Temp Gauge Gone Crazy

[MoDoggie]

I have a '94 GTP and the temperature gauge has gone crazy. It is constanatly going up and down, somtimes all the way past 260 and the temp light will come on. Then it will go all the way back down to 150 them bounce around between 150 and 210 for awhile then jump back up to 260 and so on. I had it in and had the cooling system flushed out and it is still doing it. The garage where I took it said they hooked the computer up to it and the temp sensor never sent a temerpature reading higher than 220. Is it possible for the gauge to go wacky like this, just out of the blue? or is there something else I should e checking. Please give me any ideas you have, this is very distracting when your trying to drie.

Thanks,

MoDoggie

[GTP Dad]

It is possible for the guage to go wacky but I would replace the temp sending unit to the guage. Chances are that it has gone bad. Also don't forget the thermostat as it could be sticking and causing the wild swings you are seeing.

[ericn1300]

check your anti-freeze protection with a hydrometer, sounds like you have ice or air blockage in the radiator.

[MoDoggie]

When it started doing this I tore it down and replaced the intake gaskets "again", thermostat, and temp sensor. It seemed to get worse after all that. I took it in and had the cooling system flushed and it still is doing it. I am just leary of banking on the gauge being wacked.

Thanks

[GTP Dad]

The next step would be to purchase an aftermarket guage and install it. This will ensure that the guage is right. They come with a calibrated sensor for the guage and that should ease your mind somewhat. If the problem continues then you have other issues.

[richtazz]

When you installed the new guage sensor, did you put any thread sealant like teflon tape or pipe dope on the threads? If you did, that's the problem. That sensor needs to ground to the engine, and thread sealer will interfere with the ground. The new sensor should have either tapered/self sealing threads or electrically conductive thread sealant pre-applied.

The other issue could be air trapped in the cooling system. These cars need to be bled of air any time a cooling system component is changed.

[MoDoggie]

I also just had the water pump replaced. It seemed to get worse after that also. Can these be put in wrong? I seem to remember them having a certain bolt patter which would only line up one certain way.

[richtazz]

The water pump will only go in one way. I still say it's an issue with air trapped in the cooling system.

[MoDoggie]

What is the best way to bleed the air out of the system? This is why I took it in to have the cooling system flushed, I figured they would bleed the system when they were doing that.