02 745i coolant leak (Please help!)

[ryunohadouken]

Ok, so I overfilled my coolant the other day and drove it for about 30 miles. When I got home and turned the car off, I could hear the coolant running out. I opened my hood and the cap was off and coolant spilled out everywhere in my driveway. I filled it to the min line and let it sit for a day. I drove it to work today and back home. There was a small leak of fluid in the driveway. I checked and it appears it's coming from under the expansion tank. I just drove it again for 20 miles and back home. Even smaller leak of fluid. thanks I was searching forums and I did a semi-bleed to push air out of the system because my heater, while it gets pretty warm, it just doesn't feel as hot as it used to when I had it all the way up. Any suggestions? Thanks in advance!!!!



Smaller leak just now:

[WadiM3]

Try bleeding the car properly with the nose being jacked up 5-6"'s and then we can start having an idea. The bleeding procedure could be found at the FAQ's on the top of this forum

[MIKYZZ4]

Check and fill to the min. line every morning on a cold engine for 2~3 days,
that should eliminate the air in the coolant.

[WadiM3]

Oh I thought you have to open the bleed screw to bleed the car while adding coolant with the engine running until no more air bubbles come out of the bleed screw preferably with the front jacked up

[MarcoZandrini]

Overfilling the cooling system is verboten. What’s likely happening is coolant got everywhere and what you’re serving is the remnants dripping. BUT, definitely keep an eye on the coolant level. If the cap came off you’ll need to buy a new one.

[MIKYZZ4]

Oh I thought you have to open the bleed screw to bleed the car while adding coolant with the engine running until no more air bubbles come out of the bleed screw preferably with the front jacked up

Yes Wadi,that is a proper bleed procedure, along with having the heater controls set to MAX-to include the heater core as part of the bleed. OP has performed an initial fill to min line and bleed((mini?). My recommendation is an addition to what has already been done.

[WadiM3]

Ooohh right! I was just wondering and thought the E38 might of had a different procedure!

[shadowpuck]

just to clarify - a 2002 745 is more likely an e65 or e66.

[Cobra1956]

If you over filled it, is it possible that you cracked the overflow bottle? Or is there a sensor on the bottom like the e36 tank that can leak on occasion?

[ryunohadouken]

Yes Wadi,that is a proper bleed procedure, along with having the heater controls set to MAX-to include the heater core as part of the bleed. OP has performed an initial fill to min line and bleed((mini?). My recommendation is an addition to what has already been done.

Someone told me the cap might be faulty. I replaced the expansion tank cap and it worked well for about a week, then started to have that small leak again. Any suggestions?

- - - Updated - - -

See above reply

[bmwdirtracer]

You need to take the car to a BMW pro. A pressure test of the cooling system will be step 1; but you may be facing far greater issues than whether the expansion tank is leaking every now and then. You might have compression in the cooling system (in other words, blown head gasket), you might have the hugely common water pipe failure in the middle of the "V" of the engine.....or maybe you've got a bad hose at the expansion tank or elsewhere. Have you replaced the expansion tank itself? It's WAY overdue, as are all the hoses and plastic pipes in the system.

Just so you know, a BMW which cost ~$70,000 new requires about $3000 a year in maintenance and repairs. An '02 745 is probably the most troublesome and failure-prone BMW ever made. Well, at least until N63 engines came to be........