LARRY BRUDZYNSKI Posted October 13, 2008 Share Posted October 13, 2008 We have had quite a few mis-diag's on bad fan clutches that were actually bad radiators. I thought I might put my /forums/images/%%GRAEMLIN_URL%%/2cents.gif in here and maybe some of us will get something out of it if not maybe a refresher on these clutches. The obvious failures are either bearing failure or leaking fluid. To understand whether the fan clutch is operating properly or not, you have to understand how it operates. The fan clutch contains a viscous liquid that allows the fan blade to turn at a percentage of the water pump speed. The temperature at which it engages is controlled by a thermal spring on the front of the clutch. This bi-metal spring is temperature sensitive, and is the control, which allows the engagement of the fan clutch at a certain temperature range. It is AIR temperature that controls the bi-metal spring action, not water temperature. The air that crosses the face of the clutch controls the engagement of the clutch. Proper diagnosis procedure: Start with a cold engine. The thermal fan clutch will be engaged for a short period of time. This length of time depends upon the specifications of the vehicle tested. When air temperature is sufficient enough to activate the bi-metallic spring the fan clutch should engage. The pitch of the fan blade controls how fast the clutch disengages at cold startup. To measure the pitch of the fan blade, place it on a flat surface and measure the vertical height of the blade. When the vertical height is 2.5 inches or greater the fan blade requires a heavy-duty clutch. If it is less than 2.5 inches the blade will need a standard duty clutch. Quote Link to comment Share on other sites More sharing options...
Aaron Posted October 13, 2008 Share Posted October 13, 2008 Isn't determining the correct replacement part the parts guy's job? /forums/images/%%GRAEMLIN_URL%%/cover.gif Just pullin' your leg Larry. That was a really good read. I've saved it and put it into my big book of knowledge. Thanks! /forums/images/%%GRAEMLIN_URL%%/laugh.gif Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted October 13, 2008 Share Posted October 13, 2008 Good write up, Larry, though it does miss the visctronic drive fan a bit.... What I see... most of the radiators I look at are wearing a fine fur coat of dust, leaves, bugs, plant dander, mud dirt.... you name it.... No - stop looking at the AC condenser - it's clean.... Give up.... the CAC is clean too.... Yes - that's it look at the front of the rad.... see how over 3/4ers of it is blanketed off... YECHHHHH!! From what I can see, this is a forgotten diagnostic step - one that has cost countless hours and even the occasional engine... Sorry for the hijack, Larry. Quote Link to comment Share on other sites More sharing options...
LARRY BRUDZYNSKI Posted October 13, 2008 Author Share Posted October 13, 2008 As for the Visctronic clutches most of the diag's are thru the ECM, unless it a mechanical failure. Here is a PDF file that I have gotten off of my Borg-Warner site. http://thermal.borgwarner.com/PDFs/Visctronic-Auto-DirAct.pdf Quote Link to comment Share on other sites More sharing options...
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