roadmax

During driving last night, outside freezing temps, after a breaf moment of reaching 5K rpm during shifting the Low Coolant error message displayed and after a minute or two could notice the cabin heat stopped.
So was pretty sure a hose broke somewhere, after parking and checking the engine compartment noticed the upper radiator hose completely popped out with the metal ring still attached.
No other error messages appeared during this ride.
How complicated it is to replace it? Other potential issue to look while there?

txag_530i

It is a very easy fix. The messy part is draining the coolant- but that's already been done on your car! I recommend that you buy the genuine BMW hose.

roadmax

Ordered the upper hose plus 2 gallons of coolant, have the distilled water ready as well.
It appears involves removing the old one and attaching the 2 sides of the new main hose and 2 smaller hose ends, part #2 on the diagram.

How many drain plugs are there?
Are any drain plugs on the engine block?
I know there is one (red color) in radiator, would this be the only coolant draining plug?

turbineguy

Hi,


I had the same thing happen on my 545i this summer while travelling to Quebec. It seems like the factory clamp was not tight enough. I removed the factory hose clamp, put the hose back on the plastic fitting and used a regular hose clamp to hold it in place. It has been working for at least 6 months.


Cheers.

DanielFD

Could be a bad expansion tank cap. Those caps regulate the pressure. If its stuck closed too much pressure is building. Its only 12$ from the dealership, cheap insurance.

westsidebalto

There are two, the red one which you found and one on the engine block. However, you should be fine with just using the red one. Also, you will probably not need more than 1 gal of coolant and 1 gal of distilled water, but always good to have more on hand, since it doesn't exactly go bad like brake fluid if you open it.

roadmax

Did not use the hose clamp method as I was concerned of the plastic/composite material being old and brittle from high coolant temps so it might break again soon.

Interesting tip about expansion tank cap, thank you.

Drained from red plug located in lower radiator corner (passenger side), additional coolant was drained from the system after removing the old hose.

Did not bother the complication of removing the engine block drain plug but is there 1 on passenger's side as well?

It took exactly 2 gal (1 BMW coolant + 1 distilled water) to fill completely.
Initially when starting the engine, the electric cooling fan stayed on and after few minutes turned OFF.

westsidebalto

Did you run the bleed procedure? You need to run that and get the air out of the system. I dont have the steps memorized but it involves running the car with the head on low and the temp cranked up or something.

roadmax

I think these cars are self bleeding but turned both heat knobs to max and vent on low before running the engine.
After filling with 2 gal and running the engine as a result of bleeding had to add around 3/4 gal more in order to bring the coolant level to normal.It did not take the entire 3/4 gal at once but in few times, the last amount added next day after driving around the block.

Now the level is in normal range and will monitor if more coolant is required.

Next step would now be washing the engine before mounting back both underbody splash covers.