Overheating with thermal imaging - Defender Source
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  #1  
Old June 7th, 2011, 11:08 AM
Seanh
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Sean Hanagan
94 D90 ST #910 Matilda
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Overheating with thermal imaging

I have the dreaded overheat issue and decided to utilize some borrowed technology. My situation goes like this. Needle creeps close to red under load both at highway speeds and crawling. I have not experienced a boil over or steam. I have attempted to;
Top off coolant
Replace thermostat
Check fan clutch=ok
Take thermal images

My motor is a 94 3.9 with 184XXX

Here is the (#1) lower hose, (#2) upper hose and (#3) radiator top and (#4) bottom at normal needle position. Next set of images are from an overheat I created last night under highway load. Image (#5) is lower hose, (#6) is lower radiator through grill (#7) is hottest spot I could find on the motor just behind the lower hose. (#8) is the guage position from the overheat. The one image I lost was the upper hose which was 193 degrees. I was hoping someone could help determine if the radiator is the problem or should I look elsewhere?
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  #2  
Old June 7th, 2011, 11:14 AM
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Jason England
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Cool toy ... has the radiator ever been replaced / flushed??? I can't figure out from your pictures but if the bottom of the rad is cooler, potentially it is a bit blocked and reducing the flow.

I had over heating problems and after having the rad replaced and various other efforts it turned out to be the pressure cap on the expansion tank ... get a new one and that will ensure that the system pressurizes and the cooling is most effective.
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  #3  
Old June 7th, 2011, 11:31 AM
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Tony Sims
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Temps under 200f shouldn't push the temp gauge into the red. The temps in the Flir pics don't look way out of line, and you say no boiling over. You might just need a new sender, or to provide a better ground for the gauge.
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  #4  
Old June 7th, 2011, 12:10 PM
Seanh
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Sean Hanagan
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Edited to show the temp gauge last night. I've seen it go just below the red.
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  #5  
Old June 7th, 2011, 01:33 PM
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Do the hoses stay hard after you shut off the truck?

If so, I would bet on the rad. If not, find the pressure leak and fix it.
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Old June 7th, 2011, 01:43 PM
Seanh
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Sean Hanagan
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I took it to a mechanic and he pressurized the system overnight and said it wasn't loosing pressure.
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  #7  
Old June 7th, 2011, 01:55 PM
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Rich Campbell
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Those temps don't seem high to me. I would check the sender's ground. Also check and see if the gauge moves up when you put on all the lights, ac. heater ect. Mine did this and it turned out to be a bad ground.
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Old June 7th, 2011, 05:47 PM
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peter
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My gauge used to get to about the same point under the same conditions. I installed a Vdo gauge and sender and I have yet to see it go above 200 on the new gauge. I'm guessing it's the sender or gauge. Temps shown on the infrared don't look unreasonable.

I did install a dedicated ground for the new gauge, otherwise it wouldn't work. FYI if you go that route.
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  #9  
Old June 8th, 2011, 12:06 AM
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jim pendleton
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Would have to agree. I would be looking for a ground circuit problem for the guage. The radiator needs to be rodded and cleaned if it is an original part as a matter of maintenence really. Good radiator shop can comment on the condition of the radiator when you take it in for a rodding and cleaning.
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  #10  
Old June 8th, 2011, 12:39 PM
Seanh
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Sean Hanagan
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Thanks all!
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  #11  
Old June 8th, 2011, 02:32 PM
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Craig Dickson
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When you turn off the truck and immediately restart the engine does the temp gauge go back up toward hot? If the gauge goes back to the middle than I would suspect the gauge.
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