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Old 10-19-2018, 07:09 AM
rswapp rswapp is offline
Join Date: Oct 2018
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Originally Posted by Qsilver7 View Post
You don't mention if you checked the coolant level sensor...which is not the "float" that you see when you undo the tank's lid (yes, it does fool many owners).

The sensor is screwed in from the bottom and is probably in a "dry" well (if like the expansion tanks since the m60-m62tu engines.

See #3 in the diagram below...and also check if the electrical harness (#6) is plugged in correctly to the sensor:

For example, in the pic below of an e39's expansion tank split can see the float (it's goldish-tan in the 1st pic) in its normal "full" location inside the tank...and the "level sensor" is sitting to the far right (just below the split-opened tank). Again, the level sensor screws up inside a dry well in the tank...which is near the bottom of the float mechanism inside the tank. You can also see a "staple" sitting on a circular magnet in the bottom part of the float. I believe magnetism is somehow used to communicate the level of fluid in the tank to the level sensor. As the fluid lever drops inside the tank, the float lowers closer to the level sensor...and when the low point is reached, the proximity of the bottom of the float to the level sensor triggers the warning (see the 2nd image below):

(all images below: courtesy of Bluebee)

In this last image can see that the internal "float" is at the very bottom of its range as if the tank was can see that the bottom half which contains the also surrounding the "dry well" that the level sensor is screwed into...thus my assumption that the magnet is how the coolant level sensor recognizes that the tank is not full.

If for some reason your level sensor has gone bad...or the bottom half of your float is still down near the level sensor (are you sure your float is intact) need to check the coolant level sensor or its electrical harness.

It just amuses me to see how many people don't know what or how a magnetic reed switch works. The Magnet operates the reed switch which is the coolant level sensor. It operates like a door alarm switch where you have a fixed magnet and a fixed switch. As the magnet gets into the proper proximity of the switch it either opens or closes the switch depending on if it's a NC or NO switch. Pretty easy circuit to understand. So it's not the magnet that is communication with the system but the magnet is operating the reed switch that then tells the system if the coolant is low or okay.
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