Erratic Coolant Temperature Readings!

[ron]

A very interesting thing happened while on the way home from work today. The analog temperature guage in my 1993 Vette began to show very erratic readings with the needle going from the normal temp, reading to way past the 260 mark to the limit of the needle arc and then back to normal. It seemed to be more likely to do this strange "dance" swing? when I would accelerate, but not always. Also it doesn't overheat as evidenced when I switch to the digital readout and temps read normal. Also it doesn't seem to occur until the car is warmed to operating temp. I replaced the coolant sensor and no change. Thanks in advance for suggestions as to exorcising this gremlin!

Ron

 

[Fiddler's Gold]

Hmmm

Did you pass through the eye of the storm or the middle of the sun? Perhaps you ran through a crop circle!!!!

Check for gremlins and don't feed it or fuel it after midnight and don't give it any water. No matter what.

Fiddler

 

[ron]

Temp. Reading Revisited

Fiddler, I don't recall being involved in any of the suggested paranormal events that you mentioned; however, I have another observation to present. The bouncing needle doesn't occur until the beast gets up to normal operating temperature. Is there another sensor besides the one located at the front of the engine? This is the one I changed with no success in fixing the problem. I guess I should feel fortunate that I still have the digital readout, but I really would like to resolve this mystery and be able to work on some other Vette issues. Another thought - could it be a poor ground? If so where would I begin to look? Thanks for any help.

 

[Ethan]

Temp reading

Check for air in system all Lt1,s had two bleed valves that you loosen with the engine running that will bleed off air in the system loosen them one at a time air will come out then a steady stream of fluid. Maybe will cure your problem?

 

[intruder9]

Where are those bleed valves located?

(Not that I have an LT1, I'm just curious!)

 

[ron]

location of bleeder valves

Intruder 9, One valve is located near or on the thermostat housing and the other is located on the driver's side of the throttle body. I have bled both and still no change in the status of the guage malfunction. Since I still have the digital guage as a backup and the durn analog guage doesn't act weird all the time, I guess i will just live with it until I get to Eureka Springs next weekend. I know someone at the rally will have a solution and a way to get that gremlin outta there! Ethan, thank you for the suggestion of bleeding the system. I can see where it might work, but unfortunately not for me this time.

 

[ron]

Gremlin Exorcised

Finally solved the problem of the errant temperature guage. There are TWO coolant sensors on the LT1. The one on the front of the engine (which I changed first and didn't solve the problem) goes to the computer. There is another sensor on the driver's side about mid-way down the block with one wire going to it. This sensor goes to the guage. Replaced the sensor ($20.00) and put new insulation on the wire (which could have been the problem all along) and the guage works like a charm. The sensor is in a rather awkward position, but is quite doable once the engine cools down. You can actually replace the sensor without draining all the anti-freeze if you quickly get the new sensor started as soon as you remove the old one. Sorry for the lengthy post, but maybe this "gremlim" will rear its ugly head with someone else.