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Is this normal?

GazCaff

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Apr 30, 2006
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'05 E280 CDI Avantgarde
Today I went up to IBWs garage to change the glow plugs on my car. The job went smoothly enough, infact we were pleasantly surprised at how easily the plugs came out given some of the horror stories seen on this forum. However, when we removed the plug from number one cyliner (or the one at the front) I was alarmed to find it covered in engine oil! When I say covered, I mean the whole shaft (but not the tip) was totally coated in the stuff!

My car does not blow out oil smoke, nor does it use any oil and it runs fine. If the amount of oil on the glow plug was getting into the cylinder I would be sure to notice (and would most likely be invited to stop by the boys in blue). It is our assumption that #1 glowplug goes through an oil gallery and this would explain the state of it, but I would like my mind putting at rest. So has this been the case for anyone else?

Like I say, the car is running perfectly fine.
 
The plugs don't go through an oil gallery. My bet goes on oil finding its way there from a leaky inlet manifold joint or from sloppy oil filling.
Are you sure it's engine oil not diesel from a fuel line or the filter. Also could it be power steering fluid.
 
Dieselman said:
The plugs don't go through an oil gallery. My bet goes on oil finding its way there from a leaky inlet manifold joint or from sloppy oil filling.
Are you sure it's engine oil not diesel from a fuel line or the filter. Also could it be power steering fluid.

It definatley wasn't diesel. It was black engine oil. The oil was on the shaft of the glow plug beyond the threaded part, so it definatley came from the inside. I'm not sure how it could be PAS fluid! It certainly is a puzzler to me.
 
GazCaff said:
It definatley wasn't diesel. It was black engine oil. The oil was on the shaft of the glow plug beyond the threaded part, so it definatley came from the inside. I'm not sure how it could be PAS fluid! It certainly is a puzzler to me.

So was it below the tapered seat or above it towards the threads?
 
Dieselman said:
So was it below the tapered seat or above it towards the threads?

It was on the shaft of the glow plug between the threads and the tapered portion. There was none on the element itself, apart from what had got on to the element when it was removed.

Ian might be able to explain it better than I am.
 
If we split the glow plug into 3 parts for description only you have :-

a) The thread and electrical contact
b) The long shaft
c) The tapered working end, the hot bit

The oil was on part B. It looked as if it ran though an oil way. As Gareth says, no blue smoke after and all is well with the running of the engine. A mystery to me. However its a diesel so who knows :p :o
 
I've been thinking about this through the day and have come up with two possible reasons that I want to sound out,

1. There is a casting flaw in the head allowing engine oil to harmlessly come into contact with the glow plug.

2. Something has happened to the pre-chamber, if it is an insert like on some idi engines it may have become cracked or dislodged, but this would more likely result in oil getting into the cylinder.

I'm tempted to remove #1 injector in the near future to see if this sheds anymore light.

There is a third possibility but I think it's very unlikely... my car has suffered a serious failure of #1 cylinder resulting in oil ingress and zero compression and I bought it in this condition. I think this is unlikely given how well my car performs. I'd also end up filling the sump with diesel if this was the case and eventually cause an engine run-away failure.
 
A fourth possibility is that the oil is from an external leak and has found its way down though the threads but has subsequently been cleaned off and the leak fixed.

If it's internal then it will be the pre-chamber is slightly loose, though I would expect the oil to migrate to the outside of the threads as it would be under pressure.
 
I really wish I'd took a picture of the offending glow plug. The oil on the shaft of the plug was thick and black, it looked like it had been there a while, there was no sign of it on the threads at all.

Would a loose pre-chamber be a major cause for concern? I know the old Peugeots used to run around quite happily indefinatley with cracked pre-chambers, but I'm not so sure about a loose one.
 
There is always the possibility that the plug wasn't properly seated in the pre-chamber so was allowing some gas to blow by. This would be black and possibly oily due to diesel contamination.

Don't worry about it too much, just drive the car and pull the offending plug at some point. You will probably find it's Ok.
 
Thanks for the help. I'll do like you suggest and I'll leave it a month or two before I have another a look at it (though I'll probably have forgotten about it by then!).:o
 

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