Nitrile is what is recommended for exposure to automotive coolant in the temperature range of modern day engines. It can take temps up to 121 C. The b 58’s engine is designed to run at a higher temp than some others because bmw knows that the hotter you can safely run an engine the more efficient it will be. Do not use regular rubber o rings in these hoses.

Seriously what's wrong with BMW and their choices of part. My Lexus, Hondas never had issues for coolant and I had many over a decade.

Well my X3 had the leak from the turbo to the pump where it just crumbled in my fingers (a total shock). I bought the replacement cable assembly but cut the band off off to take the connector to replace the original connector. I imagine I'll have to do this again 5 years from now. So far no leak there now.


I had secondary leak at the upper radiator hose, right at the radiator area. Debating cutting off the plastic and put a O ring clamp there to seal it.. this is assuming that the plastic had weaken and is now causing the issue. Surprising on the engine side of the hose there's no leak.

Otherwise I'll have to replace the whole hose.. and if I do that, I'm trying to figure out if I want to try to blindly unbolt the BMW Engine Coolant Hose Flange and remove the upper radiator hose (hoping that I don't drop a bolt). or just go all in and replace the Oil Filter Housing and the other hidden hose connections around there.

Mr Fix It wrote

I just went through this on a smaller scale. I had two weeping leaks …one on the secondary cooler and the other to the heater hose. Both were weeping at the primary radiator sites, one on the radiator itself and the other was at the radiator hose t connector. After a fair amount of research I order the ht12 coolant and a set of nitril metric o rings from Amazon. Long story short both leaks fixed for under $1 excluding cost of the coolant. I simply replace the o rings on both. 300 miles later it is still doing fine. The adverage guy with some mechanical knowledge can do this. You do have to be gentle with the hose removal. I used a hair dryer to heat up the connection and o ring seal before I tried to remove the hose. That helped a lot but you still have to be gentle.

Do you remenber what size O-rings you used? I think I have the same leak as you on my B58 X3 and want to try replacing the O-ring. Mine is leaking from the hose that connects the main radiator to the aux radiator, on the main radiator connection.

Old post but I will be doing the upper coolant hose very soon and also ordered the hose flange at the engine end - does anyone know (or where to find) the bolt torque for that flange?
I oped for the aluminum one and going to try without removing the intake manifold.
THANKS for all the great info on this thread!

kevinkay wrote

Old post but I will be doing the upper coolant hose very soon and also ordered also the hose flange at the engine end - does anyone know (or where to find) the bolt torque for that flange?
I oped for the aluminum one and going to try without removing the intake manifold.
THANKS for all the great info on this thread!

10NM goes for pretty much everything down there

kevinkay wrote

Old post but I will be doing the upper coolant hose very soon and also ordered the hose flange at the engine end - does anyone know (or where to find) the bolt torque for that flange?
I oped for the aluminum one and going to try without removing the intake manifold.
THANKS for all the great info on this thread!

Beware! There's recent evidence that the aftermarket aluminum connector pipe has a flawed seal resulting in leakage at the flange soon after replacement.

My local independent just replaced the aluminum connector pipe they installed last year with the OEM plastic version in order to remedy a leak.

If you check the reviews at FCP Euro for the aluminum version you will see that many have experienced this - seems like the OEM plastic part is the safest option at this time. Others have stated to use the OEM gasket with the aluminum pipe but I don't see any confirmation that this is the best solution.

yes I just did this a few months ago. i swapped the Rein gaskets out for new OEM BMW gaskets for it and the OF housing.

Found it, 8nm to be exact
But like always, try and fit my torque wrench!
(Plan change to use to original BMW plastic flange)
THANKS ALL!

kevinkay wrote

Old post but I will be doing the upper coolant hose very soon and also ordered the hose flange at the engine end - does anyone know (or where to find) the bolt torque for that flange?
I oped for the aluminum one and going to try without removing the intake manifold.
THANKS for all the great info on this thread!

I have the same leak. Anyone have experience with Rein parts? Half the price of oem. For the mechanically inclined, is this a couple hour job. Seems rather simple, other than time to remove the dme/holder. Bleeding procedure not as simple as the e90 series was.

I pulled the full instructions from ISTA if anyone needs them. You can skip all the pulling the wheel well cover part. That’s just to make it easier to catch the antifreeze.


https://www.autohausaz.com/catalog?k=17127535529&b=&page=1&sortby=r


https://www.rockauto.com/en/partsearch/?partnum=17127535529

I was all prepared (with the part and mentally) to change out the flange at the engine and then chickened out OR should I say -frustration changed my mind and I just did the upper hose.

1. I dropped the clip from where the heater hose joins the front upper hose and never found the clip. I dropped the bottom splash guard 2 times - once after hosing/spraying water (thinking it would push everything down), then after a drive and never found it. Hold it and completely pull it off because it wants to fly giving it a quick "jerk".

2. Leaning over, my elbow rested or hit the small overflow tube, it snapped like a twig and antifreeze shot at me. ($50 part at FCP but I got the $15 Ebay knockoff)

3. I followed this YouTube in removing the ECU, he gives good detail on how the different clips un-clip.
4. MARK the elec. connectors because the colored fabric markers fall off when your moving the plugs around

5. In doing the bleeding procedure you will get a notice on the dash "diagnostic" after some seconds if you did the "3 presses" correctly and then when you end up staring the car (after holding the accelerator 15s) the car should automatically idle at 1200.

6. I am now leak free and can't tell if the plastic was cracked or just the O ring failed.

THANKS to all those before me that have shared their experience!

I did this in about three hours. It would have been quicker if I had a longer pick tool to reach the hose release clip for the end coming out of the engine block. It’s a bit of a tight fit to get your hand in there. I also accidentally broke the radiator coolant return line to the reservoir. I’d recommend disconnecting that to tuck it out of the way or pickup a cheap one beforehand.

It’s rather difficult to catch the coolant unless you have a large pan. Maybe a third went into my drainage pan, with the rest soaked up with cat litter. Took less than a gallon to refill.

I used this vacuum filler and it worked great.

OEMTOOLS 24444 Cooling System

https://a.co/d/0eG8QX0a


Replacement radiator coolant return hose

https://a.co/d/0j2Ks8RQ

Thanks for the info ... I just purchased my X3 m40i, with just under 70k, how many miles does your car have? My mechanic did a complete check and no leaks or issues, but for my awareness I'd like to know as I keep this issue on my radar

MrSmileyDC wrote

I did this in about three hours. It would have been quicker if I had a longer pick tool to reach the hose release clip for the end coming out of the engine block. It’s a bit of a tight fit to get your hand in there. I also accidentally broke the radiator coolant return line to the reservoir. I’d recommend disconnecting that to tuck it out of the way or pickup a cheap one beforehand.

It’s rather difficult to catch the coolant unless you have a large pan. Maybe a third went into my drainage pan, with the rest soaked up with cat litter. Took less than a gallon to refill.

I used this vacuum filler and it worked great.

OEMTOOLS 24444 Cooling System

https://a.co/d/0eG8QX0a


Replacement radiator coolant return hose

https://a.co/d/0j2Ks8RQ

br2wdc wrote

Thanks for the info ... I just purchased my X3 m40i, with just under 70k, how many miles does your car have? My mechanic did a complete check and no leaks or issues, but for my awareness I'd like to know as I keep this issue on my radar

2019 49k. It had been leaking for awhile and only until recently need topping off the coolant monthly.

Dealer quoted $1700 to fix it. Parts and tools set be back $350. A competent mechanic that’s done this before should be able to do it in two hours. Removing the DME was a little intimidating at first with all the plugs, but it’s sort of idiot proof plugging it back in since the connectors won’t actually plug into the wrong ones.


The parts diagram in later models show they got rid of that side branching piece. Assume BMW realized it was a design flaw with how common it leaks there.

I recently replaced my upper radiator hose too. Dealer quoted ~$7k to replace several "necessary" hoses and the radiator as well. Truth be told, it was just the o-ring inside the hose where it meets the plastic connector attaching to the top of the radiator. I was able to pull the old hose and replace it from the engine block without pulling anything off the engine - it just took patience and I taped some tools together to make them a bit longer. Had I known it was the o-ring I may have just tried that first. Flushed and then re-filled by hand and used the automated purge function and the level hasn't budged in ~15k miles since (2018 X3 xDrive 30i).... and no need to replace the radiator as proscribed by the stealership. Total cost ~$40 for the hose which I bought on Amazon. YMMV.

cohibafan wrote

I recently replaced my upper radiator hose too. Dealer quoted ~$7k to replace several "necessary" hoses and the radiator as well. Truth be told, it was just the o-ring inside the hose where it meets the plastic connector attaching to the top of the radiator. I was able to pull the old hose and replace it from the engine block without pulling anything off the engine - it just took patience and I taped some tools together to make them a bit longer. Had I known it was the o-ring I may have just tried that first. Flushed and then re-filled by hand and used the automated purge function and the level hasn't budged in ~15k miles since (2018 X3 xDrive 30i).... and no need to replace the radiator as proscribed by the stealership. Total cost ~$40 for the hose which I bought on Amazon. YMMV.

u bought a oem hose or aftermarket on amazon?

OEM-ish? lol