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


When I was browsing for a auto to exchange my E46 325i difficulty kid, I experienced my head set on an E90. I have constantly liked the style, felt the cabin was fashionable sufficient to not truly feel outdated, and I honestly wanted to test out the N52 engine, just after listening to so quite a few superior items about it on boards. Even though executing my study on N52 engines, and E90s in general—their trustworthiness, upkeep, tips and tricks, and just total owners’ opinions—there had been a handful of factors I knew I want to get carried out as before long as I acquired just one. So here are the number of points I acquired, what I did to my vehicle so significantly, and what the system was like.

The BMW N52 appears like a single of the brand’s all-time greats, if I’m getting trustworthy. For a person matter, I like working with it. It’s underpowered by today’s expectations, especially in my 2006 325i (the weakest E90), which only has 215 horsepower. Nonetheless, it is so silky smooth and its electricity supply is so linear and responsive that I generally delight in revving it out. It will help that the clockfaces on its gauges are among the best each and every fitted to a BMW (E92 M3 gauges are finest). It’s also a very trusted engine (knock on wooden) and shockingly easy to operate on so far.

BMW E90 3 Series 13 830x552

Even so, there are a couple of routine maintenance goods it calls for that can not be neglected. The 1st of which is the oil filter housing gasket, which is literally a gasket that seals the top of the oil filter housing to the cylinder head. If you really don’t change the gasket, it will get really hard and loses its seal, which then will allow oil to drip straight only the serpentine belt (as very well as everywhere you go else, the entrance of my engine was a mess thanks to a neglected gasket). If oil repeatedly leaks on the belt, it can bring about that belt to swell, crack, and crack, which can be disastrous.

Another definitely essential little bit of servicing is replacing the coolant flange (nicknamed “Mickey Mouse flange” due to its shape). Fundamentally, it is a modest flange that connects a coolant hose to the entrance of the cylinder head and the inventory flange’s neck is designed from plastic. Just after many many years and several miles, that plastic neck breaks and, when it does, will dump all of your coolant onto the highway, leading to your car to right away overheat. It will clearly show indicators of leakage initially, nevertheless, and when it does leak it drips its coolant on to the serpentine belt, once more resulting in potential concerns.

Because both of those of those people problems can problems the serpentine belt, it is also good to substitute the belt and its pulleys, as the whole belt/pulley kit is comparatively very affordable and extremely simple to do. If you are an E90 (or E91, E92, E93) owner with an N52 motor (325i, 330i, 328i) and you haven’t performed these factors, probably this posting can support you out.

Here’s What You are going to Need:

  • Oil Filter Housing Gasket Package
  • Coolant Flange/Hose/Clamp
  • Serpentine Belt
  • Tensioner Pulley
  • Idler Pulley
  • Socket Set
  • Socket Wrench
  • E-Torx Socket Established
  • 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 Really Suggested

The to start with issue I did was drain the oil and the coolant. Make confident to get some capture pans all set or you’re gonna make a massive mess. The oil pan has a drain bolt on the base, beneath the motor, I just unbolted it and allow the oil movement into a pan. Underneath the radiator, on a person aspect or the other (dependent on the design), there is a large screw with a big “+” form head. I used an enormous flathead screwdriver (but a quarter and pliers operate very well also), as a regular screwdriver will hurt the plastic head. I unscrewed it and permit the coolant movement into a pan. Definitely, I did this with the engine chilly, or both of those fluids would have been extremely very hot.

Just after that, I removed the oil filter, to assist the oil drain from the pan. Once the fluids were being draining, I took the air intake box and duct out, to give me improved accessibility. Then, after all the fluids were being accomplished, I screwed the oil pan and radiator drain plugs back in and received to do the job.

BMW E90 3 Series 07 830x552

The initial point I did was choose the serpentine belt off, by employing a T60 socket on a 1/2-inch, 15-inch prolonged breaker bar to launch the belt rigidity on the tensioner pulley. Just after the belt was off, I eradicated the two pulleys, which were being held on by one bolt each and every. Super uncomplicated stuff. At the time they pulleys had been off, I got to function on the oil filter housing gasket. This is the only difficult aspect of the whole position. It is held on by three E-torx bolts (exterior torx), which is why you have to have the E-torx socket established. Nevertheless, one particular of the bolts is difficult to get to and the finest way to do it is to use an E10 swivel socket on a lengthy 1/4-inch extension and sneak it amongst the oil filter housing and ingestion manifold. The moment you do that, it’s really tremendous effortless.

Once people bolts ended up eradicated 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 grimy. Then I replaced the gasket in the housing, which can be irritating if you never have any picks, which I really do not. So I employed a razer utility knife, diligently sliced the gasket, and made use of my smallest flathead screwdriver to dig into the slice, select one conclusion up, and pull the rest out. Then I changed it with the new gasket, which was of course super simple.

Immediately after that, I cleaned up the housing with some brake cleaner, dried it off, and reinstalled it. As soon as you get a really feel for that one difficult bolt, it is simple to get it again on. Nevertheless, I hugely endorse making use of a torque wrench to reinstall any of the bolts on this motor, as they are all aluminum bolts. The cylinder head is an aluminum/magnesium alloy, so the bolts need to be aluminum and they can quickly split. They’re all also just one-time-use bolts and the new areas need to come with new bolts. So make guaranteed they’re torqued to the suitable spec. I don’t have torque wrenches but thankfully I have develop into excellent at getting a experience for how restricted I can go just before breaking bolts. Question me how I figured out the tricky way … I’d fairly use torque wrenches, I’m just inexpensive.

When the oil filter housing was again on, I started on the coolant flange which, if you invest in the appropriate kit, is super uncomplicated. Only two 10mm bolts maintain it on and they’re simple to get to. I unbolted those people and gently wiggled the flange out of the cylinder head. I utilized a smaller flathead to gently pry it absent since you never want to crack the plastic neck off, so as to not get plastic bits in your coolant program. Once out, I actually just observed the other conclusion of the hose, which is attached to the drinking water pump in close proximity to the base of the motor, and disconnected it, because my package arrived with a new flange hooked up to a new hose already.

The rationale for that is that the stock hose clamp is a compression fitting and can not be taken off. So fairly than battle the fighting and breaking it off, which is hard to do with out harmful the hose, I just reinstalled an totally new flange and hose in just one shot. Wonderful and uncomplicated.

Just after that, it was time to put the serpentine belt again on and fill the automobile again up with fluids. So I stuffed it up with Liqui Moly’s Leichtlauf 5W40 entirely artificial motor oil, which is my favourite oil for high-mileage German engines. Then, I manufactured a 50/50 mixture of BMW’s blue coolant with distilled drinking water (1 gallon of each, makes two gallons of blended coolant), and filled it up. Then I reinstalled the air intake and did my absolute favourite section of the occupation: bleeding the air.

In older BMWs, bleeding the air from the coolant strains was a flipping nightmare. I wished to generate my E36 into a river when accomplishing it. However, for the reason that the E90 (and all more recent BMWs) has an digital drinking water pump, the motor vehicle will do it for you. Just tighten the cap up, get inside of the vehicle, push the commence button devoid of your foot on the brake (accent), transform the heat to entire and fan speed to reduced, and then press the gas pedal to the floor for about 12-15 seconds. That minimal sequence initializes the bleed treatment and you’ll listen to the h2o pump kick on and get started bleeding the air. It requires about 10-15 minutes but it will cease itself when it’s finished.. I experienced a beer while I waited. It was brilliant.

All in, I used about 4 hours, together with jacking the automobile up, acquiring all my equipment out, and cleansing up at the conclusion. I also took my sweet ass time and did not rush, so it could likely be finished more quickly. Now, nevertheless, my engine feels significantly smoother, possible many thanks to fresh oil (I have no strategy what the preceding operator set in and when he did it) cleansing up the valve lifters, and the new pulleys and belt owning no slack. Also, the delicate drone from the aged pulleys is long gone and the engine sounds brand new.

None of people jobs ended up challenging, anything was easy to arrive at, get off, and reinstall, and the complete expense was less than $300, even immediately after acquiring the E-torx socket set, swivel socket, and fluids. There are a several more points that want to be accomplished on my vehicle, but I’ll go over them in one more tale. For now, if you have an E90, individuals jobs can be completed in a single sitting down, for a relatively minimal price tag, devoid of a ton of mechanical know-how, and they’ll assistance your N52 engine operate greater, absolutely free from the potential risks of leaking coolant and oil. If you are seeking to invest in an E90 with an N52 engine, factor these employment into your initial servicing cost and have them carried out correct away.


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