Can't diagnose white smoke out of exhaustpipe

[Josh Slade]

Hi there,

i've got a 260z with roundtops on, and it idles like a bag of spanners, and emits a ridiculous amount of white smoke out the back. Normally you would think this would be a blown headgasket, but it is a brand new headgasket, torqued down correctly. I have even tried draining all the water from the system and starting it for a short period, but with the same cloud of white smoke. What else could this be? a warped head maybe, or vacuum leak? Really getting to my wits end with it now.

 

[Turn & Burn]

Have Nissan voted in a new Pope?

Seriously tho, is the water system pressurising? That would suggest head gasket fail. You would normally have oil in the water too.
There’s isn’t a load of water in the exhaust is there thats steaming off?

 

[MaximG]

It sounds to me that you still have a headgasket problem.

 

[chris frizzell]

i had the same problem with my 280z white smoke every how and then . come to the conclustion it was my exhaust holding a little water . but i looked at my timing ,did a compresion test and mayo in the oil ,timing was out a little but all ok

 

[Josh Slade]

So i have done a compression test

1- 100
2- 95
3- 90
4- 95
5-90
6-90

So very low. As i said, it has a brand new head gasket, so could this indicate all the rings are gone? I also had to re grind all new valves in as 10 of them were bent, so perhaps I haven't done it well enough as it was my first time

Any other help would be very much appreciated

 

[jonbills]

So i have done a compression test

1- 100
2- 95
3- 90
4- 95
5-90
6-90

So very low. As i said, it has a brand new head gasket, so could this indicate all the rings are gone? I also had to re grind all new valves in as 10 of them were bent, so perhaps I haven't done it well enough as it was my first time

Any other help would be very much appreciated

did you try the compression test with a few cc of oil in each plug hole? (and was the throttle wide open?) that would confirm if rings or valves.

 

[Josh Slade]

did you try the compression test with a few cc of oil in each plug hole? (and was the throttle wide open?) that would confirm if rings or valves.

No i didnt whoops... i will do that, should i do a dry and wet one with the throttle wide open?

 

[jonbills]

yes - always throttle wide open, and wet and dry numbers helps identify where any problems are.

 

[peter_s]

My 280Z did the same thing with the stock engine. White smoke from time to time, in certain situations. Mainly coming off the gas
The way my engine drank oil, it was probably both ring blow by and valves...

 

[Farmer42]

If you bent your valves, you could have damaged the seals and guides and that could be why your compression is down and you have smoke. Did you replace all that when you replaced the valves? Also, have you checked your crankcase breather pipe is not blocked?

 

[AliK]

With compression figures like that, I would strongly suspect water leaks around the head somewhere. Do you see milky oil? Or oil film in the water? Have you gone for a long drive and monitored the coolant levels before and after?

White smoke is nearly always water / antifreeze (some armoured / fortified cars dump antifreeze in the exhaust as an effective smoke screen)! You don’t need a lot of it to make huge smoke.

Are you at all in the Southeast? If so, happy to meet up and have a look for you.

My money is on a less than flat head. Was it doing it before the new head gasket? Were there any signed of water leaks on the old H/G?

Defo do the compression wet and dry and closely look at the state of each spark plug . This is what my old Smokie engine was doing (but that one was burning oil as you can see on the plugs)...

 

[Josh Slade]

With compression figures like that, I would strongly suspect water leaks around the head somewhere. Do you see milky oil? Or oil film in the water? Have you gone for a long drive and monitored the coolant levels before and after?

White smoke is nearly always water / antifreeze (some armoured / fortified cars dump antifreeze in the exhaust as an effective smoke screen)! You don’t need a lot of it to make huge smoke.

Are you at all in the Southeast? If so, happy to meet up and have a look for you.

My money is on a less than flat head. Was it doing it before the new head gasket? Were there any signed of water leaks on the old H/G?

Defo do the compression wet and dry and closely look at the state of each spark plug . This is what my old Smokie engine was doing (but that one was burning oil as you can see on the plugs)...

Thanks for your reply, i am based in Waterlooville, just north of Portsmouth. I bought the car as a full on restoration project, so I have never driven it, it had been sat in the Arizona desert for possibly decades. If i flush all the water and replace it, there does seem to be some sort of film in the radiator after running for a little while, but no milky oil. When i tried to initially get it started, the little nub on the front of the camshaft that holds the cam sprocket in place sheared off and bent 10 valves before it ever ran, so I have no idea how it would have ran before the new head gasket, i just decided to change all the gaskets when i had the head off. I will do a dry and wet compression test shortly, do I need to take all the spark plugs out to do this?

 

[jonbills]

yes, plugs out for the compression test.

 

[AliK]

Wot he said [emoji115][emoji115]

I also put a battery charger on the battery at the same time to negate the effects of a battery running down as I do it.

Strangely, I’ve never seen a difference with throttle open or shut while doing the test - but that could have just been due to all the air leaks I’ve been tracking down . In all seriousness, throttle fully open and crank for 5-8 compressions per cyl.

Other possibility which I wouldn’t get too paranoid about is a potentially cracked head. Have you had it tested while it was off?

You can get water in the chamber I guess without mixing with oil depending on where it’s coming from.

 

[Josh Slade]

Here is a video of it running if it helps, idling at about 1000 rpm, and the smoke is quite a bit more white in person

 

[Bazzateer]

i am based in Waterlooville

Have you seen the 240Z at your local Nissan dealership?

 

[Rob Gaskin]

Mmm, I'm not sure that it is white smoke. It looks like oil smoke and it's also blowing from the manifold.

Ok I know you said it's whiter 'in the flesh'.

With those compression pressure all across the cylinders I'm thinking that the engine is in need of a rebuild?

Just my thoughts.

 

[Josh Slade]

Have you seen the 240Z at your local Nissan dealership?

I keep meaning to go in a see it! apparently its amazing

 

[Josh Slade]

Mmm, I'm not sure that it is white smoke. It looks like oil smoke and it's also blowing from the manifold.

Ok I know you said it's whiter 'in the flesh'.

With those compression pressure all across the cylinders I'm thinking that the engine is in need of a rebuild?

Just my thoughts.

I think it is definitely in need of a rebuild. The manifold is just loose which is why there is smoke coming out of it

 

[AliK]

Having seen the video I’m with Rob on this one. Water / antifreeze would be a lot less see through - in my experience.

Also if you keep it on a steady throttle, you will see a constant stream of smoke from water but not oil. With oil of you leave it idling and blip the throttle, you will get a good puff.

Again, if steady throttle then a blip you get oil smoke. But water should be a more constant steam effect.