way2fast91

After the coolant tank install and verifying that the coolant was no longer leaking, I did unplug the sensor harness for a few days to stop the blinking. So I can confirm that if I unplug the harness from the coolant level sensor, the blinking does stop.
I could also try unplugging the harness, and plugging in a spare sensor without installing it under the tank, then starting the car and using a magnet to close the circuit and confirm that the light stops. If this works, I think it would prove that the issue is with the position of the magnetic float in the tank.

Porschetech3

Yes exactly !! Now you understand how the simple system works ...well almost .....the sensor/switch is normally OPEN, when you put a magnet close by the circuit CLOSES ( Grounds the circuit to chassis ).

A little logical common sense along with some experience goes a looooong way ...

way2fast91

Observations:
Started the car with harness disconnected, no warning light.
Plugged in the spare coolant level sensor (loose in hand, not installed under the tank), no warning light.
Held a magnet up to the sensor, waited 19 seconds and the warning light began to slow flash.
Also, for future folks who may read this, moving the magnet away from the sensor, the flashing continues. Unplugging the spare sensor from the harness, flashing continues. Seems the low coolant flashing, once triggered, will not stop until the car is turned off.
Turned the car off.
Tried tapping on the side the tank (without removing it) to see if that might dislodge the float.
Plugged the harness back into the sensor installed under the tank and started the car, warning light flashing.

Do you recommend the next step be to remove the tank and test the float/find some way to verify if it's lodged and then dislodge it? If so, I will likely wait for cooler weather this fall and just monitor the coolant level manually until then.

Porschetech3

Is this an OEM Porsche coolant tank? Its extremely rare to have a float failure..

The float is the only moving part in the tank, and it is not accessible. It is built into the tank during manufacturing. I suppose you could remove the tank and turn it up-side down and hit it and maybe jar the float loose, but that wouldn't give me piece of mind that it will not stick again...

way2fast91

It's an aftermarket Mahle tank from FCP Euro. The price for the Porsche tank was exorbitant. I have read all the feedback on the Porsche tank, however the FCP Euro Mahle tank came with a lifetime warranty and they are a reputable parts distributor.

wyovino

The Porsche tanks IS exorbitant, but having to repeat the job every year or two in order to save money with a 3rd party tank is not the best approach. I did that once and that tank lasted less than two years. I had been assured by the seller that it was exactly the same as the Porsche tank. It wasn't. That's not a mistake I'm willing to repeat.

way2fast91

The research I did showed the same results that you mention, however the feedback seemed to be centered around the URO tank and similar OEM tanks. I decided to take a chance with FCP Euro seller and the Mahle tank after my research showed FCP Euro seems to be a trusted parts supplier and they offer a lifetime warranty and Mahle seems to be a supplier to BMW for factory installed parts/coolant tanks similar to the one they make aftermarket for Porsche applications.

Honestly, after having gone through the process once, it was not an overly difficult or time consuming job, once I got over my stubbornness and bit the bullet and lowered the engine down to allow for space. I figure if the Mahle tank does crack and leak within a couple years and the seller will replace the part, I don't mind going through the install process again if it saves me $700. After all, one of the things I enjoy about wrenching on this car is the money I save in labor costs.

SleepyCyclist

https://rennlist.com/forums/996-foru...996-1-a-2.html

the 996.2 tank (much cheaper OEM) can be made to fit in the 996.1

way2fast91

FCP Euro agreed to send me another tank to try. Wanted to run my thinking by this group and see if it makes sense. If I hold the new tank upside down, I assume gravity will cause the float mechanism to slide to the top position simulating a full tank. If I then install a second sensor in the new tank and plug the harness into it, I could then start the car and see if the warning light blinks or not. If it doesn't blink, then I could turn the tank right side up, causing the float to slide down to empty/low coolant position and see if the warning light starts to blink. If that works, then I would be confident it's the old tank and proceed with installing the new replacement tank.
If the warning light still blinks with the tank upside down (simulating full tank), then I know the issue is likely not related to the float in the current tank.
Am I overlooking anything here?

996-CAB

I don't have a wiring diagram to guide me, but you can see if the float is doing the right thing using a voltmeter. If you don't have one, now is the time. Set the voltmeter to the lowest OHMS setting and touch the ends of the probe together. The meter needle should move to the opposite side from where it was, indicating a closed circuit. Now hook those leads to the tank. Tip the tank over to simulate full and the needle should move to the other side. The needle will either read closed one way and open when tipped the other direction. It may not be that simple, but that is usually the way a float works. It is either a closed or open circuit.

way2fast91

If I am following you correctly, you are suggesting a similar test except removing the wiring harness from the equation. Is that correct? Your method would simply test the float and the sensor's ability to read/respond accordingly to the float (magnet). As this method is an easy first step, I will do it to confirm the new tank float setup before moving to the second test (more elaborate method I mentioned, involving the harness and starting the car to check the warning light blink).

996-CAB

Yes. The process of diagnosing a problem is to isolate the components. Using a voltmeter to test the float before it connects to the rest of the circuitry will allow you to determine if it is the float or some other part.

URO Support

Hi Way2fast, is this regarding Expansion Tank 996 106 147 56? We'd love to hear your feedback, please send us a PM with the details so we can investigate.

Tags: 99610614756, 996 106 157 04, 99610615704

hbdunn

if you’re gonna do that, I would use rubber gloves and rubber bands to seal up the holes and fill it with water so you’re actually simulating the float moving with the level of the water.

way2fast91

Thank you so much for this tip. Finally some decent temps today locally, so I tested the new replacement tank. First, I plugged the new tank (uninstalled) with sensor into the wiring harness and held it upside down to simulate full coolant condition. No blinking occurred. I then turned the tank right side up and could here the float slide down into to the bottom of the tank simulating empty/low coolant condition and after 19 seconds the low coolant light started to flash. I was convinced it was time to start removal and install of the new tank, however based on the comment above, I decided to take the time to plug and fill the new tank with water, hold it level, plug in the harness and start the car and much to my surprise after 19 seconds the slow flashing light occurred again.

The one thing to note here that has me scratching my head, why did it take 19 seconds for the light to come on in this last test with the new tank filled with water?

With the currently installed tank, the light comes on the second I start the car. In the first test of the new tank I ran without fluid in it (holding it upside down), if I hold it right side up (empty condition) and start the car the light came on the second I started the car. Why then, when I filled it with fluid and held it right side up, did it take 19 seconds for the light to come on?