New AC Delco coolant temp sensor and cooling fans still wont turn on

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0
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Buick Ownership
Roadmaster Limited
Hello everybody I am new here. Anyways... I own a '94 Roadmaster Limited LT1 that has a cooling fan problem. Neither will turn on. I have replaced so far both cooling fan fuses, both cooling fan relays, and both coolant temp sensors... (The one next to the headers and spark plugs and the one under the water pump) The one near the headers and spark plugs is from Oreilly Auto but the one under the water pump is from the Dealership... it's AC Delco... Which Im guessing is OEM. It used to be from Oreilly as well until I took my Roadmaster to a local mechanic so he can diagnose the fan problem and he unplugged the coolant temp sensor (under the water pump) and the fans finally turned on! He then asked where I got the sensor and I said Oreillys and then he said to get the sensor from the dealership and not Oreilly. So I did... I installed the AC Delco part today but sadly the fans still wont turn on. Btw I have tried disconnecting the sensor near the spark plugs and headers with the Ac Delco sensor still connected but the fans still wouldnt turn on. What do you guys think could be the problem? Maybe the AC Delco part is faulty as well? Any help/ insight on what could be the problem with my Roadmaster would be greatly appreciated. Thank you!!!
 
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1
Buick Ownership
Roadmaster Limited
At what temperature is being checked and how are checking to know they are not working?
I let it go all the way to half temperature when I check... maybe even a bit over half. By the way the coolant starts to leak out of the coolant drain hose everytime I check so I'm pretty sure something's not right there... severely too not just drops. (But to add... when the fans are on after I disconnect the sensor under the w/p it doesnt even leak a drop of coolant)
 
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6,456
119
63
Buick Ownership
1996 Roadmaster Limited Collectors Edition 58k - 1996 PAU
Do you have any pressure leaks in the system, like the coolant reservoir pressure cap, or the radiator? Do a pressure test first and see if it will hold 15-psi pressure without dropping. If you have the duel electric fans, the first fan is programmed to turn on @ 215-deg+ and the second fan @ 235-deg, unless the A/C is on which will command the low speed fan to run while the compressor is running normally. Does the low speed fan run with the A/C compressor engaged??
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5
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1
Buick Ownership
Roadmaster Limited
Do you have any pressure leaks in the system, like the coolant reservoir pressure cap, or the radiator? Do a pressure test first and see if it will hold 15-psi pressure without dropping. If you have the duel electric fans, the first fan is programmed to turn on @ 215-deg+ and the second fan @ 235-deg, unless the A/C is on which will command the low speed fan to run while the compressor is running normally. Does the low speed fan run with the A/C compressor engaged??
I'll test that out as soon as I can (Friday) and get back to you on that
 
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43
Illinois
Buick Ownership
2007 Lucerne CXL. and 1995 Lesabre currently, past 1973 Riviera, 1968 Riviera
The dash gauge may not be a really accurate way of seeing engine temp as some have seen it hit up to 3/4 before the first fan hits. If that's how you are looking at it maybe a more accurate direct read off the engine would confirm if there is a problem. As HotZ28 mentioned, check the pressure, but if someone has done work on this engine you may need to confirm what was replaced, thermostat temp and radiator cap, that they are working correctly. Also as parts being replaced it may need to bleed it out if there is any air in the cooling system. Can't say these are all the answers but options to maybe cover.
 
5
0
1
Buick Ownership
Roadmaster Limited
The dash gauge may not be a really accurate way of seeing engine temp as some have seen it hit up to 3/4 before the first fan hits. If that's how you are looking at it maybe a more accurate direct read off the engine would confirm if there is a problem. As HotZ28 mentioned, check the pressure, but if someone has done work on this engine you may need to confirm what was replaced, thermostat temp and radiator cap, that they are working correctly. Also as parts being replaced it may need to bleed it out if there is any air in the cooling system. Can't say these are all the answers but options to maybe cover.
I'll go to Pepboys today and pick me up a new coolant tank cap... and yeah as mentioned tomorrow I will get to work on it and test the cooling system pressure... I'll keep you guys updated
 
5
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1
Buick Ownership
Roadmaster Limited
Thank you and HotZ28 for the help. Anyways... A mechanic helped me and my dad find the problem... It was leaking coolant ONLY because we unplugged a purposely plugged hose that's on the coolant tank... my dad thought someone just unnecessarily plugged it so he took off the plug (when we first bought it) the mechanic helped us figure out the problem when my dad mentioned that we unplugged it. So yes... it now goes to half temperature without leaking out any coolant and the fans turn on!!! Now that the plug is on. (We used a old spark plug lol) thanks again guys.
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6,456
119
63
Buick Ownership
1996 Roadmaster Limited Collectors Edition 58k - 1996 PAU
Thank you for the feedback. It sounds like someone tried to eliminate the coolant bypass to the T/B with an inferior plug. This thread may help someone with the same problem. The system has to hold pressure to function properly!
 
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