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Discussion Starter #1
well, i've searched the section and found a lot on coolant leaks, but nothing like my situation.

i have a 2004 4.7L dakota. high miles (241,000) but everything has been running great, but lately i have had some problems with my cooling system. i noticed that my truck temp would start to get higher & later found that my E fan had died. i ended up replacing it with a higher output fan and deleting the fan clutch. everything has been good with no issues for a little while. but then i noticed one day that i could smell coolant. later i found (what i thought) was a leak from the radiator. so i had that replaced.

fast forward to present. i found after parking an odor of coolant again. but when i checked, it appears that it is coming out of the overflow tube. but when i looked in, the level appears to be fine. i thought that it appeared to be bubbling a little, but i'm not sure if that was just from the engine running. later after the engine cooled, i added a little less than half a gallon via the radiator cap. i still notice the coolant leak sometimes when i park (odor & visual fluid around the side & plastic skid plate). when the engine is cool, i still have to add coolant via radiator cap. after i add coolant, i have no problems what so ever. i can tell when the coolant is low b/c when sitting @ idle for extended periods of time, i notice the temp gauge starting to climb. thing is, the overflow bottle doesn't seem to change. it seems to stay the same level no matter if it's been sitting overnight or right after i get done driving and i know that some coolant has leaked out.

anyone have any pointers on what else i can check out?
 

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Check/replace the cap and the lines to the reservoir.

You are supposed to add coolant to the reservoir, not via the cap. As the engine heats up fluid will go into the reservoir, when it cools, it returns to the system.

A bad cap or a leak in the lines and it doesn't work.
 

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Discussion Starter #3
sorry, forgot to mention, i replaced the both upper and lower hoses (so cap is new with the upper hose) when i replaced the radiator. hoses & radiator are less than a month old.

i did not know i was not supposed to add through the cap & only through the overflow. but if that is the case, i would not be adding anything b/c the overflow bottle is full. thing is, the level doesn't change, which is weird b/c i have seen coolant (although just a drop or two) coming out of the little downward facing tube, but the side of the radiator & plastic skid plate are wet. after i add coolant through the cap, when i'm sitting at idle for a while, there are no problems and the gauge is where it should be. but after it has leaked some, the temp gauge starts to climb if sitting at idle. but when i look at the overflow, it is not low or empty.
 

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Something is making it drip and you should be seeing the level change if it does.

I'm wondering if you have a small head gasket lead. Put a pressure tester on the system and see what happens.
 

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Discussion Starter #5
i will have to try again. i had it done just before (that's how i found out the fan was dead) and they said they couldn't find a leak.
 

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Discussion Starter #6
just an update in reference to my situation.

i didn't think i had a problem with the thermostat since if i topped off the coolant & sat in traffic, i didn't have a problem. only when i lost coolant out of the overflow tube & drove with a low level (in traffic) would the needle start to rise. well, i replaced the thermostat and everything appears to be good so far (knocking on wood). no more signs of the coolant spitting out of the overflow tube, and no more worrying about overheating. i wish i would have tried this first instead of replacing the radiator, lol.
 

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Discussion Starter #7
well, looks like i'm back at square one. everything was good for about 10 days, but now the overflow is spitting out fluid like it was before.

if anyone has any other suggestions, please let me know. i'm going to try flushing the system and then replacing the thermostat again.
 

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Did you stick with a Mopar thermostat? I've had no luck with aftermarket ones on the 4.7s but as soon as I stuck the Mopar ones back in they worked fine - go figure. I would try and burp the system again and see if you've got any trapped air in it - put the nose up a little and make sure the heat is on high. On the 4.7s I've owned it's taken a couple of times to completely get the system clear of trapped air. Also while the system is pressurized check the heater hoses. I had a small pinhole on one in my Ram that wasn't very noticeable but during the cooling phase it actually allowed air into the system creating the "heater core gurgle". A bad radiator cap could indeed allow too much coolant to enter the reservoir during the thermal expansion phase. One thing I've learned over the years is "new" doesn't always mean "functional". I've gotten more than my fair share of bad parts straight out of the box.

Having done that I would say if all the hoses are good and you have a known good thermostat it's time for a leakdown test.
 

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Discussion Starter #10
crossing my fingers.......i replaced the thermostat again (with a MOPAR thermostat). also found i had a leak from my water pump, so i replaced that too. all the hoses look good. no leaks or anything. everything is running as it should, no coolant coming from the overflow for now. last time i did it, it was good for about 10 days.

the only thing i don't get is when this does happen, the level of the overflow doesn't change. even though the fluid is coming out of the blow out tube.
 

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Check/replace the cap and the lines to the reservoir.

You are supposed to add coolant to the reservoir, not via the cap. As the engine heats up fluid will go into the reservoir, when it cools, it returns to the system.
I know a lot of people are taught to do this, but I would strongly recommend against this practice. The purpose of the overflow reservior is to capture coolant that escapes the system due to expansion and over pressurization. The overflow reservoir replaces the previous way of just dumping coolant onto the ground. To work correctly, the overflow reservior is supposed to be a sealed system and the theory is when the system cools down, negative pressure in the radiator draws the captured coolant in the overflow reservoir back into the radiator.

If you fill the overflow reservoir when the engine is cool, there are two consequences with that.
1) When the engine has been cool for awhile, there is no negative pressure to draw in new coolant, the pressure differences in the system stabilizes and no coolant will flow between the overflow bottle and the radiator. Because there is no additional coolant in the radiator, overheating is still a reality and you can't really tell how low the level is from observing the overflow bottle. You can have plenty of coolant in the overflow bottle and still be dangerously low inside the radiator.
2) Once the engine warms up, positive pressure begins to rise and coolant is more likely to flow towards the overflow bottle, if you've topped off your coolant by pouring it into the overflow bottle, there will not be room in the reservoir bottle if coolant from the radiator has to flow into the reservoir. This will result in overflowing the bottle and causing a leak which negates the pressure differential which the system works on

If you try filling the reservoir while the engine is warm, there are similar issues. Once you remove the cap, you lose the pressure differences that allow the coolant to flow back and forth. And when pressure is lost, you can lose the drawing pressure for the coolant to get back to the radiator.

The correct way to top off your coolant level is the same way it's been done long before manufacturers added the overflow reservoir. Allow the engine to cool, remove the radiator cap, physically look into the opening and pour the coolant in until you see it about an inch below the opening. This is the correct way because you will physically see the level. You can never tell how low the coolant is inside the radiator, by filling the overflow. (Those "max" and "min" marks on the reservoir aren't there to tell you how much coolant to add, they are there to tell you how much coolant in the system has expanded, and to let you know if the overflow system is working)

Ed
 

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/\

From the 2000 FSM:

"Do not remove radiator cap to add coolant to system. When adding coolant to maintain correct level, do so at coolant reserve/overflow tank."

and

"COOLANT LEVEL CHECK
The cooling system is closed and designed to maintain coolant level to top of radiator.
Remove radiator cap. The coolant level should be to top of radiator. If not, and if coolant level in coolant recovery bottle is at ADD mark, check for:
* An air leak in coolant reserve/overflow tank or its hose
* An air leak in radiator filler neck
* Leak in pressure cap seal to radiator filler neck"

In a properly functioning system, you only add to the overflow.
 

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I still have to disagree;

"The cooling system is closed and designed to maintain coolant level to top of radiator.
Remove radiator cap. The coolant level should be to top of radiator.
"

If you ever suspect being low on coolant, you can not determine the level of the coolant in the radiator by the overflow bottle. Thats just a fact. Unless you have X-ray eyes, you can never see how much coolant is in the radiator. The only way to tell is to remove the radiator cap and look inside. If it's low, you add coolant to the radiator, not the overflow bottle.

Ed
 

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FSM = Dodge Factory Service Manual.

If you're low on coolant the overflow tank should also be low. It should be drawn back in as the engine cools - in a properly functioning system.
 

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Discussion Starter #15
well, this is where my situation doesn't make sense. the overflow bottle level *never* changes. after i see the coolant spitting out of the overflow tank tube (depending on how many days i wait to add), i can add as much as 1/2 gallon of coolant through the radiator cap. but the level in the bottle is *always* the same. i will know that i have to add b/c after it has come out of the overflow tube, if i sit in traffic the temp will start to climb.

the other thing that doesn't make sense is why is everything fine for a week or so, but then all of a sudden it starts spitting it out again.

this gets frustrating. i have replaced the thermostat twice (last time with a MOPAR thermostat) and flushed the system with prestone super flush once.
 

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well, this is where my situation doesn't make sense. the overflow bottle level *never* changes. after i see the coolant spitting out of the overflow tank tube (depending on how many days i wait to add), i can add as much as 1/2 gallon of coolant through the radiator cap. but the level in the bottle is *always* the same. i will know that i have to add b/c after it has come out of the overflow tube, if i sit in traffic the temp will start to climb.
How is the coolant spitting out of the overflow tank if it isn't filling up?

Are the hoses and tank in good condition? No cracks?
 

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Discussion Starter #17
How is the coolant spitting out of the overflow tank if it isn't filling up?

Are the hoses and tank in good condition? No cracks?
i have no idea. that's what is annoying me is that no one seems to know why. when i drive to work and i check, i can see coolant has come out through the tube (opening of the tube is wet and all under the tube & around the battery is wet), and i have popped open the overflow and it was still at the same level as it always is.

all hoses and tank is in good condition. upper & lower radiator hoses were replaced with the radiator less than 4 months ago.
 

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The coolant is going to expand as it warms up and go into the overflow tank. If the system is overfilled it may overfill the overflow tank.

When did you see the bubbles that you mention in your first post?

Can you rent a pressure tester and put it on the radiator fill neck and start the engine? Watch the pressure as the engine warms up. It should be smooth. If it pulses you have a bad head gasket.

The radiator cap, is it OEM? What pressure is it rated for?
 

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Discussion Starter #19
the radiator cap is not OEM. but it was replaced with the upper hose assembly & radiator. it is rated @ 16lbs (i think)

i will have to try to see if i can get my hands on a pressure tester. thanks for that tip.
 

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Not sure with the '04 Dakota but in '01 it used a 21 psi cap. It should open between 19 and 23 psi according to the FSM.

The '04 Durango says the cap should hold 19 psi and open at 20, a 20 psi cap.

Something to consider.
 
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