Piston Ring or Stem Seals ??

M.ibreik · 08-08-2022, 10:28 AM

Greeting all,

Need the opinion and the help of some experts on this. I'll try to give as much details about the problem.

I have a 2014 M5 f10 with 90,000 Miles on it. Have issue with white smoke coming out of the exhaust noticeable almost at all time starting when the car slightly warm up but it really gets worse when when the car is idling and you step on the gas it exhausts a plume of whiteish blue smoke (The longer it idles the more the smoke when accelerating. However, the smoke doesn't starts immediately after the car starts from cold.

I know it's a bit difficult to diagnose the symptoms since its little on the piston ring and little from the stem seals side.

I took the car to a mechanic to replace both new turbo (Which i bought already) along with the valve stem seals and I was okay with it.
The main issue that the mechanic told me that he did both compression and leak down test and results were good without any issue indicating that the pistons are good and the cylinders are holding pressure. When the mechanic started to work on replacing the stem seals, upon disassembling the cylinder head he told me that "from the look of your pistons looks like the issue is also resulting from bad piston oil ring as well" despite the results of the compression and leak down passing the test and I would need to replace this piston ring and pretty much do an engine rebuild since you cant just replace the piston oil ring without doing the rest of the .

I'm not convinced that this is the issue and my assumption he is trying to make the job bigger and leading me into doing an engine rebuild.

What do you think now you have an idea about the situation and see the pictures below of piston surface and the valves yourself?

M5Rick · 08-08-2022, 04:25 PM

I don't think even an expert could tell but if you're happy with just the stem seals then it's that and a good carbon clean off maybe with a valve re grind too, the spark plugs look in sorry state.

M.ibreik · 08-08-2022, 05:52 PM

Quote:

Originally Posted by M5Rick

I don't think even an expert could tell but if you're happy with just the stem seals then it's that and a good carbon clean off maybe with a valve re grind too, the spark plugs look in sorry state.

I know it’s a mess but I just want to get to the bottom of it and solve the issue with the smoke coming out my exhaust without having to rebuild my entire engine. Man, what a headache this car is but driving it makes you forget all this pain hahahah.... the power of M

BMWSauberF1 · 10-07-2022, 02:57 AM

My gf had a 550i with the n63 and she had the exact same problem with especially when she'd be at a light then go so much smoke would come out. It was her PCV valve. get some catch cans and that'll solve your problem. with the engine on remove your oil filler cap and if your pcv's are clogged you'll have a shit load of vacuum when you pull the cap off

technician117 · 10-10-2022, 02:00 PM

The problem you describe has been posted here before. As stated above, it's likely to be a PCV system problem. I'd replace those hoses in the system, install the rebuilt heads and turbos and go from there. IMO there's no need to replace piston rings.

Side note - oil control ring problems won't show in a compression and leak down test.

Also - dirty injectors and those crappy looking plugs can cause the combustion to be inefficient as well, which would show up as more carbon deposits, etc. I'd spend money on spark plugs, ignition coils and injectors well before replacing piston rings.

08-08-2022, 10:28 AM	#1
M.ibreik New Member 6 Rep 15 Posts Drives: BMW M5 F10 Join Date: Feb 2019 Location: Qatar iTrader: (0)	Piston Ring or Stem Seals ?? Greeting all, Need the opinion and the help of some experts on this. I'll try to give as much details about the problem. I have a 2014 M5 f10 with 90,000 Miles on it. Have issue with white smoke coming out of the exhaust noticeable almost at all time starting when the car slightly warm up but it really gets worse when when the car is idling and you step on the gas it exhausts a plume of whiteish blue smoke (The longer it idles the more the smoke when accelerating. However, the smoke doesn't starts immediately after the car starts from cold. I know it's a bit difficult to diagnose the symptoms since its little on the piston ring and little from the stem seals side. I took the car to a mechanic to replace both new turbo (Which i bought already) along with the valve stem seals and I was okay with it. The main issue that the mechanic told me that he did both compression and leak down test and results were good without any issue indicating that the pistons are good and the cylinders are holding pressure. When the mechanic started to work on replacing the stem seals, upon disassembling the cylinder head he told me that "from the look of your pistons looks like the issue is also resulting from bad piston oil ring as well" despite the results of the compression and leak down passing the test and I would need to replace this piston ring and pretty much do an engine rebuild since you cant just replace the piston oil ring without doing the rest of the . I'm not convinced that this is the issue and my assumption he is trying to make the job bigger and leading me into doing an engine rebuild. What do you think now you have an idea about the situation and see the pictures below of piston surface and the valves yourself? Attached Images __________________ ///M is Life
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08-08-2022, 04:25 PM	#2
M5Rick General 59627 Rep 19,450 Posts Drives: M5 F10 DCT Gunmetal Join Date: Aug 2018 Location: Southern England iTrader: (0)	I don't think even an expert could tell but if you're happy with just the stem seals then it's that and a good carbon clean off maybe with a valve re grind too, the spark plugs look in sorry state.
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10-07-2022, 02:57 AM	#4
BMWSauberF1 Private First Class 36 Rep 112 Posts Drives: 2013 BMW M5 Join Date: Jul 2022 Location: San Francisco iTrader: (0)	My gf had a 550i with the n63 and she had the exact same problem with especially when she'd be at a light then go so much smoke would come out. It was her PCV valve. get some catch cans and that'll solve your problem. with the engine on remove your oil filler cap and if your pcv's are clogged you'll have a shit load of vacuum when you pull the cap off
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10-10-2022, 02:00 PM	#5
technician117 Captain 251 Rep 606 Posts Drives: 2000 M5, 2001 M5, 2013 M5 6MT Join Date: Jul 2018 Location: Buffalo iTrader: (1) Garage List 1990 BMW M5 [0.00] 2000 BMW M5 [0.00] 2013 BMW M5 [0.00]	The problem you describe has been posted here before. As stated above, it's likely to be a PCV system problem. I'd replace those hoses in the system, install the rebuilt heads and turbos and go from there. IMO there's no need to replace piston rings. Side note - oil control ring problems won't show in a compression and leak down test. Also - dirty injectors and those crappy looking plugs can cause the combustion to be inefficient as well, which would show up as more carbon deposits, etc. I'd spend money on spark plugs, ignition coils and injectors well before replacing piston rings.
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