nyda88

Hey, I'm new to the board but I recently became the proud owner of my own 545i. I've been searching online trying to figure out where this leak is from, and this board gave me a bunch of options on past topics. As of now the car is leaking antifreeze, I haven't filled it up yet but when it's parked in the driveway i looked under and I see a puddle of antifreeze, there's no hose directly above it, it looks like a screw was knocked off of the underbody cover and its dripping from there and when i stuck my hand in i felt antifreeze, but the hoses also have antifreeze on em not sure if this is just the steam coming out from the underbody and onto the hose or if the actual leak is from a hose and is just spraying everywhere. I'm not exactly sure what it can be? any ideas? and how much it would cost to fix them at a mechanic?

i don't think its the head gasket, my exhaust isnt really smoking and I had no issue with the car until today when i stepped on the gas a little harder and the low coolant sensor came on. any help would be appreciated!

Cruiser565

I just had to replace my coolant reservoir tank for a pinhole leak on my '04 545i. Apparently it is pretty common across the BMW lineup for these coolant reservoirs to rupture. In my case it was pretty obvious where it was coming from though so yours maybe elsewhere, but if it is the tank, it is a VERY easy fix for the DIY.

Will

nyda88

Hy so this morning I poured water in to see where the leak was and it looks like a heavy leak in the underbody cover, any idea what it could be??

Stephen Max

Lots of possibilities. Check all hoses, hose connections, overflow tank, radiator, water pump. Also, the gasket for water cooled alternator can leak.

jaycal3

My money would be on the water pump. Have a 545 and had to do mine... when it went, the leak was flinging coolant all over the place from the belt. When water pumps begin to fail, there is usually a leak that starts out a weep hole under the pump/pulley.

DavidF

The '04 545i does NOT have a water cooled alternator. Like others have said, most likely the radiator or coolant expansion/recovery tank. Of course it could also be the dreaded coolant transfer pipe o-ring failure that will cost about $1k DIY or $3k + Indy.

syrousd

MOst likely is the reservoir and the expansion tank. 545 's are know to have this issue. I am guessing you have a round 60k or 70k on this car? Around that kind of milage is when the reservoir and expansion tank starts to go coocoo!

Also it could be the water pump,upper/lower hose...etc.

jgt

I just replaced the radiator on my 530i with 80k but our symptoms don't sound the same at all. I had a VERY small leak around one of the bottom welds of the radiator. There was never any coolant on the ground just an expansion tank top off every 3-4 months.

Let everything dry off and get a bright flashlight to try to see where its pouring out of. Hopefully its just a cracked expansion tank or hose for a real easy DIY but since its an 04' it could be any part of the cooling system.

Stephen Max

Thank you, that's good to know. What years/models came with the water cooled alternator?

jgt

No E60/1 has a water cooled alternator.
Now I'm curious to what make and model actually has a water cooled alternator... time for some google.