[Coffinspired]

Sorry to come here and post an essay - but I see BMW clamped down on service manuals being spread online. So that's fun. Guess if we buy the car I'd be around the forums anyway for sure. I will be anyway as she's stuck on this car - would just have to go find another M235i/240 if this is a walkaway.

I can't even find an official answer online for what the OEM service pressures/Cyl variances are for a compression test for the M235i N55.

Going to call a BMW dealer for OEM service compression numbers and more importantly call some BMW tune shops for the actual advice I'm looking for in this post later today when they open up I guess. Would LOVE y'all's help though.

More than the "service limits"...I'm more concerned with what's considered "normal" for a healthy stock M235i N55's compression @ ~60k mi. in the community and if ~175psi across 6cyl is a bit low - even if it's...y'know the point, even. If the overall compression isn't bad...sounds alright. And the car's otherwise great. But is it overall alright @ 175psi?

Car's out of State so it was tested at a reputable shop (which I hate I wasn't there but hey) - I'll be following up with the shop later today, I assume the compression test was done with a proper seal/gauge and on a cold engine until told otherwise. Shop owner called her with those figures last night and said "car's great overall, no glaring issues, and the test is fine, I'd say it's good to go".


Plans for the car is only BPU and DD'ing. At most intake/exhaust/light tune with the GF barely pushing it DD'ing to work honestly. Definitely never getting past stock turbo/fuel.



On the car we're looking at:

- Totally stock - don't have the options on me right now but not totally base - 6MT

- All maintenance done on time from first owner @ BMW with records to 54k mi.

- Second owner (current seller) bought @ 54k in 2023 did nothing but oil and the charge pipe that cracks (and some "black exhaust tips to match" lol) Barely drove it. 62K now.

- None of the common issues ever cropped up yet (Filter housing/Waterpump/valve covers/etc) - no leaks at all.

- Otherwise mechanically clean (more than I'd expect for the mileage on the surface honestly). Totally dry runs well.

- (Not that it matters really even if it's not a bad deal, we're not trying to waste any amount of money on a bad car - but we've settled on $20K)

Give me some insight here guys. I'd really appreciate it.

A Google search points to a random forum post saying "less than 180psi = worry about the motor" on a tuning forum and a few other ones elsewhere like Reddit that seem to be citing that one totally random forum post. None of these one sentence posts prove I should take them as fact. But it obviously that makes me worry - even if it's not exactly useful info there....at all...but I'm not seeing much else online.

Thanks for any help here

[BringBackButtons]

https://www.bimmerpost.com/forums/sh...php?p=26058056

175 is less than 180, and definately less than 210ish.

Low compression could be carbon buildup on valved if it was barely driven or monitored, but at that point your in a for a diagnosis without guarentee.

[Coffinspired]

Originally Posted by BringBackButtons

175 is less than 180, and definately less than 210ish....

Hhm, I see...so it seems that random post on the forum was accurate.

Yeah car's been mostly sitting - drove about 8k miles in 3 or so years. Owner travels for work and drives a company car when home.

Hate that it's in a window where I have a doubt here. Not terrible numbers and not that I'd expect a perfect motor @ 60k mi...but it's definitely not 200+

I would suspect it would be something like that over rings as it's normaliz

Appreciate it

[ferraricare]

Normal compression
Gasoline Engines: Readings typically range from 120 to 175 PSI
Ideally, the compression readings across all cylinders should be fairly consistent
No more than a 10% to 15% variation between the highest and lowest readings

[BringBackButtons]

Im going to drop this video specifically related to our n55 ewg platform. 175 seems to be the magic healthy number. 210? Maybe brand new.

Stumbled on this guy a week or so ago, not flashy but pretty knowledgable and relatable.

No endorsement. Just information.
Now I feel bad if I potentially scared a fellow enthusiast away from interwebs searching and bad data.

Sorry, mb.


ttps://youtu.be/urPKMh0jpHc?si=6BcJc5zUKx4ko1s7

[FrostyMornings]

Originally Posted by Coffinspired

- None of the common issues ever cropped up yet (Filter housing/Waterpump/valve covers/etc) - no leaks at all.

If they really haven't been done, you're right in the range for them to start appearing - so be ready for the housing gaskets at the least.

Relatively easy DIY's though, and not expensive if you're just doing gaskets.