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Old Jul 21, 2009 | 02:07 PM
  #1  
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Default Water Temp Question:

I drove the car to an event this weekend, and about 3/4 of the way there it started to run really hot.. probably in the 240 range. Before that it had been running between 200 - 210 on the way down, and had been staying at that point for the last couple of months when driving around.

It seemed to stay right in the 240 range the rest of the way there (never over heated), and when I drove it back after the event was over it went to the same temp again and stayed there.

Anyone have any ideas? Im thinking the t-stat is going out but if anyone else has a suggestion I'll try that first.
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Old Jul 21, 2009 | 02:22 PM
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a thermostat not opening up would cause overheating.

they are cheap and easy to replace so it wouldnt hurt however if the thermosat was working correctly remember that it will only regulate temp under the rating. once the temp gets to what it is rated at the thermostat will open completely.

since you said that the car drove ok i would look at the gauge itself.
maybe something wrong with the sender,
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Old Jul 21, 2009 | 02:26 PM
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My 68 (327) will run up there real quick if the outside temp is above 85 degrees and I am in traffic (less than 20 MPH). I still have the original radiator and have my eye on DeWitts to solve the problem.

If your T-Stat is not working at all the temp would continue to climb till something blows..like a hose or connection.
You didn't mention what the outside temp was the day you drove the car. 240 is not good at all. Did this just start to happen or has you car always run hot?
Things to check are; T-Stat, Fan clutch, rad fluid level and flush, air flow through the radiator.
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Old Jul 21, 2009 | 02:30 PM
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Engine cold, let it idling, open the hood, look at the temp gauge from time to time and touch the water hose between thermostat and radiator. It should stay cold until you reach normal operating temperature. When you begin to feel the heat with your hand, it means that the thermostat begins to open, then have a look at the temperature gauge again and see what it says.
If you have a digital thermometer with a probe, check the temperature on the sender body at this time. This will tell you if the thermostat is not functionning correctly or if it is the gauge.

Last edited by 73StreetRace; Jul 21, 2009 at 02:42 PM.
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Old Jul 21, 2009 | 04:59 PM
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It just started Sunday. It had never really gone much over 210 before, normally staying just a little below that. I was thinking that the thermostat may be sticking a bit.. not opening all the way that might be causing it since it does not actually over heat.

I should also say I have an aftermarket OEM style radiator and an electric fan. It stayed around that temp moving a little bit up and down regardless of speed.. from 80 on the turnpike to 25 on a side road to just sitting in traffic it seemed to stay there.. but the car was noticeably warmer than normal.

It was about 90 out.. not as hot as it has been lately but not exactly cool out.
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Old Jul 22, 2009 | 01:18 AM
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Mr Gasket makes a very good high performance thermostat :

http://www.summitracing.com/parts/MRG-4364/

I have purchased one a few years ago and it was a huge improvement in comparison with the stock one
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Old Jul 22, 2009 | 01:21 AM
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Question : What kind of electric fan do you use ?
Does it have enough air flow ?
You need at least 2600 cfm air flow to cool your engine in the hardest conditions...
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Old Jul 22, 2009 | 07:48 AM
  #8  
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If you were running at 210 and didn't stop and let the car cool I doubt your thermostat closed and caused it to go to 240. They just don't work that way.

I would check what temperature causes the fan to come on. I'm thinking the sensor for the fan is the problem. Start the car cold and watch the fan. When it comes on check the temperature. I'm guessing it will come on at around 240.
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Old Jul 22, 2009 | 08:51 AM
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The thermostat requires the removal of two bolts to take it out and hold it in your hand. A new gasket costs $0.79 at my local NAPA. Whenever I have a cooling problem, it is always a good idea to take the stat out and test it. If it is working properly, put it back in (with the new gasket), and you have removed one possibility.

The electric fan not coming on will make a difference idling or crawling in traffic. But if you were moving along nicely, the radiator shouldn't need the fan at all to maintain a reasonable operating temperature.

I also agree that it could be the sender/gauge.
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Old Jul 22, 2009 | 09:16 AM
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Originally Posted by Kevins77
... I should also say I have an aftermarket OEM style radiator and an electric fan. It stayed around that temp moving a little bit up and down regardless of speed.. from 80 on the turnpike to 25 on a side road to just sitting in traffic it seemed to stay there.. but the car was noticeably warmer than normal.

It was about 90 out.. not as hot as it has been lately but not exactly cool out.
Check for lower rad. hose collapsing. How old is the rad.?
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