coolant temp gauge help please

[joelych]

hello everyone, i have a 92 240sx with ka24de, car drive normal but i notice that when my rpm go up to 5000, my coolant temp gauge drop to all the way down. is that normal? or can anyone tell me what is wrong?

[brndck]

That is definitely not normal. Do you have access to another instrument cluster? Easiest way is to swap in another cluster and see if it still continues. Then you have determined whether it's your cluster that is bad, or something outside your cluster that is causing it.

[High_240sx]

Check your connection on the coolant temp sender for the cluster, may be loose and vibrating or may be bad. Check your grounds. Also make sure your upper harness along the fuel rail is secured good, cause that will add vibration to your coolant temp sender connection.

[joelych]

thanks guys, i will check that.

[Frank_Jaeger]

If you have a blown HG, the air bubbles introduced into the cooling system at higher RPMs can cause your gauge to drop. I've had this happen to me. I've also had the reading on my gauge drop because the connection itself was loose.