The Last Coolant Level Sensor
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Joined: Jan 2003
Posts: 16,945
Likes: 1,053
From: Double Oak, TX
Only available from Porsche - they restocked. NLA according to the Wholesalers.
I have some in stock.
I have some in stock.
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Pro
Joined: Jan 2011
Posts: 655
Likes: 0
From: Cary, NC
Before I ordered a unit from Roger I decided to test the existing coolant float assembly to see what is actually wrong with the device. The problem has been that the check coolant level warning goes on after the car reaches operating temperature. After it cools down it functions normally.
Firstly, it is a PITA to remove. The float buoy moves without friction and has 0 ohms when low and approximately 1000 ohms when fluid is at correct level. Im making these measurements in my kitchen so any temperature effect of that may effect the buoyancy is not taken into account. Also, I need to test if the float gets more porous as it heats up, which would make it float less.
Does anyone know if these resistance levels are normal. I have not found any documentation.
Firstly, it is a PITA to remove. The float buoy moves without friction and has 0 ohms when low and approximately 1000 ohms when fluid is at correct level. Im making these measurements in my kitchen so any temperature effect of that may effect the buoyancy is not taken into account. Also, I need to test if the float gets more porous as it heats up, which would make it float less.
Does anyone know if these resistance levels are normal. I have not found any documentation.
Pro
Joined: Jan 2011
Posts: 655
Likes: 0
From: Cary, NC
I looked up the density of water and glycol densities versus temperature and both go down but not dramatically as temperature increases. Thus the float will become less buoyant(because it displaces less mass of coolant) and sink as temperature heats up and cause the problem. I suspect that the float has absorbed fluid and other particles over time and is now heavier which makes it very sensitive to density changes of the coolant as temperature rises.
The float is a piece of plastic wrapped around a magnetic collar that causes the resistance to change when the correct level position is reached. Its pretty heavy so its easy to see how the displaced coolant by volume may not be enough to float the float.
Rather than hack a new floatation gizmo to increase buoyancy Ill be placing an order with Roger. At least I can be reasonably confident this is the root cause unless this basic float mechanism has some bizarre relay dependency on the hatch release mechanism.
The float is a piece of plastic wrapped around a magnetic collar that causes the resistance to change when the correct level position is reached. Its pretty heavy so its easy to see how the displaced coolant by volume may not be enough to float the float.
Rather than hack a new floatation gizmo to increase buoyancy Ill be placing an order with Roger. At least I can be reasonably confident this is the root cause unless this basic float mechanism has some bizarre relay dependency on the hatch release mechanism.
Burning Brakes
Joined: Nov 2010
Posts: 901
Likes: 1
From: Alpine - Southern CA.
Team Owner
Joined: May 2004
Posts: 31,179
Likes: 4,172
From: Philly PA
FWIW if you have a suspect sender its best to replace it,
fitting a used unit you will usually find its FUBAR
shorting the wires together will not make the light go out,
removing the original from the tank is a bit of a task and should only be done when you have a new unit to install.
Once you remove one of these senders you will appreciate the value of slipping in a new part VS swapping out a few used units hoping that it will work. BTDT.
The electronic system on the sender is usually what fails once it cant sense the proper resistance then the light turns on, sometimes the float also fails.
Again removing the failed part without a new part to slip in will be very frustrating.
You can also use a O ring for the cap seal if the original is somehow damaged.
I hope Roger can find more of these parts
fitting a used unit you will usually find its FUBAR
shorting the wires together will not make the light go out,
removing the original from the tank is a bit of a task and should only be done when you have a new unit to install.
Once you remove one of these senders you will appreciate the value of slipping in a new part VS swapping out a few used units hoping that it will work. BTDT.
The electronic system on the sender is usually what fails once it cant sense the proper resistance then the light turns on, sometimes the float also fails.
Again removing the failed part without a new part to slip in will be very frustrating.
You can also use a O ring for the cap seal if the original is somehow damaged.
I hope Roger can find more of these parts
Rennlist Member
Joined: Jan 2008
Posts: 4,077
Likes: 331
From: Friday Harbor, WA
Stan,
Roger said he had some in stock, above. I just ordered one from Sonnen Porsche for $55.
Cheers,
Roger said he had some in stock, above. I just ordered one from Sonnen Porsche for $55.
Cheers,
Pro
Joined: Jan 2011
Posts: 655
Likes: 0
From: Cary, NC
Thanks for the feedback guys. Roger is shipping a new unit today. For grins Im going rig up a 1.5Mohm resistor across the leads to mimic a full coolant tank to keep the light off until the new unit arrives.
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