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Fan Problems

Discussion in 'Performance & Fuel' started by Chad513, Jun 15, 2012.

  1. Chad513

    Chad513 Rockstar 100 Posts

    I just dropped a 5.3L into my truck. I had problems with my old engine over heating before because the fans weren't kicking on and now its doing it with the new engine. I noticed that my temperature gauge in the cluster is off. I have my bully dog set up to read engine temp and it reads like 220 and my cluster gauge reads less than 205. I think the fans aren't coming on because my gauge cannot read something right. Does anyone know what that problem could be and how it could be fixed. I have another question as well, would my running hot make me get less mpg and horsepower??

    I have one more question. I just got that engine put in and the oil pressure is at like 20, is that bad or average or what? My old 4.8L was at 40.

    Please and thank you!

    P.S. sorry if i posted this in the wrong thread.
  2. dpeter

    dpeter Rockstar 4 Years 500 Posts

    I am not sure if the computer looks at the same sending unit as the gauge but my experience is that there is a seperate coolant temp. sensor that is for engine management. Does your Bully dog get its info from the ECM, if so it is seeing what your computer is seeing and it probably wants the fans to run. First, do the fans work? Are the fuses good? Is the fan relay good? Is the ecm sending power to the relay? The first "no" answer you get is where to start looking for your problem.
  3. 08_rado_rocker

    08_rado_rocker Member 2 Years 500 Posts

    Definitely sounds like a variance in what the sending unit/ computer are seeing. Also agree with [MENTION=39755]dpeter[/MENTION] on the above issues to start looking for and troubleshooting.
  4. Chad513

    Chad513 Rockstar 100 Posts

    That's the problem. My mechanic hooked his scanner up to it and turned them on low and high and they worked on both modes. he turned on the ac and they run when the ac is on. I think it has something to do that my cluster gauge is not reading right. the gauge is not reading right so the fans are not turning on, but i have no idea that just makes sense to me.
  5. dpeter

    dpeter Rockstar 4 Years 500 Posts

    If you can operate the fans Via a scan tool then all is working and that is a good thing. What exactly leads you to believe you are overheating? I cannot recall but I think my owners manual suggests that 220-230 is normal if towing and nothing to get excited about. I'll check and get back to you.
  6. Chad513

    Chad513 Rockstar 100 Posts

    When it starts to get hot it feels as if I'm driving with my e brake on. it seems like its hard to accelerate and when i let off the gas it is like I'm engine braking. my old engine ran at 204, i don't see why it wouldn't with this engine because it is the same computer.
  7. dpeter

    dpeter Rockstar 4 Years 500 Posts

    Checked my manual, says gauge will read 210 or less most of the time, going up hill or towing it may reach 250 and that would be normal, if it reaches 260 or more then it is working beyond its capacity. From what you describe, I would be looking for dragging brakes. Maybe transmission selecting wrong gear. Does not sound like motor issue to me.
    Do let us know what find out. Good luck.
  8. Chad513

    Chad513 Rockstar 100 Posts

    Yeah that's the thing. It shouldn't be at 220 in town. That's too high when it says it should be less than 210 most of the time. I just got a new Tranny put in like 5k miles ago so I doubt that would be the problem.
  9. Chad513

    Chad513 Rockstar 100 Posts

    Drove it today on the freeway and it seemed like it was working really hard to stay at 80mph. it was jumping into 3rd gear then back into 4th. it does that sometimes on inclines or with strong wind but there was neither today. the temperature read anywhere from 210-221. I don't know how but i think that the fans not turning on is making it lose power because of pressure. Its starting to make me mad because my truck hasn't been right for the longest time and I'm getting tired of having to keep putting money into it. Does anyone know anything about any of this stuff??
  10. dpeter

    dpeter Rockstar 4 Years 500 Posts

    220 degrees by itself is not a problem but when you add to it that the motor is larger than original so the radiator may not be big enough and you have oil pressure on the low end, (used motor?) with bearing issues. You could have several issues contributing to the problem..Water pumps can go bad, thermostats go bad, radiators plug up, could have straight ani-freeze in it. Are the part numbers the same for both engine's coolant temp. sensor? You mentioned same ecm used for 5.3 as the 4.8, could there be a mismatch of components causing you problems? Now I'm just guessing.Hopefuly someone will chime in with something more useful.

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