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Discussion Starter #1 (Edited)
Hi all,
Have a 1988 Nissan 300zx coupe Automatic 3.0L car and I am worried that the car runs too hot. It goes this high when I go 65mph on the highway for 10 minutes or more.
Screen Shot 2018-05-04 at 1.22.20 PM.png

The coolant is full, and there are no leaks found. The Car only has 56K miles on it.
The Gauge never goes higher than this. Is this ok?
 

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When this happens, is your cooling system venting steam? If your gauge is correct, your coolant should be at ~260 degrees F and the pressure in you cooling system above 20 psi. Unless you have a coolant cap that can hold that much pressure, your system should be venting some serious steam.

I would work to get accurate water temperature and oil pressure readings available in your car.
 

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Discussion Starter #3 (Edited)
My car is not venting steam. Maybe my gauge is wrong?. I guess I need to measure the temperature separately.
I opened the hood, and I see nothing wrong. No steam, no leaking, nothing. It is not overheating looking at the engine.
My Oil pressure is fine also.
 

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Im with thansen. When mine got close but not quite that high it was steaming a bunch and sounded really bad. My guess would be to replace the CHTS and harness wire which are behind the timing belt. Or if you just want to wing it you can keep driving it like that. Also overheating in an automatic is very bad because the atf can burn so your transmission would start to be destroyed, in which case I would replace the CHTS just incase so you actually know if/when it is overheating which would not be good
 

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when it does this, look under the hood and see what the overflow tank is doing. like the others have already said, should be venting steam somewhere. the overflow tank will usually boil over and start spewing coolant out of the end cap (makes a big mess all over the front end of the engine) and you will sometimes hear a howling noise, but this is normally when your coolant is gone and the engine is overheating. if you still have a good system and don't see any leaks, it is possible that you have an air bubble trapped in there somewhere or other blockage. check the front of the radiator and make sure no garbage or other junk is up in there blocking the air flow. its also possible that your thermostat is stuck and not letting coolant flow the engine. you can overheat as well if the water pump ceases, but in that case you would probably loose your coolant which will definitely cause overheating. just some ideas on things to check. my guess is thermostat. you can also run the diagnostic on the ECU and test to see if your CHTS is failing. good to do before you make the effort and pull it all apart.


Bon
 

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The cylinder head temp sensor (CHTS) has been mentioned in this discussion. I bring this up because the CHTS is not the sending unit for the dash temperature gauge.

This is a CHTS: 5S1535__ra_t.jpg

This is the dash sending unit: TS125Tphoto primary__ra_t.jpg

Please check me on this.
 

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The cylinder head temp sensor (CHTS) has been mentioned in this discussion. I bring this up because the CHTS is not the sending unit for the dash temperature gauge.

This is a CHTS: View attachment 99601

This is the dash sending unit: View attachment 99609

Please check me on this.

and the good thing about this, is you can access the dash sending unit easier as opposed to getting to the CHTS for removal.


Bon
 

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Discussion Starter #10
If anyone is interested, it ended up being a problem with the the Radiator cap. A $7.00 replacement cap fixed the issue.
 

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sometimes its all it takes. something small, cheap and easy to fix.
first thing you should check. some folks look too deeply into the inner components of the cooling system without trouble shooting the basic parts first.
glad you got it good now. keep a spare cap in your car. you never know.


Bon
 
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