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Michael
09-10-2001, 12:31 PM
Had a problem just surface, and happened twice now.<p>After driving for about 3 hrs (with coolant topped up), my temp gauge will go from half to full with the "Check Coolant" warning msg coming on simultaneously. When I check the levels, it turns out I have lost a gallon or so of coolant (but not all). When I check for obvious leaks, there doesn't seem to be any. Just sitting for several days, the car's coolant doesn't drop noticeably.<p>Anyone have a guess what is happening...or where the coolant leak might be occuring?<p>There is no dripping under the rad, and all the hoses look fine.

Ekkehart Rackete,Bochum Germany
09-10-2001, 01:09 PM
If there is no visual trace its vapor. Either a bad cylinder head or a bad cylinder head gasket. So the steam is blown out through the exaust.<p> I would check the expansion tank and watch for air/gas bubbles. Be careful when the system is hot. Inspect top for oil emulsion (yellow/brown) <p>Have a shop attach a pressure gage and let car idle. Increase RMP for short time (careful ! transmission, if auto does not like high RPMs in N or P for more than approx. 10s) Pressure should not increase. Slight needle fluctuation is normal. <p>Have shop check water for carbone monoxyde. The above should give a info regarding the head/gasket. Ekkehart <br>

Mark Dorr
09-10-2001, 01:23 PM
I was losing coolant without any sign of dripping. Turns out the head gasket was leaking and the coolant vaporized when driving it. When I finally let it idle in the garage a small drip occured.<p>Mark Dorr<br>88 735i 98K <p><i><br>Had a problem just surface, and happened twice now.<p>After driving for about 3 hrs (with coolant topped up), my temp gauge will go from half to full with the "Check Coolant" warning msg coming on simultaneously. When I check the levels, it turns out I have lost a gallon or so of coolant (but not all). When I check for obvious leaks, there doesn't seem to be any. Just sitting for several days, the car's coolant doesn't drop noticeably.<p>Anyone have a guess what is happening...or where the coolant leak might be occuring?<p>There is no dripping under the rad, and all the hoses look fine.<p></i><br>

Dario
09-10-2001, 07:23 PM
Michael:<p>The only way to properly check the coolant is to wait until the engine is cold. Open the coolant reservoir and attach a special tool to pressurise it (it takes about 15-30 lbs). Maybe you'll discover that the hoses in the back of the engine may have a leak only when the system has pressure.<p>Regards,<p><p>Dario<p><i><br>Had a problem just surface, and happened twice now.<p>After driving for about 3 hrs (with coolant topped up), my temp gauge will go from half to full with the "Check Coolant" warning msg coming on simultaneously. When I check the levels, it turns out I have lost a gallon or so of coolant (but not all). When I check for obvious leaks, there doesn't seem to be any. Just sitting for several days, the car's coolant doesn't drop noticeably.<p>Anyone have a guess what is happening...or where the coolant leak might be occuring?<p>There is no dripping under the rad, and all the hoses look fine.<p></i><br>


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