2003 4.6 2v Need Opinions

[ThatBlack4.6]

So I bought an 03 7 or 8 months back and immediately regretted that decision. The day I first drove it, it over heated at idle in a driveway. Ever since, I've been chasing the issue to no avail. Replaced Water Pump, Thermostat, Radiator, and the Coolant tank. It will take water until full, I'll drive maybe 10 minutes and it'll overheat. Left me on the side of the highway once, so I need to get this fixed asap.

It had a plug blow and had to be retapped before I'd gotten it. It may have blown again, kinda loud on the driver's side rear of the block.

Anyway, the problem is, it's using ALOT of water, overheating, and idles rough like it's missing. What I don't understand, it still runs good. It'll get up and go still, doesn't smoke like a head gasket, no coolant or water in oil, I'm stumped at this point. It'll just get hot and steam out of the coolant cap.

What could it be? No leakage on the ground, no water in oil, nothing coming out of the exhaust. Anyone have this problem before? It did sit for a while before I bought it, a while as in years.

 

[Shuttleman83]

Check rad cap, make sure rad coolant level is 50/50 mix, relieve system of air bubbles.

 

[ThatBlack4.6]

Check rad cap, make sure rad coolant level is 50/50 mix, relieve system of air bubbles.

Does the coolant mix really matter short term? On a budget currently, so I have to use tap water until I can get rolling.

Also, how could I tell whether my coolant cap is bad or not. When it gets hot, it'll spew steam from somewhere around the rad, so I think it's the coolant cap unless there's somewhere it's supposed to vent when over pressured.

 

[weendoggy]

That uses a degas tank and the cap is pressurized to a point. It will expell if hot. These are much easier to purge than a normal system. My question is, does the fan work?

 

[Shuttleman83]

Also check thermostat gasket, direction and flow, and also whether it is fully opening.

 

[Shuttleman83]

Tap water is bad, use distilled water and only for a short period. You need a true 50/50 mix and to expel all air bubbles.

 

[weendoggy]

Does the coolant mix really matter short term? On a budget currently, so I have to use tap water until I can get rolling.

Tap is fine for testing. I use softwater and have for years with no issues. Use the correct coolant diluted and you'll be fine once done.

 

[Shuttleman83]

It's ok for testing but it won't boil as well from my testing. My car overheated much easier with tap vs straight distilled.

 

[Hot Stang]

Check out heater core for leakage.

 

[TIGGER]

Other things to check are the intake manifold and that coolant tube that runs under it. Sure is a weird problem. Hope you figure it out.....

 

[Hot Stang]

If you get an air pocket it will overheat. Fill rad then you can put cap on Start and let run till it warms up just enough for thermostat to open. Turn it off and leave sit a few till you can take cap off. I think you'll find it might be low. You should be able to top it off with car running now.