My truck has been trying to climb up to the H every few days in this past week and a half. It is really annoying and alarming me. I was driving down to SC 2 weekends ago and it started to overheat out of the blue. I looked and the coolant was pretty much gone. I had it towed back, the Tstat replaced, system flushed at the local garage (smart people there) and the problem went away for ~5 days...now it is back. I just added about 2 quarts of water to the truck tonight with the heater running full blast. I did notice that the coolant was "frothing" at the neck of the radiator while I did it. I really don't believe the system has any in air it. I just replaced the radiator cap tonight also just as a precaution. Where could the coolant be going? I'm not mixing it with the oil, I'm not leaking anything, the floor boards are dry (heater core would be shot if they were) and I don't believe I'm burning it so what gives? I'm sort of stumped. I'm hoping to plug it the Consult port and see if any codes are coming up. TIA.

quote from you

My Frontier kept "loosing" fluid and come to find out the upper rad. hose was shot and the fluid was "evaporating" from the upper hose through the center (where the string stuff is) of the hose.

could it be the same prob? is there white smoke from the exhaust?

No white smoke from the exhaust. I know the hose is going bad...AGAIN, but I don't think I could loose that much in just a few days. Then again you never know. I tried to buy one tonight but the parts store closed 10 min. before I got there. It is on the task list tomorrow. We shall see how it goes.

is the the hose that runs from the cap to the coolant resevior clogged or pinched ? if it is=then that can spike the temp and it wont be able to vent so it ends up being reciruclated=and bingo! its starts to overheat real fast

happened to some pepz i know.

Heck Az-Ser, I didn't really think of that. That hose is just a cheap 1/4" hose so I'll replace that too. I'll post back with results as time goes on.

I filled it back up last night and replaced the radiator cap and it still tried to overheat to day. Well I think I finally found the problem out...air in the system. I opened the air relief valve and heard it gurgling (? spelling) and hissing with air. I did a quick bleed to the system according to the FSM, left it idling for ~10-20 minutes and haven't had a problem yet. Before I couldn't leave it for 5 minutes without it kicking the fans on. The service garage did the work. I will see how everything goes in the next week or so.

I think what originally caused it was the coolant level got too low, let air in and the rest is obvious from there. I'm going to replace the hoses this weekend just for a precautionary measure (age of the hoses and the upper needs to be replaced anyway).