Jerry

That Sounds Great!

Ill keep you posted once received.

Thanks Again for doing all of this. :cheers:

Mj, its going to be interesting to see just what you come up with for testing this later style sensor. The first test will be fairly simple in just determining that it can be installed in the 928. I'm not concerned about that one, but you are going to have to turn the connector over for it to work.

The next issue, which ROG100 says is not a show stopper, and which I have not accomplished, is to see just how it may function in a 928. That has to do with the shorter length of the new sensor compared to the original. One thing for sure is that it is going to need to function with the coolant level in the expansion tank/bottle at right at 1 inch higher level. I too thought that was not going to be any significant issue, but now a thread pops up that suggests that the coolant level in the tank is going to always be at one or another particular level, and may not be subject to simply filling to a level one inch higher. If that is the case, most of this effort may in fact be wasted, because of the difference of one inch in the on/off range of float of the cork on the respective sensors.

First I think we need to determine if the coolant can be kept at a one inch higher level from that suggested in the manual. If that is too high and will cause a loss of that much coolant, we are likely to end up with the low level warning on all the time. Then I think the only solution to that is going to be a different tank with the sensor mounted in a recess on the top that is one inch lower than the rest of the top. However, even that, with this sensor, is likely to be only a few dollars more that the 180 to 230 cost of the factory sensor.

And then, the mounting neck on the new tank could be one to accomodate the cap that should come with the new sensor rather than the replacement one I have designed. That's of course assuming that one could buy one of the new sensors with a cap, which I have been unable to do except for two of those that I received.

So, I think the test is going to need to be simply filling the coolant tank an inch higher than stated and then driving it to see if there is any coolant loss after reaching full operating temperature. If there is no loss then I am sure this sensor conversion will work fine. If the level drops back to the recommended level, with the extra inch being dumped overboard, then - - - - -

There is about a 1" difference between the two sensors in question.
Taking the normal level to be the center point (joint of both section halves) of the expansion tank and about 2.25" of coolant.
The original indicates a level of less than 1" when the float reached the bottom of travel.
The new sensor about 1.75".
I have not tried with water in the tank as yet so indication points may be slightly different.

Either way the sensor will tell you when the level has dropped about 1" or more from the standard fill mark.

Once the sensor is tested in the application you will know if it does the job or not.

I tested the floats on both of the sensors, new and original, and find that the original one floats to the top only when it is 3/4 submerged in water and the new one at 7/8 submersion. Based on that, what Roger says about how much coolant will be in the tank when either float is at the bottom of its travel is going to be pretty accurate.

The owner's manual (81 anyway) says that, after draining the system, one should fill the tank to the bottom of the filler neck and then run the engine to operating temp. At that point the coolant should be at the mid point in the tank. My first thought about that is that the coolant level drops because the coolant in the top half of the tank is filling up some voids or air bubbles throughout.

However, I went out and looked at one of my S4s and could not see any level markings on the tank except for a sticker flat on the top of it. The botton line says: "COLD WATER LEVEL." Now I am wondering how the coolant expands as it cools off.

In any case, if the starting point with a cold engine is to the top off the tank, there is no opportunity to add more to try to accomodate this shorter new sensor. However, I'm not sure about that; and based on Roger's calculations with 1 3/4 inch of coolant in the tank when the new float is at the bottom, the new sensor is simply going to tell us that the coolant level is low when it drops about half an inch to 3/4 inch below the middle of the tank rather than about and inch and a half. Then there is another eighth of an inch in our favor since the original sensor float travel is 7/16 inch and the new one is only 5/16 inch. At least I think that is in our favor.

Therefore, when you get a coolant level low indication, which should be rare anyway, it is still an indication that you are loosing coolant. Maybe that is all it is supposed to be in any case.

I have this project essentially completed, at least so far as the development goes, and including much of the fabrication of components. I have found that in the process of sharpening the nitrile cutting die for the seals that the outer diameter tended to get smaller and I ended up cutting about a hundred of them slightly smaller than I want. I then re-sharpened the cutter and now it is cutting just where I want it and I have it sharpened at the right angle to stay sharp now thru another hundred seals, and likely many more.

I have also received and tried the new HSS mill bit and it is cutting the flutes with a bit of fuzz, but which can be simply rubbed off. I am however still deburring the flutes with my pocket knife, but that takes only about a minute or less each.

Before I list these for distribution in my small business membership I think we need to know how high in the coolant expansion tank the level of coolant can be held above the cold fill mark without loosing coolant. Hopefully the level can be held at about an inch higher than the mark without the coolant leaving thru the fill cap; or that the sensor can still function at the original coolant level and still float the cork on the new sensor without sending the warning.

Hey Jerry

I recieved mine on Tuesday but haven't had a chance to get up to the shop to install it yet. I plan to get up there on Monday, So i will hopefully have feedback for everyone by Monday evening.

Thanks Again.

Went this far and still don't know what level the sensor is getting triggered at?

Roger and Sean have actually tested one of these sensors electrically and since all of the ones I have bought have corks that move freely up and down, the only other test that is really needed is to determine just how high in the expansion tank the coolant can be maintained above the cold fill mark without loosing coolant. Anyone with a 928 can determine that without the need to remove the tank to install one of these replacement sensors.

At this point we have only one data point and that is the one posted in the other thread by F4GIB where one of you state that your coolant level likes to be at 1/2 inch above the middle tank seam. Even at that level this sensor will work just fine because the coolant will have to drop nearly a quart from there to drop the cork enough to give the low level warning. That would be a significant drop/loss that should not occur in the normal fluid expansion and contraction.

So, the only test that is really needed is several more data points showing just how high in the expansion tank the coolant can be maintained. When I am comfortable in knowing what the highest level of coolant is that can be maintained without loss I will either put these on the market or put them on the shelf. So far half inch above the middle says put them on the market.

Is anyone else willing to add about a quart of coolant to their system and run or drive it to operating temp then send me or post the respective coolant levels?

I wonder if Greg Brown would be willing to torture test it for you (us). When he's doing a dyno run on one of his engines, he could swap out the existing sensor of one of these. In a matter of weeks, he (or one of the other professional 928 mechanics) could document how it works on several different cars under a wide variety of conditions. If the new sensor works, I assume it would be a benefit to Greg's customers -- unless he's got a private stash of sensors to draw upon.

As for me, I'm not volunteering to test the unit because my sensor is working and I don't want to risk damaging it by removing it for the test. I'm not suggesting that the risk of breaking the sensor for someone competent with a wrench is all that high. I just know my limits. If it's possible to break a difficult to find part, I'll find the way!

This is a low coolant sensor so as long as it sets the light off when the sensor drops to a low level in the expansion tank then it works.
When the coolant gets hot it expands and the level rises which is not an issue as you only want to detect low coolant levels.

The factory set the minimum level triger point for a reason. If the replacement sensor is innacurate then it isn't really doing what it supposed to (warn the driver that the coolant is at the minimum). It would be just a coolant level loss sensor.
Relative to the overflow tank seam, how far does the coolant need to drop to trigger the OE sensor?

There is likely no particular "reason" for the cold coolant level to be set where it is and I suspect it is set there very arbitrarily. Too, there is probably some "minimum" level of coolant for the system, but it is not likely at the point that the original sensor gives the low coolant warning.

For many decades automobiles all over the world ran with the coolant expansion space simply in the top of the radiator. There were no expansion tanks then. That suggests that the minimum amount of coolant in any such system is in fact when there is some coolant missing not only from the expansion tank, but also from the radiator.

All the coolant low sensor is telling is that the coolant level has dropped, not that it has reached some "minimum" level. It drops only because it is being lost and not "used up." The engine in a 928 does not use coolant like fuel and to some extent oil; so the only purpose of the sensor is to tell that you are loosing coolant. You should then not only fill up the system but you need to figure out where or how it is being lost.

Therefore, we still need only to know at what higher level, if any, the coolant can be maintained in the expansion tank. If it can be held, hot or cold, at about an inch above the indicated levels, then this new sensor will function exactly as the original. It will tell you that you have lost about an inch to inch and a half of coolant in the tank which you should not be loosing.

Nothing Porsche did arbitrarily. It was tested, re tested and tested more before limits were established. As with anything engineered there is always some amount of safety margin built into these limits. However, to say that these limits are arbitrary is simply isn't so. The systems that don't have an external expansion tanks have them in the radiator so they all had expansion thanks or some sort. The factory sensor tell you more than that you've lost coolant, it warns you that coolant has reached a minimum level and you need to top it off. The shorter sensor that you have eliminates this part of the sensor's function. This sensor will only tell the driver that the coolant level has dropped, nothing more. Why not just redesign your cap and lower the sensor to the factory height?

It might be interesting if there was any authority for your speculations.

As to the redesign--why haven't you already done it?

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.