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The mkiv Supra Owners Club

Confused. Not smoking anymore


Pig

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My car has recently been smoking LOTS on start up. The is confirmed to be the dreaded blue smoke by matt harwood and lucifer!

However the last couple of times i have turned the car on there has been no smoke??? my oil light came on the other day so put lots of oil in....any ideas?

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Flled it up a couple of days ago so level will be fine. Been driving her a fair it lighter, could this be anything to do with it??

 

Dont feel as though i have much to prove anymore :D

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Guest Bulldog

Stem seal wear will only cause an engine to smoke on start-up or after any over run (eg. after coasting down hill with your foot off the throttle.) If your engine smokes when under load

1, check your breather system is not blocked up

2, check the oil level is not to high

3, check with your bank manager to see if you can afford a re-bore a set of pistons & maybe a full new set of valve guides

& then speak to Lucifer & ask for a good deal

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Stem seal wear will only cause an engine to smoke on start-up or after any over run (eg. after coasting down hill with your foot off the throttle.) If your engine smokes when under load

1, check your breather system is not blocked up

2, check the oil level is not to high

3, check with your bank manager to see if you can afford a re-bore a set of pistons & maybe a full new set of valve guides

& then speak to Lucifer & ask for a good deal

nope stem seal wear will cause a supe to smoke on start up on a fairly random basis like someone has said i think it depends on where the cams fall when the engine is switched off, it is not a massive concern (just a little embarrasing) mine ran like this for a year and a half, when i took the head off everything was nice and shiny but the stem seals were absolutely shot

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Guest Bulldog

It depends on where the cam falls??

How dos the position of of a rubber seal on a precision ground or coated valve stem affect its abillity to prevent oil from passing? unless the valve stem has worn which is very un common on the 2jz engine that hasnt been subject to oil starvation

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It depends on where the cam falls??

How dos the position of of a rubber seal on a precision ground or coated valve stem affect its abillity to prevent oil from passing? unless the valve stem has worn which is very un common on the 2jz engine that hasnt been subject to oil starvation

really dont know fella, one and a half years of intermitant smoking on start up, changed the stem seals and hey presto smoking gone completely

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Guest Bulldog

And lets not forget the hundreds of engines that have a much larger clearence from the guide to the valve & yet dont have any stem seal at all why dont they intermitantly smoke?

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Valve stem seal failure is one of the most common causes of intermitant smoke on startup. Most are getting pretty old and brittle by now. Rope trick( MKIV.com) or head off, Dude did announce he had a tool for this just before he was taken from us. Almost all cars have no smoke after seal replacement.

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And lets not forget the hundreds of engines that have a much larger clearence from the guide to the valve & yet dont have any stem seal at all why dont they intermitantly smoke?

sorry if this doesn't sit with your way of thinking but intermitant smoke on start up on a MKIV is valve stem seals FACT, i have stripped my head down to component level done light porting, polished the hell out of it, changed the valve seals, re-fitted it and guess what, it NEVER smoked again on start up

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Guest Bulldog

A tempory fix im affraid!!

After 15 years of engine reconditioning & becoming the owner of my own reconditioning company Ive realized that an engine will only rely on stem seals when the correct clearance in the guide has been lost due to wear or when crank case pressure is increased by tired bore walls & rings

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ok buddy whatever i think we'll have to agree to disagree hear, have you taken a set of exhaust valve stem seals off a MKIV if the answer was yes you would appreciate the reason they leak they litterally come of in bits, i can appreciate some engines dont use stem seals and thats a different argument alltogether but the fact is Mr Toyota (who knows a little about engine building) put stem seals in the 2JZGTE and after high miles they fail, simple, i stripped my head verifing tolerances as per Mr Toyotas manual and the valves and bores were in tolerance if they weren't they would have been changed (i'me fussy like that), there really isn't an issue here mate if the car smokes on start up and its a few years old its pretty much guaranteed its the stem seals

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Guest Bulldog

Agreed valve stem seals do fail on the 2jz at about 4-5 years old not due to wear but due to oil contamination slowly making the rubber go brittle, however providing its serviced regularly the valve stem & guide should last at least 90-100k (approx 9-10 years ave) before relying on the stem seal which has long since perished & needs replacing in order to mask the real problem.

If I was Mr Toyota I would be ashamed if my brand new engine was relying on a .25mm thick contact of cheap rubber to prevent it smoking & I would probably want to recalibrate my measuring equiptment too!!

P.S Dont mean to piss you off but I do love a bit of banter

Cheers!!

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Agreed valve stem seals do fail on the 2jz at about 4-5 years old not due to wear but due to oil contamination slowly making the rubber go brittle, however providing its serviced regularly the valve stem & guide should last at least 90-100k (approx 9-10 years ave) before relying on the stem seal which has long since perished & needs replacing in order to mask the real problem.

If I was Mr Toyota I would be ashamed if my brand new engine was relying on a .25mm thick contact of cheap rubber to prevent it smoking & I would probably want to recalibrate my measuring equiptment too!!

P.S Dont mean to piss you off but I do love a bit of banter

Cheers!!

 

 

Sounds about right to me.

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Stem seals are fitted by the manufacturer to REDUCE oil drain down the guides when running & at shutdown otherwise:

1) the valve guide would be over lubricated,

2) the oil would get into the combustion chamber & contaminate the incoming combustion charge (when off boost)

3) oil would contaminate the exhaust & catalysts

4) the excess oil on the valve stems would burn into a gummy carbon mess that would cause valve sticking

 

The guides need them from day 1. Turbo engines run with wider valve to guide clearances due to the higher thermal loadings on the valves (to allow for more expansion).

As the guide stem seals deteriorate, the problems begin to occur as listed above, and this is probably exactly what Mr Toyota found during initial development.

 

Shame they didn't find a better material that could last the life of the engine (PTFE?)

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Guest Bulldog

due to the angle of the valves in the head, the low position of the oil return holes & the fact that the valve stem only recives an over spill feed from the cam journals in the 2jz & in most multi valve (shimmed) heads oil drain down is not that big of an issue. I still maintain that smoking on start up or after long periods of over run is not so much stem seal but dew to irregular wear on the stem & guide. although changing the stem seal will mask the problem for a while.I have stripped many 2jz heads that have crumbling stem seals & yet my customers have told me there are no signs of smoke at all....Explain!!

 

PS valve sticking is caused by repetative short journeys that dont allow the tiny amount of oil that dos reach the valve head to be burnt clean. When I have a head for reconning i can always tell from the carbon deposits if its a motorway car or a town car.

Hmmm more food for thought!!

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