coolant problem

[noblebrown]

99' 3.0
as winter started here in PA I had to replace the coolant assembly that sits on the firewall due to severe rust. Now I appear to have a leak at the reservoir. Im thinking that its coming from the pressurized cap. When I turn off the car I can actually here what sounds like a boiling water sound from the engine if its hot enough. The temp gauge will suddenly jump from nothing to normal temp after I've been driving it for 10-15 mins. I'm wondering if I either have air in the system, a bad cap, a bad thermostat or a bad head gasket. Are there any other possibilities and how should I go about eliminating them while troubleshooting this problem?

[peterf1992]

most likely the reservoir they are well known to leak

[soundu]

Originally Posted by noblebrown

99' 3.0
as winter started here in PA I had to replace the coolant assembly that sits on the firewall due to severe rust. Now I appear to have a leak at the reservoir. Im thinking that its coming from the pressurized cap. When I turn off the car I can actually here what sounds like a boiling water sound from the engine if its hot enough. The temp gauge will suddenly jump from nothing to normal temp after I've been driving it for 10-15 mins. I'm wondering if I either have air in the system, a bad cap, a bad thermostat or a bad head gasket. Are there any other possibilities and how should I go about eliminating them while troubleshooting this problem?

Take the degass tank off and carefully inspect the bottom for cracks.
If you have any, replace it along with a new cap.
Put a new motorcraft stat on while your at it,

If your lucky,you don't have a head gasket going bad.

If the car is high mileage, a water pump replacement is not a
bad idea either

[Automender12345]

Buy the degas tank and cap from Ford because the aftermarket tanks have quality problems. I also have heard the threads on the aftermarket tanks won't hold the cap on right. You may not see open cracks but look close and you will see lines that are not supposed to be there. I had the same issue on a 2001 Taurus, both the heater manifold and the tank. Also make sure the little upper hose from the bottle to the radiator is secure. Last week I was dripping a little coolant and I could pull that hose off both connections even with the spring clamps on.

[noblebrown]

ok thanks ill check into it and let you know what i find

[noblebrown]

ok so im kinda broke rite now but wanted to get a better idea of what was wrong so i removed the cap to the degas tank and ran the engine hoping to see something telling. i added a little bit of fluid to bring to the cold level where it should be before turning on the car btw. I watched the fluid level stay steady with no movement for a few minutes and then the level began to rise (meaning the thermostat and water pump are working, right?). after another few minutes an air bubble or two popped up. i turned off the car thinking it might overflow soon. replaced the cap and ran the car at idle for about ten minutes or so. no leakage that i could notice. Considering the bubbles that I saw I checked around the headers to see if anything was leaking. nothing. no water in the oil or billowing blue or white smoke. also it didnt overheat, but like i said it was only idling. when I worked on the coolant system just recently I replaced the whole assembly at the heater core (just the hose assembly) and I dont believe I "burped" it properly. Does this sound like my likely problem considering the observations i mentioned earlier?