Running hot randomly after new water pump

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Mississippi Hemi

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Burp line and check for leaks. I had this issue which turned out to have a leak in my Heater Core allowing air in the lines on top of the aux fan being burned out. Hope this isn't your issue. Burping and resetting the thermostat should be the easy fix. I forget those too often.
 

Hardracer

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I'm surprised no one has said u have to clock the t-stat....the little toggle pin thingy up(if I remember right,I dunno).I changed my pump awhile back along with the t-stat....exact same issue you complain about...took the stat cover off again and sure enough, clocked in the wrong place....I believe this doesnt let an air bubble bleed out(reason for little pin I guess).....I freaked on a 80 mile trip and mine hit 224 area....babied it back home to keep the temp down...next morning did the job and after some researching.....some things are so simple that are oftened overlooked.mine does run 203-204 area now when before it never went above 201,both(as far as I know) oem stat......my 2 cents here...have a look and see.
 

Brent 1955

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Here is my 2 cents worth when you replaced the water pump was the impeller cast iron or Teflon. Makes a difference when pushing hot water. Teflon will get soft as the water gets hotter and won't move as much water. Cast will stay rigid. I was having this same problem on my Ram 3500 brought it in to a dealership they replaced it with a teflon one it got worse. I took it home ordered a cast one and changed my thermostat since I had to drain the water my problem went away.
 

Bob1313

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I have seen this type of problem many times. Often it is caused by an air block. This is where an air bubble gets trapped in a high spot in the system and doesn't allow proper circulation. This became more frequent when radiators started being of cross flow construction. (Tanks on the ends of the core instead of top and bottom)
I have seen two different methods used to eliminate the blockage.
Cheapest but less sure is to drain most of the coolant, start engine and when thermostat opens (should be able to see coolant flowing rapidly with cap off. S-L-O-W-L-Y fill keeping in mind that you do not want to put antifreeze in so quickly that the thermostat closes. Doesn't hurt to jack up the side of the vehicle that the radiator cap is on.
Second way, my favorite, is to use a tool called an "AirLift". (Example here: https://www.cpsproducts.com/automotive/cooling-system-tools/
This creates a vacuum in the cooling system and sucks the coolant back into the system.
Used this set up in the truck shops I have worked in.
I have seen heads crack when truck run with air lock. Also can cause wacko gauge reading as the sensors don't work correctly when surrounded with steam.
 

bargainnow

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Check for emissions in radiator fluid . I'm not endorsing any brands or where to buy . They all work pretty much the same

BT-500 Combustion Leak Test Kit or equal​

 

GTyankee

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OK
bleeding air from the coolant system is so simple, no fancy tools

With the engine cold, not running, vehicle on flat ground or pointing slightly up hill.

Look at the water pump, top left there is a plug, That plug is the AIR BLEED

346919-758fe1246a02536a11bac867c3751527.jpg
IF that plug is screwed up & can't be removed, there is an alternate Air Bleed point.
just over on the right side of the pump there is a pipe type fitting with a sensor & a wire
air can be let out there with the engine cold

video of what i am attempting to explain, this guy knows more about our Rams than most people

 

CaptQ

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I was having temp fluctuations from 186-219 (factory setup). Changed the thermostat with a OEM thermostat and no change. Flushed the system and no change. Started getting worse after a yr, 177-221. While waiting on factory parts I changed the temp sensors with a Durlast part from AutoZone and now the max temp swing is 185-206. Stays around 195 normally. Outside air temperature is below freezing. I’ll be changing it again in a few weeks with an OEM temp sensor to see if there’s a difference.
 

RedSRT4Me

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I was having temp fluctuations from 186-219 (factory setup). Changed the thermostat with a OEM thermostat and no change. Flushed the system and no change. Started getting worse after a yr, 177-221. While waiting on factory parts I changed the temp sensors with a Durlast part from AutoZone and now the max temp swing is 185-206. Stays around 195 normally. Outside air temperature is below freezing. I’ll be changing it again in a few weeks with an OEM temp sensor to see if there’s a difference.

You're saying the temp sensor was bad?
 

Sherman Bird

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The radiator cap was off so that any air burped when the thermostat opened. And yes I agree the thermostat did open, hadn’t had enough coffee this morning when I typed that. I guess this thermo just opens a little hotter than the other.

Still don’t know why it’s jumping up to 221* randomly when driving the same routes I always do.

Temps I took just now.

Dash reading:
View attachment 510239

Top hose:
View attachment 510241

Bottom hose:
View attachment 510242

Thermostat:
View attachment 510245

Water pump:
View attachment 510246
Why do you think a cooling system is pressurized, in the first place?
 

Dean2

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Why do you think a cooling system is pressurized, in the first place?
Why do you think it isn't. Rad caps run from 4 to 30 PSI depending on the application and need to be tested occasionally to ensure they are still holding that.

Hope this helps explain it.

Radiator Coolant Recovery Cap, Replace 68442532AA Compatible with Chrysler Dodge Jeep Ram EcoDiesel - 2014-2021 Cherokee Ram 1500, 2017-2021 Pacifica..

61e3mtqcB5S._AC_SL1500_.jpg


What Does a Radiator Cap Do?​

Now let’s talk the same pressure advantage but in an automotive application. A standard coolant mixture of 50 percent water and 50 percent ethylene glycol (such as our own DeWitts High Performance Coolant has a boiling point of 223 degrees. A cooling system using a 15 psi radiator cap will add 45 degrees to the boiling point for a final boiling point of 268 degrees. The real purpose of pressurizing your cooling system is to give the vehicle a higher operating zone in case of extreme conditions. For example, let’s say your classic car normally runs at 180-190 and boiling is not a concern. Then on a hot day the coolant temperature goes to 200-210. This is not a problem either, but then traffic stops, and you can’t move. Now the temperature starts to rise to 240 and without a pressurized system the coolant would boil and spew all over the place. The loss of coolant would eventually fill the radiator with air and the temperature would rise even higher. Remember, none of the above running temperatures have anything to do with the cap rating. They are simply conditions of the cooling systems capability, the ambient air temperature, and air flow. Pressurized or not, air flow through the radiator is critical to maintaining system temperatures. We prefer electric cooling fans but even with a mechanical fan you must ensure the fan is properly spaced within your fan shroud using a fan spacer.

Now if you add the 15 psi radiator cap to the same system, we have increased our boiling point to 268 degrees Fahrenheit as we stated previously. In our stopped traffic scenario at 240 degrees, we will be able to prevent system boiling. While no one likes to see a temperature that high on their dash gauge, with a properly functioning system 240 degrees is not harmful. So, you may be asking yourself why not just install a higher rated radiator cap at 18 or even 21 psi? While yes, this would raise the boiling point further, the extra pressure places a tremendous amount of strain on the rest of the cooling system. You must remember it isn’t just the cap we’re talking about here, but the complete system. Cooling hoses, your heater core, water pump gaskets/seals, and more all become stressed at these higher pressures, which is why we prefer and only sell radiator caps rated at 15 psi for our radiators.



Coolant_Temp_VS_Pressure_Chart_1024x1024.jpgEngine Coolant Boiling Point vs Pressure Chart
 
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Sherman Bird

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All good information, and accurate. But' it leaves out one major reason the coolant surges out of the radiator fill point with no cap present, and what the significance of that is..... cavitation and its properties. Cavitation is mitigated by pressurizing the system.

When I service a cooling system and there is still air present, I can fill the radiator fill point full, install the cap, and in some instances fill the overflow reservoir up high. I run the engine until the temp gauge reaches between 1/2 and 2/3. I shut the engine off, don't touch anything, and go away and let the cooling system cool off completely. Invariably, when I return, the reservoir has gone down considerably, and sometimes the radiator has sucked it all back in. I repeat this process as many times as it takes until the level doesn't change in the reservoir or the radiator stays full or both. I let it cool completely and remove the cap and top off or add to the full mark, if necessary.

As the cooling system builds pressure, the air compresses, and, as physics has it, that air is now a much more compact mass and will seek top. That air will get out through a properly working pressure cap valve, and as the cooling system cools off, it will suck liquid back in. Patience is required, along with working knowledge of how these dynamics work together.

I just now performed replacement of a thermostat in a 2008 4Runner V-8. I did the process as I just described. Works like a charm.

Another process is to pressurize the cooling system as the car warms up, to speed up the process, but it is risky and messy, and I do not do it any more. I have time for the patient, safest way.
 

Dean2

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All good information, and accurate. But' it leaves out one major reason the coolant surges out of the radiator fill point with no cap present, and what the significance of that is..... cavitation and its properties. Cavitation is mitigated by pressurizing the system.

When I service a cooling system and there is still air present, I can fill the radiator fill point full, install the cap, and in some instances fill the overflow reservoir up high. I run the engine until the temp gauge reaches between 1/2 and 2/3. I shut the engine off, don't touch anything, and go away and let the cooling system cool off completely. Invariably, when I return, the reservoir has gone down considerably, and sometimes the radiator has sucked it all back in. I repeat this process as many times as it takes until the level doesn't change in the reservoir or the radiator stays full or both. I let it cool completely and remove the cap and top off or add to the full mark, if necessary.

As the cooling system builds pressure, the air compresses, and, as physics has it, that air is now a much more compact mass and will seek top. That air will get out through a properly working pressure cap valve, and as the cooling system cools off, it will suck liquid back in. Patience is required, along with working knowledge of how these dynamics work together.

I just now performed replacement of a thermostat in a 2008 4Runner V-8. I did the process as I just described. Works like a charm.

Another process is to pressurize the cooling system as the car warms up, to speed up the process, but it is risky and messy, and I do not do it any more. I have time for the patient, safest way.
I completely agree and you have an excellent handle on how the coolling systems work. So given that, what confuses me is why did you ask me why I thought the cooling sysstem was pressurised?
 

Dodge 1500 4X4

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It's pressurized for 2 simple facts for every 1lb of pressure it brings down the temperature of the coolant 3 degrees, so a 15psi radiator cap will be 3 for degrees times 15 psi radiator cap rating total 45 degrees cooler for a pressurized system, this also aides in antifreeze on a (hot engine) to expand thus filling the overflow jug, and when it contracts, (cooling down) to draw antifreeze out of the overflow jug.
 

Dean2

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It's pressurized for 2 simple facts for every 1lb of pressure it brings down the temperature of the coolant 3 degrees, so a 15psi radiator cap will be 3 for degrees times 15 psi radiator cap rating total 45 degrees cooler for a pressurized system, this also aides in antifreeze on a (hot engine) to expand thus filling the overflow jug, and when it contracts, (cooling down) to draw antifreeze out of the overflow jug.
Actually that is not quite correct. The pressure increases the boiling point as described above, but the pressure does not make the engine run cooler. You see the same thing boiling water in a pot a 15,000 feet sheep hunting, it is only semi hot at full roll boil due to the decreased air pressure. All the pressure does is keep it from boiling the coolant out when it exceeds its un-pressurized boiling point.


What Radiator Cap Pressure Should I Use?​


We are asked this question daily and most people misunderstand what the pressure cap does. The cap’s pressure rating has nothing to do with regulating your engine’s coolant temperature, nor will it make your engine run cooler. Depending upon the original application you will see original radiator caps rated for anywhere from 13 psi up to 18 psi. This is the cap’s relief point, at which the pressure exceeds the cap’s designated pressure rating and vents the pressure to atmosphere, either through a drain hose right to the ground (often seen in classic cars) or to a recovery/expansion tank. We highly recommend updating your vehicle to use an expansion tank of some sort if it currently just vents to the ground, such as our universal expansion tank available in several sizes to fit most any engine compartment. But before we go any further let’s discuss boiling points and what it means for your cooling system.
 
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Ramrob20

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1. I replaced the water pump, thermostat, radiator cap, coolant and belt with all genuine MOPAR parts.
2. I made sure the thermostat was clocked correctly (pin at top)
3. This morning I removed the bleed screw and sender unit to confirm there was no air sitting behind the thermostat (there wasnt)
4. Also confirmed the external reservoir is still between min-max.
5. Radiator is full.

I am not overly concerned with 204-208 temps its just odd that under normal driving (45mph and same route I normally drive when it is 204) the truck jumps up to 221 quickly and for no observable reason (not overloaded, extra people, uphill etc).

Ill replace the thermostat with another unit and then test for gases in the coolant, hopefully its just a funky stat or sending unit.
 

Jack W

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1. I replaced the water pump, thermostat, radiator cap, coolant and belt with all genuine MOPAR parts.
2. I made sure the thermostat was clocked correctly (pin at top)
3. This morning I removed the bleed screw and sender unit to confirm there was no air sitting behind the thermostat (there wasnt)
4. Also confirmed the external reservoir is still between min-max.
5. Radiator is full.

I am not overly concerned with 204-208 temps its just odd that under normal driving (45mph and same route I normally drive when it is 204) the truck jumps up to 221 quickly and for no observable reason (not overloaded, extra people, uphill etc).

Ill replace the thermostat with another unit and then test for gases in the coolant, hopefully its just a funky stat or sending unit.
 

Jack W

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I'm fighting the same battle now. We're about to replace the radiator, water pump and tstat. It all started with replacing a clogged heater core and a new tstat. Only thing we can figure is the radiator is partially plugged or the wp impeller is spinning free of the shaft.
 

Sherman Bird

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I'm fighting the same battle now. We're about to replace the radiator, water pump and tstat. It all started with replacing a clogged heater core and a new tstat. Only thing we can figure is the radiator is partially plugged or the wp impeller is spinning free of the shaft.
Replace the radiator. Jack the truck up. Put it on good sturdy stands. Disconnect the battery ground. Remove the starter. Next, knock out both rearmost cylinder block "freeze" core plugs on either side. Obtain a working garden hose and attach a nozzle which will produce a strong stream. Crawl under truck and douche out the coolant passages through those core plug openings. Knock new core plugs in, reinstall the starter, fill with 50/50 coolant and distilled water. Reconnect the battery, start the truck after making sure the cooling system is full.

If the heater core was full of crud, so are the block passages. So is the radiator.
 

Jack W

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Oh jeez, that sounds expensive. I'm not a mechanic and too old to do that job. But thanks for the advice.
 
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