I have smoke coming out of my exhaust and I am trying to diagnose it. It is light gray in color, it starts out in the pass side tailpipe with the drivers side being clear, then it will switch over to drivers side, sometimes it will be both, sometimes it alternates, sometimes it stays out of the pass side, but it always seems to start with the pass side. If you rev it up, it seems to get better or go away. I know white smoke is coolant, black smoke is oil, but it smells like neither. I have had a cracked head before, so I know what burning coolant smells like. I just changed the oil and the spark plugs and did not notice any evidence of coolant. I did a compression test and got ~185 psi all around. It smells like my truck does when it first starts up. The car has had the AIR system removed, but it does have high flow cats. Would a rich mixture cause noticable smoke? It does not smell like gasoline, it just smells like a car that just started up, but my truck will eventually go clear and I can put my face in the exhaust and it hardly smells for the truck. Now I have not finished getting the car ready for the road and taken it on any extended rides, just idling or a drive around the nieghborhood long enough to get the coolant up to temp, so I am thinking maybe it just takes the cats longer to heat up and start working? Do the two pipes stay seperated or do they mix in the resonator in the middle? Any ideas on how to figure this out for sure what it is?

 

It sounds more like moisture in the exhaust system boiling off as the system heats up. Does it go away once the car is fully warmed up?

 

I havent really been able to drive it as I just got it and have been doing some work on it. I have brought the car up to temp while idling, but I havent really had it driving around to let the exhaust heat up.

After looking some more, I am afraid that maybe it is actually a head gasket, I can smell coolant in the engine compartment on the pass side, but when I pressurized the system to check for leaks, it held the 15 psi, and the compression all checked out, so I dont know. I guess if the leak were small enough, it would look like water vapor in the exhaust without really smelling like burnt coolant? I am going to wipe down the head and block really well (There was a pretty bad leak on the valve covers and intake manifold) and then keep an eye on it. Is there any way to definitively tell if a head gasket is bad without taking the head off? Is there a way to tell if the head has a small crack somewhere so I dont go through all the trouble of replacing a head gasket and still have the same problem? Whenever I have had a problem like this, it has been really really obvious what it was, like a quart of water in the oil pan, water pouring out of wherever the leak was when you pressurize the system, etc etc.

 

White smoke with a sweet smell is coolant. Light blue is oil, black is fuel and running rich

 

Forgot to update, I got the car on the road this past weekend and I think it is just water vapor burning off. It was nice and clear when I checked it at work (~8mi drive) I think exhaust is still rich though, kind of burns the eyes a bit. I have to upgrade to heated O2 sensors in my long tubes because it keeps going into Open Loop at idle.

Still trying to figure out the coolant smell in the engine compartment though. I can't find any obvious leaks anywhere. The heater hoses do not appear to be original, they are light blue and dark blue. It is almost like I can smell the coolant through them. Anyone ever heard of this? Can also smell coolant if I sniff around the filler cap, but no leaks. I guess I am just going to drive it around and see if I am actually losing any or what and take it from there. From idling around the driveway for a month while I have been working on it, it hasn't dropped.

 

Check your overflow tank and the hose to it. You could have a small hole in either of them. It only takes a very small amount to get the odor.