GaryDoug

Make sure you are testing the ground wire with the ignition off. If it is still higher than a few ohms, the problem is with the connector or wiring. Since the ground wire is shared with the TPS, and if you have no throttle position problem/code, the break is between the connector and the splice to the TPS sensor.
The engine temp has nothing to do with this failure.

Slayer

I'm not having any throttle response problems, so I guess I'll just order the SLP fan switch kit and hook it up.

GaryDoug

Not so fast. If the ECT isn't working correctly, the engine will not be running very efficiently. Using a fan switch will not solve that problem.

Slayer

Even though the temperature gauge on my dashboard has been operating, I decided to pull the temperature sensor in the head and test it. I used Shoebox's chart as a guide (4th Gen LT1 F-body Tech Articles), and when I tested the sensor connector, I got a reading of 12 VDC. However, when I tested the sensor, I only got a reading of 1 ohm, no matter which ohm range I selected on my multimeter.

If that sensor is bad, would the temperature gauge on the dash still be working normally? Also, that sensor only controls the temperature gauge on the dash, so it wouldn't have anything to do with the fans not coming on, would it?

GaryDoug

First, you are not reading the meter correctly. What you are seeing is an over-range reading (off scale). It is showing a completely open circuit.

Second, forget about that sensor, only used for the gauge.

Slayer

Yeah, I realized that was a stupid idea. This is probably another stupid idea, but is it possible that my water pump is bad?

Injuneer

You are assuming that the engine is operating at 260*F, based on the gauge. If the sensor for the gauge is defective, you are getting faulty info. Maybe it isn't anywhere near that temp, explaining why the fans aren't coming on.

Slayer

True. I'm still waiting on my friend to come over with his scanner, but he's been busy at his shop.

Slayer

On Christmas, I hooked up the SLP manual fan switch, and I drove the car to work this morning (three miles) with the intention of taking it to my friend's shop after workl, so he could hook up his scanner. With the fans on high, the car still overheated by the time I got to work. The temperature gauge was past 260 degrees, and when I popped the hood, I could hear a lot of popping from under the radiator cap. I'm at a total loss now. Radiator? Water pump?

Injuneer

.....blown head gasket????

Slayer

I hope not because that was the problem two years ago, which led me to rebuild the top half of the engine. The dipstick still shows oil, not a milkshake, and I don't see any white smoke pouring out the exhaust like two years ago.

Slayer

After three hours of my mechanic friend messing with the car in my work parking lot, he's almost positive the water pump isn't circulating the coolant, so I'm going to replace it soon.

Injuneer

If it's not the head gasket causing the "popping", what is it? Faulty radiator pressure cap could be allowing the coolant to boil, but wouldn't seem to explain the 260* temp - and you already replaced it. Could be a t'stat stuck closed - but you already replaced the t'stat. Have you checked to see if the front of the radiator is blocked by a plastic bag?

Water pump is always a possibility. And not many other possibilities.

Slayer

He hooked up his scanner and ran the car. The temperature gauge was reading much higher than the coolant temperature. Every time we heard popping from the radiator, he would open the bleeders, and they would spray air for a while until he filled the radiator with more coolant. He kept running the car and bleeding the system, all while monitoring the coolant temperature on the scanner versus what was showing on the gauge. Finally, he got all the air out of the system and drove the car for a couple miles with the scanner still hooked up. The gauge and scanner were both showing around the 210 degree mark, so we thought it was fixed. A few hours later, I drove the car home, and the same thing happened. I opened the bleeders and got nothing but air. I removed the radiator cap, and the radiator was almost empty because most of the coolant had been pushed into the overflow tank, and it was starting to overflow. My friend seems to think that the water pump is bad and not letting the coolant properly flow to the heads and block. I checked the build sheet from a couple years ago when I had the engine rebuilt, and the water pump wasn't replaced. The last time I replaced the water pump was probably in 2003. The car still runs perfectly fine. No hesitation or missing like it did a couple years ago when I blew the head gasket. Even this afternoon, when I got home, the gauge was reading past 260 degrees, but the intake manifold was cool to the touch, and once I opened the bleeders, I was able to take off the radiator cap without any coolant spraying me.

bw_hunter

A bad water pump doesn't explain the symptoms. You don't see any overheating on the scanner indicating good circulation but the cooling system fills with air. Sounds like a bad head gasket to me. Anyway, have the coolant checked for hydrocarbons from combustion gasses. do a compression test as well. Not every failed head gasket yields water in the oil...

The intake manifold is almost always cool to he touch compared to he rest of he engine...it's dry so there isn't any coolant to warm it up.