** » Sun Sep 27, 2009 11:54 pm

It's worn engine - rings/pistons/bores etc! Everyone wants to blame the valve guides/seals - and sure they do play a small part - but as long as the seals are present -they will be doing a good enough job. Solution to the problem is - knock it into neutral and cost down the hill! The car has brakes to slow it - no need to stress the engine !

Post by **David53** » Wed Sep 30, 2009 4:54 am

Ummmmmm no can't see it being a worn engine. Engine was fully rebuilt with new bearings, rings etc when restoring nthe car. Head was also fully reconditioned. Also, no smoke at all when I rev it hard in the driveway, only after this long downhill run with accelerator right off.

Coasting is not an option - hill is VERY steep and long and would result in me careening down at over 70 mph with no engine to slow me down!

Post by **bmcecosse** » Wed Sep 30, 2009 8:11 am

Sounds ideal then - 70 mph with no engine!
'Full rebuild' is a lot more than just bearings and rings - it will be oil being drawn up past the rings when the engine is on the over-run. But - don't worry about it! At least you know it's being lubricated.

Post by **MarkyB** » Wed Sep 30, 2009 8:36 am

A really worn engine will smoke after every bit of deceleration.
The little bit of smoke you are seeing after an extreme downhill deceleration probably highlights the limitations of the design of the oil control rings rather than any wear.