Hi, all.

My first post here and am hoping for a little help with coolant issue that has me stumped. The truck is an 03’ Dakota. It has a 4.7L with 263K on it.

For the past few months, I seem to be losing a little coolant every few days. So far I’ve replaced the coolant filler neck and radiator cap. The radiator is only a few years old. I ran a pressure test which found a minor drip in a heater bypass hose, which I’ve fixed. It seems the drip only showed up with the pressure test because the area always dry before that. Current pressure tests show less than 1 PSI drop, after leaving it pressured for 20 minutes at 21 psi. I’m guessing that’s acceptable.

Now here is the thing. I can fill up to the neck with coolant while cold and leave the overflow at half capacity. After a day of driving, and full cool down, the overflow bottle ends up full and the neck is empty. In other words, it seems to be pushing coolant out to the overflow tank, but not sucking it back in when cool, as it’s supposed to. Overall, I’m still losing coolant somewhere though, as I end up adding here and there. I found no further leaks, none in the heater core either. If this was a head gasket issue, I guess I’d have coolant in the oil and vice versa… I see nothing, plus again, it passes pressure tests.

Maybe you guys have come across this before. It’s a minor annoyance now, but I want to figure it out before it gets worse.

Thanks.

Oil and coolant clean.




Overflow started out with half capacity, now full after a day or two


Coolant neck shows no coolant after day or two. Takes about an ouce or two to refill.


20 min pressure test start

20 min pressure test end