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Ok, if you have a leak and are low on coolant, there will come a point the coolant level will be too low and you'll overheat. If your heat out of the vent problems is because of low coolant level, then you're likely pretty close to that point you'll start to overheat.

Ummm, WK2 coolant isn't any more special than any other vehicle, they all have their own specific anti-freeze recommended for them.

20 years ago the manufacturers started switching to long life anti-freeze with varying results, so they started developing their own types of long life anti-freeze. So there are a dozen different types of anti-freeze out there, many of them incompatible to mix with one another, and the manufacturers recommend only one specific one for their vehicle.

The problem is that the aftermarket is selling anti-freeze without identifying what type it is, most of it is just Dexcool, and they allude to it being a universal anti-freeze, which Dexcool is perhaps the least compatible with other anti-freezes of all of them. Prestone has been sued in Trademark Court and the court found they could not substantiate their claims for their "all makes, all models" anti-freeze. But they still make the claim.

If your O.M. recommends HOAT anti-freeze, Zerex G-05 is the aftermarket equivalent, the exact same formulation for HOAT that Chrysler, Ford and Mercedes used for years. You can find it at most Auto-Stores, it dyed the Ford Amber instead of the Chrysler/Mercedes Pink/Orange, probably because there are more Fords than them.

If your O.M. recommends OAT anti-freeze, I haven't seen anyone figure out which of 3 or 4 types of OAT it is. Nor have I seen anyone identify a specific aftermarket equivalent. So you're kinda of stuck with having to get the coolant from the Dealership if you don't want to take any chances.
 

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Ok, if you have a leak and are low on coolant, there will come a point the coolant level will be too low and you'll overheat. If your heat out of the vent problems is because of low coolant level, then you're likely pretty close to that point you'll start to overheat.

Ummm, WK2 coolant isn't any more special than any other vehicle, they all have their own specific anti-freeze recommended for them.

20 years ago the manufacturers started switching to long life anti-freeze with varying results, so they started developing their own types of long life anti-freeze. So there are a dozen different types of anti-freeze out there, many of them incompatible to mix with one another, and the manufacturers recommend only one specific one for their vehicle.

The problem is that the aftermarket is selling anti-freeze without identifying what type it is, most of it is just Dexcool, and they allude to it being a universal anti-freeze, which Dexcool is perhaps the least compatible with other anti-freezes of all of them. Prestone has been sued in Trademark Court and the court found they could not substantiate their claims for their "all makes, all models" anti-freeze. But they still make the claim.

If your O.M. recommends HOAT anti-freeze, Zerex G-05 is the aftermarket equivalent, the exact same formulation for HOAT that Chrysler, Ford and Mercedes used for years. You can find it at most Auto-Stores, it dyed the Ford Amber instead of the Chrysler/Mercedes Pink/Orange, probably because there are more Fords than them.

If your O.M. recommends OAT anti-freeze, I haven't seen anyone figure out which of 3 or 4 types of OAT it is. Nor have I seen anyone identify a specific aftermarket equivalent. So you're kinda of stuck with having to get the coolant from the Dealership if you don't want to take any chances.
I will go to my local mechanic this Saturday and top up the coolant - he said he has some Chrysler brand name coolant. As far as overheating: engine runs a bit colder than usual (usual temp is abot 3/8 of gauge and now it is between 1/4 and 3/8) at highway speeds - is this a sign of low coolant or thermostat stuck open? I watch that needle like a hawk all the time.

If I top up the coolant this Saturday - should I reset check engine code? Or is it better to leave it so that dealer can see it?

Related question: if coolant low is actually a problem and I fix it by topping up - is Check Engine supposed to go away by itself eventually? Or does Check Engine always need to be reset explicitly?

Also: wouldn't I get a "Coolant low" message on EVIC? It does this for windshield washer fluid which is much less important.
 

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I checked coolant level in the radiator by removing radiator cap and it was not low, just were it was supposed to be.

Then one hour later I started driving and noticed that "Check Engine" light is no longer on. Go figure...

I also filled up the coolant in the overflow tank because it was at the "Add" level there. I overfilled about 1.5" over "Full" mark - is this a problem? Should I try to remove an excess?

Note that there are 2 kinds of Mopar coolant: one is already diluted with distilled water (1:1), another one is not and you need to dilute it yourself before adding. Dealer I was at today only had non-diluted.
 

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Thank you so much everyone for the different perspectives and scenarios. It helps keep my cool and my money in my pocket before running and spending $$$ on perhaps parts I don't need.


I recently did a cooling system flush. Drained everything, refilled with distilled water, ran the jeep with heater on until fans kicked in. Drain and repeat for about 5 cycles. Then I proceeded to refill with recommended coolant and repeat the process. then drained it and put more fresh coolant just to avoid having too much water in the system. Jeep has ran great no issues until it sat over night and on my way to work the light turned on. Took it to AutoZone to read the code, and P0128 popped out.


I have not seen it go over 193 degrees, and stays around 185-188 while driving on the highway. It goes up on city traffic to 193 but then it comes back down no problem.


Just idling in the parking lot it wont go passed 176...


I made sure I bleed and burped the system well.


Based on what everyone has shared, I will wait about a week, to have 4-6 cold to hot cycles and then if it still remains, I will replace the Tstat.




Thanks!!
 

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well after a week with it ON, I came home last night and disconnected the battery overnight and so far it has not turned on yet. but temps are good and steady.
 

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I checked coolant level in the radiator by removing radiator cap and it was not low, just were it was supposed to be.

Then one hour later I started driving and noticed that "Check Engine" light is no longer on. Go figure...

I also filled up the coolant in the overflow tank because it was at the "Add" level there. I overfilled about 1.5" over "Full" mark - is this a problem? Should I try to remove an excess?

Note that there are 2 kinds of Mopar coolant: one is already diluted with distilled water (1:1), another one is not and you need to dilute it yourself before adding. Dealer I was at today only had non-diluted.
The overflow tank is just what it says it is, when the coolant gets hot it expands and forces it way past the pressure cap and into the overflow tank, when the coolant cools and contracts it creates a vacuum and sucks coolant back in from the overflow tank. The tank level itself doesn't indicate anything other than, if the system is working properly and not sucking air from a leak, then the level will go down first on the tank.

If you overfill the overflow tank, it does nothing, the worst that will happen when the system gets hot and forces fluid out in the tank and there is too much it goes out the drain at the top of the overflow tank.
Thank you so much everyone for the different perspectives and scenarios. It helps keep my cool and my money in my pocket before running and spending $$$ on perhaps parts I don't need.


I recently did a cooling system flush. Drained everything, refilled with distilled water, ran the jeep with heater on until fans kicked in. Drain and repeat for about 5 cycles. Then I proceeded to refill with recommended coolant and repeat the process. then drained it and put more fresh coolant just to avoid having too much water in the system. Jeep has ran great no issues until it sat over night and on my way to work the light turned on. Took it to AutoZone to read the code, and P0128 popped out.


I have not seen it go over 193 degrees, and stays around 185-188 while driving on the highway. It goes up on city traffic to 193 but then it comes back down no problem.


Just idling in the parking lot it wont go passed 176...


I made sure I bleed and burped the system well.


Based on what everyone has shared, I will wait about a week, to have 4-6 cold to hot cycles and then if it still remains, I will replace the Tstat.
Those temps are low, you should have a 203°F thermostat, meaning it fully opens at 203°F, so you can run a few degrees lower, but not much lower.

I, and I've seen others post, they maintain 193°-195°F minimum, no lower. That can easily climb up to 203°F for heavier loads or stop and go traffic, where air is not be forced into the radiator by forward motion.

If you sitting still with the engine idling, depending on the outside temp is, the engine temp will slowly climb above 203°F until it gets to 222°F, and then the electric fan will turn on and cool the engine down to 203°F before shutting off again. This is normal.

If you're maintaining temps below 193°F once you've reached full operating temp, it sounds like something is wrong. You thermostat could be bad and stuck open and allowing lower than designed temps. And you should be seeing it go over 193°F.
 

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Quick question for the group. New to this forum so thank you in advance for taking the time to read and respond. I will verify once again but I believe I have the P0128 code. I am going to proceed with the thermostat replacement but wonder why I wasn’t able to erase the code. Any ideas?
 

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Quick question for the group. New to this forum so thank you in advance for taking the time to read and respond. I will verify once again but I believe I have the P0128 code. I am going to proceed with the thermostat replacement but wonder why I wasn’t able to erase the code. Any ideas?
Check first if you are low on coolant, and that requires opening the pressure cap to the radiator (ONLY WHEN THE ENGINE IS COLD). If you're low on coolant, that could be causing the engine to take longer to warm up. So clearly you need to find your leak and fix it.

Is the engine running at normal operating temp while driving? If not, its likely the thermostat. If it is, not likely the thermostat, if you're changing it yourself the thermostat is cheap, so it can't hurt to try a new one.

What were you using to read the codes, some tools do NOT erase codes or require you to follow a specific procedure to erase the code. My OBDII tool will only erase the code when you have the ignition on but the engine NOT running, then you have to turn the vehicle off and back on again after erasing the code and before removing the tool. I don't have those conditions set when I try to erase the code, it won't do it.
 

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Thank you for your response. That did the trick. I need to push the start button twice in order for the vehicle and my scan tool to sprecken ze same lingo. Once I figured that out i was able to clear the code. I have yet to change out the thermostat/housing but will get to that this weekend and no doubt will have to clear the code for a third and final time. Once again, thank you for your response. Now I need to find someone to help with a transmission filter replacement snafu that I brought on myself. I dropped the pan and let the fluid out (at 80K miles it needed it) but neglected to measure how much I took out. When I originally went to the dealer with my plan to change all fluids (except coolant) they asked what I wanted to do. I said "everything it needs, not sure what that entails". They asked for the last 8 of the VIN and provided me with a list from which I selected a) rear differential, b) front differential, c) transfer case, d) transmission, e) engine. They loaded up a box of goodies and almost 400$ later I set out on my way confident in what I needed to do. With vehicle level, the front and rear diffs were straight forward as was the transfer case (even though they gave me the wrong fluid and then proceeded to argue with me about that). Engine oil, easy peasy. Where it gets interesting is the transmission. Again, I neglected to measure what I took out because any research I did online pointed in the 5qt. range. I didn't have the warm fuzzies about that so I did more research and found where the level is dependent on fluid temp and that you need a special dipstick to verify quantity (in mm's). According to the chart provided with the dipstick as well as any online research the consensus appears to be that at 167-170 deg F the level should be 60-70 mm. Problem is is that at that temp and with 5 qts replaced the dipstick was showing just north of 100 mm's. Which simple math tells you that at 60-70 mm's it should only take 3 to 3.5 quarts. I am slightly dubious of that. I can't quantify that since my dumb#$$ didn't measure what came out but 3 to 3.5 quarts seems a bit low. Dealer told me over the phone ( and they were less than helpful btw) that it would be somewhere between 5-8 quarts. Any thoughts?
 

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Discussion Starter · #70 ·
Well guess what at 187k I got p0128 again. I totally forgot I did this back in 2015. Looked up this thread and see me on it. Will time to do again. This jeep has been very good so far
 
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