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Possible cheap coolant level sensor replacement?

 
Old 10-17-2016, 06:38 PM
  #166  
Jerry Feather
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I found the COLD WATER LEVEL indication on the side of the coolant tank in my 88 S4. It consists of an arrow from the sticker on top down to just about half inch above the tank's middle seam. Then, with the aluminum replacement tank I have been doing some measurements with I find that the new sensor will just barely float the cork when the coolant is at the low level mark. Just about anything below that will drop the cork and turn the low level warning on.

Compared to the original sensor, as stated numerous times in this thread by me and Roger, that is about an inch above where the original will give the cold level indication.

Nothing in the information about this sensor and its indications even suggests that the level of coolant when the low indication is given is also some kind of "minimum!" The only purpose of the sensor it to tell when there has been a coolant loss of something less than a quart. With the level at the COLD mark, just about any loss of coolant is going to give the Low Level indication. What needs to happen to justify use of the new shorter sensor is to determine if the coolant level can be maintained at about half inch to inch above the original cold level mark.

Last edited by Jerry Feather; 10-20-2016 at 10:50 AM.
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Old 10-17-2016, 08:31 PM
  #167  
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Originally Posted by Jerry Feather View Post
It might be interesting if there was any authority for your speculations.......
Speculation? What part is speculation?
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Old 10-17-2016, 08:43 PM
  #168  
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Originally Posted by Jerry Feather View Post
........Nothing in the information about this sensor and its indications even suggests that the level of coolant when the low indication is given is also some kind of "minimum!" The only purpose of the sensor it to tell when there has been a coolant loss of something less than a quart. With the level at the COLD mark, just about any loss of coolant is going to give the Low Level indication. What needs to happen to justify use of the new shorter sensor is to determine if the coolant level can be maintained at about half inch to inch above the original cold level mark.
You really believe that the trigger point of the OE sensor doesn't mean minimum? Is it logical to expect that this point is a minimum established by the factory during severe weather and severe condition testing (then they added a bit more for safety)?
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Old 10-17-2016, 08:50 PM
  #169  
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Originally Posted by ROG100 View Post
Actually I am not 100% with you on this - most sensors perhaps I would agree but the level of water in the coolant tank plus or minus maybe an 1" is not going to make much difference in the grand scheme of things. This will not make any difference to the performance of the cooling system providing the warning is heeded.
In the case of the BMW sensor it is going to tell you that you have low coolant about 0.75" sooner than the Porsche sensor so not a bad thing.
Will it work on the 928 and not give premature warnings is more of interest.
I agree, in most conditions a 1" higher level of coolant wouldn't matter but still the new sensor will not be accurate so it's purpose will not be as designed. It's like having an inaccurate oil dipstick. It will tell you the oil is dropping but that's it.
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Old 10-17-2016, 08:58 PM
  #170  
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Originally Posted by Imo000 View Post
Speculation? What part is speculation?
Imo -- Jerry is referring to your statement that Porsche precisely determined the minimum amount of coolant for the 928 and labeled the coolant reservoir accordingly. That is, your assertion that a sensor that sends a "too low" signal earlier or later than the original sensor would have is providing false information, and your hinting that using such a sensor might be worse than having no sensor at all (because it might give the driver a false sense of security or cause the driver to ignore warnings). This, lumped together, is speculation on your part. Unless you have personal knowledge of what the Porsche team did or did not do in this regard, you are speculating as to what they did and what they knew. Your speculations may be based on reasonable assumptions, but they are still speculations. The size and shape of the reservoir bottle may have more to do with the space available than it did with an extensive study. Similarly, where they set the fill mark may not have been determined with any precision. It's possible there was a range they were comfortable and simply picked somewhere within that range for the fill mark based on other considerations, such ease of manufacture.

The real question is why you're so determined to tell everyone it won't work? Jerry, after significant time and effort, is tying to test the sensor to verify that it works. If it doesn't, Jerry will either come up with a fix or he won't sell it. So, in the interim, what is the harm in waiting on the test results? It's not as if Jerry's trying to foist an unproven product on the public.
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Old 10-18-2016, 05:53 PM
  #171  
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Mj reports that he installed the new sensor in his 928 and that it functions just as the original one, with no low warning either hot or cold. He doesn't, however, report what the coolant levels are in his tank, either cold or hot. I have asked him for those readings.

I found one other data point online in a lengthy report by someone who showed his way thru replacing his expansion tank in a 928. The most interesting thing about it is at the end he shows maintaining the coolant level at about an inch or little more below the top of the tank, rather than just above the middle seam.

I need more input about the ability to commonly keep the cold coolant about an inch or inch and a half above the mid seam. If I have to do all of this myself it will be some time before I am comfortable trying to market these new sensors.

Again, I know exactly where the new and the old sensors will trigger the low indication; and that is right at about the middle seam for the new one and about an inch and a quarter below for the original sensor. The cork on the new sensor does not float until it is fully submerged, at least in plain water; the original one at about 3/4 submerged. That means that if Mj's is working correctly and he is starting at the Cold Level Mark, just about any loss of coolant is going to send the low warning, rather than nearly a quart of loss for the original.

I'm not sure just what all circumstance are that might lower the coolant level below the Cold fill level, except loss, and it may be that the only one is coolant loss, but I am not comfortable thinking that any minute loss is what we want for the warning to come on about.

I am still hoping that some of you will go out and add either a pint or a quart of coolant to your tank and tell me what happens to it hot and cold.

Last edited by Jerry Feather; 10-21-2016 at 12:27 PM.
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Old 05-20-2018, 10:06 AM
  #172  
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Reviving this thread to find out what the outcome was. After reading the whole thing and sitting at the edge of my chair the discussion abruptly dies... What happened?! Is someone selling the cap and seals to make the BMW sensor work?
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Old 05-20-2018, 11:17 AM
  #173  
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I completed the development of the alternate Coolant Level Sensor/Sender and left it pretty much just where the last post by me says. I did recently sell one of them to a new young member with his order for some of my other items, but have not started a thread about the availability of these generally because of the lack of any additional testing or feedback about keeping the level of coolant in the overflow bottle a bit higher than the level mark on it.

If anyone else is interested in trying one of these in their 928 they are available for $45 plus $5 for S&H.
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Old 05-20-2018, 11:51 AM
  #174  
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Thanks for the reply Jerry. I am going to pull mine out and fully characterize whether it's functioning or not as the "coolant" indicator seems flaky right now. And rule out pressure sensor malfunction.

Do you have a website describing your offerings? Can't find it on The Google...
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Old 05-20-2018, 12:03 PM
  #175  
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I don't have a web site, but my offerings are listed in my signature. You can probably do a search and find a thread about most of them here on Rennlist 928, which is just about the only place I do any marketing.
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