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Old 06-03-2016, 07:38 AM
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Default Over heating diagnostics?

Hey all,
With the finally arriving heat, I find my 89fj62 running hot & almost over heating over & over. It will run all day in stop & go traffic or around town without any issues it seems. But once I get on the highway I overheat within a few miles. So what failure does this indicate?

The coolant is really old so I think that could be it. But does old coolant lose its ability to cool? Or just get dirty & gross? I was also thinking this could be a bad water pump, that just can't flow enough water to keep up with increased heated highway RPM's.

The fact that it is cooling properly at low speeds makes me think it wouldn't be the fan/fan clutch or thermostat, as I would think they would also indicate at slow speeds.

Does this all make sense, or am I way off?
Thanks
Abe
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  #2  
Old 06-03-2016, 07:45 AM
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Radiator needs flushed?
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  #3  
Old 06-03-2016, 09:11 AM
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Hey Abe, make sure your gauge is working. Mine would do this, after hours of troubleshooting, I found out that the gauge itself was creeping up. When it looks like it's over heating, give the gauge a few nice taps and/or confirm with a more reliable gauge.

Also make sure your thermostat is functioning properly, or just replace it when you do the flush and put new coolant in.

Good luck!
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Old 06-03-2016, 10:02 AM
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My thoughts would be what Bruce and Jackson suggested. Also, check that your radiator does not have a bunch of dirt or debris stuck to the outside of it. Seriously doubt it's your water pump. In my experience they usually start to weep or leak first or the bearing goes out.

Also, check your radiator cap
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Old 06-04-2016, 12:36 AM
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Quote:
Originally Posted by gr8fulabe View Post
Hey all,
With the finally arriving heat, I find my 89fj62 running hot & almost over heating over & over. It will run all day in stop & go traffic or around town without any issues it seems. But once I get on the highway I overheat within a few miles. So what failure does this indicate?

The coolant is really old so I think that could be it. But does old coolant lose its ability to cool? Or just get dirty & gross? I was also thinking this could be a bad water pump, that just can't flow enough water to keep up with increased heated highway RPM's.

The fact that it is cooling properly at low speeds makes me think it wouldn't be the fan/fan clutch or thermostat, as I would think they would also indicate at slow speeds.

Does this all make sense, or am I way off?
Thanks
Abe
I had the same problem with my 1971 FJ40 coming back from Cruise Moab in 2004. I had to scratch my head and ask "what has changed?".

I had mounted an 8274 winch on an across-the-frame-rail mounting plate and it was sitting up high and obstructing air flow through the perfectly good radiator. With the clutchless orange metal fan and relatively new radiator I knew it wasn't a fan clutch issue or flow issue with the radiator. I built a new winch mount bumper after I returned from the event and it completely solved that problem.

After that experience, I have always been leery of mounting things like driving lights and things that might obstruct airflow through the radiator at high speeds, when the engine is dissipating the most heat and needs that air flow the most.
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  #6  
Old 06-04-2016, 09:46 AM
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Abe, I'd do the following:
  1. Drain and Flush the radiator, and the heater.
  2. Fill it with new properly mixed coolant
  3. Add a new OEM thermostat
  4. Check and clean the fins of the radiator
  5. Verify the shroud is unobstructed
  6. Verify temps with an outside thermometer, I have a laser one if you need it
  7. Check for blockage like a winch or new bumper
  8. Make sure your coolant levels are good, and properly burp the system.
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  #7  
Old 06-04-2016, 11:33 AM
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gr8fulabe gr8fulabe is offline
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Awesome! Thanks for the advice everyone! I've got a new thermostat & hoses, plus coolant & flush in the car & a good plan of attack. Thanks a bunch.

One question, how do I drain/flush the heater? Just make sure it is at temp & open/running, or more to it? Also should I drain the block hole too, or is the radiator peacock enoug?

Thanks
Abe
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  #8  
Old 06-04-2016, 12:31 PM
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Abe, yup just run the heater on full heat.
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  #9  
Old 06-24-2016, 09:07 AM
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Quote:
Originally Posted by Rzeppa View Post
I had the same problem with my 1971 FJ40 coming back from Cruise Moab in 2004. I had to scratch my head and ask "what has changed?".

I had mounted an 8274 winch on an across-the-frame-rail mounting plate and it was sitting up high and obstructing air flow through the perfectly good radiator. With the clutchless orange metal fan and relatively new radiator I knew it wasn't a fan clutch issue or flow issue with the radiator. I built a new winch mount bumper after I returned from the event and it completely solved that problem.

After that experience, I have always been leery of mounting things like driving lights and things that might obstruct airflow through the radiator at high speeds, when the engine is dissipating the most heat and needs that air flow the most.

I'm experiencing the same symptoms as Abe, but I have new coolant, radiator, etc...This comment from Jeff hit home, as I installed some fog lights last fall, and never ran them in the heat.

My fairlead fašade I made to kind of resemble the hood silouette of my 40, and I liked how it looked....but started thinking there was too much there restricting the air flow. I got a torch, and cut off much of the plate, as I like how the lights look where they are, and want to keep them there. I haven't gone on the highway yet, but will report the results.
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