Has anyone try using a block tester on the cooling system. This test would let you know if you are leaking exhaust gasses into the cooling system.

 

Not sure about a block tester but we would use the sniffer from an emissions tester. Just stick the sniffer in the opening of the coolant reservoir or just over the radiator cap and check for HC readings. Any HC readings would indicate combustion gasses getting into the coolant passages (leaking head gasket).

Was nearly 100% accurate.

 

ok i drove the truck to work today. once i got back home i popped the hood and took another look at the overflow reservoir. I gave it throttle and let it idle. I did not see any bubbles. I did replace the radiator cap. It still made the noises under the dash when i took off from work but stopped once i was out of the parking lot.

 

Drive it for a few days and see if the noise goes away or gets worse.

 

Just make sure there is enough coolant in the system. Low coolant, because of a head leak, may result in no coolant in the heater core, therefore, no sounds! Just like in nascar, when the temp gauge runs hot, then drops, it means there is no water in the system to heat the gauge.

 

ok i will drive it when i can but like i said in the beginning. it started when i got the truck back from the dealer and i have been driving it since on and off. i havent had overheating issues or low coolant. its just an annoying noise at first.

 

Are you sure the sound isn't coming from your A/C refrigerant lines? My truck had developed a "whooshing" and light "bubbling" sound awhile ago from behind the dash, and noticed it was in conjunction with A/C compressor engagement. A reading on the low-pressure refrigerant side indicated the level was below minimum, and a 12-ounce can of R-134a from the local auto parts store with a charging hose solved the problem. That said, the A/C had never stopped blowing cold the whole time...So while the refrigerant level was low enough to produce a sound, it was not low enough to affect perceived performance in this truck...Which could have easily led to the misdiagnosis of a problem in the cooling system, or worse.

Are you mechanically-inclined enough to check your refrigerant level, or can you have it checked?

 

I never really thought about it being the a/c system. that was the main reason i took it to the dealer because you have to uncharge and charge the system. i dont really have any tools for an a/c system but how do you go about checking the system? i believe myself to be mechanically inclined. i just dont fool with a/c systems much at all.

 

I used this: http://shop.advanceautoparts.com/p/a...=charging+hose

And followed the pressure specifications for this truck from the service manual, which are ambient-temperature specific. One other thought just crossed my mind: If the problem is the A/C system, you could tell right away by starting the truck with the A/C system completely shut off. No sound = Take it back to whoever replaced your heater core and have them properly recharge your refrigerant level.

 

drove the truck a bunk sunday and it still has full coolant and makes some noise at start up. i dont know what is up with it but it still runs like the day i bought the truck. im affraid they left something loose under the dash somewhere.