How does one know if valve stem seals are bad???

[Supra Blues]

Upon startup and for the first minute of driving I get a considerable amount of smoke from the exhaust pipe. After that it goes away.

This is a 7MGTE swap. The bottom end is brand new. New everything. The head I bought used which apparantly had been rebuilt recently.

The turbo is also used, but appears to be working just fine.

I am leaning toward valve stem seals, but what are your thoughts?

I have read/heard about leakdown tests. How is this done????

 

[aye mate]

My car used to smoke right after start-up then when I rebuilt the head and I put new valve stem seals in and it hasn't smoked since. I too would like to know what a leakdown test does and how its done.

 

[Idealsupra]

My car used to smoke right after start-up then when I rebuilt the head and I put new valve stem seals in and it hasn't smoked since. I too would like to know what a leakdown test does and how its done.

http://www.type2.com/library/engineg/leaktst.htm

will get you started as far as leak down tests go...

as for valve stem seals...usually if you are driving and when you push in the clutch it smokes..meaning between shifts...or when you get on it and then letoff and push in the clutch and it smokes...OR at idle while at a light etc... that is mainly from valve stem seals....

a lot of times gasket set valve stem seals wont work properly and will do this...toyota brand is the only way to go as far as that goes IMO...

 

[Supra Blues]

It seems to me that at idle I can smell burnt oil or when slowing down or accelerating from a stop.

Startup is the worst though and for a minute or so after that.

 

[prsrcokr]

I think thats a little backwards. Geners\ally valve seals will cause smoke at startup (bluish cloud) This is due to oil sitting against the valve seals while the engine is not running and once started the worn seals allow oil to sneak by.

A bad turbo seal will cause oil to be burned during deccel or sitting at a light.
Brian W

 

[Idealsupra]

I think thats a little backwards. Geners\ally valve seals will cause smoke at startup (bluish cloud) This is due to oil sitting against the valve seals while the engine is not running and once started the worn seals allow oil to sneak by.

A bad turbo seal will cause oil to be burned during deccel or sitting at a light.
Brian W

i disagree... a bad turbo will blow smoke on acceleration and under boost IMO...

when theres vacuum the valve stem seals will produce the smoke...and theres vacuum between shifts and idling...

 

[lagged]

A bad turbo seal will cause oil to be burned during deccel or sitting at a light.

anyone else care to chime in? i am hoping that the turbo would cause oil to be burned on deccel. i just got my rebuilt motor running and i burn oil during decceleration only, possibly while boosting as well but i have not been doing much of that (break in) and i havent had anyone drive behind me to look for smoke.

i know i burn oil on deccel cause when i finally come to a stop the cloud of oil smoke catches up to me.

 

[Darkcyde]

Could be piston rings. If they are worn or in your case, not seated properly, vaccum will pull oil past them into combustion chamber when you let off the throttle.

 

[Ckanderson]

i disagree... a bad turbo will blow smoke on acceleration and under boost IMO...

when theres vacuum the valve stem seals will produce the smoke...and theres vacuum between shifts and idling...

A bad turbo can smoke anytime... when ya boost, when your idliling.... whatever...

valve stem seals are VERY easy to check for... drive the car up to 6500 in 1st gear.... and let off the throttle... DO NOT PUSH IN THE CLUTCH watch in your rear view to see if smoke starts coming out... if it does... thats valve guide seals.

 

[Idealsupra]

A bad turbo can smoke anytime... when ya boost, when your idliling.... whatever...

valve stem seals are VERY easy to check for... drive the car up to 6500 in 1st gear.... and let off the throttle... DO NOT PUSH IN THE CLUTCH watch in your rear view to see if smoke starts coming out... if it does... thats valve guide seals.

6500? lmao we dont ALL have 1jzs

but yeah i guess reving high and letting off would work for a test...its basically creating nistant vacuum....

 

[Ckanderson]

That is the old school way of doing it... works EVERY time. i suggested 6500 cause it's the 6m crank's redline... take it up to 6k thats fine too. you just want lots of vacum for a extended period... 1st gear works well since your going slow... so smoke really doesnt dissapate much.

 

[Supra Blues]

I notice it upon starts, ecspecially in the morning and upon decel.

But normal freeway driving I don't really notice it at all.

Looks like my used/rebuilt head has old valve stem seals... :thumbsdow

 

[prsrcokr]

i disagree... a bad turbo will blow smoke on acceleration and under boost IMO...

when theres vacuum the valve stem seals will produce the smoke...and theres vacuum between shifts and idling...

I haven't seen bad seals on a turbo cause smoke during acceleration. My current turbo showed a bad seal after the first week. It has never smoked under acceleration, only under high vacuum, low rpms on deccel. Maybe it is the rings as mentioned. Have you done a compression test?
Brian W