SMOKING AND HOT EXHAUST

knysnamark · Post by **knysnamark** » Thu Jan 27, 2011 3:54 am

My wife came home in our 3.0 diesel after a 12Km drive with smoke billowing from the exhaust. I also noticed that the exhaust was extremely hot, with the silencer/cat under the drivers seat glowing red hot. I even started melting the heat shield underneath it. The engine seems to run smoothly, it starts easily and runs without any strange noises. I am going to check the breather filter, but wondered how the exhaust would get so hot.

dwgwyther · Post by **dwgwyther** » Thu Jan 27, 2011 7:29 am

Hi Knysnamark I spoke to a friend who used to work for BMW as a mechanic about this the other day and from what I remember he said the cat is blocked if it glows red hot (what you were probably looking at), the one he remembered doing started burning the insulation under the seat (a very nasty burning smell), from what he said you will need to replace the cat as it blocks exhaust gases from escaping causing it to super heat the cat. One point he did say you do not want to be driving it very long at all as it soon heats up and cause the car to catch fire.
Basically get it replaced somewhere close and get it there when its cold.
Hope this helps
BTW
you will also have to check what is causing the blockage (oil from somewhere) see
viewtopic.php?f=21&t=1133
Darren

Turks · Post by **Turks** » Thu Jan 27, 2011 10:47 am

Oil has come from somewhere which when gets trapped in the CAT just gets hotter and hotter as there is nothing to cool it - just hot exhaust gasses. I would check out the problem before replacing - you don't want to change it twice! Not at them prices!

Check Breather, and also check Turbo seals - could be on its way out if it hasn't been looked after.

Turks.

knysnamark · Post by **knysnamark** » Thu Jan 27, 2011 4:02 pm

OK, firstly thanks everyone for all the guidelines. I pulled the whole thing apart this morning and found the breather was completely blocked. Crankcase oil pressure was obviously high enough to force it's way where it shouldn't have. I have now replaced the breather filter assembly along with the airfilter. I started the car up and it ran perfectly, no smoke and as smooth as usual. Checked everything, cleaned up and prepared for a test drive to monitor the cat temp and see if the smoke was gone for good. Clouds of blue white smoke started again. The oil level has dropped substantially . My next culprit to investigate is the turbo. How does one check the turbo integrity, seals vanes shaft etc. I am loath to go to the dealers as their prices are very high and I won't know if they have done it properly.

J_K · Post by **J_K** » Thu Jan 27, 2011 5:32 pm

How many miles has the car done?

To check the turbo, pop the pipe off the front where it goes forward and down to the intercooler (jubilee clipped).
Now try to move the spindle in the middle of the turbo (turbo shaft). ANY movement isn't good but side to side movement means the bearings have collapsed.
However, the seals can fail on turbos and then you get oil in the inlet so check the inside of the pipe.
The seals can also fail on the exhaust side but to check that, you need to remove the down pipe from the turbo which is a little more complicated.

X5Sport · Post by **X5Sport** » Thu Jan 27, 2011 7:38 pm

If you do find that oil is getting into the inlet stream I would very seriously advise against driving it. There is a rare but interesting problem called 'Turbo Runaway' which occurs on diesel engines with oil leaks in the turbo, especially into the inlet air stream. What can happen is the oil replaces the fuel in the cylinders and ignites. This process continues even if you turn the engine off which cuts the fuel off, but not the oil. The engine continues to run and accelerate (because the turbo spools up increasing pressures) uncontrolled until either the oil runs out, the turbo fails, or the engine seizes. None are good options. There is a video on Youtube of an X5 suffering a runaway. It's impressive, not pretty and VERY expensive.

Hopefully yours will not be that bad. Did the oil level drop before or after you had put everything back together? It sounded like it was fine before you went out?

knysnamark · Post by **knysnamark** » Thu Feb 24, 2011 3:34 am

Well, I replaced the turbo and various other bits of piping. Removed the CAT completely as it was blocked solid. Cleaned out the intercooler and exhaust system. Changed breather filter and replaced oil, oilfilter and diesel filter. Started her up and she runs like a dream.

Thanks for all the advice

knysnamark · Post by **knysnamark** » Thu Feb 24, 2011 3:38 am

I have now purchased a " No-Limit " chip tuning box, which I am going to install and test. Anyone else tried one of these yet ?

BL02WAS · Post by **BL02WAS** » Thu Feb 24, 2011 10:07 am

i have a diesel tuning adaptiv spider box installed in mine. Been in for over a year, and makes a hell of a difference!! the car performs really well!!!

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BL02WAS · Post by **BL02WAS** » Thu Feb 24, 2011 10:09 am

with regards to turbo runaway....surely a towel stuffed into the air intake would help??

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X5Sport · Post by **X5Sport** » Thu Feb 24, 2011 7:44 pm

[quote=""BL02WAS""]with regards to turbo runaway....surely a towel stuffed into the air intake would help?? [/quote]

It probably would as long as you were brave enough to try it and a wet towel would be better. Need to be a good size so that the turbo didn't try and digest it too of course..

Here's a couple of BMW turbo runaways...

http://www.youtube.com/watch?v=58SoI7YK ... ata_player

http://www.youtube.com/watch?v=dHOpUPR5 ... ata_player

Turks · Post by **Turks** » Fri Feb 25, 2011 3:07 am

I haven't seen the turbo on the X5 Diesel, but on my mates Skyline there is an oil feed to the turbo... wouldn't detaching this help? There should be enough oil left in the turbo to lubricate it and prevent damage but not enough to provide fuel to the engine? Stick the towel in for good measure...

Turks.

BL02WAS · Post by **BL02WAS** » Fri Feb 25, 2011 8:07 am

Yep reckon that would definitely help!!! The turbo runs away on the oil doesn't it, so cut supply job done, but as mentioned a big towel stuffed into air intake should help too, it wouldn't be munched by engine, would only if anything go as far as filter etc so no worries there, I would gladly do this to stop this from happening

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