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Cat Man
Cat Man, Caterpillar Engine Expert
Category: Heavy Equipment
Satisfied Customers: 8822
Experience:  23 Years Caterpillar Engine experience.
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The the highest the water temperature on a 1987(NNN) NNN-NNNN model cat

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Could u please tell me what would be the the highest the water temperature on a 1987(NNN) NNN-NNNN model cat can reach before it would damage the engine?

Hi. Thanks for using JA! I will try and help you out.


237 to 240 degrees is when damage can happen to the engine. At this temperature the plastic water grommets in the spacer plate under the head will begin to melt. If the truck continues to be driven, the temperature will rise to over 250 degrees and at that point, the oil is too thin to do it's job and you will begin to wipe out rod and main bearings. It will not take but a minute or so to lose a bearing at this temperature.


Please let me know if you have any more questions or need more help.

Customer: replied 6 years ago.
Ok so if it does get up to 230 and dont any higher it wont hurt the engine at all. The fan on this truck is running pretty much all the time in this hot weather loaded or empty. Is this normal

Correct. If your temperature did not go above 230 degrees, the engine should not be hurt at all.



The fan should not run all the time. If your fan is running all the time, you may have a partially clogged radiator. That is what I would suspect. You do not have a water pump or thermostat problem or it would overheat all the time.


Please let me know if you need more help.

Customer: replied 6 years ago.
Ok now this truck has the fuel turned up pretty high. Would this have a factor with the fan running all the time. It has a 190 thermostat in it and the fan should come on at 205 but according to the heat gauge that is in the truck it dont come on till 210 or 212 and also if the truck has been setting for a good while and completely cooled off the heat gauge will be on 110 to 120. What does this tell u? What should i do in your professional opinion?

Thanks for the information.


Yes. Having the fuel turned up is a factor in the engine running hotter than normal and making the fan stay on. The engine is producing more heat than it is designed to and will cause the engine to run hotter.


I would have the temperature gauge on the engine verified if you haven;t already. You are correct, the fan should come on around 205. It is possible that your temperature gauge may be off and not reading accurately. I would put a temperature heat gun on the engine and see how compares with the gauge.

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