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FIXITMAN
FIXITMAN, Master Technician
Category: Buick
Satisfied Customers: 17144
Experience:  ASE MASTER CERTIFIED, AA DEGREE AUTO/DIESEL TECH
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Buick Century Custom: Just bought a used 1999 century

Customer Question

Just bought a used 1999 century for my son. Has 130,000 on the car, the 3.1, and was well taken care of by an elderly woman who passed away and I bought it from her son-in-law. When driving on highway it runs at correct temp (slightly below the middle on temp gauge) but temp creeps up in stop and go traffic, and once got too high so I turned on heat and it went down. A/c works fine, no antifreeze leaking anywhere, coolant level good. I checked the relays and two were verified good by trying switching them out with ignition relay. Third one I just bought a new one. Also bought a new radiator cap. When a/c is one the two fans kick in but don't appear to be going that fast. When I stop car and turn it off, the fans don't continue to run to cool the system back down. Is it a bad sensor send info to the fans?
Submitted: 1 year ago.
Category: Buick
Expert:  FIXITMAN replied 1 year ago.
Hello, my name is***** for the question. If I am not online when you return please give me some time to get back to you. Can you tell me if the fans are running when the engine is getting hot and the a/c is off?
Customer: replied 1 year ago.
I'll check first thing in morning. It's after 1am and I didn't know you'd still respond tonight. For sure I don't think the fans stay on after turning off the car when I expect them to run for a while to cool the engine down some.
Expert:  FIXITMAN replied 1 year ago.
This car does not have the design of a lot of newer cars that have fans that stay on with a timer after it is turned off. Let me know what you find with the fan functions I mentioned. If they are coming on then the radiator may be restricted internally causing this.
Customer: replied 1 year ago.
Ran the car to get it up to temp, without a/c on the fans are not turning on. Once I turn on a/c they turn on.
Expert:  FIXITMAN replied 1 year ago.
Thank you. It sounds like a circuit issue. It can be caused by a number is ***** So that I know how you would like to continue can you tell me if you have a voltage meter to run some tests.
Customer: replied 1 year ago.
I do have a voltage meter that I use for home appliances, etc but I believe it's ac and dc. I changed the coolant temperature sensor but that didn't solve the problem.
Customer: replied 1 year ago.
Just saw this online but find it hard to believe that the fans won't turn on until it gets that hot. Is this post true? I didn't wait until it got that hot to check if the fans went on.
Check to see if the cooling fan on your 1999 Buick Century comes on when the Air Conditioning is turned on. If it does the system is probably OK. The cooling fans on most late model vehicles will not turn on until the temperature is 220 - 225 degrees. That would most likely be with your temp gauge reading about 3/4 but not yet in the red.
Expert:  FIXITMAN replied 1 year ago.
On your vehicle the fans should come on by about 200-210 degrees. If you did not wait that long then you should try it again. I do not want to start you in the wrong direction on this.
Customer: replied 1 year ago.
The temp was way above that. I took the connection off the coolant temp sensor and now the fans run whenever the engine is running.
Expert:  FIXITMAN replied 1 year ago.
That is what they should do if it is disconnected. Do you happen to have a computer scan tool that reads live engine data while the car is running?
Customer: replied 1 year ago.
I don't have a scan tool but could use the one from the auto parts store. By the way, the check engine light went on once I pulled the connector off the coolant temp sensor. Is there a reason why I can't just run the car with the sensor disconnected?
Expert:  FIXITMAN replied 1 year ago.
You can run the car like that but it will affect your fuel mixture also and can cause the car to run very inefficiently. I would be curious to know what the computer is seeing at the warmed up temperature.
Customer: replied 1 year ago.

I'd like to solve the issue if possible but don't want to spend a lot of money. How would I check the computer at the warmed temp?

Expert:  FIXITMAN replied 1 year ago.
The only way to see what the computer is seeing is with a scan tool that will see engine data. If you do not have one this will be very difficult. Let me take another look at the schematic and see what other options I can give you.

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