BMWs from the 2000s offer a driving experience you won’t find in many other places. The brand used to call itself the Ultimate Driving Machine and its products lived up to it. However, if you buy one of these beauties today, your car might have a problem lurking in the shadows just waiting to pounce and ruin your day. Your plastic cooling system parts might be ready to blow, which can strand your car in an instant. Here’s how you might be able to prevent it from happening.
Back in December, I had a triple whammy of a bad day. My beloved 2008 Smart Fortwo destroyed its exhaust flex pipe, my former Zero electric motorcycle press loaner was totally dead, and then my 2007 BMW 530xi Touring puked its guts just casually driving out of my neighborhood. The failure of the BMW was surprising as the wonderful gent I purchased it from, our secret designer the Bishop, was so anal about taking care of the thing that I got a folder of service records an inch thick.
The failure was something neither the Bishop nor myself saw coming. One of the many small plastic couplings in the BMW’s cooling system shattered, allowing the car to pump out two gallons of coolant in an alarmingly short amount of time. Had I not caught this, the slick BMW’s straight-six engine could have overheated, or worse. Yet, the coolant failure still stranded the car. I got lucky, but you might not. Here’s how you can fix this issue before it happens and I have good news because it might be easier than you’d expect.
Nothing Lasts Forever
Now, I first want to start by clarifying something I said in my previous piece on this subject. Back in January when I first wrote about this issue, I said:
Modern cars are great. You get to enjoy the benefits of over a century of advancement, plush leather, innovative toys, fresh design, and smile-inducing power. However, sometimes modern cars have some interesting quirks, like having critical parts including oil pans, valve covers, water pump impellers, and coolant hose connections made in plastic rather than metal. Plastic saves weight and can be formed into all sorts of neat shapes. However, years down the road you might find yourself on the business end of a catastrophe.
Cars have had plastic cooling parts for decades. Remember the fabled GM 3800 V6? Even that had plastic cooling elbows. While it might be somewhat common for those elbows to blow now, you have to remember that the cars with these engines are now around two decades old if not older. My BMW is 18 years old with 180,000 miles. From what I can tell, my cooling system was still wearing its original parts. So while plastic cooling system materials might not last the entire life of the car, they’re still relatively robust.
Still, nothing lasts forever. So if your car has been around the block for nearly two decades on its original cooling parts, it might be worth checking into their condition.
Catastrophic cooling system failures are sinister. Everything happens quickly and if you don’t immediately snap into action, the damage can multiply. Either way, your day is ruined because you’re stuck at the very least.
Back in December, I decided to enjoy an unusually warm day by driving my E61 with the windows down and the glass roof open. I fired up the vehicle, topped up its tires, and tried to revive my dead Zero motorcycle tester one last time. By the time I got back to the car, the engine was nice and warmed up. I didn’t even make it out of my neighborhood before seeing the James Bond-esque cloud of steam in my rearview mirror. The only indication from the car of something horrible happening was a low coolant indication in the instrument cluster.
I popped the hood and at first, I couldn’t see anything immediately wrong. So I let the car cool for an hour before nursing it back home. A trail of coolant followed behind me. I was lucky as I wasn’t even a quarter mile from my parking space when it happened. Had the ruinous failure happened anywhere else, I would have had to call for a tow truck.
On inspection, I discovered what happened: The connector that secures the upper radiator hose to the engine had effectively shattered, permanently separating the hose from its connector. The only real fix to my problem was to replace the entirety of the upper radiator hose.
A ridiculous number of BMWs across the company’s portfolio use plastic cooling parts and my upper radiator hose failure isn’t even the most notorious part that fails. That distinction goes to the infamous plastic flange that BMW owners have called the “Mickey Mouse Flange” due to its resemblance to the beloved Disney character.
The failure mode for this part isn’t really any different than my upper radiator hose. The plastic effectively shatters and blows out, leading your BMW to squeeze out its vital juices at a cataclysmic rate.
The flange in question can be found in a huge list of cars, from my last piece:
FCP Euro says you’ll find this plastic flange in the BMW 1 Series, the BMW 2 Series, the BMW 3 Series, the BMW 4 Series, the BMW 5 Series, the BMW 6 Series, the BMW 7 Series, the BMW X1, the BMW X3, the X4, the BMW X5, the BMW Z4, the BMW 1 Series M, BMW ActiveHybrids, and finally, the BMW M2.
Basically, if you own a BMW made from 2006 to 2018, you should check this FCP Euro page to see if your car is included and to also see the ridiculous breadth of part numbers.
If you pop open the hoods of these cars and more, you’ll find ol’ plastic Mickey accompanied by plastic cooling system parts. In my case, the offending flange was only inches from where my upper radiator hose failed. These parts may begin leaking before they fully fail, or they might just blow apart like my hose connector did. That’s the menacing part about this.
Easy DIY Fix
Thankfully, I have great news. BMW’s cooling system parts are largely similar in connector design. Yes, you’ll find the cooling system parts in different shapes and sizes, and they might be easier or harder to reach depending on your model and engine, but they use familiar connectors. BMW loves linking hoses using male and female connectors that are secured using C-clips. As I discovered over the weekend, replacing these parts can be easy!
What you’re about to read below is specific to my E61, but you’ll be able to use my general advice to get through your project. You should be able to find a YouTube video or online write-up for your specific model. That being said, it looks like you’ll have an easier time if your BMW has one of the smaller engines for its model.
To fix my car, I picked up part number 17127546064 from FCP Euro. The upper radiator hose goes for as cheap as $43 for the Rein model to $109 for BMW OEM. You might be able to find them for even cheaper on eBay, but I probably wouldn’t chance it.
While my Mickey Mouse flange wasn’t broken yet, I picked up one of those from FCP Euro as well. You can get this flange from countless websites, even sellers on Etsy, for around $22 or so. If you’re unsure exactly what part you need, a parts seller like FCP Euro can usually guide you to the right place. I also recommend looking up a diagram for your model and engine.
Here’s an example of what my E61 N52’s diagram looks like with the part I replaced highlighted in red:
My 2007 BMW 530xi has a little 3.0-liter straight-six under its hood. The E60 platform housed engines as large as 5.0-liter V10s, so my engine bay had a lot of space to work in it.
Getting to my hoses was pretty easy. First, I removed the airbox. It’s held on with two T30 bolts that came out with ease. At the rear of the box is flexible piping and the mass air flow (MAF) sensor. A slotted screwdriver loosens the clamp on the pipe and the MAF just un-clips.
Your real challenge will be at the front of the airbox, where the inlet from the bumper has a little plastic ramp to secure the box in place. Use your screwdriver to pry the ramp out of the way and free the airbox.
If you have one of the smaller engines, that’s all you need to do to reach your cooling system parts. If you have a larger engine, you may need to remove the radiator header panel and the fans to get enough space to work. To give an example of how it would be different for a larger engine, a BMW 545i E60 owner would want to remove the intake duct to get to their upper radiator hose. From there, the process is similar to what I’m going to show you.
Once you get access to your hoses, removing them is as easy as taking the screwdriver from earlier and prying up at the tops of the clips on each connector. The clips should lift up and eventually disengage. Then you just wiggle the connector away from the housing. In my case, I needed to do this four times since my upper radiator hose had two tributaries.
I started with the big ends and worked my way down to the small ends. Three of my E60’s hose connections were female with one male end. The process is the same no matter what end you’re working with.
Once you pull everything apart, be sure to check the fittings to ensure you didn’t leave behind any broken plastic or O-rings. In my case, the radiator hose connection that shattered left behind an O-ring and a ring of broken plastic.
Adding the new hoses in is the inverse of removal. In most cases, you’ll be able to just slide the new hoses on. You’ll know they’re secure when you hear a satisfying click from the C-clip. If you can’t seem to get the new hose to fit, I’d recommend opening the new hose’s clip, sliding the connector on, and then closing the clip.
I was able to do this job in about 30 minutes on a cold winter morning. It wasn’t super involved. I do recommend picking up a pack of C-clips from your local auto parts store in case you lose one or one is very corroded. I lost one of the lower clips and a box of replacement clips from Dorman were perfect.
If you want to go further and attack the infamous coolant flange, things do begin to escalate. Once again, this depends on your exact model and engine, but the flange might be harder to get to than the upper radiator hose. My E60’s flange was out and in the open. Nothing was in my way.
However, if you’re working on something like an E90 3-Series, you might find that you have to remove your radiator fan to get to the same flange. Here’s a helpful video on getting there:
Once you’ve made your way to the flange, removing it should be relatively easy as it’s held in with just two 10mm bolts. If your flange is intact, getting it out may require some hard pulling, wiggling, and prying to free it.
Then, you’ll have to take a metal cutting tool to snip the clamp band off of the flange to get the old one off. Here’s the process on a 1-Series:
From here, you can install one of the many metal replacement flanges on the market. Sadly, I have a cold right now and it seems I might not be in the best of shape because no matter how much I tugged and wiggled I couldn’t get my flange out. But hey, at least mine isn’t leaking right now. I’ll work on it again when I’m feeling better.
Thus far, we’ve covered the most common cooling system failure points. If you want some real peace of mind, you may choose to just replace all of the plastic cooling parts. If so, Pelican Parts has a helpful guide you can find by clicking here. But I will warn you that such a job would probably take you a whole weekend and a bunch of dough.
For now, I’m addressing the more common failure points and will have to return to the other parts later.
Top It Back Up
Once you’re done with your project, it’ll be time to fill your ride back up with coolant. Since my E60 puked out its guts, I didn’t have to worry about draining coolant. So, I skipped straight to filling and bleeding. I followed the Pelican Parts guide for this:
Install the expansion tank cap and be sure all bleeder screws are tight. Turn the ignition ON (do not start engine). Set the temperature controls in the vehicle interior to full warm and blower fan speed to Low. Start and run the engine at idle until it reaches operating temperature and check the cooling level, top up as needed. When done, check the cooling system for leaks.
On late 6-cylinder models with electric coolant pumps: Install the expansion tank cap. Turn the ignition ON (do not start engine). Set the temperature controls in the vehicle interior to full warm and the blower fan speed to Low. Press the accelerator pedal to the floor and hold it down for ten seconds. Run the electric coolant pump for about 12 minutes to circulate coolant and bleed air from the cooling system. Once the pump has run the cycle, check the level of coolant in the expansion tank and adjust it as needed. Start and run the engine at idle until it reaches operating temperature and check the cooling system for leaks.
In my case, I picked up three gallons of Zerex G48 coolant from my local O’Reilly Auto Parts for about $20/gallon. The BMW gulped down 1.5 gallons through the reservoir, then drank another 0.5 gallons after running the pump cycle. I then took the car for a relatively spirited drive and checked temperatures and levels along the way. All appeared to be well. Since my car takes 10.6 liters of coolant, that suggests a bit under a gallon of coolant was still left in the vehicle after the mishap.
Overall, this project took me a couple of hours and less than $200. In theory, the upper radiator hose will now last for the remainder of the life of the car. Once I fit the metal replacement for Mickey it’ll be the same case there as well.
So, if you happen to buy a BMW that’s about two decades old and you have no idea how well it was serviced, you may end up running into an issue like this. If your connectors fail, you’re going to have a very bad day on the side of the road. A failure may happen without warning and if you don’t act fast, you’ll be dealing with worse than some hose replacements. It might be worth replacing these parts before it gets to that point. The good news is that, depending on your exact situation, DIY might be both fun and easy!
These are in the same category as the Chrysler 3.6 V6 oil filter / cooler housing. Pretty much guaranteed to make it through warranty and then good luck. Although the failed Chryslers I’ve seen are more of a slow not sudden death failure mode.
I was typing exactly this when your message popped up (great minds…).
You know it’s a bad design when Doorman makes a better part than the factory!
Every time I think I might want to get a fun driving BMW, I see articles like this. It’s budget death by 1000 cuts. I’ll probably end up getting an older Miata or GT86.
I have a Mickey Mouse connector on its way, as we speak. I’m installing the oil-to-water heat exchanger on my 128i that your car already has. I needed to pull the flange to access one of the bolts on the oil filter housing gasket. The flange broke as I was trying to pull it off.
High output variants of the N52 got this heat exchanger and it’s a well-integrated upgrade to knock down the oil temps a bit for the short track sessions I occasionally do. Note that I’d recommend a custom oil-to-air heat exchanger for N52 engine cars that see any regular track time.
I’m surprised a reputable indie didn’t check or recommend the service long before failure. Maybe it’s because they’re in the desert, but my Tucson Volvo indie recommended we replace pretty much all of the radiator and thermostat piping and housings at around a decade of service, regardless of mileage—just because once they start cracking they can see some pretty catastrophic failures, and a triple-digit desert summer day is not a time to be stranded. Our San Jose indie corroborated this and did the service for two of our other Volvos.
Nice! Somewhat related, but I decided to dust off my ‘01.5 Passat after nearly a decade of sitting in the driveway and do some rehab. Already got new tires, a basic wax job (mostly to stave off the lost clearcoat on the roof and hood…door paint is still 9/10 condition!).
One of the perennial issues with it is the clogged heater core. The nipples that go through the firewall are plastic and once they’re snapped off completely, I’m just gonna have to bypass the heater core entirely. Because my 5-7 previous efforts to flush the core have progressively made things worse. Now it’s about 5 hose clamps (where there used to be 2) and about 4-5 sections of replacement hose (where there used to be 2). It’s just a time bomb. In fact, I need to go ahead and keep “heater core delete” parts in the trunk so I can at least salvage the engine once those hoses give up.
I should also note that the heater core nipples are a SERVICE ITEM. That’s where you have to bleed the cooling system. Those absolutely should have been metal from Day 1.
Great article, love the variety on the site!
Typical BMW (lack of) quality.
Germans are never wrong – I know – I worked with them for yeeaaarrrrrrsssss.
My new BMW rule is 7 years or 70000 miles for the cooling system. Everything that can be replaced, should/will get replaced. Plan on $2k minimum.
I appreciate that you started with some background info before getting into the parts failure.
You know, prose before hose. 🙂
BMW guy: As long as you keep up on the maintenance, you can’t kill these cars.
20 year old BMW: I’m going to die whenever I want, you aren’t the boss of me!
The connection between the radiator and the upper radiator hose is a common failure point on E36s as well. Mine went twice before I got fed up and put an aluminum radiator in. One of my friends had his go out while driving his newly purchased car back home, between Texas and Arizona. Fortunately, a car full of “recent immigrants” stopped and helped hum jury rig a solution that got him to the next large town.
Those coolant elbows on the 3800 are to run coolant through the serpentine belt tensioner, because why not?
The demand for cost efficiency, more power, and less weight (in trade for the power and luxury items) means the margin for error has been largely eliminated. Sure, engineers can now design and produce things with tiny margins but once wear and environmental variables start to build up all those calculations go out the window.
Older engineering had very real limits but that meant that they had to build things that could handle a wider range of possibilities. There was also a strong tendency to build in specific failure points that would ensure the entire system didn’t fail due to a relatively minor issue.
Cars have become more and more disposable as the years have progressed. Car makers don’t build things to last beyond their warranty; there is little incentive to do so. Just look at the degree to which they have stopped supplying replacement parts beyond a fairly small window.
To me, this era is PEAK FEA. IOW, these cars were designed to maximize the FEA results, leading to plastic walls that are right on the fringe. And, when the warranty expire, so do the parts. I don’t know much about the newer ones, but this era certainly seems to exemplify that ethos.
For sure. I had a graduate stats professor who was a huge Six Sigma proponent. He and I did not get along. Twenty years ago, I told him that his methodology would lead to a time when all products would essentially be garbage. That all the “error reduction” he got a stiffy over would be considered to maximize share price because that is the only goal of every modern corporation.
He is likely retired now. Maybe I should send him a note….
The engine plastics the vien of anyone who works on a BMW. I’ve heard people say they used cheaper plastic then they do on the interior. Luckly always a lot of people in the bmw community coming up with fixes and making better parts. Part of me wonders if the coolant isn’t the issue but I guess the vanos self destructs too.
I couldn’t wait to get rid of my wife’s well loved 2000 E46 convertible. Almost all of the parts that failed were plastic. It was a monthly occurrence unfortunately. She still misses that car….I dont.