[B50AteYourRide]

So today, I noticed that this fluid was coming from my passenger side wheel well.


Anyone know what this is?


Car was running fine, but as I passed it in the driveway I saw that there was a pool of this green/blue fluid.


Any help would be appreciated.

[VipinLJ]

Wiper fluid?

[dawidd3]

Coolant or washer fluid.

[B50AteYourRide]

It doesn’t have that usual coolant smell, but maybe BMW uses something different. It seems rather dark to be wiper fluid. I guess I’ll have to open it up either way.
Anyone know what that heat exchanger over there is?
It does seem to be water based, as in washes off the hands with soap and water.
It’s an M Sport.

[bellguy]

Looks exactly like coolant to me.

[B50AteYourRide]

Here is a more useful picture.
Seems to be coming from this exchanger right here, or the hose right by the wet spot. Anyone know what that is?

A secondary radiator of some kind?

[///S58]

Originally Posted by B50AteYourRide

Here is a more useful picture.
Seems to be coming from this exchanger right here, or the hose right by the wet spot. Anyone know what that is?

A secondary radiator of some kind?

Yes that's a heat exchanger and it appears to be leaking. If you have the tracking handling package it will have 2 and if you don't then it has just 1 iirc.

[kern417]

it's just an additional radiator for engine cooling. find the leak and replace whatever was damaged. it won't be covered under warranty if you have one.

[B50AteYourRide]

Thanks everyone for the helpful replies. I did some more digging and it's definitely one of two auxiliary radiators that I have. From my internet research, most if not all have an auxiliary radiator on the driver side (US Spec), but a smaller subset have a second auxiliary radiator on the passenger side; M Sport and Track package, but perhaps others as well.

To my knowledge, this car did not come with the track package, but it is an M Sport.

The part number is on the side: 17117628057


It seems as though the same part is for either the driver or passenger sides.
These are about $200.00 online and seem to be very easy to replace.

No warranty concerns here.

[G.Newt]

This seems related to the weak heat exchanger the Bx8 engines are becoming known for. Rocks are puncturing those things and BMW retroactively created a rock guard kit lol.

[B50AteYourRide]

A guard is probably not a bad idea. For the auxiliary radiators as well?
I speculate this was a rock that cracked a tube in the aux radiator.

The main radiator is behind the condenser and intercooler exchanger I believe. It may not get all that much airflow.

[weehe126]

Originally Posted by G.Newt

This seems related to the weak heat exchanger the Bx8 engines are becoming known for. Rocks are puncturing those things and BMW retroactively created a rock guard kit lol.

You are thinking of the main radiator, not the aux in the wheel wheel. There is a long way for a rock to go to damage the aux cooler.

[weehe126]

Originally Posted by B50AteYourRide

A guard is probably not a bad idea. For the auxiliary radiators as well?
I speculate this was a rock that cracked a tube in the aux radiator.

The main radiator is behind the condenser and intercooler exchanger I believe. It may not get all that much airflow.

It's hard to tell from the pics, but the plastic 90° connectors are notorious for getting cracks for the last 20 years.

[B50AteYourRide]

Originally Posted by weehe126

It's hard to tell from the pics, but the plastic 90° connectors are notorious for getting cracks for the last 20 years.

Good to know. They seem ok for now.

[B50AteYourRide]

Originally Posted by kern417

it's just an additional radiator for engine cooling. find the leak and replace whatever was damaged. it won't be covered under warranty if you have one.

Hey, maybe you know this. I replaced the aux radiator and topped off the coolant. I want to make sure that I am using the correct process for bleeding the system. A video by Keis Motorsports for a 335i shows a process where the engine doesn’t run. You put the car in accessory mode and hold down the gas pedal for 10 seconds. The car does its thing for 15 minutes, then you top it off again.

Another process I saw, that I think is specific to the B58, is similar in that you go into accessory mode, but you start the engine. The engine runs, and for a few cycles you are supposed to hold the gas to 3,500 RPM for 10 seconds, then back to 1,200RPM, for 30 seconds, then repeat a few times. Then it seems you just let it idle till it’s done. It seems rather different, mainly because the engine is running.

Do you know the correct process for the B58? Basically, should the engine be running?

[kern417]

Originally Posted by B50AteYourRide

Hey, maybe you know this. I replaced the aux radiator and topped off the coolant. I want to make sure that I am using the correct process for bleeding the system. A video by Keis Motorsports for a 335i shows a process where the engine doesn’t run. You put the car in accessory mode and hold down the gas pedal for 10 seconds. The car does its thing for 15 minutes, then you top it off again.

Another process I saw, that I think is specific to the B58, is similar in that you go into accessory mode, but you start the engine. The engine runs, and for a few cycles you are supposed to hold the gas to 3,500 RPM for 10 seconds, then back to 1,200RPM, for 30 seconds, then repeat a few times. Then it seems you just let it idle till it’s done. It seems rather different, mainly because the engine is running.

Do you know the correct process for the B58? Basically, should the engine be running?

For the aux radiator, you need the engine running so that the mechanical pump is flowing too. That's why they rev the engine up, to increase the pumps flow and push out air in the system. For the intercooler system you can do it without turning on the car.

[B50AteYourRide]

Originally Posted by kern417

For the aux radiator, you need the engine running so that the mechanical pump is flowing too. That's why they rev the engine up, to increase the pumps flow and push out air in the system. For the intercooler system you can do it without turning on the car.

Thanks so much! You are an asset to the community.

It also says I should plug the battery to a charger. If the engine is running, why would I need to do that? Wondering if I can safely skip that step.

Just checked, the N55 has an electric water pump. I didn’t know that.

[weehe126]

I would skip the charger while the car is running. Probably mentioned as just idling won't really charge the battery, but I personally would feel safer with the charge when the car is off...

[kern417]

The engine circuit has an electric pump and a mechanical pump, the intercooler circuit only has an electric pump. Both pumps can be activated with a specific sequence of buttons/pedal in the car, so if you're doing that with the car off then a charger is recommended.

I did it without a charger and didn't have any issues. Even if the battery does die or the car cuts off, it just turns off the pump. Not really dangerous.

[B50AteYourRide]

I ended up borrowing a NAPA charger from the neighbor just to be safe. It did seem ridiculous, but that's what the manual said. It probably is overkill. I even took it off wrong and made a nice spark. Probably more harm than good.

Everything works though.

Shutting down NewTis didn't help.

Here are the steps for anyone with this problem in the future:

They say you can only refill the coolant (assuming the system has been completely drained) with a vacuum filler device.

In this case I just topped it off and started from here:
• Adjust coolant level in coolant expansion tank for high temperature to maximum .
• Shut the sealing cap on the coolant expansion tank for high temperature.
• Connect battery charger.
• Close driver's seat belt.
• Switch on ignition by quickly operating the START-STOP button three times.
• Adjust blower to lowest Level, adjust heating to maximum temperature.
• Floor the accelerator pedal and hold for 15 s.
• The automatic cooling system bleeding routine is being introduced.
• Start engine.
• Idle speed is automatically increased to 1200 rpm.
• Operate accelerator pedal till approx. 3500 1/min , hold engine speed 10 s .
• Idle speed for 30 s.
• Operate accelerator pedal till approx. 3500 1/min , hold engine
speed 10 s .
• Idle speed for 30 s.
• Operate accelerator pedal till approx. 3500 1/min , hold engine speed 10 s .
• Idle speed for 30 s.
• Operate accelerator pedal till approx. 3500 1/min , hold engine
speed 10 s .
• Idle speed for 30 s.
• Operate accelerator pedal till approx. 3500 1/min , hold engine speed 10 s .
• The cooling system bleeding routine has finished approximately 11 min after the engine starts.
• Engine speed drops to idling speed level once again.
• Switch off engine.
• Allow the engine to cool down.
• Adjust filling level in coolant expansion high temperature to maximum and overfill with 200 ml.
• Close the sealing cap (1) until it lines up with the arrows.

Here is an illustration they give you for the sequence of engine revving steps.


So there it was. Had to submerge it in a 5 gallon bucket with my thumb and an air compressor to find it. Must have been a stray bit of something. It was experiencing some high velocity airflow that day.