[JoHnMuir]

Just over 32k. Diagnosis was made by me. If your coolant reservoir runs out every few hundred miles, and caps don't fix it or it worsens, I think it's likely to be this problem. Easiest to see if you run the car for maybe a minute or so and check for seeping on the engine block below the water pump pulley. Make sure the engine is cold, like after it's sat for a weekend. I'm just happy it's not the turbocharger.

[auburnf30x]

Following up on this one...

Once I got everything bled/evened out properly, I tried to keep tabs on how much coolant was leaking. It leaks very little, maybe a capful every few days. My original fill of a 'cup tops' was wrong, though...once everything burped itself over a day or two, it needed about a liter of coolant before things evened out. Haven't had to add any in several days. Threads around the cap stay wet, though. And I know I'm not doing it, I use a funnel and dry them off every time I'm in there.

New replacement caps came today. I think I'm just going to replace the little one since it seems to be the only one actively leaking. I'll check back in a while to see how it's held up.

[auburnf30x]

Last update and final thoughts...

Actually replaced both since I already bought them anyway. They are both Vaico brand from Rockauto. Big one has the locking detent, little one does not. I just lined it up like the old one, picture forward, and not completely screwed in.

Fit on the big one is about the same, pretty snug. But it wasn’t leaking. The old one on the little side rattled even when screwed in all the way. New one is a very snug fit.

Threads stay dry, and coolant loss has completely stopped.



Before



Now

Some other notes...

If you’ve got a persistent, relatively slow loss of coolant, check these first. If they feel loose, the threads stay wet, or you see white, powdery residue on the outside of the tank, $10 and a jug of coolant could save you a trip to the dealer.

But, if you have a sudden, large loss of coolant, or find it dripping on the ground under your car, this probably won’t fix the issue.

If the coolant level gets too low in the main tank, you can’t just top it off...the system will need to be bled, too. It’s not hard, and there are several how to videos floating around.

I’ll pop back in if anything else comes up, but it looks like this will be another finished entry in the maintenance book.

[2017F30]

@auburnf30x hate to ride your coattails but (and I mentioned this in the other thread) our vehicles are identical down to the mileage essentially. Purchased mine in January with 29,215KM (18,250 miles) and currently at 32,450KM (20,280 miles) and after the car sat for 12 hours I had a look this morning. See images - slight residue on the exterior, secondary reservoir bone dry with cap showing evidence of white residue, primary tank at minimum and slight white reside. I have extended warranty but upon review of the paperwork this wouldn't be included? Would current caps from the dealer be defective as well or have they been improved upon? I believe coolant sold at the dealer is already diluted but correct me if I'm wrong? If DIY just top up coolant and replace with new caps from dealer?

[2017F30]

Excuse the general dust all around in the engine bay - did some woodwork the other day. Have to clean it all off.

[auburnf30x]

Originally Posted by 2017F30

@auburnf30x hate to ride your coattails but (and I mentioned this in the other thread) our vehicles are identical down to the mileage essentially. Purchased mine in January with 29,215KM (18,250 miles) and currently at 32,450KM (20,280 miles) and after the car sat for 12 hours I had a look this morning. See images - slight residue on the exterior, secondary reservoir bone dry with cap showing evidence of white residue, primary tank at minimum and slight white reside. I have extended warranty but upon review of the paperwork this wouldn't be included? Would current caps from the dealer be defective as well or have they been improved upon? I believe coolant sold at the dealer is already diluted but correct me if I'm wrong? If DIY just top up coolant and replace with new caps from dealer?

In a perfect world absolutely that should be covered under the warranty...

I guess the issue is how long it would take to get around to it. First thing they'll do is top it off and pressure test both, which is probably not a bad idea for peace of mind. Once it starts losing coolant again, then they'd probably get to looking around at other things and probably change the caps.

But, I don't think the replacement parts from the dealer are any different than the original ones, except they are going to charge you dealer prices. I don't think the aftermarket ones are really any better either, but they are cheaper.

Same with the coolant...you can buy BMW spec blue stuff at pretty much any part store. Pre-diluted to 50/50 so all you've got to do is pour it in. Keep an eye on the secondary one, it's going to burp air out and will need topping off until it's fully bled. I filled mine up with a warm engine, then started the motor to get things moving. Kept adding little amounts until the air bubbles stopped.

My engine is the same way...now that we're getting carpet bombed with pollen, I can't keep the dust off.

[2017F30]

Originally Posted by auburnf30x

In a perfect world absolutely that should be covered under the warranty...

I guess the issue is how long it would take to get around to it. First thing they'll do is top it off and pressure test both, which is probably not a bad idea for peace of mind. Once it starts losing coolant again, then they'd probably get to looking around at other things and probably change the caps.

But, I don't think the replacement parts from the dealer are any different than the original ones, except they are going to charge you dealer prices. I don't think the aftermarket ones are really any better either, but they are cheaper.

Same with the coolant...you can buy BMW spec blue stuff at pretty much any part store. Pre-diluted to 50/50 so all you've got to do is pour it in. Keep an eye on the secondary one, it's going to burp air out and will need topping off until it's fully bled.

My engine is the same way...now that we're getting carpet bombed with pollen, I can't keep the dust off.

Covered under the extended warranty you figure? I sent off an email to the sales advisor as he’s taken care of things in the past - if he says to stop by and pick up the caps at no charge I will purchase the coolant myself and DIY. So if the dealer caps haven’t been improved to date this will require monitoring still?

[auburnf30x]

Originally Posted by 2017F30

Covered under the extended warranty you figure? I sent off an email to the sales advisor as he’s taken care of things in the past - if he says to stop by and pick up the caps at no charge I will purchase the coolant myself and DIY. So if the dealer caps haven’t been improved to date this will require monitoring still?

You'll want to check it from time to time, but basically the same as you would any other car. I like to check mine before and after long trips and during oil changes. The new ones should work fine out of the box, but it's possible they'll end up doing the same thing again eventually.

[2017F30]

@auburnf30x appreciate the insight once again. Picked up a pair of new caps from the dealer and a gallon of BMW premixed coolant. Started by cleaning around both tanks and then topped up the coolant in each - I figure ~150mL total was required to bring both to proper levels. Engine was warm and watched as the air bubbles burped themselves out before securing the new caps in place. Given how little I added and the secondary (smaller) cap showing more white residue underneath as compared to primary (larger) cap I’m confident these caps have reached the end of their life cycle.

Will make it a point to check each time the summers are swapped over to winters and vice versa. Thank you again to all for the helpful contributions in this thread.

[440i6MT]

Bump reminding all to check their coolant.

[toxik]

Got a low coolant warning about 4 months after buying my car, cap and threads had residue all over it. topped up the reservoir, then topped it up again about 6 months later. Then 6 months after that (this past spring). decided to get a new reservoir cap. Just did a check of the coolant level last week, and for the first time ever, the level was same as before, zero loss. so a new cap with clean threads solved my coolant loss issue.

[Catman4115]

New caps seemed to solve my issue as well. I haven't seen loss since replacement.

[440i6MT]

Originally Posted by Catman4115

New caps seemed to solve my issue as well. I haven't seen loss since replacement.

OEM BMW cap?

[Catman4115]

Originally Posted by 440i6MT

OEM BMW cap?

Yes, I grabbed them from FCP Euro

[Bootboot340]

I've topped mine off twice in 70k miles.

[440i6MT]

Picked up a new cap from the dealership (eh, I don't mind the up charge. I went in for a separate plastic part that I needed & thought would cost $15, they asked $58. Ended up buying a teddy bear instead)

I can say with the new cap so far: the heavy coolant smell when driving with the sunroof open is virtually gone. I'll keep a note on whether it is still faint at idle or with the windows down at any point.

[B58 parts]

My intercooler tank was completely empty. There was a code for the pump running dry, and it wouldn't make any power after the first pull. It wasn't running too great for a week.

The level has been steady for a week since refilling. It was totally empty.. took a good 2/3 of a gallon, and much time to bleed it all out. Main coolant circuit has been mint 60k miles and is nice and full. So what the hell?

I do use the bm3 max cooling mode. The cap had some funk on it, it seems okay today, but I don't know what else happened. I haven't checked in a long time, maybe it very slowly lost volume. ? I never saw any smoke or coolant smell, I don't think it all leaked out.

Is there a thermostat or software change to get it to run cooler? It's always been at 230f..

[BWbimmer]

When you talk about 230f, then you mean the coolant temp? Why should a software change have an effect on the intercooler behaviour?

[kern417]

Originally Posted by YuminNuman

My intercooler tank was completely empty. There was a code for the pump running dry, and it wouldn't make any power after the first pull. It wasn't running too great for a week.

The level has been steady for a week since refilling. It was totally empty.. took a good 2/3 of a gallon, and much time to bleed it all out. Main coolant circuit has been mint 60k miles and is nice and full. So what the hell?

I do use the bm3 max cooling mode. The cap had some funk on it, it seems okay today, but I don't know what else happened. I haven't checked in a long time, maybe it very slowly lost volume. ? I never saw any smoke or coolant smell, I don't think it all leaked out.

Is there a thermostat or software change to get it to run cooler? It's always been at 230f..

Originally Posted by BWbimmer

When you talk about 230f, then you mean the coolant temp? Why should a software change have an effect on the intercooler behaviour?

The water pump(s) are electronically controlled. The intercooler pump ramps up speed based on the tune to increase cooling when you need it. That's what max cooling mode does.

However, 230F has to be engine temps. No way you'd see that in IATs without grenading the engine. There is also an engine cooling control module that manages that, and max cooling mode can reduce those temps (particularly when you go full throttle).

[94boosted]

Bump. 2017 with 28K miles, low coolant light came on. Had to add nearly a half a quart to the bigger overflow reservoir, small (intercooler) one was still full. White residue on the threads, going to order a new cap from dealer soon here, hopefully it’s just that.

[ashkanvafaee2]

Bump. 2016 340i w/ 60k miles, low coolant light came on. Same as above comment, took half a quart to the bigger tank. Prior to this, the low coolant light came on 1.5 years and ~7k miles ago. At that time I just cleaned the threads of the cap but didn't order a new one. Might get a new one this time around

Alternatively, has anyone tried using thread-sealing plumber's tape on their existing cap? Wondering if such material can handle the temperature or if it will likely just melt into the coolant.

For example: https://www.homedepot.com/p/Oatey-1-...403D/202078116

[BWbimmer]

I would try just the cap, first. It helped me and they are not really expensive