Here Are Some Maintenance Tips I’ve Learned About the BMW N52 Engine


When I was hunting for a motor vehicle to substitute my E46 325i dilemma little one, I had my mind set on an E90. I have normally loved the style and design, felt the cabin was fashionable enough to not truly feel previous, and I actually wished to attempt out the N52 engine, following listening to so numerous superior things about it on message boards. When executing my study on N52 engines, and E90s in general—their trustworthiness, upkeep, recommendations and tips, and just general owners’ opinions—there were being a few factors I knew I need to get completed as before long as I purchased one. So here are the handful of points I acquired, what I did to my motor vehicle so considerably, and what the method was like.

The BMW N52 appears like a person of the brand’s all-time greats, if I’m remaining truthful. For a person issue, I enjoy making use of it. It’s underpowered by today’s criteria, in particular in my 2006 325i (the weakest E90), which only has 215 horsepower. However, it’s so silky smooth and its electricity supply is so linear and responsive that I often love revving it out. It helps that the clockfaces on its gauges are among the most effective just about every fitted to a BMW (E92 M3 gauges are ideal). It’s also a very reputable engine (knock on wooden) and shockingly uncomplicated to do the job on so significantly.

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Even so, there are a handful of routine maintenance items it demands that simply cannot be neglected. The initially of which is the oil filter housing gasket, which is practically a gasket that seals the prime of the oil filter housing to the cylinder head. If you do not alter the gasket, it will get challenging and loses its seal, which then makes it possible for oil to drip right only the serpentine belt (as very well as almost everywhere else, the entrance of my motor was a mess thanks to a neglected gasket). If oil continually leaks on the belt, it can cause that belt to swell, crack, and crack, which can be disastrous.

Yet another really important little bit of maintenance is replacing the coolant flange (nicknamed “Mickey Mouse flange” thanks to its condition). Basically, it’s a modest flange that connects a coolant hose to the entrance of the cylinder head and the inventory flange’s neck is manufactured from plastic. Following numerous several years and lots of miles, that plastic neck breaks and, when it does, will dump all of your coolant onto the highway, creating your vehicle to promptly overheat. It will clearly show indicators of leakage 1st, however, and when it does leak it drips its coolant on to the serpentine belt, again triggering possible problems.

Simply because equally of those people problems can damage the serpentine belt, it’s also very good to switch the belt and its pulleys, as the total belt/pulley kit is rather reasonably priced and quite straightforward to do. If you are an E90 (or E91, E92, E93) owner with an N52 motor (325i, 330i, 328i) and you have not completed these items, maybe this write-up can aid you out.

Here’s What You’ll Require:

  • Oil Filter Housing Gasket Kit
  • Coolant Flange/Hose/Clamp
  • Serpentine Belt
  • Tensioner Pulley
  • Loafer Pulley
  • Socket Established
  • Socket Wrench
  • E-Torx Socket Set
  • 1/4-inch E10 Swivel Socket with 6-inch Extension (or for a longer period)
  • T60 Socket
  • 1/2-inch Breaker Bar
  • 7 Quarts of Oil
  • 1 Gallon of BMW Coolant
  • 1 Gallon of Distilled Drinking water
  • Torque Wrenches Remarkably Advisable

The initial point I did was drain the oil and the coolant. Make positive to get some capture pans all set or you are gonna make a big mess. The oil pan has a drain bolt on the bottom, beneath the motor, I just unbolted it and allow the oil stream into a pan. Beneath the radiator, on 1 aspect or the other (dependent on the model), there’s a big screw with a huge “+” condition head. I utilized an huge flathead screwdriver (but a quarter and pliers perform very well too), as a regular screwdriver will hurt the plastic head. I unscrewed it and enable the coolant stream into a pan. Clearly, I did this with the motor chilly, or equally fluids would have been really hot.

After that, I removed the oil filter, to aid the oil drain from the pan. At the time the fluids were being draining, I took the air ingestion box and duct out, to give me much better access. Then, when all the fluids were done, I screwed the oil pan and radiator drain plugs again in and acquired to work.

BMW E90 3 Series 07 830x552

The initial detail I did was choose the serpentine belt off, by utilizing a T60 socket on a 1/2-inch, 15-inch lengthy breaker bar to release the belt stress on the tensioner pulley. Right after the belt was off, I removed equally pulleys, which were held on by one particular bolt each and every. Super quick stuff. Once they pulleys ended up off, I acquired to do the job on the oil filter housing gasket. This is the only challenging aspect of the complete position. It is held on by a few E-torx bolts (exterior torx), which is why you have to have the E-torx socket set. Nevertheless, one particular of the bolts is difficult to get to and the very best way to do it is to use an E10 swivel socket on a prolonged 1/4-inch extension and sneak it involving the oil filter housing and consumption manifold. Once you do that, it is really super easy.

As soon as all those bolts have been removed and the housing was off, I sprayed some brake cleaner paper towel and cleaned the cylinder head, exactly where it satisfies the housing, as it was dirty. Then I changed the gasket in the housing, which can be troublesome if you really do not have any picks, which I don’t. So I utilised a razer utility knife, meticulously sliced the gasket, and made use of my smallest flathead screwdriver to dig into the slice, pick a person conclude up, and pull the relaxation out. Then I replaced it with the new gasket, which was naturally tremendous effortless.

Following that, I cleaned up the housing with some brake cleaner, dried it off, and reinstalled it. At the time you get a really feel for that one tricky bolt, it’s simple to get it again on. Nevertheless, I extremely recommend employing a torque wrench to reinstall any of the bolts on this motor, as they’re all aluminum bolts. The cylinder head is an aluminum/magnesium alloy, so the bolts want to be aluminum and they can very easily split. They are all also a person-time-use bolts and the new parts really should arrive with new bolts. So make guaranteed they’re torqued to the proper spec. I really don’t have torque wrenches but luckily I have turn out to be fantastic at getting a truly feel for how restricted I can go right before breaking bolts. Talk to me how I discovered the tough way … I’d alternatively use torque wrenches, I’m just low-cost.

The moment the oil filter housing was again on, I begun on the coolant flange which, if you acquire the correct package, is tremendous simple. Only two 10mm bolts hold it on and they are uncomplicated to get to. I unbolted individuals and carefully wiggled the flange out of the cylinder head. I used a modest flathead to carefully pry it away mainly because you do not want to split the plastic neck off, so as to not get plastic bits in your coolant procedure. The moment out, I basically just found the other conclusion of the hose, which is attached to the h2o pump around the bottom of the engine, and disconnected it, since my kit came with a new flange connected to a new hose currently.

The cause for that is that the inventory hose clamp is a compression fitting and simply cannot be taken off. So instead than struggle the battling and breaking it off, which is hard to do with no harming the hose, I just reinstalled an entirely new flange and hose in a single shot. Great and uncomplicated.

Right after that, it was time to place the serpentine belt back again on and fill the vehicle back again up with fluids. So I stuffed it up with Liqui Moly’s Leichtlauf 5W40 totally synthetic motor oil, which is my most loved oil for substantial-mileage German engines. Then, I produced a 50/50 combination of BMW’s blue coolant with distilled h2o (1 gallon of every single, makes two gallons of combined coolant), and loaded it up. Then I reinstalled the air ingestion and did my complete favorite part of the job: bleeding the air.

In older BMWs, bleeding the air from the coolant strains was a flipping nightmare. I required to push my E36 into a river when executing it. However, for the reason that the E90 (and all newer BMWs) has an digital h2o pump, the automobile will do it for you. Just tighten the cap up, get inside of the auto, push the start button without the need of your foot on the brake (accent), change the heat to whole and lover speed to lower, and then push the gas pedal to the floor for about 12-15 seconds. That minimal sequence initializes the bleed procedure and you are going to listen to the h2o pump kick on and start bleeding the air. It normally takes about 10-15 minutes but it will prevent alone when it’s performed.. I experienced a beer while I waited. It was amazing.

All in, I expended about four hours, like jacking the car or truck up, finding all my equipment out, and cleansing up at the conclusion. I also took my sweet ass time and didn’t hurry, so it could almost certainly be done more quickly. Now, nevertheless, my engine feels significantly smoother, probably many thanks to new oil (I have no plan what the preceding proprietor place in and when he did it) cleaning up the valve lifters, and the new pulleys and belt obtaining no slack. Also, the subtle drone from the previous pulleys is absent and the engine appears manufacturer new.

None of all those jobs were hard, almost everything was effortless to get to, choose off, and reinstall, and the total price tag was underneath $300, even immediately after obtaining the E-torx socket established, swivel socket, and fluids. There are a few more matters that need to be accomplished on my car, but I’ll talk about them in a different tale. For now, if you have an E90, those people work can be accomplished in 1 sitting down, for a relatively lower cost, devoid of a ton of mechanical know-how, and they’ll support your N52 motor run better, free of charge from the risks of leaking coolant and oil. If you’re seeking to get an E90 with an N52 engine, aspect these employment into your first routine maintenance charge and have them finished proper away.


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