Updated: Temperature Gauge STILL Not Working - Now What?

[DC Turismo]

Here is my most recent post which sums up my troubles thus far:

Well I have two venues to partake now.



This info was provided to me by a fellow TD'er who knows his stuff:

In your pic, the sensor on the cylinder head just to the
left (as you look at the pic) of the distributor cover. It
has only one wire going to it. The parts manual calls it
both of these and references two different part numbers
also:

Sending unit, engine temp gauge 4504203
Sensor, engine temp 4437313

I don't know why it has two listings and two numbers for the
same item (and I am looking at the 90 factory parts manual).

The 2 wire sensor in the t-stat housing is the coolant temp
sensor and is what the SBEC looks at to see engine temp.
The two sensors are not interconnected in any way.

So, I went ahead and ordered that new sensor today and it will arrive tomorrow.

The other option I have is heading over to Heath Farquhar's house if this does not work, and we are going to run a voltmeter test on the gauge itself.

I'll keep you posted.

Basically, the temp. gauge on my '90 Daytona did not work prior to pulling my motor, and I thought that putting in this new motor (new sensors) would fix that problem. Well, it hasn't.

Today I went and ordered a new 'Engine Temp. Sensor' that screws into the head to the left of the distributor cap. However, while I was there, my Chrysler Master Tech buddy told me to pull the plug off and place a piece of wire in the plug part and very quickly tap a piece of metal (radiator clamp is what I used). This would ground it out and by tapping the metal quickly, a person inside the car watching the gauge would be able to see if it would jump or not.

So, I did this, and the person watching the gauge gave me a nod every time it jumped - right on cue with when I tapped the metal with the wire that was inside the plug that attaches to this sensor.

So, from what he told me, if this happened, then the sensor itself is bad. I thought I'd try another spare sensor that I had on a head at my garage, and after changing it out, it too, did not work, a.k.a. my gauge still doesn't register????

What makes me mad is that this 'sensor' is basically a bolt that screws into the head and it is submerged in antifreeze. So I think that the plug just reads the temperature of the bolt itself?

But, I guess I'm going to go ahead and buy the new sensor tomorrow and try it now. Does anyone else have any other ideas? Seeing that I could make the gauge bounce when grounding it out shows that all wiring is working, correct? I just really want this fixed since this new motor is in place - I can't afford and will be devastated if something were to happen to it heat related and I couldn't foresee it coming.

All suggestions appreciated!

[cordes]

Yep, just ground it to see if the gauge works. Replace the sensor and all should be well. I just got done doing this on my 90' shadow, and all is well in temp gauge land now.

[TopDollar69]

If the head isn't grounded, the sensor will not have anything to reference to. Probably not the problem, but it's something to think about.

[DC Turismo]

Cordes:

So you bought a brand new sensor and everything turned out OK? I wouldn't mind getting the new sensor as well, but it puzzles me as to why the used sensor I tried tonight also didn't work, when the head it came off of came from a running, fully functioning car as well?

Ben:
Where is the point at which the head is usually grounded? There is a ground strap that I was unsure of where it came from and placed one end on the passenger side engine mount and the other on the frame right by the coil?

[JDAWG]

do you have the ground from the back of the intake to the firewall hooked up?

[Tony Hanna]

Just an oddball thought, but you're not wrapping the sensor in teflon tape before you screw it into the head are you?

The ground for the head should be bolted to the back pass. side corner of the intake.
It's kind of hard to see the bolt hole, but it's there.

[TopDollar69]

That sounds right for the other ground. I believe the main ground for the head is the main ground wire coming off the battery. I cant remember if it bolts to the head, or one of the transmission bolts. Either way, what I would do is check resistance with a multimeter between where you were grounding the gauge wire and the bare metal of the head. You should have pretty close to 0 ohms.

[BLUEBALL]

The wire itself does not read the sensor. The sensor changes resistance value with heat and gauge in car is pretty much an ohmeter. If needle moves with wire grounded then you have a prob with sensor most likely. Another common prob is not enough contact inside connector. try lightly squeezing the connector so the round wire end squeezes the sensor post better.

[DC Turismo]

I did use teflon tape! Is that what's causing the problem??? I wrap the threads of any coolant line or sensor threading with it to prevent leaking.

The ground from the back of the intake is attached to the firewall. It was a PIA to attach with the power steering pump mounted already let me tell ya!

I did squeeze the plug itself and it is definitely! making enough contact with the sensor.

So, tomorrow I should go forth and buy the new sensor and to put it in without taping it up with teflon then? How tight into the head should I tighten it? I don't want to overtighten it and have it snap off.

Thank you for the assistance! I really hope this works!!!

[Tony Hanna]

I did use teflon tape! Is that what's causing the problem???

The sensor grounds through the threads where it's screwed into the head.
Since teflon tape doesn't conduct electricity, it can't ground. Try pulling your old sensor out, cleaning the teflon tape off of it, and reinstalling it. I bet you won't even have to spend the money on a new sensor.

As for tightening it, I think the sensor body is brass which is pretty soft, so just snug with a ratchet or box end wrench should do it (think tightening up a spark plug). If it leaks, you can always tighten it up a little more later.

[DC Turismo]

Sounds great! I'll definitely do this tomorrow before I go to pick up the new sensor I ordered. If this works then I'll be so happy, and won't have to buy that sensor! WOOT!

Man Tony, this is two specific problems this week that you diagnosed for me! Thanks!!!

Now, does anyone have any tricks on how to take this out and put a new one in without antifreeze gushing out? Stupid question I know. I took off the radiator cap to decrease the compression of the antifreeze, unscrewed the sensor, and hurried up and swapped them. I still got a good flow of antifreeze all over the towel I had tucked into place. Oh well. I guess you just gotta be quick with it, huh? ahha

[Tony Hanna]

Sounds great! I'll definitely do this tomorrow before I go to pick up the new sensor I ordered. If this works then I'll be so happy, and won't have to buy that sensor! WOOT!

Man Tony, this is two specific problems this week that you diagnosed for me! Thanks!!!

Now, does anyone have any tricks on how to take this out and put a new one in without antifreeze gushing out? Stupid question I know. I took off the radiator cap to decrease the compression of the antifreeze, unscrewed the sensor, and hurried up and swapped them. I still got a good flow of antifreeze all over the towel I had tucked into place. Oh well. I guess you just gotta be quick with it, huh? ahha

Glad I could help.

To keep from losing a bunch of antifreeze (is it just me or has that stuff gotten really expensive lately?) try this. Pull you radiator cap off, slide a clean drain pan, bucket, or whatever you have under the drain on your radiator. Drain about 1/2 to 1 gallon out of the system. The temperature sensor is pretty high up in the system, so this should be enough to drop the coolant level below it and keep everything fairly dry while you have the sensor out. Once you have the sensor back in, pour the coolant back into the radiator, bleed the air out of the system, and you should be good to go.

[cordes]

yep the new sensor worked with no problems. I also used the stick style plumbers sealer stuff which worked great.

[DC Turismo]

Awesome Tony, I'll try that!

Thanks cordes, if need be I'll definitely go through with that new one!

[mcsvt]

Have somebody put their finger over the hole while you clean the tape off?

[turbovanman²]

Use some liquid teflon sealer, works everytime.

Remove rad cap to relief pressure, put it back on. Loosen old sensor so its just barely in, have new sensor ready with sealant, then with one hand remove old one and quickly install new one, if done right, you'll loose a teaspoon of coolant. Also, if the engine wasn't grounded properly, it wouldn't run.

[Tony Hanna]

I'm having a hard time understanding the need for any type of sealer at all.
Regardless of what the sensor body is made of (I was thinking brass earlier, but I may have been mistaken), it's threading into a relatively soft aluminum casting. I've always just installed them dry and never had a problem with one leaking.

[cordes]

I'm having a hard time understanding the need for any type of sealer at all.
Regardless of what the sensor body is made of (I was thinking brass earlier, but I may have been mistaken), it's threading into a relatively soft aluminum casting. I've always just installed them dry and never had a problem with one leaking.

I like to use a little sealer just because it serves as a little bit of lube for removal. I had one that was corroded in the head and broke off in the omni. I had to drill it out and tap it. It was not any fun, so I use a sealant now, and there are no problems.

[TurboJerry]

Also checking resistance of the sensor with a DVM would show if the sensor is open circuited. I usually have a bunch of used ones that I can try out in case of these situations. Another good sealer is the red anaerobic stuff. Easy to remove the sensor later......

[JDAWG]

Have somebody put their finger over the hole while you clean the tape off?

haha gary, I had my dad do that a while back "when I screw this out put your finger there" lol