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10/23/17 12:08pm - Original Message: '89 C4 white smoke from exhaust'
JensenBreck
Former Member
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Joined: 10/6/2017
Posts: 6
Hello,

I am going to be finished paying off a C4 in a week and will be picking it up at the same time. It has been in a heated garage for 5 months during winter and when we started it up a bit of white smoke was coming out of the magnaflow exhaust. i even have a video so you can see. Its probably from sitting around for a long time but im not a mechanic. Thoughts?




|UPDATED|10/23/2017 10:08:45 AM (AZT)|/UPDATED|


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10/19/17 11:08am - Reply: 'Re: 89 C4 white smoke from exhaust'
Carmichaels89
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Valley Center, CA - USA

Vette(s):
Original owner 89 C4 Coupe,Silver with Red Int, late model C6 wheels

Joined: 7/11/2016
Posts: 3
Check the vacuum modulator unit on the transmission and line from the transmission to the intake. Once the rubber diaphragm inside the modulator ruptures, the engine will suck ATF into the intake causing white smoke. It could be just a pinhole in the diaphragm at this point You may find trans fluid in the line or dripping from the modulator once the line is inspected. Replacing the modulator is easy and it is usually preset from the manufacturer. A small set screw inside the unit, accessible from the vacuum port, is a fine adjustment to shift points. Hope this helps.

Macho007 is correct about the smoke color. ATF has a tendency to appear white. If the issue is only at start up it is likely not the modulator valve. One diagnostic tip: If it is the modulator, during deceleration (as in coasting down a long hill or from a freeway off ramp) added vacuum will pull fluid to the intake which will be visible upon acceleration. Watch your mirror for telltale vapors or have someone follow you to verify what is taking place.

The smell of the emissions will also be a tip to the origin. We all know the smell of oil, coolant and fuel. Pure water or condensation will smell slightly musty or damp. There may not be enough to have any odor at all.

Assuming there is no oil/water cross contamination there could be a small intake gasket leak but usually the white smoke would be constant not just at start up. It could be a small enough leak where coolant/water  accumulates when the vehicle sits over night or for days.


|UPDATED|10/19/2017 9:08:35 AM (AZT)|/UPDATED|
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10/19/17 9:43am - Reply: 'Re: 89 C4 white smoke from exhaust'
Macho 007
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Plant City, FL - USA

Vette(s):
1988 Corvette Hatchback. Interior and exterior Black. Automatic.

Joined: 5/16/2015
Posts: 16
The white smoke may also have been caused by condensation of moisture collected from sitting for an extended time. White is usually water, blue is oil, and black is a rich fuel mixture. Hope this helps.

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11/1/17 11:57am - Reply: 'Re: 89 C4 white smoke from exhaust'
vintageracer
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, - Canada

Vette(s):
1987 Corvette - Targa Top, Automatic 1985 Corvette - Targa Top, Automatic

Joined: 11/4/2012
Posts: 31
I agree completely with Macho. I'm saying condensation also.



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11/1/17 12:29pm - Reply: 'Re: 89 C4 white smoke from exhaust'
Barn find
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Lakeville, MA - USA

Vette(s):
1987 convertible

Joined: 4/19/2014
Posts: 8
I'm experiencing the same issue. depending on temperature, and length of time sitting. Now, although a lot of the time it can look white It has a light blue  to it and you can smell oil. It was suggested to me that the valve seals are the culprit.  Any thoughts on this ? After 4 years I am hoping to get to it this winter before I totally destroy the catalytic converter ....I know remove it. Unfortunately I'm a keep it stock stock freak.
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11/1/17 4:41pm - Reply: 'Re: 89 C4 white smoke from exhaust'
Strats-N-Vettes
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Atchafalaya Basin, LA - USA

Vette(s):
Black 1979 L-82 Black 1996 LT1 Black 1999 Coupe

Joined: 3/20/2009
Posts: 432
depending on temperature, and length of time sitting. Now, although a lot of the time it can look white It has a light blue  to it and you can smell oil. It was suggested to me that the valve seals are the culprit.  Any thoughts on this ?
 
 
 
 
 
 
 
A lot of the times; yes.
Every time? No.
 
Plenty of aftermarket stuff and OEM out there.


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11/14/17 4:20pm - Reply: 'Re: 89 C4 white smoke from exhaust'
Macho 007
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Plant City, FL - USA

Vette(s):
1988 Corvette Hatchback. Interior and exterior Black. Automatic.

Joined: 5/16/2015
Posts: 16
If blue smoke comes out of exhaust for a short period when car is first started after standing for a time or when idling at a stop sign or red light, I would put in a new set of valve stem seals. This can be done without taking the heads off by bringing the piston for the cylinder you are replacing seals on all the way to the top of its stroke and removing the spark plug and inserting a compression gauge hose into the spark plug opening and attaching a air connector from an air compressor to the to the hose. The air pressure will keep the valve from falling into the cylinder after you remove the valve spring retainer and spring. Remove the old valve stem seal, which will probably crumble if it is hard, and install new seal, replace spring, and retainer and repeat on each cylinder. I am a retired Mechanic of 40 years and have done this countless times. If you are unsure of the procedure I would recommend taking it to a professional or it might be a good time to have the heads reconditioned. Hope this wasn't to confusing. Good Luck! 

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11/15/17 12:19pm - Reply: 'Re: 89 C4 white smoke from exhaust'
MDMC4
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Glenbeulah, WI - USA

Vette(s):
1988 Blue Coupe

Joined: 9/5/2009
Posts: 4
Lately I have been having the same problem with my 88, is common to have the smoke from only one tailpipe? Mine is only coming from the passenger side.

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11/20/17 11:15am - Reply: 'Re: 89 C4 white smoke from exhaust'
Macho 007
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Plant City, FL - USA

Vette(s):
1988 Corvette Hatchback. Interior and exterior Black. Automatic.

Joined: 5/16/2015
Posts: 16

If exhaust is from each side of engine without any crossover in between the problem exists on that one side of the engine only.  Besides being an issue with valve stem seals another cause of oil smoke could be a bad oil control piston ring. As long as the valve stem seals are tight around the valve stem and soft and pliable, they should be doing their job. Once they become hard and brittle, they become a problem. Unfortunately I have no tests I can think of for checking condition of ring except for an engine teardown to remove pistons and visually inspect rings. Also a compression test might give you some idea of the engine condition.  Hope some of this information helps. (White smoke from one side could be blown cylinder head gasket.)



|UPDATED|11/20/2017 9:15:48 AM (AZT)|/UPDATED|


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