This reminded me of when I worked as mechanic. Another shop had a chevy that overheated on the highway, I told him to replace the fan clutch. He said I was insane as that at 60mph the fan was not needed. I told him, If the fan clutch did not fix the problem I would personally pay for it (of course he had replaced everything else). Well he was shocked to find it fixed the problem.
The thing he did not realize is that if the fan clutch is bad at highway speeds the air from front of car will try to make fan turn backwards. The engine will try to make it turn forward. The net result is fan stops and blocks a lot of air flow. As far as how to check the fan clutch, here is what I do. Drive car to get up to operating temperature. Turn car off and let sit for awhile, then open hood and try to turn fan. What happens is the fan clutch has to get warm to engage. Thus if the radiator is plugged up you do not get hot air on clutch and as such it will never engage. However if you turn car off and let sit the engine heat will get clutch hot and let it engage. This is a very simple test and will kept you from replacing a good clutch due to bad radiator. Of course if you are really anal you will use an IR temperature gun to measure the temperature of the fan clutch before testing. Trampas -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Brian Smyla Sent: Monday, May 29, 2006 6:58 AM To: 'Mercedes mailing list' Subject: Re: [MBZ] Quick fix for freewheeling fan clutch Thanks for the input, Kaleb and Jim. The aux fan runs, but apparently only when the A/C refrigerant pressure rises above 325psi. My hot running problem wasn't at idle, only at speed, and even then, only under load (climbing a mild grade, speeds over 80mph, etc..) when the ambient temperature is over 85 degrees F. I will check to make sure the radiator tubes aren't clogged ahead of the fan clutch, but I'm fairly certain that's not the case. I did drive the car again yesterday, and the temp gauge never rose more than one needle width above 80. I tried grounding both of the single wire sensors in the upper radiator hose outlet on the head, but neither of them made the aux fan run. Am I looking in the wrong place for the sensor that cuts the fan in? There's another sensor mounted in that outlet, but it's a two wire sensor. I'm assuming that's not the correct one. Thanks again! -brian _______________________________________ http://www.striplin.net For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://striplin.net/mailman/listinfo/mercedes_striplin.net
