Hey all, the temp gauge is acting funny.When I first got the car the gauge only read about 140 deg so I changed the sending unit.That was fun. Ill use 3 or more swivels next time.Ive noticed that there has been coolant leaking at the sending unit at some point in time but not now.Go figure. After changing the SU the gauge read correctly. Now its going crazy again,running at 140 deg then jumping all the way to 260 deg then back to 180 deg.Ive replaced the coolant elbows recently with the aluminum ones and no leaks there.A strong hot coolant odor is present and I saw coolant dripping somewhere by the firewall.The overflow jug was not empty,maybe half full so I added water.I know I need to find the leak but is it the cause of the gauge to act like this?Im pretty sure the thermostat has been changed, prolly when I replaced the rad last year.Can change it again if needed.Any help is greatly appreciated. Muley I forgot to say my car is a 99 Z34 3800

 

How quick is this jump to 260? Might be air in the system...

 

Sometimes the intake manifold gasket will go bad and make the thing go stupid crazy. I had that on a few cars latest was my Pontiac, but I replaced this on the 3800's in the past. Just a thing to consider.

 

I had to send my Instrument Cluster to a Shop to have all the Stepper Motors replaced.
Heat went first! Scared the **** out of me, too. Was going along fine, ... then the needle went right off the scale.

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Well guys, update on this problem.I changed the sending unit in the rain yesterday so that took about 6 hrs. As I was filling the rad up I glanced over at the rad on the driver side and saw a light brown gunk on the rad. Must have been the old Dex cool? So I reckon Ive got a leaking rad that is maybe 2 yrs old.Boy, when it rains it pours, huh? The low coolant light has been on for a pretty good while.Now I know why.A friend at work gave me a bit of insight that I hadnt really considered. If water isnt getting to the TSU it wont read correctly.Well. Oh,and the cap was shot also. So Ive gotta get a new rad at 177.00 clams! I didnt know the rad was leaking til yesterday.Sheesh.
The gaskets were replaced recently, they could be bad also. Im right partial to this car even with 196k miles.Still runs great,cold a/c stereo, just things like the starter,battery, now this.Im gonna fix it.I am grateful for all replies about my car and Ill check everything that was mentioned. Nitehawk, the gauge would jump to 260 then back to semi normal. After changing the sending unit its not pegging out now.