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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29585
Experience:  GM Grand Master Technician 2007. 14 years experience.
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2000 Chevy Venture temperature gauge not working, fluctuates

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2000 Chevy Venture temperature gauge not working, fluctuates a little just barely getting over the "C" mark on the gauge. No codes given from ECM, heater works just fine and coolant levels are normal.
Welcome!! How does the heat inside the van feel?
Customer: replied 8 years ago.

The HVAC for the interior works just fine, the heater blasts out plenty of heat.

OK, I would start by looking at the sensor and wiring at the engine. These are on the drivers side of the engine, beside the upper rad hose in the lower intake manifold. Look for damaged wires or bent terminals. Also look for coolant leaks while you are in the ares. Did you confirm the coolant level on the bottle or in the Rad?
Customer: replied 8 years ago.
Coolant on the bottle only. Let me check the wiring and look for leaks.
OK, these engines are notorious for leaking at the intake manifold. I would advise you to take the rad cap off when the engine is cold and verify the coolant level in the rad.
Customer: replied 8 years ago.
Engine is still pretty hot, I just finished driving it to make sure the heater would work and that the thermostat wasn't the problem. Got the hood up and garage open, going to let it cool for 20 minutes or so.
Just be careful. I'm on all day so take your time and don't get burnt.
Customer: replied 8 years ago.
I'm back, had to run some errands. I removed the sensor and it looks fine. Wiring connector also seems to be fine. Did not notice any leaks from the intake manifold or any of the hoses. I checked the radiator now that the engine is cool and it is full.
OK, now we need to confirm the thermostat. With the engine cold, start it and keep your hand on the upper rad hose, rubber part. As the engine warms up, the hose will a small amount, but then when the thermostat opens, the upper rad will get hot, in a few seconds. If the hose warms up gradually, then you need a thermostat. What part of the country are you in?
Customer: replied 8 years ago.
Charlotte, NC
OK, check the thermostat and let me know.
Customer: replied 8 years ago.
I didn't notice any immediate temperature change in the hose, so it was gradual.
From cold to hot, there needs to be a 60+ deg spike when the thermostat opens. It sounds like you need to replace the thermostat.
Customer: replied 8 years ago.
I'm going to replace the sensor and the thermostat to play it safe. I was reading up on this problem on other threads (different sites) and someone mentioned that there were two sensors: one with two wires which sends the information to the ECM, and the other sensor with only one wire which is directly linked to the gauge on the instrument panel. Is this true? Also, would the thermostat be the problem for improper readings on the gauge?

There is only 1 sensor. The older systems used 2. The thermostat has a big impact on the readings of the sensor. If the thermostat opens early, the reading will not go very high. These are inexpensive parts and usually the first things I replace.

Customer: replied 8 years ago.
OK, thanks. One last thing, the thermostat is on the lower intake manifold on the side close to the sensor right? Which means I need to remove the throttle body and, more than likely the upper manifold, to more easily access it?

The thermostat is behind the upper rad hose housing at the sensor. I usually don't remove anything to change it. I take the lower bolt out completely, then note the angle of the upper hose, remove the top and fish it out that way. But, that bottom bolt is tricky to get out, and back in. You won't need to remove the upper intake manifold.

Customer: replied 8 years ago.
Thanks, I'm off to the store to get the parts. Will buzz you if I hit any snags. Appreciate your help!
No problem. Make sure the thermostat has the rubber seal on it.
Customer: replied 8 years ago.
You still there?
Customer: replied 8 years ago.
I'm in the process of trying to replace the thermostat on this van, and there is absolutely no room to even get to it. I had to remove the flex hose from the throttle body to the plenum just to even get my hand near the coolant-to-block connection where the thermostat is. Also, there is less than 1/2" clearance between the coolant tube and the exhaust manifold next to it, there's not enough room to pull it off with the exhaust manifold that close. Are you sure you don't have to remove anything to replace the thermostat?
Absolutely certain!! There is no extra room, and when you get the housing loose, the thermostat needs to stay in the manifold side to get the clearance. You can also pry gently on the heat shield of the manifold go get a bit more clearance. It is a tight squeeze, but that is how I do it.
GM Tech (Cam) and 2 other Chevy Specialists are ready to help you
Customer: replied 8 years ago.
You da man, I'll give 'er a go.
I pocket magnet will help when it is time to put the bottom bolt back in, and I hope you have small hands because there is very little room.
Customer: replied 8 years ago.
Ha ha, I'm good with the pocket magnet... The small hands are another story!! I'm 6'3" - 225, small hands don't run in my family! But I'm used to busted knuckles and car bites! Gotta love maintenance!!
Customer: replied 8 years ago.

I have to finish up tomorrow, but I'm sure it will be fine. Thank you very much for all of your help!

You are welcome. You cam reply to this post at any time and I will continue to assist you even after you have accepted.
Customer: replied 8 years ago.

You guys rock, wish I knew about this site a long time ago! Thanks again for everything, have a good night.