streetstang

Hey everyone, I was hoping I'd never have to post here about something like this, but here it goes. Long story short, 05 GT, STS Twin Turbo 10psi, 100k on the car, 80k while turbo'd (please don't bash on my setup LOL, it's been good to me since 04 , and yes I've been lucky to have gone this far with a stock motor.). I've talked to local San Diego speedshops, and none can give me a straight answer. The car smokes on decel. While boosting, there's no smoke. Only a slight hesitation/detonation from some oil leaking past the valve stem seals? When the car decelerates, it smokes a TON. It won't smoke at idle, won't smoke on cold start, but I think the valve stem seals are JUST bad enough that they smoke while stressed with boost. I've tried a catch can, doesn't work. Tried cleaning the filters and checking STS oil pump, tried valve cover breathers, nothing. Anyone else have this problem? The turbos have been rebuilt on schedule twice by a pro, and the charge pipes are clean as they'll ever be. Any ideas or any shops that could help me out in the San Diego area, please let me know! I'm too sad/embarrassed to drive the car now! Friends call me smoke screen now, LOL. Btw, I heard valve stem seals are a somewhat common problem, and somewhat of a you-know-what to fix.


sincerely (and desperately LOL)

CJ

Simon1

So I would guess the cars makes boost like it normally would, spooling and peak, but only after boost it smokes or every decel?

I would suspect a bad thrust bearing in one or both turbos since the thrust bearings STS used were not the best. But if it has been rebuilt twice (why two times?) then the better oiling stuff should have been put in there. So the easiest thing to do is pull off the air filters and wiggle the impeller on the shaft to see if there is play. If there is, you may have an oil leak in the turbo. Your intake pipes could be very clean and the oil could be coming out the exhaust side of the compressor.

How about a compression test for the motor? It may let you know you have a valve leaking or stem that is bad? Im not that versed in the tech side of the valves and such.

jlc41

Subscribed, I think Simon is on the right track and I would do a compression test valve seals.

moosestang

That's exactly what I was think and I don't know dick about turbos. I doubt it is a problem with the engine.

streetstang

Phew. Thanks guys. I thought nobody was going to reply for a second. haha. I forgot to mention though (you always forget some crap..) that on a COLD START, I get a LOUD KNOCK/TICK from the valvetrain. Smoke started happening AFTER I got the sound one day. Car always has sufficient oil, and there's no play from both ends of the turbo. Sounds like a compression test and maybe a leakdown test are in order. @Simon: The turbos were rebuilt once because of an oil pump failure, and once again just for safe measure by G-Pop Shop. <==they're great btw, and the car ONLY SMOKES in DECEL AFTER BOOST. Sorry for not being specific . Was in a rush to type.

Thanks again, everyone. Appreciate the help!!

Simon1

Well I am not sure what you had done when they were rebuilt, but if they ever are again, I would convert them to a BB style if they already are not.

They run much cooler than turbos that are placed in the engine bay so water cooling is not needed. However, I would have a turbo timer on the car that is of the automatic style. It's very imortant to not let the turbohave the oil shut off to it and stop spinning at the same time when it's really hot. At the minimum, when you are parking your car after a longer heated ride, let it idel for a minute or two so the turbos keep spinning and oil is fed thru at the same time.

Do a compression test or atleast ask if a compression test will show what you are thinking is the problem.

streetstang

Thanks for the advice! Yeah, I had an Apexi auto turbo timer installed a week before the turbos and it was set for 1:30 to 2:30 depending on the reading from the oxygen sensors (which was pretty damn spot on haha. Would totally recommend it to anyone.). I'll have tests done soon and I'll check back. Thanks everyone!

-CJ