N52 plugged oil filter!

80stech · #1 08-11-2025, 04:06 PM

So had a screeching/high pitch buzzing noise start coming from my oil filter housing and sure enough the filter (recent Mahle) was plugged with fine brown crap like you would find on the inside of the valve cover. A week or 2 earlier I went to get some 15w40 oil to add to try and diagnose more what's going on with my sometimes noisy lifters. The only brand name 15w40 they had in stock was Rotella T and I even talked to the parts guy about how Rotella T back in the day was known to have high detergent and was good for cleaning out engines and how Castrol was known for creating sludge so should be perfect since previous owner likely used Castrol! I only put about a 1 1/2 liters of "T" in and even though I knew what might happen I wasn't ready for it to be so quick! The filter sure is tiny though and maybe being a Mahle was on the fine side. Just before the noise started I gunned the engine a bit on the highway and something didn't seem right as if the timing got cut back and sure enough now have some knock codes! It's all good now though, power is back and lifters are totally quiet!

Hopefully it stays that way and I didn't shorten the life of the engine too much!

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80stech · #2 08-11-2025, 04:39 PM

Well I just finished reading up on the N52 oiling system and apparently it has a variable volume oil pump which means that it reduces volume with pressure and likely did that with the plugged oil filter! ;( Probably the noise I heard at the filter housing was not a by-pass valve but oil being forced around the ID oil filter gasket which I thought the Mehle had a better design with a rubber seal instead of the paper edge but probably made the problem worse! I guess at least the rubber gasket made a noise whereas the paper one probably would have allowed oil to flow by more easily but also not give any warning! Let that be a lesson!

So there is a bypass valve in the filter cap so that is probably what I was hearing, so maybe not so bad considering it was bypassing at idle when the pump is supposedly feeding more oil

80stech · #3 08-12-2025, 10:42 AM

Has anyone come across a better designed cap that holds the cage better so it comes out with the cap like it is supposed to ?? Did BMW improve their design ? The one that was in the car when I bought it pulled apart when I took the cap off and of course made a mess so I ordered a new one (I think FEBI) but it has the same problem.

josiahg52 · #4 08-15-2025, 08:28 PM

My diesel had Castrol dealership oil changes all it's life until I bought it. I've used Mobil 1 since then. Engine looked and looks great. Castrol TWS was the "Gold Standard" for my M5 in the day. The Rotella may have additives that can quickly foul catalytic converter, SCRs, DPFs, DOCs so be careful. The original oil filter cap retains the oil filter, quite tenaciously, when I unscrew it and lift it off. There is resistance pulling it out of the filter housing, too. Is that what you're asking about? The diesel and gas may be different.

80stech · #5 08-15-2025, 10:08 PM

Yes, the cap that was on the car didn't hold the cage at all (maybe wasn't original) and the replacement Febi cap isn't much better. Maybe I'll try an OEM cap. It sure would be nice if the cage would stay on so the oil filter housing would drain!

I'm gonna use "some" Rotella T and change the filter frequently and see what comes of it.

My lifter noise is back slightly again. It seems when I change oil/filter the noise goes away but then comes back, now I'm wondering if the Mehle filters are a bit too fine and maybe the variable volume pump starts to cut back before the by-pass valve in the filter cage opens ?? The whole N52 lifter saga is pretty crazy!

80stech · #6 09-07-2025, 09:26 AM

I finally have a place in Canada were I can order OE parts so I ordered OE filter cap and it does look to be made better. I changed the filter again in the meantime though, engine got quieter but now lifter noise is coming back a bit at times so I'm going to change the filter again and install the OE cap this time

I was using Mehle filters but switched to WIX with the last change. I like that WIX and Mehle filters use a rubber seal because I don't see how the OE type filter with the paper ring doesn't bypass oil around it. It does seem more and more though that what is happening is that the variable displacement oil pump is cutting back flow as the tiny filter gets restricted which is maybe made worse by extra fine filter media, and who knows what the previous owner had done. Ironically having some bypass from a crappy paper filter seal, or poor fitting cage/bypass valve might be better for the oil flow! Maybe this explains a lot of the noisy lifter issues and spun brgs on some (I think N54 is worse) engines.

josiahg52 · #7 09-09-2025, 09:24 AM

When you say cage, do you mean the part that fits inside of the filter? That part should stay with the cap. I completely unscrew the cap from the housing, just leaving it sitting in top of the housing threads and the housing and filter have always been fully drained when I get back to it after draining the sump; there's no oil left in the housing. I've understood when the cap is loosened and the filter comes out of the housing that little bit, that it opens the drain in the housing. Then, I can pull the filter off the cap and the (what I think you are calling cage) cage and cap come off the filter together. If you're housing and filter are filled with oil after loosening or removing the cap, that isn't right. If the cage is coming off of the cap, that isn't right either. Sorry if I'm just confirming your problems, but when you mentioned the housing draining issue, it caught my eye.

I used to use MANN all the time, used a couple Hengst years ago, but the last few OEM were Mahle, but now I just buy OE from the dealer. They're like (or were because I haven't purchased in some time) $12-something with my discount. No hassle, no shipping, and even if it was really expensive, I'm not changing the oil twice a year any more.

80stech · #8 09-09-2025, 09:32 AM

Yes, that is exactly right. Looks like the new OE cap is made better and I'm going to switch it in the next couple of days. I think the Hengst and Mann filters just have the paper end seals ?? Our local dealer is a dick so it's nice that I now can order OE on line from Canada!

I ordered an OE gas cap as well and it's MUCH better than any of the after market ones that I tried for just a few dollars more.

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