Smoke Cloud on Restart
Smoke Cloud on Restart From a cold start the car starts up fine, idles, warms up, drives perfectly normal just cruising or under full boost. The issue is if I stop, say for gas, and let the car sit for 5-10 minutes and start it back up it has a tendency to dump LOADS of smoke out the down pipe. Like James Bond disappearing act amount. If I shut the car off and turn it back on within a few minutes, no problem, no smoke or smell or nothing. I can't figure it out. I brought this up a while back and dismissed it as my catch can being full and pulling oil in to the turbo however after constantly checking that it's empty it has been happening again I feel the problem is somewhere else.
I feel like if it was a turbo seal or head gasket issue the problem should be persistent right? Not just at short term shut downs and restarts. I have a scavenge pump so I thought maybe after the car shuts off and stops pulling oil there may be a little sitting in the turbo pooling up until it's restarted but i'm not sure hoe I would test that theory. The oil feed and drain is not 100% vertical but I don't think it's enough to create a oil back up problem, especially with the scavenge pump.
Any ideas or past experience with this would be helpful.
Thanks,
I feel like if it was a turbo seal or head gasket issue the problem should be persistent right? Not just at short term shut downs and restarts. I have a scavenge pump so I thought maybe after the car shuts off and stops pulling oil there may be a little sitting in the turbo pooling up until it's restarted but i'm not sure hoe I would test that theory. The oil feed and drain is not 100% vertical but I don't think it's enough to create a oil back up problem, especially with the scavenge pump.
Any ideas or past experience with this would be helpful.
Thanks,
Couple thoughts-what transmission, if like a turbo 400, and using a mod. valve, they can go bad, the vac. line can suck the oil into the engine, leave a cloud of smoke. Another is valve guides, on startup if oil is slipping past the seals, they can do that. If it was the turbo, I would think you would see oil in the intake tube, TB. Another thought was PCV valve, kind of happens, but sounds like you have replaced that with a catch can. And I guess you have to ask, is it smoke or steam. 706 heads were reported to crack where the head bolts go, under the valve covers, not sure if that leaks in the comb. chamber. Thats all I got, lol.
Couple thoughts-what transmission, if like a turbo 400, and using a mod. valve, they can go bad, the vac. line can suck the oil into the engine, leave a cloud of smoke. Another is valve guides, on startup if oil is slipping past the seals, they can do that. If it was the turbo, I would think you would see oil in the intake tube, TB. Another thought was PCV valve, kind of happens, but sounds like you have replaced that with a catch can. And I guess you have to ask, is it smoke or steam. 706 heads were reported to crack where the head bolts go, under the valve covers, not sure if that leaks in the comb. chamber. Thats all I got, lol.
Thanks for the advice.
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Stock T56 w/ Tick stage 2. If it was the turbo or a cracked head wouldn't you think it would smoke all the time? not just at restart? They are LS3/L92 style which have had problems cracking under boost in the past. but its weird that if I shut it down and turn it back on after a few minutes its fine? I thought it could possibly be a bad valve seal and once the car runs for a while and then shuts off it sits and leaks down the valve and pools in the cylinder. guess ill have to pull the valve covers to find out. Honestly can't tell if its smoke or steam, big fluffy white clouds. Maybe i'll try to grab a video next time I have it out.
Not sure where the water would be getting in. And like I mentioned before why is it intermittent and not all the time if it's a cracked head or something like that?
Thanks for the advice.
Not sure where the water would be getting in. And like I mentioned before why is it intermittent and not all the time if it's a cracked head or something like that?
Thanks for the advice.
As for where its coming from...that's a looong list of possibilities. Head gaskets is where I would be suspect if its coolant. If it's really oil smoke then the turbo or valve seals is where i would start.
Coolant, oil, diesel. Can see through an oil cloud, can't see through a coolant or diesel (just for reference)
I really don't have much more than that observation. I've popped a lot of engines in my time(small ones mostly) but when it leaves a cloud you can't see through, its always coolant. Oil makes literal blue smoke and its more like a cloud of smog, dark and hazy. If you can't see through the cloud I would bet dollars to doughnuts its coolant. The amount of oil it takes to make that kind of cloud also basically fouls the plugs and kills the engine. But a teaspoon of coolant makes a big dense cloud. You should be able to tell through smell too if its this bad.
As for where its coming from...that's a looong list of possibilities. Head gaskets is where I would be suspect if its coolant. If it's really oil smoke then the turbo or valve seals is where i would start.
Coolant, oil, diesel. Can see through an oil cloud, can't see through a coolant or diesel (just for reference)
As for where its coming from...that's a looong list of possibilities. Head gaskets is where I would be suspect if its coolant. If it's really oil smoke then the turbo or valve seals is where i would start.
Coolant, oil, diesel. Can see through an oil cloud, can't see through a coolant or diesel (just for reference)
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I'll bet you a chicken dinner its a head gasket then. Buddies Duramax was locked up every morning when he tried to start it. Key would engage the starter and the motor would not turn over until you tried about 2-3 times then would fire. Cylinder was filling up with coolant over night was totally fine otherwise. It's probably leaking when you turn it off and the coolant pressure spikes for those couple min after when the pump isn't circulating. Like I said, it only takes a couple drops to make a big cloud. The glycol in it makes it just like those annoying vape clouds, just lots of volume for a small amount of liquid.
Last edited by LetsTurboSomething; Apr 27, 2020 at 03:16 PM.
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Verdad Gallardo Thanks for the help. I have a bore scope ill try to take a peak in the cylinders before I go and yank the heads.
Anyone know if you can get the heads off with studs without taking the studs out? I'd like to try and keep them in if I can.
Anyone know if you can get the heads off with studs without taking the studs out? I'd like to try and keep them in if I can.
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If you need a scavenge pump cause the turbo is that low id say try a check vlave in the feed and one after the pump in the return first. I had a low mount turbo. Same symptom was the oil from the long feed line filling the turbo after shutoff due to gravity. Pump was off and it would slowly drain past the seals into the turbo. Start it up cloud of smoke.
If you need a scavenge pump cause the turbo is that low id say try a check vlave in the feed and one after the pump in the return first. I had a low mount turbo. Same symptom was the oil from the long feed line filling the turbo after shutoff due to gravity. Pump was off and it would slowly drain past the seals into the turbo. Start it up cloud of smoke.
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I reread that i kinda sounded condecending. It wasnt meant that way. How is the drain and feed run it could be a plumbing thing. Mine had a long feed that was higher then the turbo so when you turned it off all the oil in the line would run into the turbo and the none pumping pump would hold it in the turbo and let it leak by the seals. If i started it quick it didnt have time to drain past the turbo seals. If i waited over night the exhaust wasnt hot enough to burn the oil out as smoke. It took me awhile to figure it out.
If you need a scavenge pump cause the turbo is that low id say try a check vlave in the feed and one after the pump in the return first. I had a low mount turbo. Same symptom was the oil from the long feed line filling the turbo after shutoff due to gravity. Pump was off and it would slowly drain past the seals into the turbo. Start it up cloud of smoke.
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Coolant /white smoke will smell much different than oil. You could take a look at post turbine O2 sensor (after smoke out) and see what's on it. If oil, I would expect wet from being burned in turbine or... take a peak at the plugs to see what's being generated in cc.
Last edited by tblentrprz; Apr 28, 2020 at 07:43 PM.
pulled the plugs, I could only get 6 with the tools on hand, passenger side rear 2 I didn't have the right extensions to get at them, but the 6 I pulled all looked all looked normal to me. might try the valve covers next to check valve seals.
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My plugs showed awesome too cause smoke show was caused by the turbo after the engine. Valve seals would be smoke on start up after sitting overnight. Oil leaks past the seals into the cylinder so its burned on start up. That doesnt fit your symptom.