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Bluebirds fan in USA
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Discussion Starter #1
Trying to figure out where this is coming from. You can see where it's been spraying on the passenger side. Thought it might be the expansion tank cap but I replaced that and it's still leaking. Only happens when driving. I can let the car sit in my drive and rev it up to 2k rpm and it won't leak. Not bad now but I'm sure the day will come when it'll let loose and I'll be calling a tow truck (and possibly buying a motor).
 

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Warm up the car by( driving it around the neighborhood ;don't go too far) or get a pressure tester to see where it's coming from.
 

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Its tight in there but check the little bolts holding the water pump...
You can also, with the car off, gently pull the end of the hose going to the pump, if pump not secured coolant will drip down on the belts.
Maybe a long shot but one of my bolts, the lower, was loose and in your case one could imagine a spray of coolant coming out then.
 

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Bluebirds fan in USA
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190 Posts
Discussion Starter #4
Warm up the car by( driving it around the neighborhood ;don't go too far) or get a pressure tester to see where it's coming from.
I drive it all the time. It's not much of a leak but enough that I top it off once a week. It can sit in the drive at normal operating temp and i can keep revving up the motor but it will not leak until I'm cruising down the interstate. Won't leaking when running around town (30-40mph) either. Only on the highway.


Its tight in there but check the little bolts holding the water pump...
You can also, with the car off, gently pull the end of the hose going to the pump, if pump not secured coolant will drip down on the belts.
Maybe a long shot but one of my bolts, the lower, was loose and in your case one could imagine a spray of coolant coming out then.
I'll check that tomorrow. I know the PO replaced the water pump, thermostat and radiator (receipt says 17 months ago) I guess it's possible something came loose.
 

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Under the lift arms
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Cap or bleeder,

very obvious its coming from the expansion tank somewhere
 

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528iaut, you say it's not the exp tank. In the US, and on my 528i, it's on the pass side. Is it different in Spain? Have you considered the hose that runs across the top of the rad? It's hidden from view and tee's in to the expansion tank via a nipple and hose clamp. The barb could be cracked, hose loose/cracked, the black plastic screw with the big + in the top of it's head could be loose, etc. However, I can't explain why it would only leak at hwy speeds, although maybe the car needs to see that amount of coolant flow and heat to activate the leak.
 

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Sounds silly but mine was doing this just last week... turns out my cap was not on tight (not sure how that happened) ... it was that simple!


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- Don't replace things in bits and pieces.
- When dealing with cars at this age/mileage, best is to do a cooling overhaul. Info in forum re what to replace and what brand (such as HEPU water pump, Sachs Fan Clutch, Conti belts, INA pulleys etc. etc.).
 

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2001 BMW E39 540i Automatic Sedan, 192 K miles
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The gasket inside the cap of the expansion tank becomes brittle and causes that splash when driving at high speed....Replace it., and tighten it.
Or better yet , buy a new cap. Or a whole new expansion tank with a new cap.
 

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The gasket inside the cap of the expansion tank becomes brittle and causes that splash when driving at high speed....Replace it., and tighten it.
Or better yet , buy a new cap. Or a whole new expansion tank with a new cap.
OP sez he replaced the cap.

Have you done any maintenance on the cooling system? If so, what. The cooling system is the weak link on these cars. If you don't stay up on it you will pay the price.
 

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4th BMW
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Last year when my expansion tank cracked...

i could not see the crack until it was off the car and still it was hard to see. You just have to assume the *normal* posture, flat on your back , belly pan (shroud) off and let it drip on you to track it down with a flashlight...
 

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Another reference point for leaks is to check the aux water pump just below and behind the power steering fluid reservoir. Mine had a small drip because the gasket had failed. The dang thing is like $500 so I just took it apart and resealed it with blue rtv.
 

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The spray pattern looks like it has to be coming from the front of the engine and blowing back.
 

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Under the lift arms
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Bluebirds fan in USA
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Discussion Starter #16
Have you done any maintenance on the cooling system? If so, what. The cooling system is the weak link on these cars. If you don't stay up on it you will pay the price.
As mentioned, the PO replaced the water pump, thermostat and radiator.


Another reference point for leaks is to check the aux water pump just below and behind the power steering fluid reservoir. Mine had a small drip because the gasket had failed. The dang thing is like $500 so I just took it apart and resealed it with blue rtv.
I'll have to look at that since I can only ~assume~ that the mechanical pump was replaced.

I looked at the expansion tank and the only thing I noticed is that it's not secure. The bottom moves around quite a bit getting real close to the A/C compressor. Isn't it supposed to clip into place? It looks like it's only being supported on a bracket below the tank :confused:
 

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At the risk of sounding stupid, the splash marks on the engine cover do not look like coolant. It looks like a one time splash of something. Have you ever pressure tested the cooling system? Is everyone looking in the wrong spot for the leak?
 

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Sounds like a cracked expansion tank. Mine only leaked when very hot. Otherwise, without pressure, it sealed fine. Couldn***8217;t see the crack. Only found it from the white residue the escaping coolant left.
 

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I had the same problem and the new aux fan temp sensor I installed did not fit tight enough. Under pressure (when hot and driving) it was leaking. I pulled the sensor and I know it's not 100 % kosher, but I added a small O Ring underneath the O ring that came with the sensor. It was just enough increase in size to seal things up nicely. Now no more coolant dripping.

Tough to get an old BMW to not leak oil, antifreeze, atf, power steering fluid, windshield washer fluid, rear end diff oil... it never stops!!
 
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