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2008 IS-F, white smoke/vapour from right side exhaust?

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Hi all, my first post on this forum, I wondered if anyone had any pointers?

I've had the car a couple of months, due to lockdown, done the grand total of about 100 miles in it, it drives well with good power, however....

In the first, say 10miles of driving there's a lot of steam/condensation in the exhaust when pulling away from a standstill, it clears after about that roughly speaking.

A pal of mine was driving behind me the other night, he noticed on hard acceleration dense white vapour coming out of the right tailpipe... if I didn't know better I might be forgiven for thinking 'head gasket'!

I've done a couple of simple tests.. no, the condensation in the exhaust tip isn't sweet tasting (antifreeze), the coolant is clear and pink, no residue in the tank, I've tested the coolant for combustion gases (the liquid doesn't go yellow), no bubbles in the coolant, the hoses don't go hard on a cold start-up. Next step will be checking the compression in each cylinder.

All this is for piece of mind you'll understand... it could all be caused simply because it doesn't get driven a whole lot and the exhaust has condensation in it... I'll monitor the coolant level and keep an eye on the oil level and condition...

I had a thought that the there could be an issue with the valley plate, perhaps there are coolant galleries that pass into the cylinder heads and that coolant could leak directly into the intake system from there. I can't find a cooling system diagram, but looking at the various google search results it seems as though they leak externally not into the engine.

Any comments/ideas would be helpful.

Many thanks,




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Yeah sounds like simple condensate, it takes a while for entire exhaust to get hot enough to boil it off, so if car is not driven often or not driven for longer journeys (where exhaust get's hot enough to dry-off remaining condensate) this is what you can expect. Right side if I am not mistaken is longer pipe, so it makes sense it take longer to boil-off there.

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Yes, I'm inclined to think that way too,  Linas thanks.

My car has a custom bi-modal system (in the back boxes) on it, I've not been under the car yet, I'd guess there'll be an X pipe or at least a balance pipe between the LH and RH pipe which complicate diagnosis if I need to go down that road...

Thanks again.


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The standard system layout is Y pipe under the axle (you probably can call it X, but I consider X-pipe to be something else), meaning both exhaust pipes merges just before rear axle into resonator and then splits again into two silencers at the back. However, the resonator and entire system is offset to the right to go around rear diff, making left pipe slightly longer for the rear section.

This is just my assumption, but longer pipe = more resistance = less flow. This means majority of the gases goes via right side, thus you see more condensate coming out from right side. If you rev it up, then maybe rear silencers becomes the bottle neck equalising the gasses to both pipes and you may see condensate blowing from both pipes.

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