So I was helping my friend with his 240 again...he has his second SR swap inplace but we still have a few bugs that we can't figure out. We did a compression test on all the cylinders and they came out just fine.

Issues include:
1. Smoke from exhaust after about a couple minutes of running. It seems almost as if it's burning oil, but I don't see any oil leaks, and my buddy says it might be the turbo even though it was just recently rebuilt.

2. While the engine is running, the radiator bubbles like crazy and a white foam forms.

Any ideas what this could be? He's close to just getting rid of the car and going with something cheap and stock. Thanks for the input in advance fellahs.

 

By "240", which vehicle are you taking about.....a Datsun 240Z, Volvo 240, Nissan 240SX, or something else?

With the issue of oil burning, if there is enough oil burning to have visible smoke (bluish-white in color, as opposed to simple white steam/fog), then you will usually be able to smell it and detect its odor. Older vehicles, without catalytic converters (like the Nissan 240Z), with an engine in proper running condition, should not have any smoke out the pipe, except perhaps for a small amount on start-up. Blue/white smoke, of course, indicates oil-burning. Black smoke indicates an overly-rich carburator (too much gas, too little air). A white steam cloud would indicate coolant getting into the combustion process.....possibly from a bad head gasket or a crack in the engine block.


On newer vehicles (Volvo 240, Nissan 240SX, etc....) with unleaded fuel and catalytic converters, it is more or less normal to get some steam and water vapor out the back of the tailpipe. That's because the platinum pellets in the converter change the exhaust gases (CO, NOX, etc...) into water vapor and a small amount of sulfuric acid vapor (with a converter, that's why you sometimes get a sulfur-rotten egg smell out the tailpipe when the fuel mixture is too rich).

You mention that the car has a turbo. A turbo wouldn't normally cause smoke out the exhaust unless, somehow, oil from the turbo bearings is somehow getting past the bearings into the compressor or engine and heating up to the point of combustion. Some newer turbos are water-cooled, with a jacket of anti-freeze around the turbo housing to keep it near engine temperature. If anti-freeze is somehow leaking out of the jacket into the turbo-induction system, that could also cause steam (not smoke) out the tailpipe. That may (?) also account for some of the problems you note in the radiator, especially if there is another leak in the cooling system adding to one in the turbo.

 

Yes sorry, it is a 240sx, but it has the JDM SR20-DET engine in it.

 

Judging by the white foam presense in the radiator and smoke after running for a few minutes, I would lean towards a headgasket/cracked head issue. Could also be from extra air in the cooling system, try getting some of that air out first.

 

I strongly agree on both counts. As I stated above, while not 100% certain, those symptoms are suggestive of a head gasket or a block-crack issue.

 

Thanks guys I'm going to pass this on to him. He was kinda worried it might be a BHG, but we were hoping it wasn't.

 

Those are, of course, the worst-case scenarios....BHG or a cracked engine block, with major engine work involved. But there are also a number of smaller, less-expensive issues that could cause it, as I outlined above. And a BHG does not always cause major engine damage if caught and repaired in time....Subaru had years of HG issues on the N/A 2.5L.

 

doesnt sound good.