How to change the water sensor for the water temperature gauge (#102450)?

[larsmhh]

Hi!
I need to change my first inaccurate and now not-reading water temperature sensor, located at the rear right end of the engine block.
I am a little afraid, what happens if I screw the sensor out. Do I have to expect some/a lot of water to drain out of the sensor hole from the block? Do I have to bleed the water cooling system after changing the sensor?
Or is this just half as problematic as I think it is? Maybe someone has already changed this sensor before (I would expect this :o ) and gained experiences?

Thank you very much and best wishes from cold Germany,

Lars.

[82DMC12]

Hi!
I need to change my first inaccurate and now not-reading water temperature sensor, located at the rear right end of the engine block.
I am a little afraid, what happens if I screw the sensor out. Do I have to expect some/a lot of water to drain out of the sensor hole from the block? Do I have to bleed the water cooling system after changing the sensor?
Or is this just half as problematic as I think it is? Maybe someone has already changed this sensor before (I would expect this :o ) and gained experiences?

Thank you very much and best wishes from cold Germany,

Lars.

Yes, the overflow tank will empty out through the hole where the sensor was as well as whatever it takes to drop the block level down to the hole as well. If you haven't changed the coolant in the last two years, you should just do it now. Loosen and disconnect the lower coolant pipe hoses near the transmission and drain everything down from there. If you don't want to spill anything from the sensor hole, you're going to have to pull one of the block plugs as well. the one on the driver side is easier to get to.

I'd want to drain everything down before replacing the sensor because I don't like getting coolant stuck in the Valley of Death.

[larsmhh]

Hi Andy!

Thank you for your answer!

The new sensor arrived today and I will check it, before I will put it in. But now I know that it might get hard to change it...
I will write a report, when I did it (I think I will wait for the weekend...).

Best wishes,

Lars.

[David T]

If you do it real quick you won't lose much. Take the old one out, stick your finger over the hole and then quick put the new one in. You shouldn't lose much and you don't have to bleed afterwards. If your coolant looks or smells funky, if it tests high on PH or is not good to -20 F (or is over 5 years old) it should be flushed out and replaced anyway. The temp sensors don't go bad so much, usually when they go bad it is either because you ran with very low coolant or you overheated the motor. More likely it is just a dirty connection. Change it and see if that fixes you up.

[DMC-Ron]

Hi Andy!

Thank you for your answer!

The new sensor arrived today and I will check it, before I will put it in. But now I know that it might get hard to change it...
I will write a report, when I did it (I think I will wait for the weekend...).

Best wishes,

Lars.

Lars,
Consider doing a temperature test before installing the sensor. This is similar to what you might do when checking a thermostat. If you have a portable hot plate, pot with water, and thermometer; you can connect the sensor to the car (An extension wire can be used). Secure the sensor in the pot so just the sensing element is in the water. Turn on the hot plate and compare the pot thermometer with the instrument cluster readout as the pot heats. Eventually the pot will stabilize at boiling temp (~212 degF). Now verify what the instrument cluster reads. Even though the critical temperature during normal operation with your car will be 10 to 15 degrees higher (depending on pressure cap and antifreeze concentration), its good to have a reference to a known value just to understand if your cluster temperature reading is high or low by X amount. Plus, it verifies it's working before you make all the effort to install it.
Ron

[dmc4087]

If you do it real quick you won't lose much. Take the old one out, stick your finger over the hole and then quick put the new one in. You shouldn't lose much and you don't have to bleed afterwards. If your coolant looks or smells funky, if it tests high on PH or is not good to -20 F (or is over 5 years old) it should be flushed out and replaced anyway. The temp sensors don't go bad so much, usually when they go bad it is either because you ran with very low coolant or you overheated the motor. More likely it is just a dirty connection. Change it and see if that fixes you up.

I was able to replace my temp sender this way, and I didn't lose too much coolant.

[Rich]

I was able to replace my temp sender this way, and I didn't lose too much coolant.

And an old towel below the sensor port can keep most/all of the leaking coolant under control during the sensor replacement.

[larsmhh]

Hi,
I wanted to write a summary, how the case went on.

Thank you for the hint to check the (old) gauge and/or the (new) sensor about their cooperation due to the exchange!!!
The new sensor reads 320 - 340 Ohms at 100 C boiling water, but my gauge just wants 90 - 95 Ohms to show 104 C equal to 220 F.
This means, the new sensor will also not work propperly in my car! :frown:

I then used a potentiometer and collected the correct resistance to show the 4 landmarks of the gauge.
I found a website from VDO instruments, which offers a lot of different sensors for their water/oil/gas/... gauges and shows tables with temperature vs. resistance. (https://vdo-webshop.nl/de/34-temperaturgeber?page=1)
I found a sensor that fits in principle, if I add a resistor of 40 Ohms to its measurements. It is the VDO A2C1755260001 :thumbup:

Next problem: It does not look like our sensor #102450 and the thread does not fit. I do not really know, what kind of thread the PRV-engineers used. The one that may fit is a metric one (M14) with a pitch (<- is this the right word?) of 1,25, which VDO does not use (they use a lot of M14, but a pitch of 1,5).

So I talked to a turning shop. They suggested to buy a sensor with a thread of M16 and then they will try to thred a M14x1,25 to the sensor. This can be done at earliest in january 2023...

I am still waiting for the new M16 sensor to arrive and so I will report, if I have more news about this story...

Does someone know the real thread of our Delorean-sensor? Is it really M14x1,25 or maybe a british or american thread? The nut I used for testing fits and turns easily, but maybe a little too easy!? There is a large clearance...

Best wishes,

Lars :)

[larsmhh]

This is the sensor #102450 and the nut M14x1,25, that fits onto the thread of the sensor. But I?m not sure, if this is the original thread or if it simply fits...

[Bitsyncmaster]

If the nut fits on you probably have the correct size (a lot of slop would not be correct). There are different specs on the threads of some nuts and bolts as far as how tight they mate.

[Rich]

Thank you for the hint to check the (old) gauge and/or the (new) sensor about their cooperation due to the exchange!!!
The new sensor reads 320 - 340 Ohms at 100 C boiling water, but my gauge just wants 90 - 95 Ohms to show 104 C equal to 220 F.
This means, the new sensor will also not work propperly in my car!....


Are you saying you bought a replacement #102450 sensor from a DeLorean parts vendor and tested it, proving it won't work properly with your gauge?

In that case did you also check your old ("failed") sensor with same test?

It would be interesting to know if the old sensor behaves similar to the new sensor - because the problem may be in the gauge or the wiring/circuit, not in the sensor.

Keep in mind some gauges and lamps in the DeLorean instrument cluster are known to misbehave due to aging of the flex circuit.

(Note: a replacement sensor sold by a DeLorean parts vendor should plug-and-play, not require resistors or special threading.)

[Bitsyncmaster]

Look at my thread starting at post 25 and you will see I got about the same results as you for sensor resistance.

https://dmctalk.org/showthread.php?15056-Electronic-Otterstat/page3&highlight=GAUGE+SENSOR

[larsmhh]

Are you saying you bought a replacement #102450 sensor from a DeLorean parts vendor and tested it, proving it won't work properly with your gauge?

In that case did you also check your old ("failed") sensor with same test?

It would be interesting to know if the old sensor behaves similar to the new sensor - because the problem may be in the gauge or the wiring/circuit, not in the sensor.

Keep in mind some gauges and lamps in the DeLorean instrument cluster are known to misbehave due to aging of the flex circuit.

(Note: a replacement sensor sold by a DeLorean parts vendor should plug-and-play, not require resistors or special threading.)

Hi Rich!

I also checked the old sensor, which measures lower resistance tham the new one.
You are right, I could ask the ventor to take bak the sensor, because it should be plug-and-play, but I changed the gauge to the metric one and I am not sure, if the sensor ist also build to work for the metric device too...
I got a message today, that my new sensor is shipped and should arrive next week :wrenchin:

@ Bitsyncmaster
Thank you for the linked discussion. Now I know, I?m not alone with this problem :)
I will update you as soon as I will have some news to spread.

[JohnnyK]

Yes, the sending units are m14x1.25, at least the one I bought from DeLoreanGo was.

[larsmhh]

A happy new year to you!

The VDO-sensor arrived and looks a litttle different to the sensor I bought at Delorean.eu in the Netherlands.
I just wanted to show you the differences on a photo.

Currently the sensor is already in the turning shop to give it a M14x1,25 thread.
Let?s see, if this works.

Thank You JohnnyK for the confirmation of the thread!

Bye for now,

Lars :)

[larsmhh]

Hi!
I got the sensor back from the turning shop. Checked the resistance and it is the same as it was before its modification.
The hex head is shorter now, but the neck (above the thread) in return looks the same.
I am very happy with the result.

69330

So I hope that I can fit it in this weekend :)

Is the sensor just screwed in or do you use some kind of sealant (like i.e. Curil T)?
Do you expect problems due to the longer sensor body (it is about 4 mm longer than the DMC-sensor) - or is the enough space?

Best wishes,

Lars.

[larsmhh]

Hi!
I used this weekend to change the water sensor. There is so little space to work that it took me 10 minutes to loose the old sensor.
It was quite a lot water that floated out of the hole since I got my new sensor in (although I emptied the water reservoir before I started to work on the sensor). I lost about 2 liters. The new sensor fitted perfectly.

69340

The VDO sensor did show higher temperatures on the gauge than the water really was (I checked the actual water temerature with a FLIR camera), so I added an inline ressitor of 27 Ohms and now the gauge shows the correct temperature (at least about the significant temperature range between 90?C - 110?C) .

How much was this project? I paid 36? for the VDO sensor and 39? to the turnnig shop, so it was 75? for a working water temperature gauge - I think it was worth it.

Thank you for your help and
see you soon,

Lars.