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New thermostat

  #1  
Old 11-07-2018, 09:38 AM
inthedirt
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New thermostat

Got a question for everyone here: Has anyone else experienced a rising/falling temp gauge whenever a new thermostat is installed? I recently replaced the thermostat in our Ex a couple of weeks ago and have noticed my temps rising upwards of 215-220 degrees before dropping to its normal range. I've had this happen in the last 4 vehicles I've owned. As the rig is warming up, the temp spikes then drops to normal after what I assume is the thermostat opening. I've made sure to bleed the system in each vehicle and have even seen this with a professional flush, so I don't think its air trapped in the system. In the case of the Ex, I removed the Motorcraft 185 unit and replaced with a 195 (can't remember the brand, but not MC). Thoughts?
 
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Old 11-07-2018, 04:35 PM
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Haven’t noticed this in my excursion, but my ‘94 puckup does this
 
  #3  
Old 11-08-2018, 09:24 AM
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I think this is normal......although I don't recommend the 195 unit.

I have a 180 degree tstat in my supercharged X and upon inital warm up it will spike to 192 to 194 degrees. Then pop back down to 180 to 182.

If it's hot out same happens. If AC is on the temp will normalize at about 187 or so with my 180 tstat.
 
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Old 11-08-2018, 11:11 AM
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I live in Montana where the winters can be pretty brutal (Dec 2016 was -54F). The 185 was only giving us marginal heat last winter, so I wanted to give us a little more cabin heat. Our summers are usually pretty mild and I've only seen a couple of days where it gets into the 90s. Since they're easy to replace, I can always go back to a cooler t-stat once it warms back up. Just curious if anyone else had seen this happen as it didn't prior to the swap. I've had a ScanGauge II plugged into the OBD port since the day I bought the rig and can see the actual temps. The stock gauge doesn't rise and fall, just the digital SCII.
 
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Old 11-08-2018, 01:27 PM
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Intresting, I too live in a cold climate.

7800 ft in mountains of wyoming, don't even have ac at my house. Never gets above 85 degrees.

I was concerned with a 180 degree tstat but my supercharger kinda wants a cool tstat.

My ex will heat so well with a 180 you can actually be sweating when it's -20 outside.

so, if your having heat issues with a 185 tstat it could be another issue.
 
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Old 11-09-2018, 12:20 AM
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ND here..... it is already cold....185F stock temp Motorcraft unit in mine, worked well last winter at -20F,
 
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Old 11-09-2018, 12:40 AM
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Your problem is the aftermarket t stat, the wax motor is highly inaccurate in the aftermarket t stats. As most on here agree I recommend only a genuine replacement part.
 
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Old 11-09-2018, 12:00 PM
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Modern computer controlled engines "assume" a specific engine temperature governed by the T-stat. If it's spec'd in the manual for 195° F that's what you have to use, the engine will otherwise stay in permanent warm up mode and run way too rich. Use a Motorcraft thermostat and test it before installation.
 
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Old 11-09-2018, 01:27 PM
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Originally Posted by Tedster9 View Post
Modern computer controlled engines "assume" a specific engine temperature governed by the T-stat. If it's spec'd in the manual for 195° F that's what you have to use, the engine will otherwise stay in permanent warm up mode and run way too rich. Use a Motorcraft thermostat and test it before installation.
I agree, but not sure about assuming engine temp. The CTS let's pcm know when the predetermined engine temp is reached.

the 2V motors are 185 and above.
I think 3V motors have a 195 and above.

using a hotter tstat will not hurt too much.

in my case a 185 came stock, but I had to retune for supercharger and tuner fixed my pcm so the 180 degree tstat works.
 
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Old 11-09-2018, 02:27 PM
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Originally Posted by rock2610d View Post
I agree, but not sure about assuming engine temp ...using a hotter tstat will not hurt too much.
But a colder one will.
 
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Old Yesterday, 09:38 AM
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Well, I'll plan to swap to a MC 195 and see if that makes a difference. Thanks everyone
 
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Old Yesterday, 10:01 AM
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195 is ok, even though I prefer 185, you should do just fine with a 195.

now as far as I can tell coolant temp has little to do with AF ratio.

I know what everyone says but I have a wide band O2 sensor and upon startup AF ratio is pretty rich at 11:1 or so. After 10 or so seconds it's at about 12.5:1 or so. 30 seconds later it's at 14.7:1. It was 8 degrees out this am and within 30 seconds of startup that AF ratio was 14.7 to 15:1. That's not rich and coolant them was COLD.
 
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Old Yesterday, 02:19 PM
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---------------
 
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Old Yesterday, 02:23 PM
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Originally Posted by rock2610d View Post
195 is ok, even though I prefer 185, you should do just fine with a 195.

now as far as I can tell coolant temp has little to do with AF ratio.

I know what everyone says but I have a wide band O2 sensor and upon startup AF ratio is pretty rich at 11:1 or so. After 10 or so seconds it's at about 12.5:1 or so. 30 seconds later it's at 14.7:1. It was 8 degrees out this am and within 30 seconds of startup that AF ratio was 14.7 to 15:1. That's not rich and coolant them was COLD.
At startup it doesn't matter what thermostat is installed, the engine is cold and is going to stay cold for a while. The difference is upon warm up, at normal operating temperature, a given thermostat temperature rating sets the floor of the minimum operating temperature, not the ceiling. We tend to think of what temperature a thermostat opens at but it also closes at the rated temperature.

Somewhere along the way everybody got it in their head that an engine should ideally run as cool as possible, and that's not really the case. It is true for example that drag racers will use bags of ice to cool down intake manifolds and things like that, but it is often a mistake to try to take racing strategies to the street or a daily driver.

The goal of the thermostat and cooling system in general is to get the engine warmed up as quickly as practicable upon startup, and then keep it there within a range. This is true even if you live at the Equator. This keeps oil sludge and acid formation to a minimum, decreases cylinder wear, reduces pollution, and maximizes efficiency. If the engineers specified a 192° or 195° F thermostat particularly on a computer controlled engine, don't use anything other than what is called out for in the manual. It's just going to cause problems. And besides, the heater won't work with a ****.
 


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