I have a 2001 Ram 1500 4X4 with the 5.9L.about 2 months ago i started hearing coolant flowing into the heater core each morning the first time i stepped on accelerator. this continued most mornings...seems to only happen when the truck sits over night.i recently drained an flushed the system including draining the engine block also.i replaced the thermostat an refilled the cooling system.i still get the sound of coolant flowing into the heater core each morning upon the first acceleration.whenever i pop the hood,the overflow jug is up to full level and the radiator is full.what am I missing? how do i get this seemingly large air pocket out of the cooling system?i've tried parking the truck on a hill with the front end on the uphill hoping that wood help the air work its way out. any suggestions how i can get this pocket out...if infact it is an air pocket? also,the temperature gauge never seems to get very far into the normal range. i'm not sure,but it seems it used to go one or two needle widths farther than it is now.i know the water/antifreeze ratio is correct(60/40,upstate NY). i have what appears to be good flow in the raqdiator.with the cap off i can accelerate the engine by hand an watch the coolant flow out of the fins into the right side of the radiator. any help is greatly appreciated !!!!!

 

my truck has the exact symptoms you described. its been like that for over a year and everything seems to be ok. i did the same things to correct it as you did, and i had the same results. im stumpped on this one.

 

hello stumped....i guess i'll be known as stumped II...lol. i have never had this happen before.i was a tech for approx 9 years on brakes,exhaust,suspension/steering, and maintenance(tune ups,radiator flushes,etc). my coworker(our company tech,heavy truck) is also stumped on this one.he is an ASE master tech.

 

i'd guess that when it cools down its sucking in a little air. it might also be leaking just a tad. retighten all your hoses, especially both ends of both heater hoses.

 

I had this happen just before my radiator core blew out 2 weeks ago.

I'm not saying it's that, but you definitely have a leak somewhere. Check all hoses, around the radiator esp. where it crimps around the plastic mounting pillars, the t-stat housing, and take a peek at the freeze plugs around the bottom of the engine.

TIP: if you see any wet spots on your engine, under the vehicle, etc., and you don't know if they are coolant, you can use either a black light or a flash photograph and it'll show up clear as day.

 

Very interesting. I will have to check for that the next time I have a leak. Thanks for sharing the tip.

 

well, i definatly dont have a leak, i check my system regularly and i have not had a change in coolant level in three months and a pressure test on the system and cap will hold 16psi all day.

 

i also pressure checked my system and it showed zero drop. i then went an purchased a $5 bottle of dye and ran that in the system for approx 100 miles an then went over entire cooling system with a LED maglite an no leaks were detected. the LED maglite works just as well as the black lights.i performed this test before i changed out thermostat and flushed system.i then steam cleaned engine an rechecked with the light a few days later and everything showing clean.here is a pic of my temp gauge at normal operating temperature,it doesnt get any higher.is this normal positioning?

 

on your gauge pic above. that's exactly where mine sits with a 180* t-stat.
how long has it been since your last flush? sometimes it takes a week or so for all the air to perc out.

 

it has only been about 3 days but this problem was present for approx 2 months leading up to the flush.this gauge reading is with a 195 thermostat which is what the books called for.thats also what came out.i did notice the heater core seems to be the high point in the enire cooling system. seems like over time the coolant is draing back to the lower points of system.