BMW E46 Fanatics Forum banner

1 - 19 of 19 Posts

·
Registered
Joined
·
161 Posts
Discussion Starter #1
My transmission oil cooler fell out on the interstate thus dumping coolant and destroying the unit. Does ATF also flow through this cooler or is it just flowing coolant both ways? In other words will I need to top off ATF when I replace the cooler or just coolant? Keep in mind the car was rolling (trans turning/pumping) when the cooler fell out.
 

·
Registered
Joined
·
161 Posts
Discussion Starter #3
Looking at the cooler you can see that both ATF and coolant flow through it exchanging heat.
Is the cooler still attached to the ATF lines? Should be obvious if the ATF lines were breached.
Yes hoses still attached. All I could see leaking from the car/cooler was coolant. Will take a closer look once I pull it off in the morning.
908765
 

·
Registered
Joined
·
161 Posts
Discussion Starter #5
Engine did not overheat. As I was parking to shut off the needle went just past middle but not even close to the red. So just needs replacing and coolant refill/bleed? Any idea as to why this could have happened aside from the terrible original design of it being held in by a paper clip?
 

·
Registered
2004 325i automagic
Joined
·
2,374 Posts
Did you run over anything recently or hit a deep pothole?

Make sure to inspect the plastic mounting bracket connection on which the oil cooler is attached to to see if that needs replacement.
 

·
Registered
Joined
·
161 Posts
Discussion Starter #7
No didn’t hit anything that I’m aware of. I just replaced the oil pan gasket and pulled this part out but I could have sworn I put it back in correctly and checked the clip as I know it’s barely held to begin with. Wasn’t leaking at all.

Mounting bracket is fairly new as I replaced literally every piece of the cooling system about 10k miles ago but I’ll def be inspecting it.
 

·
Registered
2004 325i automagic
Joined
·
2,374 Posts
Well, maybe the oil cooler just had not seated properly and worked its way loose after some mileage. Hopefully there is no collateral damage from it bouncing around.

I forget exactly how the oil cooler mounts, but on a lot of those cooling system connections it is safer to close or insert the clip first and then insert the hose while listening for the solid click as the locking clip slides in place.
 

·
Registered
E39 E90 E46 F10
Joined
·
4,977 Posts
Looks like you dont have the plastic belly pan anymore. Without it who knows what could have caught on that flimsy locking clip. Even a plastic bag but moving 80mph could have done it. So don’t don’t forget to replace the belly pan, too.
 

·
Here to serve y’all
2004 330Ci 85k miles
Joined
·
12,364 Posts
Looks like you dont have the plastic belly pan anymore. Without it who knows what could have caught on that flimsy locking clip. Even a plastic bag but moving 80mph could have done it. So don’t don’t forget to replace the belly pan, too.
^^^This. Get yo belly pan on!
 

·
Registered
Joined
·
161 Posts
Discussion Starter #11
You know the belly pan thing is not a bad idea.... I’ve never really thought about how vulnerable that particular part is without it (and I guess others now that I really think about it). I’ve been rolling around almost a year now without it. Guess I’ve just gotten lucky up to this point....
 

·
Registered
E30M3 Race F10 535 R1150Rt M Coupe
Joined
·
1,956 Posts
Taking the side of BMW (not usual for me) since it's inception I've yet to see one of those coolers fall off by themselves.

So you Have 3 things to do.
Fix the mounting plate/intercooler/retention clip.
Fill the trans to a static fill, so you're able to run the engine. Don't skip this!
Fill/bleed the cooling system.

After you've bled the cooling, you can let the car cool off and then add in the last 2-3 liters of trans oil.

Get a belly pan. Oops that makes 4.
 

·
Registered
Joined
·
161 Posts
Discussion Starter #13
Plan to do all those items today. I’ll keep everyone posted on what I find. I’ve flushed trans and replaced fluid/filter already so checking and refill procedure is not new to me.
 

·
Registered
Joined
·
161 Posts
Discussion Starter #14
Yeah I’m just a moron. Even after specifically checking that Clip I still managed to not fully clip it in so it prob popped right out. Good news is it’s an easy repair, engine didn’t overheat, and trans fluid didn’t totally drain. I see now how the cooler functions so there’s really no fear of losing trans fluid as long as both quick disconnects are connected. Will still top off trans fluid.

Once I get the new o rings and special BMW blue coolant I’ll have it all back together And back on the road.
 

·
Registered
2004 325i automagic
Joined
·
2,374 Posts
You know the belly pan thing is not a bad idea....
Get a belly pan. Oops that makes 4.
Fwiw, I recently reinstalled the plastic belly pan after thinking about how exposed things are under there ... had been driving without one for 3 or 4 years now.
 

·
Registered
Joined
·
161 Posts
Discussion Starter #16
Yeah I kept it off because I’ve constantly been tracing leaks but I think I’m ready to throw it back on after I get it back together this time.
 

·
Registered
E30M3 Race F10 535 R1150Rt M Coupe
Joined
·
1,956 Posts
O Rings. OEM at the very least!!!!
We only use genuine. With top shelf rings, you NEVER have to think about it again.

Given the all to well documented failures of the cooling system, what is the sense of saving $5 ?
 

·
Registered
Joined
·
161 Posts
Discussion Starter #19
I’m headed to the dealership today for both side o rings and that special blue BMW coolant.
 
1 - 19 of 19 Posts
Top