XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Need help keeping car cool!!

Old Jul 10, 2009 | 11:23 AM
  #2  
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Spike, what year vehicle are we looking at here? What I would recommend doing is essentially a calibration of the temperature sending unit. All this involves is attaching various size resistors in place of your temp sending unit. For example, most procedures have you use 3 resistors (20 ohm, 140 ohm, and 260 ohm; C, N, and H respectively). It is possible that your car is running at a normal temp but with the receiving unit not functioning properly, it can cause it to indicate wrong.

After that, how is your water pump doing? To me, it is sounding like it is starting to go. What you are experiencing is that under light loads, there is enough flow to maintain the motor at its proper temp, but the thermostat is open more than it needs to be. But, when you push the car, the water pump can't generate enough flow, resulting in your over heating condition. I have seen with other vehicles that with time, the blades of the water pump will wear, resulting in the water pump not being able to push fluid like it needs to.

Hope this helps.
 
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Old Jul 11, 2009 | 06:46 AM
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Spike, what year vehicle do you have? Depending on the year, I may have the diagrams for your vehicle and can then give you step by step instructions on what to check and isolate the problem down to a single component. But, many different systems have been used over the years. So, I need a little bit of information before I can be any more specific. I should be able to give you wire colors and expected voltages.
 
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Old Aug 21, 2009 | 05:46 PM
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Default Over heating

I have a similar problem and I didn't want to start a new thread. My XJS is a 1988 coupe.
My temp marker is going 1/2 way between N and H.
My mechanic has done most everything he can think of with little changing. Today I topped up the radiator and headed out for a drive. I noticed that I was spewing some fluid out. After about 20 minutes my temp dropped to normal.
When I got home, I noticed that I had a small steam emission from the small (bleeder?) hose right at the filler cap. I have also noticed that I have a 16# radiator cap there instead of the recommended 20#.
Could/would either of these things cause overheating?
They certainly spew fluids, 1 1/2 gallon after a 15 mile jaunt.
 
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