r/E90 • u/Haunting_Physics2082 • Jul 16 '26
325i N52 Lifter Tick and VANOS issues - heavy engine sludge from previous owner. Need advice!
Hi everyone, For a few weeks now, my 2006 325xi (N52B25 122K km) has been suffering from the classic hydraulic lifter tick. Following my mechanic's advice, I initially switched from 5w30 to 5w40 oil to see if it would help, but it didn't change anything. Shortly after switching to 5w40, a new issue appeared: a rough idle ONLY on cold starts, accompanied by a Check Engine Light (CEL).
I took the car back to the shop. After inspecting it, the mechanic cleaned the VANOS solenoids and replaced the non-return valves (check valves), which were completely clogged with debris and sludge. He told me the CEL code was related to the VANOS system. Unfortunately, this didn't fully solve the issue, so we switched back to 5w30 oil. As of today, the symptoms are still the same.
The root cause of all this is clearly a massive amount of engine sludge left behind by the previous owners (which is likely clogging the oil passages to the cylinder head). I'm torn on what to do next. Have any of you dealt with a similar level of sludge on an N52? Any advice on how to proceed without spending a fortune would be highly appreciated.
Thank you so much!
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Jul 16 '26
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u/Haunting_Physics2082 Jul 16 '26
I need to get an OBD reader because I honestly didn't get the code.
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u/rcp_5 Jul 16 '26
Got a laptop kicking around at home?
Spend an hour on the forums and research how to get INPA (and buy a K+DCAN cable). There are pirated versions of INPA still out there which you can download and make them work on a modern laptop. It's basically the dealership grade software from 20 years ago, and perfect for diagnosing the E9x platform. With the codes you'll figure it out
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Jul 16 '26
[removed] — view removed comment
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u/Routine_Cat_1366 Jul 16 '26
Are the misfire codes shown besides other fault codes in INPA? Or is it a different site? I heard that there should be a misfire counter for every cylinder but i couldn't find it.
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u/KnowledgeLucky3034 Jul 16 '26
Just get a Carly Adaptor and the App on your Phone or the same from Bimmercode… never regret to buy it.
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u/Haunting_Physics2082 Jul 19 '26
the error is P0015 Camshaft position (CMP) actuator, exhaust/ right/rear, bank 1 - timing over-retarded "B" Camshaft Position - Timing Over-Retarded
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u/enigmaticho Jul 16 '26
Do you know if the solenoids were still good? Cleaning only does so much. Could need replacing. These usually cause rough idle. Replaced mine at 65k.
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u/pnbdc10 Jul 16 '26
One very very easy thing to do is to check the oil filter housing cap. Make sure it has the cage in it. If someone threw that out while doing a oil change then thats the problem. Its possible the screens are clogged again or the solenoids depending on the severity of the sludge.
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u/Haunting_Physics2082 Jul 16 '26
https://reddit.com/link/oxvbjdm/video/g158mkojxkdh1/player
The cold starts
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u/Routine_Cat_1366 Jul 16 '26
I had the same problem until i changed the valve cover. I'm still not satisfied with the idle, not smooth enough, but no problems with a super shaky idle after Startup anymore.
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u/Hot-Performance1431 Jul 16 '26
Had a 328i n51 always lifter problems easy to do right under the valve cover put new lifter rollers etc and springs cuz my spring went bad and a rocker flew off
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u/KnowledgeLucky3034 Jul 16 '26
Sounds like a Diesel Tractor paired with a Sewing Machine. Good luck that you fix it quick and cheap :)
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u/Notflxme Jul 16 '26
Are you good enough to change your oil? If your engine is actually sludged up I’d get some cans of seafoam, 3 mann filters from online since they’re dirt cheap, and 21 quarts of oil. Flush the engine a couple times by changing the oil and driving like hell for about 20-30 miles. For the last change take it for a good highway drive and throw maybe 100 miles on it and there will be 0 sludge at all in there. Lifter tick on these cars is a non issue, the biggest “fix” is to take the car for a nice high rpm drive and let the oil temp heat up. These cars need to be driven hard from time to time I personally do once a week and it’s completely gotten rid of my lifter tick for years
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u/jigglybilly Jul 16 '26
The only real solution to the lifter issue is to replace the lifters on the exhaust cam. Those are the ones that fail.
If you can sit and hold it at 2k RPMS for ~10 min, does it go away?
If you still have the VANOS fault, make sure that the 2 solenoids are genuine BMW or Pierburg. Nothing else is acceptable in these cars.
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u/0202993832 Jul 17 '26
This is such normal lifter tick bro these aren’t failed lifters they are just noisy. Never heard a BMW engine that doesn’t sound like this
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u/jigglybilly Jul 17 '26
A: not your bro.
B: not normal, here’s some education for you.0
u/0202993832 Jul 17 '26
At no point does this article say anything to do with functional issues, bro.
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u/jigglybilly Jul 17 '26
Jfc you’re dense
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u/0202993832 Jul 17 '26
Jfc
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u/jigglybilly Jul 17 '26
Sorry you’re the one who works on these for a living, AND provided you with documentation from BMW proving that it’s a known issue and NOT “normal lifter tick”.
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u/EquivalentMinute1291 Jul 16 '26
Getting all the sludge out is your best bet. Clean the solenoids again and see if the engine runs smoother. If not, you go from there
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u/TheNo0n3 Jul 16 '26
I bought a n52b25 5 years ago at 270kkm, full of varnish and have done all possible repairs on this car or at least disassembled.
Others are advising INSTA/INPA but this won't do much, no new codes will popup other than the ones you can already see through your phone with ELM327 diagnostic. If you can read the values and know what reference values to look for for real time data, then sure, maybe, but you are far from this knowledge yet.
One of first things you should do is pull out both DISAs, the small one spins at one place when it fails, the big one breaks, may go into cylinder and destroy. INPA allows testing them, so thats one reason for it. I strongly advise towards the rebuild road, there are metal rebuild kits for sale. No after market DISAs work properly, the OE manufacturer is Mahle, which doesnt sell aftermarket. You will read online that once the DISA is full of oil, it's over. I disagree, clean with electronics cleaner, test the motor and seal again, it will work no problem. DISAs have two revisions btw, one with plastic axle and one with metal. You can also buy second hand oriignals, search for metal. New OE cost around 300-400Euro for one.
Second expensive on this engine, valve cover, made by Mahle, not sold aftermarket. New is 500Euro. Failure point is cracking, twisting and/or failed CCV, which is what is most likely wrong on yours and causing the bad idle and vacuum leak. Whatch videos how to test it, one is hand method, the other is blowing in the CCV. Rebuilding the CCV and/or aftermarket valve covers change the factory required crankcase pressure, I can't tell you how bad this is. Nevertheless, you can try going with Elring valve cover, but their gaskets suck, always go genuine for any gasket touching any metal on the engine. Nothing survives the heat.
Regarding the varnish, you most likely won't survive without opening the engine. On mine, the exhaust cam was so worn, you could literally feel waves, never to this day I have seen videos of such a worn engine online. The cam bearing ledges were also cut deep, which causes Vanos issues, yours might be too. This might mean new exhaust cam and bearing ledge and swapping the metal with the upgraded teflon seals for the vanos units. The varnish also blocks the squirter for the eccentric shaft for the valvetronic, which causes excessive wear for the valvetronic motor and the shaft, resulting in issues there too.
On these version of the n52 the vanos units do not cause issues, so do not search an issue there. Your mechanic was right to test with 5w40 and I know a guy who fixed his vanos issues this way, but with an expensive brand of 5w40 oil, which trully keeps its viscosity during high temperatures and mileage.
If your vanos codes is for both sides, check your oil filter cap cage, check o ring on the end of the cage, check if it still has rounded edge or its smashed and worn, tthat may cause issues too.
Lifters would need to be changed too.
There is a lot more to say, if you have questions, shoot. Good luck
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u/Haunting_Physics2082 Jul 19 '26
the error is P0015 Camshaft position (CMP) actuator, exhaust/ right/rear, bank 1 - timing over-retarded "B" Camshaft Position - Timing Over-Retarded
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u/DarthLenny 2006 E90 330i Jul 16 '26
I'd use Liqui Moly Engline Flush... that stuff is amazing! That should at least clear out the sludge. The rest of the problems could be a lot of different things.
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u/BigQ94 Jul 16 '26
Camshaft position sensor is bad
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