Black Smoke P38 2.5 DSE

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micko2602

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Newcastle upon Tyne
Noticed last night that when I put my foot down, and presumably the turbo spins up (3000 rpm ish) there is plooms of thick black smoke coming out of the exhaust. Power seems to be fine, or as much power as you expect from the 2.5 diesel engine. Anyone got any pointers as to what I could check? I've always thought there was some smoke out of the back when I put my footdown on the motorway, just never really given it any great consideration.

Cheers

Mick
 
Black smoke normally either means not enough air or too much fuel.

Normally if you haven't done anything new on the fueling side (and these babies normally suffer from reduced fuel as they get older through wear in the fuel pump) its likely you've either an air leak somewhere between the turbo and plenum or your EGR is stuck open as Alarmfitter says. With split hoses you should be down on power a bit. Check all the hoses going too and from the intercooler for splits, if you can't find any do as Alarmfitter says.
 
Mine did the black smoke thing for a bit when I first got it, I put it down to it being pottered around in the traffic for most of it's life. A bit of hard work towing on the hills of Yorkshire and it went away. Probably EGR as Alarmfitter said.
Petrol engines that have been pottered around do the same, just the smoke is a different colour.
 
Removing Vac hose will prevent it from opening.
If the EGR is not operating correctly it will introduce exhaust gas at high revs, reducing the amount of oxygen available for combustion hence black smoke through overfueling.
Running without it for a while and working the engine hard is reported to burn off deposited carbon, gunk etc.
 
Thanks SpudH and alarmfitter I'll whip off the vac hose tonight and get it out for a good run.
I don't do a great deal of mileage and even that is just at low revs so most likely the cause, fingers crossed.
 
Had a look at this last night and I don't have an EGR. Mine is a 1998 2.5DSE. The outlet from the intercooler goes straight into the inlet manifold.
I had a look at the condition of all the hoses and they seem fine, however, I did find that the crankcase breather (think thats its name) was loose at both the end which goes into the crankcase and the end into the duct work. Its on the image shown below. I cleaned these and managed to seal them with a bit of mastic, took it out for a blast and there was ome smoke (expected from a diesel) but no where near what I had 2 days ago. Could it have been that simple?????

ScreenHunter_01Jul160857.jpg
 
Last edited:
You sure about not having an EGR?
Mines a 98DSE too but I've one, Its mounted onto the end of the intake manifold with the control unit mounted on the passenger side bulkhead.

I'm not convinced that the loose breather was the root cause. If anything it should be pumping less fuel as a leaking breather is introducing additional air after the MAF so wouldn't be counted in the fueling calculations. Thats why a split hose on the high pressure side of the turbo will bring about black smoke as the air thats lost has already been calculated on the intake side and the fuel is adjusted for that volume.
 
Dont overlook the intercooler. These get full of oil and crap wich leads to poor efficiency . Give it a good clean out with several gallons of parafin. You will be pleasantly surprised by the results.
 
SpudH said:
You sure about not having an EGR?
Mines a 98DSE too but I've one, Its mounted onto the end of the intake manifold with the control unit mounted on the passenger side bulkhead.

I'm not convinced that the loose breather was the root cause. If anything it should be pumping less fuel as a leaking breather is introducing additional air after the MAF so wouldn't be counted in the fueling calculations. Thats why a split hose on the high pressure side of the turbo will bring about black smoke as the air thats lost has already been calculated on the intake side and the fuel is adjusted for that volume.
Click to expand...

the bmw diesel does have an egr valve,one is on the outside of the manifold and the earlier type has the egr valve inside the rocker cover.
 
gemsdad said:
the bmw diesel does have an egr valve,one is on the outside of the manifold and the earlier type has the egr valve inside the rocker cover.
Click to expand...

In the rocker cover is the Mann-Hummell type breather valve, not an EGR valve. The EGR valves came in on the 98 MY, so you won't have one before then.
 
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