I just finished replacing a blown head gasket on my 83 280zx turbo. When starting the car and letting it idle for 5 to 10 minutes white smoke comes out of the exhaust. It starts as a faint mist and processed to get thicker. There is not a lot of coolant that comes out, but over time it accumulates in my garage. The car has been sitting for about a year, due to a lack of free time to work on it. When replacing the head gasket I also replaced the starter, water pump, thermostat, o2 sensor, and belts. I also replaced the gaskets for the intake, exhaust, timing chain cover, water pump, thermostat, all the turbo gaskets, oil pan and crank shaft seal. I checked the thermostat by putting it in boiling water to make sure it worked before installing it. I also drained the coolant, oil and gas and put fresh fluids in. I also took the head off and took it to a shop to have it resurfaced and new valve seals installed so I know the head is not cracked. Could this just be felt over coolant that has not been burnt off? I am not sure what else to check. I would hate to have to take everything off again to replace the head gasket again. Thank you.

 

Did you change the oil after the head gasket change ? Also leak down test the cylinders, if they hold good pressure then your head gasket is most likely good.
I have heard of someone putting the gasket on backwards, and a coolant passage isn't sealed. Also, you need to follow the torque patterns and steps correctly. Re-torquing after the engine has had a proper warm up. I'm sure the FSM should have detailed instructions on the process. If you took short cuts, you may need to take it apart and do it again. A lot of factors can cause your problem.

 

Compression check will let you know.

 

Did the machine shop pressure test the cylinder head for cracks ? That would be the first thing they should have done before replacing the seals. You did not mention the valves being lapped either. If they didn't pressure test it there could be your problem.

 

You ask if it could be left over coolant. Have you pressure tested the cooling system or looked for loosing new coolant? Does your car have a cat? I suppose it could have had year old coolant in the cat thats burning off but I would be looking for coolant loss and doing a compression and leakdown test. These three will give you your answer. Be sure you watch for bubbles in the radiator during the leak down test.

 

Yes I did change the oil, coolant, and gas after I replacing the head gasket. I don't think it is possible to put the head gasket backwards on a l28et since the timing chain area would be sticking out. I torqued the head bolts correctly and followed the torquing sequence. I have not properly warmed up the engine, to retorque the bolts, due to the coolant problem.

I just finished doing a compression test and all the cylinders had a reading of 150 after about 5 turns. This was without the engine being warmed and with out putting oil into the cylinders. Is a leak down test still needed?

The machine shop did check the head for cracks and it was fine. I forgot to mentioned that I had the valves lapped at the same time the valve seals were replaced.

I do have a cat so it might be due to left over coolant in there. From what I can tell there is no coolant being lost. I am hopping it is left over coolant, since the white smoke is very faint. I will pressure test the radiator later today just to make sure.

 

If you are not losing coolant you should be fine, the fuel is converted to co2 and h20 in the cat so you that's probably what you are seeing.

 

Did you clean the block perfectly clean? A bit of old gasket can kink the new and make a small leak. All mine burnt off in 5 minutes at temp. My oil even cleared all the water in a hour.

 

I finished pressure testing the radiator and it held pressure. I let the engine run a couple more times today and more white smoke was produced, but the coolant levels remained the same level. As mentioned before, I think what is burning is the coolant that got stuck in the cat or fuel that is being converted to co2 and h2o. Either way by continuing to run the engine I feel the problem will sort itself out. Thanks for the help guys.