zx diesel turbo sludge build up

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hollis
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zx diesel turbo sludge build up

Postby hollis » 23 Jul 2002, 22:17

I have a ZX turbo diesel and recently needed to remove the intercooler to cure a small oil leak from the rocker cover. With the intercooler off I noticed that the inlet manifold has a build up of thick black sludge up to 6mm thick. The intercooler has some oil in it that I assume is normal, but no sludge. Also what I assume is an oil drain pipe from the intercooler was full to the top of oil. The car has just passed an MOT with low emissions so no problems there.
Without removing the manifold I managed to remove as much of this as possible using very dirty fingers and noticed that the exhaust bypass pipe (part of the emissions control) enters the inlet manifiold at this point, so this may be the source of the sludge. The car has only done 44K .
Does this sludge build up indicate a fault or is it normal? Help!
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Dave Burns
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Postby Dave Burns » 23 Jul 2002, 23:58

Sound's like a later model ZX with an EGR (exhaust gas recirculating) valve, there is usually a covering of black oil in the intercooler and it's pipes, there shouldn't be pool's of the stuff though and especially not at that mileage.
The sludge will be soot from the exhaust mixed with oil, the turbo oil seal on the compressor side and probably the turbine side. must be letting oil escape or an excessive amount is being thrown out by the crankcase breather.
Does the pipe full of oil you refer to got to the top of the injection pump, or is it the crankcase breather pipe, clipped to the intercooler.
Dave
Edited by - Dave Burns on 23 Jul 2002 19:02:11
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buddster
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Postby buddster » 24 Jul 2002, 00:55

Dave,
Regarding the pipe you refer to that goes from the front of the intercooler to the top of the injection pump. Is this how the fuel pump detects when to increase the fueling via the increasing positive pressure created in the pipe when the turbo spins up forcing air into the cylinders as opposed to negative pressure when the boost pressure is negligible and the pistons are sucking in the air? Phew, what a long sentence!
Cheers Dave.
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Dave Burns
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Postby Dave Burns » 24 Jul 2002, 01:01

Yes.
Hehehe<img src=icon_smile_big.gif border=0 align=middle>
Dave
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hollis
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Postby hollis » 24 Jul 2002, 18:07

Dave, thanks for such a fast reply. The pipe does go to the fuel pump so must be the turbo boost pressure sensor. I suppose it will always fill with oil (from the film that seems to be normal) as there is no where for it to drain.
This is the first turbo model I have owned so I have no experience of what is normal. You are probably correct about the sludge being a mix of carbon and oil. As Andy has not sold a replacement turbo for a ZX I thought that it was very unlikely to be a faulty seal. Have you any experience of this type of build up?
I do not want to do any unnecessary work to fix something that may not be broken.
Steve
<BLOCKQUOTE id=quote><font size=1 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>
Sound's like a later model ZX with an EGR (exhaust gas recirculating) valve, there is usually a covering of black oil in the intercooler and it's pipes, there shouldn't be pool's of the stuff though and especially not at that mileage.
The sludge will be soot from the exhaust mixed with oil, the turbo oil seal on the compressor side and probably the turbine side. must be letting oil escape or an excessive amount is being thrown out by the crankcase breather.
Does the pipe full of oil you refer to got to the top of the injection pump, or is it the crankcase breather pipe, clipped to the intercooler.
Dave
Edited by - Dave Burns on 23 Jul 2002 19:02:11
<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
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Dave Burns
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Postby Dave Burns » 25 Jul 2002, 03:25

Hi Steve, if oil has got into the diaphragm housing it could have a bad effect on the rubber diaphragm, it's unlikely to get that far though.
Turbo oil seal's aren't made faulty but they operate in a very harsh environment, it's possible to ill treat a turbo by switching the engine off straight after it's been working hard, like tearing up the motorway and stopping at services.
In such cases the engine should be idled for a couple of minutes to allow the turbo to cool and slow down, when the engine is stopped to soon not only does it leave the turbo spinning without lubrication and oil cooling, heat can travel from the turbine along the shaft and burn oil onto it, this will reduce the life of the seal's and bearing's.
Low grade oil is also a big turbo killer.
I would clean it out and keep an eye on it, if it get's no worse I wouldn't think there was much of a problem.
Dave
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hollis
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Postby hollis » 26 Jul 2002, 17:48

I managed to speak to a mechanic at my local citroen garage yesterday, it seems the sludge is nothing to worry about but I thought it would be worth passing this information on.
The sludge build up is common on models having the exhaust bypass system, and needs cleaning out at 40-50 K miles. I suppose it could be done when the timing belt is replaced. He also said that the seal between the intercooler and inlet manifold would be swollen, due to oil contamination. He was dead right about that, I had to cut a small section out of mine just to get it to fit in its recess before I could put the intercooler back. If you are going to check yours, buy a new seal first, about £2. Since scooping the gunge out I have noticed a huge increase in performance most noticable when pulling off from a standstill.
Also it seems to have cured a strange problem I had with bad starting that only occurred when the engine is hot and had been stopped for a few minutes. If I turned the engine off and then restarted it within a minute or so there was no problem, but leave it for 5 mins or so and it took a while to start.
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