Oil Leak

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sleepy0905
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Oil Leak

Post by sleepy0905 » Mon Mar 06, 2006 12:59 pm

Right i think i have found why my engine is leaking oil I have descovered that when you remove the oil filler the engine is fuming a hell of a lot infact it has gone from only a little to what it is in about 5 months and i think the rings a letting by a little. :(
Does anyone agree with this :?: :idea:
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Post by Stewart (oily!) » Mon Mar 06, 2006 1:00 pm

Could be blow by from rings, you will have to find a fresher motor now sleepy.
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Post by ken newbold » Mon Mar 06, 2006 1:01 pm

Sounds about right, general wear and tear.
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Post by sleepy0905 » Mon Mar 06, 2006 1:03 pm

I am looking.
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Post by jeremy » Mon Mar 06, 2006 2:13 pm

Sounds like rings/bores to me. If you fancy a load of work you could always replace them. Anyone know if the pistons will come out downwards - ie do the job by dropping the sump? - using ridge-dodger top rings of course.

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Post by Mr B » Mon Mar 06, 2006 8:27 pm

jeremy wrote:Anyone know if the pistons will come out downwards - ie do the job by dropping the sump?
I think the crank might be in the way..........

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Post by jeremy » Mon Mar 06, 2006 9:47 pm

The reason I asked about the pistons coming out downwards was because it was necessary to fit pistons to Austin side valve engines this way as the big end was too large to pass up the bore. This could be done with the crank in place. Curiously even 900 cc engines had a 3.5in stroke which is the same stroke as an XUD.

Later Austin engines had the big-end joint set an an angle to the connecting rod and would pass through the bore - which was larger but still on a 3.5 inch stroke for a B series.

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Post by AlanS » Mon Mar 06, 2006 10:31 pm

I'll make 2 comments here.

Firstly what kind of oil have you been using in the c ar since you bought it?
My guess is one with a strong detergent content (as most diesel oils are) or alternatively a thinner oil than previous. This would have flushed all the carbon out from behind the rings allowing them to slop around where the carbon was holding them tight to the bore before.

With rings, if it were a petrol, then i's easy peezy; just off with the head and sump and take the lot through the top, liner, iston and the lot, but diesels don't have sleeves IIRC so it will be a case of head off, sump off and a crash course in reading a micrometer if you can't already do so as taper and ovalness will need to be checked prior to fitting just a set of rings or 1000 miles down the track you'll find yourself doing it all again.


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Post by adamskibx » Thu Mar 09, 2006 2:19 am

Where exactly does the oil leak from? I know worn rings and bores etc cause oil to be burned but ive never heard of this causing oil leaks. I suppose parts of the engine that should have low oil pressure could be experiencing much higher pressures due to combustion pressure escaping? When I had a Dyane, it leaked oil a bit and a new oil breather did cure the problem as these are known to fail on the 2cv engine and cause oil leaks where there wouldnt normally be oil leaks. I have absolutely no idea what exactly failed within them, or even if other cars have a similar system? I have an oil leak to track down on a 1.9 petrol engine tomorrow when it is removed. It doesnt leak at all when parked up but seems to spew it everywhere when under load or at speed- Thats why it failed the MOT-contaminated front brakes. I just hope its not worn out pistons and liners! I cant see why it would be, from the log book it looks as though its had regular oil changes and its only done 101K. Ill be replacing all the oil seals and I hope that cures it anyway.

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Post by jeremy » Thu Mar 09, 2006 9:10 am

Adam All engines even when new have a small amount of blowby of combustion gasses past the pistons. The manufacturers design a ventilation system to collect them and lead them into the inlet system and so get them burned by the engine.

Over time the piston rings wear. Their design is such that they can cope with considerable wear and still seal effectively - but eventually there comes a time when they cant and the amount of blowby increases.

Combustion gasses are very hot and the piston rings cope with this temperature by being made of a suitable material and by conduction of the heat away into the pistons and the cylinder walls. As they age the conduction route into the cylinder walls will becone less effective as the contact isn't so good, and also carbon will build up between the ring and the piston - and of course carbon is an insulator.

So - Now the rings are subjected to:
Increased blowby of hot gasses due to wear
reduced conduction of heat to cylinder bore due to wear
reduced conduction of heat to the piston due to the build up of insulating carbon in the ring grooves

In view of that its a miracle they seal as well as they do!

This is the reason why engines suddenly seem to deteriorate and begin to fume.

We now have a worn engine with considerable blowby. pressurised gas will always try and escape and engines are not generally designed to work with any substantial crankcase pressure - and so the gasses escape through the gaskets and anywhere else that they can - and as there's oil in the crankcase - they take the oil with them. You can change all the seals but they will never seal properly as the joints themselves are simply not designed to work under pressure. Just look at the difference in design betwen those joints that are expected to work under substantial pressure and the obvious one is the cylinder head joint. Now compare that to the design of the sump or rocker cover joint and you'll see what I mean.

The easy test for bore/ring wear is simply to remove the filler cap. If you have to take a step backwards and you choke you know you've got a problem. On a good engine a no more than a gentle haze comes out at any revs.

jeremy

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Post by sleepy0905 » Thu Mar 09, 2006 9:25 am

You then end up like mine chucking oil everywhere and there is tons of fuming and oil cooming back up the filler and breather.
My car wasnt helped by the previous owner who did absolutely no maintainance when i got the car over 5 years ago I had to replace spheres brake pad and discs LHM Gear oil which was nearly empty and then all the filters and the engine oil OH MY GOD it was that thick i had to remove the sump and scoop it out the engine was then given a good clean and three oil changes in a month it took us ages to dig the crap out of the interior we then had jobs like fixing the electric windows and panel lights that didnt work and a central locking system that did what it liked. So all in all the car was an absolute shed.
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Post by Stewart (oily!) » Thu Mar 09, 2006 4:58 pm

Yes but wait until youve finished the current round of upgrading :)
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Post by adamskibx » Thu Mar 09, 2006 6:44 pm

Aha thankyou for that very clear explaination Jeremy. I had a general idea but youve filled in all the details I wasnt sure about.