Jerry Feather

I received the sensor I found on eBay and the first point of encoouragement is that it works the same as the 928 sensor, that is, it completes the circuit when the float drops to the bottom of its travel rather than breaking the circuit as with the hundred or so "substitutes" I modified with my new caps. But, that is the only bit of encouragement since the float on the new sensor will not fit thru the neck of the overflow tank in our cars. Otherwise I think the switch in the new sensor can probably be adapted to the ones I have put together.

With the new sensor I have found the float is at the bottom but is connected to a kind of ladder-like extension up to the top of the sensor where the switch is actually located. And, the float assembly is quite a bit longer than the original 928 sensor. What that would have meant is that to adapt the float and switch part of the new sensor to the top of what I have put together would require shortening the float assembly/ladder to match the length of the 928 sensor. Again, that is if the float would go thru the neck of our overflow tank.

Now I think that I can probably adapt the switch part of the new sensor to what I have made using the top of my replacements for the connection part and my new caps, but cutting off the bottom of the float and its extension and replacing the float bulb on its bottom at a different location and with something small enough to go thru the neck of our tank. I don't have a good idea about what that float might be made of, but one thought is that I could make it out of wood and cover it with epoxy so that it does not become saturated over time; or, maybe even cork, which is actualluy a kind of wood; or even bulsa. Maybe i could machine a float out of some kind of plastic and glue it onto the ladder, but that seems like too much work.

I'll just have to think about it some. I think the whole thing would come out to about $75 to make it worth while, and for how kind of cobbled together it might end up it probably will not be merchantable, even to save over a hundred bucks over a factory sensor.

Jerry Feather

The brain is a wonderful thing. I was driving home early today from the office in one of my cars from my other collection, a 99 Eldorado, which is frequently displaying a signal that the coolant level is low. Then I was wodering where the coolant level sensor is located since I have not seen it on the top of the overflow, so I was thinking that it must be somewhere under the plastic tank. Then it came to me that the solution to the otherwise failed sensor project might very well be to figure out a way to adapt my replacement sensor/sender to the under side of the 928 tank. Volla! There is another thread on here about a smaller metal tank that I think Greg B. might have posted about. I think it deserves some further consideration in terms of putting a suitable sight gauge on one side of it and then welding on a new bung for the sensor/sender under it, plus a new bung for some kind of pressure cap on top.

Jerry Feather

My current thought is that the smaller tanks we see in the other thread, and I have about 3 or 4 of them, are just too small for the 928 application, notwithstanding the lack of a sight gauge. I think the 928 overflow tank is carefully sized to allow for just about twice the amount of expansion of coolant with heat. The minimum level for coolant at cool is about half of the tank volume and the expansion above that is just about the same so that any more than that is overflowed onto to ground. The smaller tanks that we looked at with Greg are about half the size of the originals and I think are just about that much too small. To make my sensors work with any new tank is going to take a compete new tank with about the same volume as the originals but with my sensor and bung on the bottom. I guess I need to look into the design of such a tank. I should also consider the inclusion of a sight gauge as suggested by Greg B since I doubt that I can come up with any kind of tank that anyone can see through.

z driver 88t

Jerry, thanks for continuing to think about this. I know we all wish the project had worked. I'm needing to order a sensor soon. I had a bad tank cap that led to a dry reservoir and could have overheated the engine. $200 is hard to pay for such a simple liquid level switch.

928NOOBIE

I don't know if $200 is too much to pay for one. Mine is still running strong...I have Carl's aluminum expansion tank....only issues I've had is getting the sensor tight enough so it doesn't leak at all when the system is pressurized and the hinky connector won't stay on well enough to keep from occasionally getting false alarms...

If/when mine goes...I plan on paying $200 for a new OEM one...this one is 35 years old and counting...that's a good life for a sensor that operates in a pretty harsh environment...my humble opinion. Worth $200.