4.6 2v Boiling bubbling hissing noise.

PikesPeakPony · Jul 10, 2013

Iv noticed every time I shut my car off after a descent drive(anything that allows the engine to warm up fully) I can hear a bubbling or boiling noise from inside. and when I get out It's a loud hissing. I figured it has to be something with the coolant. My gauge never shows overheating, My coolant level is good to go, coolant looks clean and healthy, Diagnostics check showed no codes. Im stumped. It's a totally stock NPI 4.6 2v. Its got 149K on it so I wouldnt be surprised if it needed some cooling system help. but im not even sure if thats what it is. anybody have/had this on theirs? I'll be posting a video soon when i leave to run some errands later today hopefully my Iphone will pick the sound up.

miss.mod.50 · Jul 10, 2013

I'd start by trying to 'burp' the cooling system, just to make sure there isn't some air trapped in there.

PikesPeakPony · Jul 10, 2013

miss.mod.50 said:
I'd start by trying to 'burp' the cooling system, just to make sure there isn't some air trapped in there.

Do I just remove the cap and run the engine to do that?

miss.mod.50 · Jul 10, 2013

Not sure if i'm doing this the 100% ford approved way but on my 02 i removed the reservoir cap, let the car idle with the cap off until the t-stat opens and that burped the air out of mine.

Your issue might also be a sign of the known NPI intake cracking, but I'm no NPI-guru so maybe one of those guys that's had it happen can chime in here to see if this sounds famaliar to them...??

joekd · Jul 10, 2013

If you smell antifreeze and/or see the steam it's likely the crossover cracking, you say you hear hissing so that;s my guess. If it is just air trapped in the system you wil likely be overheating as well, if it is just noise it could be nothing.

Here is the method taught to me by a Ford technician to get air out:

The best and quickest way to do it is. Pop the coolant temp sensor out of the intake (either one works fine) as this is the highest point in the system. Top off the reservoir tank and cap it. Fill through the intake (where you removed the sensor) until it starts to come out. Unscrew the reservoir cap and you will see the coolant in the intake drop a little. Keep doing this until you cannot fill it anymore through the intake. Put the sensor back in and run the car. Usually I wait until the fan comes on then shut the car down. Wait for it to cool then pop the sensor back out and top off if needed.

If you fill it through just the reservoir you will probably get air and the car will overheat

MustangChris · Jul 10, 2013

take out your glove box and inspect for a bad heater core.

burn the system exactly how miss.mod described as well.

PikesPeakPony · Jul 11, 2013

alright thanks guys ill give all this a shot

DeepList · Jul 11, 2013

Hissing sounds are usually just air under residual pressure. The cooling system is closed and always under pressure when the engine is at operating temperature. Sometimes even after letting the car sit for a while, you'll hear the hissing release of pressurized air when removing the expansion tank cap. As suggested above, try burping the coolant system by running it for a while with the cap off and see what happens.