# 2000 Altima - Engine Overheating porblem...



## websk8r (Mar 11, 2013)

Here's the scoop.

Car: Nissan Altima 2000 (SE)
Issue: Radiator fan does not kick in, while engine temperature gauge stays in the middle. Temperature gauge used to be always at little below middle.

History: Following work was done by a auto shop.
Work#1:
1. Install Thermostat (refill the radiator)
2. Install new spark plugs.
3. Replace engine valve gasket, since it was leaking oil all over.

So i took car home and noticed that it is running little hotter (needle in the middle, instead of little below). After few days it started overheating even more. Found out that radiator is really low on coolant, refilled with 50/50 mix, but next day it was empty again. Found out Water Pump is leaking badly and it only became worst over next day or two. Towed it back to the shop, and they did following.

Work#2:
1. Put back OLD Thermostat back (thought is thermostat is cause of overheating)
2. Install new Water pump.

Radiator fan still does not come on, and temperature gauge stays in the middle. So i took matter into my own hands.

What I've tested:
1. Turn on AC and Radiator fans come on. It means FANs and Relays are good.

2. There are 3 fan relays, i swapped them around to see if it made any difference. Same result.

3. Tested voltage at relay terminals 1&2 on all 3 relays. When AC is on i do see about roughly 14 volts, however no voltage is present when AC is off and engine temperature gauge is at 1/2 way mark. It means ECM is not triggering relays on.

4. Tested top and bottom radiator hoses when engine been running hot. Both are equally hot, which i guess means thermostat is opening fine.

5. Tried removing "temperature sensor" but it's kind of hard to reach and could not disconnect it.

6. Hooked up OBD reader to test actual temperature readings. Not sure if it is coming from "temperature gauge" or from "temperature sensor". Coolant temperature reading fluctuates from 180 to 202. Since it drops down after 202, i am guessing thermostat is functioning.

Questions:
1- What is acceptable coolant temperature range?
2- Could air in the cooling system cause over heating?
3- Could it be because of bad coolant to water ratio?
4- At this point i am thinking it could be temperature sensor gone bad or maybe some short circuit or loose wiring.
5- Any other ideas to try?
6- Is this even a problem, or i am just being paranoid 

Thanks in advance.


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## Luger (Feb 26, 2013)

1. I believe about 185-225. I have read that the coolant will start to boil with a 50/50 mixture after 225. 

2. Yes, Burp the system for air. There are many you tube videos on this if you have not done it before. 

3. The car should be able to cool itself under normal circumstances with only water so this should not be an issue. 

4. That Coolant sensor should not be too hard to get out. I have taken mine out (same car), just pull out the plug and you have to use a deep socket or box wrench to get it out. Drain part of the coolant first or it will spill out and make a mess. Loose wiring can be an issue, I have run into the other coolant sensor for the gauge causing an issue due to this. 

If there is a pull it yourself auto wreckers in your area go and take one out of a compatible Altima. At the one around my place they are only 1.99.


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