Oil dripping on to a hot exhaust smell like melting plastic?

Oil dripping on to a hot exhaust smell like melting plastic?

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TonyRPH

Original Poster:

12,963 posts

167 months

Tuesday 10th March 2015
quotequote all
Couldn't get everything into the thread title.

Would synthetic oil dripping on to a hot exhaust smell like melting plastic?

I sometimes get a smell of hot oil, but this evening I got a strong smell of melting plastic, just like when a plastic bag gets stuck to the exhaust. At the same time, I could see pale white smoke coming through the vents and coming out from under the bonnet - it was only noticeable because the sun was catching it, otherwise I probably wouldn't have seen it.

My car doesn't use any oil - so I'm not convinced there is a leak (and I can't really see anything obvious).

But at the same time I can't see any plastic melting on to the exhaust either! I checked around the manifold and the down pipes but can't see anything worthy of note.

Car is an E39 523i by the way.

Would brake fluid cause this if it was dripping on to the manifold?

TIA.


anonymous-user

53 months

Tuesday 10th March 2015
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Same here from same engine! Like there's a plastic bag melting. It happens every couple of months and there's a faint smell of sulphur too. Very strange.

TonyRPH

Original Poster:

12,963 posts

167 months

Tuesday 10th March 2015
quotequote all
V6Pushfit said:
Same here from same engine! Like there's a plastic bag melting. It happens every couple of months and there's a faint smell of sulphur too. Very strange.
It always seem to be worse when the car is facing uphill on an incline. It's almost as if oil (or something) is pooling up somewhere and then running out.


Poopipe

619 posts

143 months

Tuesday 10th March 2015
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Gearbox oil really stinks when it burns - might be worth checking that too

Fox-

13,228 posts

245 months

Tuesday 10th March 2015
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Your rocker cover gasket is leaking and oil is dripping onto the exhaust manifold. This is insanely common on M52 and M54 engined BMW's.

Mustard

6,992 posts

244 months

Tuesday 10th March 2015
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Fox- said:
Your rocker cover gasket is leaking and oil is dripping onto the exhaust manifold. This is insanely common on M52 and M54 engined BMW's.
^^^^^ This!

AJB

856 posts

214 months

Tuesday 10th March 2015
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Fox- said:
Your rocker cover gasket is leaking and oil is dripping onto the exhaust manifold. This is insanely common on M52 and M54 engined BMW's.
^ Yep - my E39 did this too, especially if I stopped in traffic or to park straight after a motorway run, without slower roads in between.

lufbramatt

5,318 posts

133 months

Tuesday 10th March 2015
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Echo the above, got the bits to tackle this job on my 530i this coming weekend. Quite easy to see where the oil is coming from the base of the cam cover, it runs round to the exhaust side due to the slant of the engine. Mine does it for a minute or two as the engine warms up then stops.

CCV could also be a possibility too though if the smell is constant, but if it's not using much oil then rocker cover gasket would be my first thing to check. The bits are about £45 from the dealer, if you tackle it yourself make sure you get the 16 round rubber seals that go around the bolt holes, the cheap kits don't include these.


Edited by lufbramatt on Tuesday 10th March 22:18

tgr

1,129 posts

170 months

Tuesday 10th March 2015
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Fox has it. £150 to sort at an indy

McSam

6,753 posts

174 months

Wednesday 11th March 2015
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Interesting. My E46 328i has always had some oil staining on those little slats directly above the exhaust manifolds. I put it down to a rocker cover gasket leak but perhaps many years old, as it gets through precisely no oil and never has done.

It is a little louder than it should be, though, especially in the mid-range and on the overrun. Just a little bit boomy. I wonder if those who've had leaking rocker cover gaskets reported similar symptoms?

TonyRPH

Original Poster:

12,963 posts

167 months

Wednesday 11th March 2015
quotequote all
@McSam the boominess will be down to the "golf t" mod on the exhaust probably.

I had a 330i and I did the mod and regretted it.

As for the leak in my car - I'm not losing any oil (as visible on the dipstick) so I'm not even sure if the gasket is leaking?

Would it show as a change of level on the dipstick, or is it just a mist leaking out?

Is this a fire hazard?

McSam

6,753 posts

174 months

Wednesday 11th March 2015
quotequote all
Thanks, but it's certainly not the golf tee thing, I tried that myself a little while back and didn't like it much, so reattached the vacuum hose. This is very different in character, is clearly engine-side, and sounds like something around the exhaust manifolds. Perhaps a manifold gasket has failed, but I really don't fancy trying to unbolt the manifolds.

TonyRPH

Original Poster:

12,963 posts

167 months

Wednesday 11th March 2015
quotequote all
Ah ok. Sadly the valve in my exhaust had seized and I ended up drilling it out - so I couldn't reverse the mod...

And yes, access to the manifolds on the 3 series is rather tight!!!

tgr

1,129 posts

170 months

Wednesday 11th March 2015
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The amount of oil lost from a weeping rocker cover gasket would not be enough to register on the dipstick but is certainly enough to smell in the cabin

anonymous-user

53 months

Sunday 15th March 2015
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Investigated further and that's exactly what has happened to mine....
Thanks for the advice.

TonyRPH

Original Poster:

12,963 posts

167 months

Sunday 15th March 2015
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Mine's going in to my indy on Tues to have the gasket done.

Hoping it solves the problem.

dhutch

14,198 posts

196 months

Monday 17th September 2018
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Fox- said:
Your rocker cover gasket is leaking and oil is dripping onto the exhaust manifold. This is insanely common on M52 and M54 engined BMW's.
Got what I hope is this too, although I must say to me it just smells like burning oil.... ans light smoke.

I understand other common areas re the gasket between the block and the oil filter housing, and the vanos hose.


Daniel

J4CKO

41,287 posts

199 months

Monday 17th September 2018
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dhutch said:
Fox- said:
Your rocker cover gasket is leaking and oil is dripping onto the exhaust manifold. This is insanely common on M52 and M54 engined BMW's.
Got what I hope is this too, although I must say to me it just smells like burning oil.... ans light smoke.

I understand other common areas re the gasket between the block and the oil filter housing, and the vanos hose.


Daniel
I had a similar smell on a Mercedes and it was a cam blanking plug had gone hard and brittle and oil was seeping past, down the block and dripping onto the hot exhaust, nothing smell more like doom than burning oil.

Get one of those endoscopic USB cams with a light on off eBay or Amazon that plugs into a laptop and you can have a good look round to see into awkward places, usually easy to spot an oily bit on an exhaust.

Good luck !

TonyRPH

Original Poster:

12,963 posts

167 months

Monday 17th September 2018
quotequote all
dhutch said:
Fox- said:
Your rocker cover gasket is leaking and oil is dripping onto the exhaust manifold. This is insanely common on M52 and M54 engined BMW's.
Got what I hope is this too, although I must say to me it just smells like burning oil.... ans light smoke.

I understand other common areas re the gasket between the block and the oil filter housing, and the vanos hose.


Daniel
Unfortunately in my case, the (plastic) cam cover had gone brittle and was breaking up rapidly.

No amount of silicon sealant could fix it.

Due to the lack of availability of a good used one, I ended up paying £300+ for a brand new one.

And a short while after, the oil filter housing 'o' ring failed too.

I have done a thread on my car, anyone looking to buy an E39 BMW 5 series would (should!) be put off by this..



GreenV8S

30,150 posts

283 months

Monday 17th September 2018
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J4CKO said:
nothing smell more like doom than burning oil.
Oil on an exhaust can be more dangerous than petrol. Petrol will boil off before it reaches its flash point, and as long as the vapor disperses before it reaches an ignition source it's unlikely to ignite. Oil on the other hand has a flash point below its boiling point so it will ignite spontaneously if you get it hot enough.