Radiator flush and thermostat replacement.

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Rusty Whitten

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Hello, everyone! Glad to have found this forum! I’ve got a 2004 Dodge Ram 1500 that I’m going to flush the radiator on and replace the thermostat. I am, by no means, an automotive genius, but I can follow instructions. :)

i’ve noticed at speeds around 55 to 60, the temperature gauge climbs past the middle mark. It doesn’t get too close to the overheating area, but still concerns me.

The last time I had this issue, the thermostat was bad. However, I do intend to flush the radiator as well. My question is this. Should I flush the radiator system, and then replace the thermostat?

Again, I’m no automotive wiz, so any advice would be appreciated!

Thank you!
 

Fast69Mopar

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Hello, everyone! Glad to have found this forum! I’ve got a 2004 Dodge Ram 1500 that I’m going to flush the radiator on and replace the thermostat. I am, by no means, an automotive genius, but I can follow instructions. :)

i’ve noticed at speeds around 55 to 60, the temperature gauge climbs past the middle mark. It doesn’t get too close to the overheating area, but still concerns me.

The last time I had this issue, the thermostat was bad. However, I do intend to flush the radiator as well. My question is this. Should I flush the radiator system, and then replace the thermostat?

Again, I’m no automotive wiz, so any advice would be appreciated!

Thank you!
Yes, flush with the old thermostat in place or do what I do and remove the old thermostat, cut the center out, reinstall and then flush with no thermostat creating pressure. I have one that I modified 15 years ago and still use it to this day.

Once the flush is complete, install the new
t-stat and be done.
 
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Rusty Whitten

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Yes, flush with the old thermostat in place or do what I do and remove the old thermostat, cut the center out, reinstall and then flush with no thermostat creating pressure. I have one that I modified 15 years ago and still use it to this day.

Once the flush is complete, install the new
t-stat and be done.

Thank you, I appreciate you taking the time to answer and help me out.[emoji1303]


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GTyankee

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I would suspect that a 2004 radiator is a good percentage blocked & some of the radiator tubes won't clean out with just a flush

I am a big believer in radiator shops, not a auto parts store, a 100% radiator shop.
Call around & see what they charge to have a Radiator Rodded out after you pull the radiator & take it to them, which is a easy job on a 2004.

They will heat the solder up on the 2 tanks & remove them
Put the radiator in a vat of special heated fluid
Then use a flat metal rod down through each of the radiator tubes.
Then they put the radiator back into the tank of fluid & then apply Air & water pressure to blow out the crud.
Then they re-solder the tanks back on, pressure test it, then paint it black & give a like new radiator back to you.

Another thing, if you ever have a bad radiator, or parts like a tank or even a core, go to a real radiator shop & you won't believe how cheap it is to replace the tanks or even the core
Do that instead of going to Autozone & pay over twice what a radiator shop charges
 
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Rusty Whitten

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I called the local radiator shop and gave them the year of my truck. He said that most of them have plastic tanks and can’t be rodded without cracking most of the time. Also, one other thing is that my heater is no longer blowing hot air. I’ve read that the heater core may have junk and debris in it and could be a cause. Will flushing the system help clean out the heater core as well?


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GTyankee

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Once you find out which heater hose is the heater supply line & which is the return line
Usually the supply line will be hotter than the return line.

Remove both heater hoses in a convenient location.
Then take either air if you have a compressor, or a water hose if you don't.
Apply the low pressure air or water into the Return line. the crud will blow out & it will be messy, so take proper precautions
You may need to use a couple of hoses to make extensions out of

...............................................

Did the radiator shop give you any suggestions about the heater core ?
 
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Rusty Whitten

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What you said about it being 2004 and probably wouldn’t come clean with a flush has got me thinking. I’m thinking I should go ahead and pull the radiator out and put a new one in. I don’t want to spend the money on something that may or may not clean it out.

I can replace the thermostat at the same time and flush the core as well.

The mechanic at the radiator shop didn’t say much about the heater core other than replacing it would be expensive and he suggested trying to flush it first.


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GTyankee

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I would take the truck to that radiator shop & let them look at it
If the core is indeed metal & not plastic
You would be ahead of the game having it rodded out

If it is plastic, ask that radiator shop what it would cost to make it right, even the cost of replacing the core
They can get all of the parts cheaper than most other places

It sure won't hurt to have it checked out
 

Dodge 1500 4X4

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Do you have access to a infra red temp gun, It will give you an idea on how restricted your radiator is, The top hose of the radiator will be the hottest, Thats the return from the engine, The bottom hose will be conciderbly cooler going through the radiator, If the radiator isn't clogged, If its the same temp as the top you know its clogged, some heater cores were to be known to have sand castings in them from factory, I know you have a 2004 so it might be clogged, try a good flush kit and get to one where you can separate the 2 heater hoses usually the larger one is your supply or hottest one, use your garden hose spray attachment and flush it through the heater core in both directions, You may get it unclogged, Let us know how you make out!!!
 
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GTyankee

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I always back flush the heater core

If everything comes into the supply line, that means the crud builds up on the side side of the core
By doing a back flush, it should break the crud up & push it out the supply line
 
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Rusty Whitten

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Thank you for your input. I will definitely flush the heater core, and make a decision about the radiator shortly. Weather isn’t going to be too good here the next few days, so it’ll be a few days before I can touch base and let you guys know how everything went. Thank you again!


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Rusty Whitten

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Update: Flushed the radiator and discovered a small leak on the right side while doing so. Looks like either a trip to the radiator shop or replacing it is in order.

I ran the engine for about twenty minutes with the heater on and honestly couldn’t tell which heater hose was the inlet or outlet. Both were warm with neither side noticeably hotter. Something else other than the heater core needing flushed?

As for the thermostat, I’ll be taking it to a buddy’s garage when he gets back in town so I can work on it there.


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Rusty Whitten

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Update #2. Radiator shop installed new radiator and thermostat. They tried flushing the heater core but it’s completely stopped up. However truck is running hotter than before. I’m taking it back over shortly, but does anyone have any idea what the potential problem is?
 
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