smoke coming from under bonnet

[ross bootle]

my nissan 2008 nav d40 has smoke that starts billowing from under the bonnet after half an hr or so. Has a real deisel smell to it. No warning lights of any sort come on and it doesnt affect driving , just makes the cabin stink.. not being real mechanical minded ive tried to pinpoint exactly where it comes from. It not that easy because the radiater fan blowes the smoke around and it comes from the the right hand side of whatever that stainless pipe is with the 2 hoses coming off it. you can see in the pic the black soot just on the left of the altinator. so where the pipe bends around its somewhere beneath those hoses. What is that pipe and where does it go , assume its exaust..Anyway as soon as the engine is off the smoke stops.. Any ideas would be appreciated..thanks

 

[YD25Frontier]

That the EGR cross over tube. It's connected directly to the exhaust and probably cracked. Does the truck feel sluggish on acceleration? The leak may make the turbo spool slower. Depending on if you live in a communist country/state or not, I would delete, tune it and never look back!

 

[ross bootle]

That the EGR cross over tube. It's connected directly to the exhaust and probably cracked. Does the truck feel sluggish on acceleration? The leak may make the turbo spool slower. Depending on if you live in a communist country/state or not, I would delete, tune it and never look back!

no , it doesnt seem any different to normal... well , this morning a know it all mate looked and decided to fill the radiator with water as it was low, now its leaking water and over heated after 10 km...So i dunno if thats anything to do with it but im guessing so .. and i cant work out where the waters coming from, certainly not the radiator, somewhere below where that pipe is ,"i think"...its dripping pretty solid onto the sump , or dripping off the sump when i got underneath. but its hard to tell. So i guess ill drain the radiator and hopefully that gets all the water out and fill it with coolant. I dont know whether thats a fix ? I had no water leaks before he filled the radiator with water... but i did stop emmitting the smoke funnily enough... Im in sydney , alexandria, my trust in deisel mechanics is to high given a few bad experiences...Anyway , thanks for the input frontier , much appreciated

 

[ross bootle]

That the EGR cross over tube. It's connected directly to the exhaust and probably cracked. Does the truck feel sluggish on acceleration? The leak may make the turbo spool slower. Depending on if you live in a communist country/state or not, I would delete, tune it and never look back!

So your saying piss the pipe off all together and put blanking plates either end?

 

[YD25Frontier]

If you're loosing coolant it could be because of that EGR cooler. It's a common problem on many diesels. I blocked mine off for that reason.

 

[ross bootle]

i saw blanking plates on sale on ebay , $8 ..and hundreds had been sold , so that tells me that your spot on about it being a common problem

 

[Old.Tony]

The only drawback with removing the EGR pipe is that it's not legal to do in Australia (emission control laws). The idea behind EGR is that if they blow enough exhaust into the combustion chamber, it will cool down the combustion process and make the vehicle use more dinosaur juice which makes Shell and Mobil and BP shareholders have more successful orgies, so blocking the EGR results in a bunch of sad rich people whining about how unfair their lives are because they're earning only 8 figures a year not 9. And it's all your fault.

Ok, seriously - EGR isn't GOOD for the car. It helps the environment by reducing the combustion temperatures to a level below which nitrogen oxides are formed. The mechanism that controls it - the EGR valve - is sometimes faulty (I don't suspect that here) but there's a tube which runs from the exhaust manifold near the turbocharger around the front of the motor through the thicker part with the two hoses (EGR cooler) to the EGR valve - now that tube is suspect, particularly in the concertina area.

There's a chance though that the EGR cooler section has developed a leak allowing coolant to flow into the EGR cooler. You can test this (for short periods, don't leave the car like this) by removing the two hoses from the EGR cooler and connect them together (short piece of pipe, hose clamps, it's fairly easy). If the problem goes away you're best off either replacing the EGR pipe completely (this is legal in Australia) or blanking off both ends and then connecting the coolant hoses together permanently (not legal but difficult to detect).

Note that in a roadside stop in Australia where they shove a gas analysis probe in the exhaust they won't be able to detect EGR - EGR is always closed at idle. Just don't rev the engine!