97 540ia, Coolant leak, but cant find the source! - BMW Forum

///Matt · 11-06-2005, 04:11 PM

On my 97 540ia, I found a fairly large pool of coolant under the car today... However, I cannot find the leak. It has to be located along the firewall somwhere, but cannot be seen from above (even after removing the engine cover) or from below...has anyone else have this problem or know where I can find help for this? ANY help would be appreciated....THANKS!

dyami · 11-06-2005, 11:10 PM

sounds like you will have to get out the ol' flashlight and start hunting for it. follow the hoses going down from the coolant resevior. dumb question, but are your srue its coolant?

mdimbler · 11-06-2005, 11:23 PM

I had the same problem a few months back. I was on the freeway when I got the "Coolant Low" message. Made it back home without the temp guage going into the red (barely). Steam was coming from under the hood, and I opened it up but couldn't really tell much... I could see that the top radiator hoses looked fine and that the expansion tank and cap looked ok. I let it cool while I drove my Honda Odyssey to the BMW dealer to pick up some coolant. Got 1 gallon and went back home.

It had cooled down, so I took the cap off and refilled with water and coolant. I immediately heard and saw the coolant dripping down under the car. I put the car up on ramps and could see the coolant dripping down around the bell housing in the front of the transmission (torque converter). I freaked out and thought something was leaking from inside the engine somewhere... visions of having to take out a 2nd mortgage just to fix the car began passing in front of my eyes. I called a Toyota mechanic friend and he came over to help me diagnose the problem. We poured some more coolant and water into the expansion tank to fill it up, and immediately heard the coolant spilling out. We looked at all the hoses going in and out of the radiator and the engine, and discovered it was the hose on the backside of the engine from the engine inlet to the water valve/secondary pump on the driver's side of the engine bay. It had burst right where the hose attached to the engine inlet. I went to the dealer and got the following part:

Part # 64218391005 - Water valve to Engine inlet hose

It was $12 at the dealership, plus I got the 2 end hose clamps for around $1

Brought it back home and took the old hose off and put the new one on. It was quite a chore... you will get very dirty. Be sure to feel and follow the hose around while it is still attached so you know where to put the new hose. I took off the engine cover and I removed both microfilter air channels that go from the microfilters to the splash wall (into the heating/air conditioning). I also detached the secondary water pump/valve so I could move it around and feed the hose down around it and back around the back of the splash wall. I took off the old clamps and then took the hose off. The hardest part was getting the old hose off the engine inlet side... It was really stuck and it took me forever to pull and twist it off. I unhooked the water valve side of the hose and then removed the hose (I unclipped the other two hoses from the splash wall down around back in order to access the damaged hose easier). You can find a pdf with some pics to help visualize it a little better at http://www.law2.byu.edu/imblerm/cars...oolantHose.pdf

Hope this helps.

CosmosBlack · 11-07-2005, 01:03 AM

Have you replaced the upper hoses and the pressure cap?
Those parts were on recall at one time, and are common E39 problems.
The other is hairline crack on the plastic housing on the radiator, but you said a puddle...so that can be ruled out.

///Matt · 11-07-2005, 03:11 AM

WOW! Thanks Mmdimbler...damn, that was thorough. What you've described sounds exactly like what I'm having. The PDF is awesome! THANKS!!!

325isBaby · 11-07-2005, 08:49 PM

check the valley pan, if all else fails...the M62/M62TU has a fairly common problem with this particular gasket. Just throwin that on out there!

///Matt · 11-08-2005, 10:34 AM

The problem has been found...the hoses behind the block are very very worn. I had someone start the car while i watched them. They balloon to about twice their size when under pressure. One of them has a hairline fracture and when under pressure, sprays coolant all over. New hoses have been ordered....

Thanks to all for your help!

sp0rky · 11-08-2005, 12:25 PM