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I’d guess it’s just the thermostat. First time I changed mine it ran warm for a while and worried me eventually settling back to normal. Now my water pump went out so I replaced the thermostat again and it fluctuates 188-204 constantly.
If you figure it out, let me know. Been suffering this for a long while just about.

200* t-state gets to 205*, then drops rapidly to 193* and then rinse and repeat. Had a whole huge thread about that lol.

On a 190* tstat I sat 185* without budging usually which is why I tried the 200*. I enjoy the 200* in the winter so it's stayed. I've tried a few different tstats from a few different brands to no change. Only change was the 190 to the 200.
 
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04 3500 QCLB, Edge Tuner, Kelderman air ride, stage 3 Meth, exhaust brake, BD Shift kit, 5” Exhaust
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Discussion Starter #22
There was probably a trapped pocket of air in the cooling system. To do the thermostat, they would have had to drain and refill the coolant.

When I do them I have a vacuum device to pull a vacuum on the system and then let it suck the coolant into the system. This prevents those air pockets. Most shops just simply pour the coolant in and then try to run the engine through a heat cycle hoping the air will purge. Their method is generally good but doesn’t always work with a single heat cycle.
If im understanding you correctly, when they refilled the coolant it looked full to them after one heat cycle but there was possibly an air pocket that has since left the system and now results in the coolant not being topped off anymore?
I just bought some coolant(not premixed) and I'[m wondering if topping off I need to still mix it with distilled water or not?
 

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If im understanding you correctly, when they refilled the coolant it looked full to them after one heat cycle but there was possibly an air pocket that has since left the system and now results in the coolant not being topped off anymore?
I just bought some coolant(not premixed) and I'[m wondering if topping off I need to still mix it with distilled water or not?
You are correct.

As for if you need to add water to the coolant before adding to the system. That’s dependent on where you live and the climate. If you live in a colder area, no. If you live in a warmer area, it is advised.
See coolant protects against freezing and against boiling. Water has better cooling properties (dissipates heat better) but can’t handle extreme temperatures as well.
 

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Discussion Starter #24
You are correct.

As for if you need to add water to the coolant before adding to the system. That’s dependent on where you live and the climate. If you live in a colder area, no. If you live in a warmer area, it is advised.
See coolant protects against freezing and against boiling. Water has better cooling properties (dissipates heat better) but can’t handle extreme temperatures as well.
The temps in my area are usually pretty mild. Our extreme is nearing 100 degrees on some days. Are these the temps you would recommend adding distilled water to the system?
 

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If you don’t need to add more than half a gallon, I wouldn’t worry about it. But you’d be better off if you do mix with water.
 
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Discussion Starter #26
If you don’t need to add more than half a gallon, I wouldn’t worry about it. But you’d be better off if you do mix with water.
Just topped off the coolant. Still running to temps of up to 210ish from what I can read off the stock gauge. Right between the zeros of the 200 mark. Now its up to the shop to tell me why its running hotter after they did the T-stat housing replacement.
 

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Discussion Starter #27
My mechanic says the fan clutch is going out and that’s responsible for the higher ECT’s. Does that make sense to anyone?
 

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Discussion Starter #28
My mechanic says the fan clutch is going out and that’s responsible for the higher ECT’s. Does that make sense to anyone?
After searching through a number of posts, I found one person mention “their fan clutch does a good job cooling the engine”. If anyone else wants to chime in I would appreciate it.
Thank you.
 

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Wouldn’t the fan clutch just keep the fan from coming on? Unless you’re towing or it’s hot outside I don’t think your fan really turns on that much. I think your mechanic is trying to pass the issue off on you.
 

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At highway speeds under truck only load, the fan doesn’t do anything. The fan is more for getting air movement when in heavy traffic or under moderate to heavy load. I have taken the fan off of several of my vehicles in the past and drove them for extended periods of time like that before I got around to replacing them.
 
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Stock tune it doesn't come on until 215* for ECT.

There is also a parameter for trans temp, think 275* maybe.

Otherwise it's AC and defrost that turns on AC.
 

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Discussion Starter #32
Damn, so far this shop has seemed legit but this makes me second guess that. They said they checked the T-stat housing they re did and it wasn’t related to that(if you believe it).
You guys have any ideas or are there so many things it could be I need to go back to the search function?
 

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Discussion Starter #33
They replaced the clutch fan and apparently it’s running at a normal temp of 195 now. Who know they might have fixed the real problem and replaced the clutch fan just for the $.
Thanks for the help and info tho guys
 

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Discussion Starter #34
They replaced the clutch fan and apparently it’s running at a normal temp of 195 now. Who know they might have fixed the real problem and replaced the clutch fan just for the $.
Thanks for the help and info tho guys
Trucks getting hotter now up to 220 if I let. That’s way too high for unloaded and stock tuned right? 220 is also the danger zone right?
 

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Discussion Starter #40
Since you started having this issue?
Yes when they replaced the t-stay and the housing it’s started getting hotter. I’m 90% sure it wasn’t happening before.
Would whether they installed a 180/190/200
T-stay make any difference?
 
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