Any 2000s BMW experts here?

"JasonStern911" (JasonStern911) 10/17/2019 at 23:21 • Filed to: None

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2003 Z4 3.0i is about to hit 70k miles and, as one would expect, the coolant reservoir appears to have a small leak. I expected this when I bought the car, and it’s a very small leak and I have other vehicles so I can procrastinate a bit. Been doing some research but still have a few questions:

* There seems to be no consensus on what brand to use as a replacement. Lots of “don’t go cheap or you’ll have to replace it twice” posts, and lots of “stick with OEM” despite the fact that OEM clearly has a manufacturing defect. I searched but can’t find a metal replacement, and most of the replacement brands are either brands I have never heard of, or brands I have heard of but never with respect to cooling systems (HELLA). Any suggestions on either a part that actually solves the leaking issue or the best bang-for-your-buck option?

* When the coolant reservoir is replaced, there seems to be two groups of people. Group 1 just replaces the coolant reservoir, and Group 2 also replaces the water pump, hoses, sensor, fan clutch, etc. What is the failure rate of the non-coolant reservoir parts? I know the plastic water pump impellers are prone to failure, but nobody ever states an expected lifespan. I’m fine sucking it up and dumping some extra cash and labor in the car if it will last me another 50k, but if these parts aren’t prone to fail before 120k, I’m also fine enjoying a few more years of not dumping money replacing perfectly good parts - especially when replacing the water pump requires detaching motor mounts instead of and jacking the engine up instead of just removing a belt and a couple of bolts.

Thank you!

MKULTRA1982(ConCrustyBrick) > JasonStern911 10/17/2019 at 23:32

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What is wrong with a little silicone on the leak? Lots of people just make coolant reservoirs so I would just go with a known brand or the one with the vest warranty. I also know nothing about 2000s BMWs except yOu HaVe To RePlAcE tHe WhOle CoOlInG sYsTeM

JasonStern911 > MKULTRA1982(ConCrustyBrick) 10/17/2019 at 23:42

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This is my first BMW - been more of a Porsche guy. With mid and rear engine cars, it’s typically a great idea to replace everything when the engine is out to avoid otherwise unnecessary labor dropping and putting the motor back in. Parts like coolant hoses and temperature sensors look easy enough to replace that, sure, while I’m here, might as well. But the water pump... It’s on the front of the engine and yet you still need to detach the motor mounts and jack the engine up to have room to replace it? While I am sure I can eventually handle that, you’re going from something I could probably knock out in an afternoon to something I may need to ask a friend for help on when I get stuck, which makes the repair significantly harder. If it’s really worth doing, then sure. But typically I hate replacing working parts for new parts as there is no guarantee that the new parts are actually better than the parts you are replacing, plus the chance of messing something up during the replacement, plus having to not be lazy and do the actual replacement...

Montalvo > JasonStern911 10/17/2019 at 23:43

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I n the 2 decades that my family have owned BMWs we haven’t had any coolant issues (mostly electrical). As for the reservoir, it i s just that, a container. I don’t think you have to be too worried because it is pretty hard to mess something up that simple. As for the pump I am in the category of better safe than sorry. If your car needs to undergo a decently sized maintenance job see if it makes sense to bundle a pump replacement in there too.

AMGtech - now with more recalls! > JasonStern911 10/18/2019 at 01:47

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It’s less about mileage than age and thermal cycling. The plastic is crap and gets brittle with age. You won’t find an upgraded part, it doesn’t exist. Hella makes tons of OE parts, not just aftermarket lights. The thinking behind doing everything at once is that if one thing has failed then other things aren’t far behind, and also if any overheating happens then parts are at much greater today of premature failure (head gaskets for instance, although those are much less common than they once were). BMW radiators from that time period aren’t exactly known to be reliable either.

If it were mine, I would just do what's leaking. But I'm in a position where fixing things is easy. If it were a client's vehicle, I'd quote it all and give them the option. Comebacks suck, especially when the client yells "why didn't you tell me this could happen!? Why didn't you fix that too!? You damaged my car!"

AMGtech - now with more recalls! > MKULTRA1982(ConCrustyBrick) 10/18/2019 at 01:55

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It’sa pressurized reservoir made of plastic. Good luck getting sealant to stick. Even if you do, the thing will probably crack and ej+ect  coolant in a rather violent manner at some point. These have been known to “explode”. Replacing the whole cooling system is best practice because they use a ton of coolant parts with crap plastic. All the crap plastic tend to fail around the same time.

Tripper > JasonStern911 10/18/2019 at 08:54

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Hello almost 13 year veteran of E46 M3 ownership. I’m a super anal example of maintenance.

This all depends on how this car has been kept up, if it hasn’t been or you don’t have records to prove services were performed, do the whole cooling system. If it was serviced at a dealer I believe the inspection/replacement of cooling components is part of “inspection II” which is generally a 70-80k mile service. Given the age of the car, I’d say you’re up for it.

As far as BMW brand or not, I take others advice or my inde’s advice if I’m letting him turn the wrench. He did the cooling system along with a valve adjustment and VANOS preventive service and used OEM parts except for the hoses because there was another brand he liked better.

I do almost all of the work on it now and honestly I spend too much time compare/contrasting OEM parts vs aftermarket and generally its over a few dollars. Seals hurt the worst as the aftermarket ones are junk and the BMW ones are so mothafuckin expensive.

If there is an aftermarket part that out performs an OEM part it is usually well touted in forums/the community in general. Especially if you’re doing the work, spend the money you saved on the best parts.

Tripper > AMGtech - now with more recalls! 10/18/2019 at 09:19

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I wish more techs did this. I don’t know how Merc dealers work, but BMW dealers make you think your car will explode if you don’t replace the cabin air filters.

The only reason I was able to own a BMW when I was young, and the main reason I’m more confident with a wrench today is because of the technician I worked with when I first got the car. He always let me know what I could get away with not doing but would lay out the possible consequences.

He’d also say things like “if you can change your own oil, you and the internet can figure this out.” He was also the first person to show me how to “make a tool out of other tools” to make really hard jobs simple.

Shift24 > JasonStern911 10/18/2019 at 09:37

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Have 2000 540i, the expansion tanks will explode if you look at them funny, just replace it with a reputable brand.

Forum over do shit and half of the one that blow up right away are ebay knock offs.

Oem w ater pump propellers seems to be a composite material, so again it could last 50k, 5k or 5 miles. Bmw plastic is garbage and hard to give a set time because its mileage + age. Thats why there is no set time on it, it just goes when it wants too.

They have metal ones so you will likely never have to worry again.

One thing I will suggest but not required is any coolant hose that has a plastic fitting attached to it. I have had 2 go out on me, lucky on start up but has stranded the car as no one has that old of a BMW part in stock.

The fan clutch is over kill but some think if it’s out might as well.

La stly sites I use regularly are FCPeuro and RMeuro. ECStuning is good but over priced as hell. FCP life time warranties every part they sell and why I go there alot. Also very reasonable on price.

If only EssExTee could be so grossly incandescent > JasonStern911 10/18/2019 at 09:48

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I’m not sure how applicable my experience is, as you’ve got the engine that replaced the one in my 528i. What I can say is you definitely want to keep digging for a pump with a metal impeller. The price of the plastic one breaking is too high, as it’ll send shards of plastic through your cooling system, blocking coolant passages and puncturing hoses.

You may want to preemptively replace the radiator while you’re in there. If it’s the same as mine, the two halves are crimped together instead of soldered, and eventually those crimps will fail and start leaking.

Check forums, there are lots of workarounds to factory procedures, there may be a way to replace that pump without undoing the motor mounts. If you remove the radiator to replace it like I recommend, it might give you enough clearance to undo the pump from the front of the engine.

AMGtech - now with more recalls! > Tripper 10/18/2019 at 10:46

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To be fair, many BMW's will explode if you don't replace the cabin filter. Or if you do! 

I think plenty do, but it gets lost in translation on the inspection form and through the service advisor. Many techs aren’t great at communicating and some advisors try to hard sell too much.