Calling all N52 cooling gurus

(Cross posting from my ownership thread for improved topic specific visibility)

This photo is looking up at the bottom corner of the radiator on the drivers side - at the hose fitting just above the drain.

What does GRM think this requires?

Can I sneak away with just a hose or will this leak confirm I need a new radiator (and water pump, t-stat, etc ".. due to age and mileage)?

Thanks. Bring more wallet!

I have never taken apart the specific hose on that car, but if its like the e46, then they "click" in. There is an o-ring on them. 

If you don't want to go all out on a new cooling system, I would get some BMW blue coolant and remove the hose to check the o-ring. I dont think BMW sells the o-ring by itself but it has to be a standard "-" and you can probably get one from McMaster. Just make sure its viton or something compatible with heat/coolant. 

Also, the hose might be tricky to remove. It took me a minute to figure out how to undo. Be patient. 

Edit: I see yours has an allen or torx holding it in. Might be just a matter of removing it and just pulling carefully. 

This might be the o-ring, not 100% sure. 
 

11537545278

Its 29 x 2.9 mm (OD x cross section)

I would need the last 7 of you VIN to better check.

In reply to Slippery :

VK75765

It's tough to say, I don't think these are as notorious for the cooling system all failing at 100k like an E36 and the recommendation to just replace everything at that time. Certain parts though that is still true.

My car (06 E90 330i with 210k on it) I just went through this and replaced a lot of original hoses and the original radiator as it had a small leak. I also did the water pump and thermostat for the second time in the cars life for piece of mind but both were working fine still.

If it were me at that mileage based on what I went through with mine, I'd replace that hose and start planning on doing a water pump and t-stat. I would leave the rad until it gives you a reason to replace it as the aftermarket parts aren't nearly as nice. I bought the Mahle rad which is very nice looking and pretty much matches OEM but it leaked (a lot) from the end tank right away and had to be returned, further research showed that to be a lot of peoples experience with them. I ended up with the CSF oem style (the aluminum versions are nice but can throw codes in cold weather due to it cooling more than oem and the car thinking it is a bad t-stat) which has worked fine but definitely isn't as high quality as the expensive OEM rad. I also had a REIN expansion tank to upper radiator hose leak at the expansion tank connection after a month or two, the amazon cheap replacement has been fine since. 

The REIN water pump service kit was good for me though and came with the OEM Pierburg water pump, the hose to the oil filter housing also has the upgraded aluminum flange that is another weak point in the system.

So to sum that all up, replace the leaky hose, inspect the rest of the system for other leaks, replace water pump, t-stat and the hoses that come with the kit and then just keep an eye on things going forward. Do not buy the Mahle rad when you need a rad.

Oh and the car does a cool self bleed procedure, just look it up online as you don't even need a fancy scan tool/INPA/ISTA to do it. Just make sure your battery is good or have it on the charger when you do it.

Edit: I would not be against just replacing that o-ring (especially if it is called out with its own part number) as the quality of aftermarket parts can be questionable as you can see from my experience.

OHSCrifle said:

In reply to Slippery :

VK75765

Ok, 14 if you want just the o-ring and 13 if you want the hose/o-ring assembly. 

You have to remove the hose anyways, so you can assess its condition.

I would personally not do the whole cooling system. If anything, I would follow adams's suggestion and do a water pump/thermostat at around 100-120k miles.

In terms of preventative maintenance, next time you have the coolant drained (whether for just the o-ring, or for the t-stat/water pump) it's a good time to replace the oil filter housing gasket as well, since it requires draining the coolant to perform the replacement.  A leaking gasket is prone to leaking oil onto the belts below and causing some very expensive slipping.  

I'll agree that this leak looks as if a new o-ring might fix it. 

In my experience, OE radiators with plastic end tanks develop cracks and start leaking around 15 years.  Assuming this rad is original to your 2009 BMW, I'd not be optimistic.

Thanks guys. Especially for the part numbers and diagram. Since the rad will need to be drained regardless, I think I'll start with the hose and o-ring. I already did the upper hose with aluminum "Mickey mouse ears" flange when I replaced the oil filter housing gasket.

Glad to know this model (2009 128i coupe) isn't as common to need the full cooling system replaced at the century mark. I only drive it 4-5,000 miles per year so I'll probably wait on the water pump until it tells me it's time. 

MINI uses a similar setup, a plastic pipe with an o-ring. Those plastic parts are notorious for getting brittle and cracking as they age, usually right at the o-ring......moral of the story, it might be the pipe has a crack in it......check it carefully.