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White Smoke On Deceleration On Dyno

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Old 04-29-2024, 04:19 AM
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Slo.c5
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Default White Smoke On Deceleration On Dyno
Had my car on the dyno for the first time today! I noticed alot of white smoke coming out of the exhaust on deceleration. Is this normal? I have a tune on it and headers, x pipe, with a slp axleback. Thanks!
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Old 04-29-2024, 06:39 AM
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Old 04-30-2024, 05:20 PM
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Originally Posted by Slo.c5
Had my car on the dyno for the first time today! I noticed alot of white smoke coming out of the exhaust on deceleration. Is this normal? I have a tune on it and headers, x pipe, with a slp axleback. Thanks!
No.
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Old 04-30-2024, 06:32 PM
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Not normal. Best guess you have a bad head gasket letting coolant into the combustion chamber. Time for a leak down test.
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Old 04-30-2024, 07:04 PM
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Originally Posted by Slo.c5
Had my car on the dyno for the first time today! I noticed alot of white smoke coming out of the exhaust on deceleration. Is this normal? I have a tune on it and headers, x pipe, with a slp axleback. Thanks!
If it smelled like coolant then it could be a coolant leak into a cylinder. If it engine is ok otherwise, it could be an overly rich condition, excess fuel on deceleration. Sometimes unburned fuel will look like white smoke.
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Old 05-01-2024, 03:03 PM
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Headgasket is my guess. Start pulling spark plugs and look for one that does not look like the others.
Last edited by 93Polo; 05-02-2024 at 01:26 PM.
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Old 05-01-2024, 03:08 PM
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Is the brake fluid level going down in the master cylinder?
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Old 05-01-2024, 04:07 PM
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Head gasket. The vacuum will draw it out of the bad gasket when letting off.
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Old 05-01-2024, 04:11 PM
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Originally Posted by Fast one
Is the brake fluid level going down in the master cylinder?
You have piqued my curiosity. How does the brake fluid correlate with white smoke from the exhaust on decel while on the dyno?
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Old 05-01-2024, 05:41 PM
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If the brake booster leaks it can suck brake fluid from the master cylinder which will be drawn into the engine under high vacuum and burn it resulting in white smoke. If the brake fluid level is stable then this isn't the cause.
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Old 05-02-2024, 01:18 PM
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Originally Posted by Fast one
If the brake booster leaks it can suck brake fluid from the master cylinder which will be drawn into the engine under high vacuum and burn it resulting in white smoke. If the brake fluid level is stable then this isn't the cause.
Ok. so the master cylinder would have to leak into the power brake booster......but in that case it should do it all the time, not just on the dyno, correct?
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Old 05-02-2024, 04:53 PM
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Yes.
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Old 05-02-2024, 06:22 PM
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Originally Posted by Fast one
Yes.
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Old 05-04-2024, 05:36 AM
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Originally Posted by C5MSG2004Vert
If it smelled like coolant then it could be a coolant leak into a cylinder. If it engine is ok otherwise, it could be an overly rich condition, excess fuel on deceleration. Sometimes unburned fuel will look like white smoke.
I think this might be the issue. I should have specified when I said tune I asked the guy to make it backfire on decel so I could pop flames lol. Still was not expecting that much smoke. Guessing this is it because I recently had my head rebuilt but I will check everything else!
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Old 05-04-2024, 05:37 AM
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Thank you everyone for the suggestions!
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Old 05-04-2024, 02:01 PM
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Only other thing I'll throw in is valve seals, though that's going to be more a bluish-white smoke. How thick was the smoke coming out?
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Old 05-04-2024, 02:11 PM
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Originally Posted by Slo.c5
I think this might be the issue. I should have specified when I said tune I asked the guy to make it backfire on decel so I could pop flames lol. Still was not expecting that much smoke. Guessing this is it because I recently had my head rebuilt but I will check everything else!

Maybe I’m just getting old, but tuning to purposely backfire 🙄. You be you and all that stuff, but I’m seriously hoping your like 18-21 and just going through some stuff.
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Old 05-04-2024, 06:14 PM
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Originally Posted by Mc556
Maybe I’m just getting old, but tuning to purposely backfire 🙄. You be you and all that stuff, but I’m seriously hoping your like 18-21 and just going through some stuff.
Yea maybe you are just getting old lol
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Old 05-04-2024, 10:18 PM
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Originally Posted by Slo.c5
Yea maybe you are just getting old lol

Na not really
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Old 05-05-2024, 01:15 AM
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Pop flames lol.I didn't know you could tune a car to do that and backfire.
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