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Author Topic: Oil Build Up Advise  (Read 2517 times)

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amba

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Oil Build Up Advise
« on: 25 July 2021, 16:27:48 »

Have noticed a regular layer of oil forming on the bottom metal part of the front "bag pipe assembly" and on closer inspection seems to be an overspill onto the top of the front engine plastic undertray visible with bonnet open.

What would cause this oil build up and before I investigate tomorrow how much oil should be ...in any ..evident in the metal curved part of the bagpipe assembly.?
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Doctor Gollum

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Re: Oil Build Up Advise
« Reply #1 on: 25 July 2021, 17:28:37 »

The bag pipes are plastic  ;)

Anyhoo, oil in there is normal. Basically oil vapour from the crank case is drawn up through the breathers to a point just before the throttle body. (this is how the breather vacuum is formed). When the oil is hot, it is fumes, however as it cools, it condenses back to oil. When you switch off, the hot oil fumes from the crank case continue to rise into the breather bridge where they condense back to oil, draining down infront of the throttle body and down past front multiram to the bottom of the intake duct.

This builds up over time, but you would need there to be a couple of litres in there before the engine intake vacuum could hoover it up, and even then, once it can draw enough air from the air filter, then it would stop lifting the pool of oil.

It will draw some oil from the surface on a prolonged run with alot of throttle, but you're talking crosscountry autobahn speeds, not daily driving. Also this is getting into the realms of fluid dynamics, which is kind of overthinking it ;D

Oil on the tray is more likely to come from the oil pressure switch of front crank seal than the air intake as I don't believe that there is a drain hole between the air filter and the throttle body (potential for debris to reach the intake).
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amba

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Re: Oil Build Up Advise
« Reply #2 on: 25 July 2021, 17:48:19 »

Thanks for explanation Al.

The N/S rubber pipework is really quite oil covered and it looks to me like the aluminium bottom section of the bagpipe assembly must be almost full of oil as its overflowed onto the top of the undertray...its a puddle quite evident as coming from the pipework and nothing else as all other areas are bone dry.

Never had this before on any of the other Omegas I have owned and only noticed it on this car over the past few months...today especially as had oil check warning come up so hence why I pulled the bonnet and was greeted by the oil.

Will remove the entire bagpipe assembly tomorrow and give it a good clean as fully expecting to find an oil pond in the bottom metal section....just curious why it forms
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Doctor Gollum

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Re: Oil Build Up Advise
« Reply #3 on: 25 July 2021, 18:55:53 »

The bottom tube is plastic  ;)

And it's supposed to be reasonably air tight, so a leak from it would suggest either incorrect assembly or damage  :-\

The only way oil can get in there is from the breathers.
« Last Edit: 25 July 2021, 18:57:40 by Doctor Gollum »
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amba

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Re: Oil Build Up Advise
« Reply #4 on: 25 July 2021, 18:58:36 »

Stand corrected.. :y...must of mistaken for the section of aluminium in the middle..will investigate oil tomorrow now.
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amba

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Re: Oil Build Up Advise
« Reply #5 on: 27 July 2021, 20:18:17 »

Removed entire bag pipe system and gave everything a really thorough clean up...found only around a 1/4 ltr of oil in the bottom U of the pipework so still struggling to understand why there was quite heavy oil traces on the join of the plastic pipework to the metal mid section ..seemed to of built up around where the jubilee clip retains the pipework so far too high up for oil puddling.

On reassembly I checked all the jubilee clips but found them to be tight and no signs of any splits in the pipework.

Gave car a full oil change today and cleaned the entire breather system to see if that could be something to do with it but found them all to be clear ..as expected really as done less than 3 months ago .

Odd part is its only on the pipework from the N/Sidebank...O/S has no oil residue at all.

Will give it another couple of days now everything is spotless and see if it returns ..but curious as to why this has happened
 
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Migv6 le Frog Fan

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Re: Oil Build Up Advise
« Reply #6 on: 27 July 2021, 20:25:15 »

It does sound a bit odd.  :-\
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amba

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Re: Oil Build Up Advise
« Reply #7 on: 27 July 2021, 20:47:09 »

Yes Albs struggling to understand why oil would appear in enough quantity to be visibly wet some 8 inch from the bottom of the bag pipe work and only on the NS  ???           
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Migv6 le Frog Fan

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Re: Oil Build Up Advise
« Reply #8 on: 27 July 2021, 23:32:08 »

One for someone much cleverer than me Im afraid. MarkDTM ( fuse 19) ideally.
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amba

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Re: Oil Build Up Advise
« Reply #9 on: 28 July 2021, 08:49:54 »

My theory was oil condensing on the curved from the throttle body and then running down and settling on the inner lip of the aluminium section and leaking by the jubilee clip.

Plan will be to see what happens in the next few days and have ordered new set of jubilee clips so will remove it again if more oil present and strip entire unit into pieces and refit with new clips.
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Andy H

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Re: Oil Build Up Advise
« Reply #10 on: 28 July 2021, 10:45:26 »

You shouldn't have any oil in the bagpipes.

The breathers are designed to function in two ways
- at idle and with small throttle openings there is a big vacuum in the manifold - the big vacuum pulls crankcase vapour through a tiny hole in the oil separator behind bank 2 cylinder head - fresh air should be pulled into the crankcase through the large breather (which connects to two ports just in front of the throttles)
- at large throttle openings there is less manifold vacuum to pull vapour through the tiny hole but there is some vacuum at the two ports in front of the throttles which will draw the oil vapour into the manifold.

What happens is that the breather pipes on top of the manifold AND the tiny hole in the oil separator get blocked with oily crap. The vapour that should get drawn straight into the manifold can't go that way so it comes out through the ports in front of the throttles. This isn't an issue when the throttles are open but at small throttle openings or idle (eg most of the time) an oily mist is dumped into the inlet where it usually coats the throttles in crap (but it might find it's way into the bagpipes).

When you clean out your breathers you should also check the tiny hole in the small spigot on the oil separator. It is a pig to get to so most people don't know it is even there..............
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amba

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Re: Oil Build Up Advise
« Reply #11 on: 28 July 2021, 13:18:28 »

Thanks for further explanation Andy....always poke a small thin piece of wire( sits in the top of my tool box for this job) down the small brass spigot behind O/S coil pack and give it a squirt of carb cleaner also the larger spigot from the 3 branch breather pipe.

All were fairly clear but have had another thorough clean along with oil/filter change so hopefully it was just a 1 off and normal service will ensue ...but will replace the jubilee clips just for piece of mind.
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Doctor Gollum

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Re: Oil Build Up Advise
« Reply #12 on: 28 July 2021, 17:29:03 »

The crankcase fumes are hot oil vapour ::)
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Re: Oil Build Up Advise
« Reply #13 on: 28 July 2021, 18:16:36 »

Ive never known them to produce the quantity of oil Andrew is talking of though.
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Doctor Gollum

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Re: Oil Build Up Advise
« Reply #14 on: 28 July 2021, 19:10:24 »

Mine did, I put it down to mileage and use :-\

Cleaned mine out once iirc and didn't think much of it.

If the car has done over 150k and the pipe has never been cleaned out, a 1/4 litre is probably normal ;)
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