I've been lurking here now for a couple months. Just had some issues come up recently, and decided to actually join and start posting. I have a '97 B2500 conversion van with the 3.9 V6.

The other day while driving down the road, the temp gauge ran into the danger zone, the idiot light came on and then the gauge died. Tried restarting the van to see if maybe it was just a fluke, but the gauge is dead. I did some searching on here and it does seem the coolant temp sensor is the culprit. Yet, I didn't read anything here that indicated the gauge spiking and then dying is the result of a failed coolant temp sensor. Any assistance would be appreciated. Thanks.

 

There are 2 CTS's. The one wire one is for the gauge. The 2 wire one is for the computer.

Check the connection for the one wire one. It's on the top of the intake manual somewhere. I'm not sure on your model year.

I'm not sure, but I think if you ground the connection it will max out the gauge.
Somebody else here will know for sure.

Did it happen right after you turned on the heat?
What is your coolant level?

 

You're correct, grounding the wire will cause the gauge to shoot up.

 

Thanks for the input, I was unaware there were two sensors. All I do know is that the gauge has not worked at all since it spiked, and I haven't seen the idiot light either. I will have to check both sensors, but what is the possibility that the gauge itself is dead?

As for coolant loss, I have to add coolant to the radiator usually once every 1.5 weeks. It has done this since I purchased it. There is no leakage from any of the hoses and I'm not loosing any coolant out of the water pump or the t-stat housing. I had thought I had a leaking head gasket, but there is no oil in the radiator, nor is the oil contaminated. I'm suspecting the coolant is leaking from the freeze plugs, but I have no way of getting under there right now to drop the tranny and find out.

Thanks again!

 

You don't say how much coolant you add every 1.5weeks. It is a possibility that the coolant is being burned in the cylinder without visibly contaminating the oil.

There is also an inexpensive test kit that detects hydrocarbons in the radiator.

I have no experience with a completely failed temp gauge, but you could test it by grounding the 1 wire sensor.

I've been visibly leaking coolant for a while now from the H20 pump area. I keep the plastic reservoir half filled and only refill it every month or so, But I don't drive very much, and it only leaks after it has had time to cool down, as far as I can tell.

I had some weeping freeze plugs at one point, those under the exhaust manifolds. It was a very slow leak, but noticeable from a distance, when looking for drops. This was about a 1.5 quart every 300 miles leak.