13 replies to this topic

[Madmax]

right guys, GW in particular

ive got a 2,500 mile old engine, i ran it in properly for 1000 miles, then changed the oil for good stuff and new plugs etc

its been constantly chucking (alot) of smoke out the back, whenever i leave from a standstill at the traffic lights

it only does it when the accelerator is depressed a very minor amount, say to get the engine to rev to perhaps 1200rpm for a slow move off from stand still, but it is quite an alarmingly large amount of smoke, its white smoke, but definatley oil. oil doesnt have to be a bluey colour.

now, when i decked my head to the block, the machine shop didnt quite get a perfect finish on the mateing surface on the head, and i had my engine builder smooth it off himself, if this wasnt done quite properly would this allow oil from the galleries to seap into the combustion chamber and cause the problem?

kinda asking on behalf of Flappyplasticbits too, as his had the same problem

those who were on the nurburgring run will know what im on about, especially minis84 and mentalist who had to put up with a smoke machine in front of them

[Madmax]

i thought it could be stem seals...but maybe its something more sinister...

[Jammy]

I think I have this problem as well?! Do your cars use a fair amount of oil?! Anyone using forged pistons?

[Madmax]

not using forged pistons, but im going through a hell of alot of oil

[Madmax]

am i noticing a trend in the fact that all of our engines are of a mild to mad state of tune

[Dan]

In my experience, large amounts of white oil smoke under sustained heavy load (such as moving off slowly or pulling uphill) tends to mean ring sealing problems in A series engines, either a cracked ring or a poor seal. I've rebuilt at least two engines which had the same sort of problem and found this to be the cause.

I hope it's not that in your case though as that is a very young engine and it would be awful to rip it apart again.

[Madmax]

that had been playing in my mind too

[Jammy]

See I was told it could either be that or valve stem oil seals, so I did a compression test and all were really high?

[mini_nutz]

Hi, I had the same problem when I rebuilt my engine. I was really confused as I had replaced all the piston rings along with homing out the cylinder. I had also rebuilt the cylinder head and replaced the stem guides and oil seals.

Unfortunately I needed the car to drive to work and so I was unable to dismantle the engine so I decided that I was going to have to drive the car for a few months and then when I next got some time I would examine the head and block. After about 2500miles it magically stopped smoking and now it runs perfectly.

I would advise that you drive the car for a few more miles and see if it stops; if it does then you wont have the hassle or expense of stripping down and rebuilding the engine again.

I don’t think that the oil burning can cause any major damage only to the wallet for the extra oil needed.

[minidaves]

did u gap the rings on assembley? sounds like a take it out and inspect job to me.

dave

[Madmax]

it had crossed my mind that it may be the rings not quite sealing properly, and maybe it needed a bit more running to cure it, so im going to give it a go and see where it goes

not going to let it get out of hand though, i know what damage i could do

[minidaves]

more running in is not going to cure the problem, if its smoking its smoking, it may already be knackered but if it was me on the bench it would be going

dave

[Dan]

A compression test does not always reveal dodgy ring sealing, as a slight leak will only be shown under sustained load (which is why it doesn't always smoke, only when you load it up). A leakdown test would be much more useful.

The little rubber seals on the valve stems are not what ususally causes valve oil leaks, as most of the oil is excluded by the tight fit of the stem into the guide. Once the guide is worn there is little you can do to prevent oil leaking through even with new rubber seals. Oil leaks through the stems will normally be revealed as a cloud of smoke on startup rather than while running, as there is relatively little oil collecting on the tops of the valves while running and it woud be drawn through slowly and continuously leaving a fine mist behind the car rather than a big cloud of fog. When the car is sitting overnight however a relatively large amount of oil can trickle down the stems and pool in the inlet port to then be drawn in and burnt when the engine is started.

Edited by Dan, 07 November 2005 - 05:04 PM.

[Pickup76]

What have you checked? theres a fair ammount of bits you can take off and check before you need to take the engine out. I had this problem about 500 miles after my rebulid and it turned out to be a valve stem seal that had come loose and was pumping oil down the valve stem intermittently. Check everthing you can before it comes out or you'll kick yourself if its something silly like a bloocked breather.