I have a 2003 Dakota 3.9L with 67k miles on it. Ive owned it since 2018 when it had 59k miles on it and havent had much problems at all with it. I started smelling antifreeze inside the cab when I would turn the heater on so I was worried about it being the heater core. I got home and checked under the hood and there was antifreeze barely dripping from where the hose joins the radiator cap on the engine side of the filler neck and when I went to squeeze the hose, it was like trying to squeeze a metal pipe. After it cooled down, I check the overflow tube by pulling it off the filler neck and blowing in it and i could hear it bubbling in the overflow tank and the nipple thats on the side of the filler neck was clear also. I drove it a few days more after that since it wasnt overheating, in fact the temp gauge never got past the center of the dial. I didnt have time to mess with it myself so I took it to a shop and they replaced the thermostat at my request (I thought it may have been stuck open and that was causing the pressure) and the upper radiator hose and cap. I went to pick it up and the smell of antifreeze wasnt near as bad inside the cab as it was before so im guessing when the old hose was leaking, the smell was getting pulled in by the defroster possibly. The wife and I drove around town some (maybe 10+miles) and it acted like it normally does other than the slight smell of antifreeze. I got home and opened the hood while it was still running and the new hose was just as pressurized as the last one...solid to the point I couldnt even squeeze it. My Haynes manual for the truck says it calls for a 14-18psi cap but it came with a 20psi cap. Even if you look up the cap for the truck from autozone or any other store, it shows it being a 20psi cap. I havent drove it at all today and the outdoor temp has been about 32-38 degrees so I went out and check the oil thinking it may be a head gasket but the oil looks fine (not frothy or milk shake looking). I squeeze the hose and it had the feel of a normal hose (not hard). I started it up with the defroster going full blast and let it run 10 minutes or so to see if the hose was getting pressurized by exhaust from a bad gasket but it never got hard until the thermostat open about 15 minutes later. Maybe this is common for this truck and I just never noticed it before but I wouldnt think all that pressure would be good for the upper hose even if it is new. Im thinking of maybe getting a lower psi cap for it and see what it does. Like I said, it never got near the point of overheating even with the old hose and thermostat on it but the smell of antifreeze in the cab is what made me look into it further. Anyone else have this problem or have suggestions on what it could be??....thanks for reading

 

Sounds normal. The coolant will expand as it heats up, which builds pressure in the cooling system. (which also raises the boiling point of the coolant.....) Pressure should build relatively slowly, as the coolant heats up. If the hose gets hard quickly, even before the temp comes up, that's a headgasket. From the way you describe it though, sounds like normal operation.

Haynes is not always the most reliable source for information here. Their manuals tend to be rather generic.

 

Thanks for the reply. I was just rather alarmed at how solid the hose was after driving it a while and like I said, I never really paid attention to it before until I started seeing antifreeze slowly coming out of the engine side of the filler neck. Im guessing it may have been the original hose because there wernt any hose clamps on it and it didnt have the re enforcement bands on each side of the filler neck like the new one has. I was getting some steam on the windshield above the defrost vent before the hose was replaced so I was worried about it being the heater core but since its been fixed, it hasnt done it, it may have been pulling it in from under the hood when the defrost was on causing the steam (im hoping). The shop filled the radiator and the overflow tank but after driving it for a while, I took off the rad cap and theres no fluid in it so I guess im gonna have to add some more but the overflow has the same level in it as it did when I got it back. I though it would pull into the rad from the overflow if it was low but I guess not....lol

 

The overflow tank will fill as the engine heats up. (at or near operating temp.) But, it doesn't go back down until the engine cools. If the overflow stays at the same level, regardless of engine temp, or how often it has cycled, something is awry.

 

Ive not ever taken the rad or overflow out before, is the only way the overflow and rad are connected is by the 1 hose that goes into the side of the filler cap down to the overflow or is it connected another way that I cant see without taking it apart??

 

Nope, just the one little hose that goes to a fitting near the cap. That's it.