Interesting (maybe?) story and question involving the cooling system

[Liquid_force]

For my 3 y/o's birthday me, wife, 11 y/o daugher, and 3 y/o son along with a few other family members and friends went to a Royals game.

Over 100 mi round trip and it was one of the first hot days of the year so before leaving a popped the coolant cap to check the level and measure concentration (hoping to clear the "low coolant level" light). Looked good.

So - drove 50-60mi to the game which included 5-10 min. idling through the parking lot. Low 80's, A/C running all the way.
Idled out of the parking lot after the game, mid 80's, drove back home and did a half hour of city street driving - air on all the time.

Pulled in the driveway -- splash. The cooling system is puking.
Uhh, ok. I guess it blew a hose.

Naturally, I raise the hood and take a look. There's my coolant res cap sitting loosely so apparently some ***** forgot to put the cap back on, or at least didn't do it very well.

That's a pressurized over-flow isn't it?

How did it keep from blowing out over a 120 mi trip with a half hour of stop-and-go?

 

[LJRuddy]

My bet is your tightened the cap but not enough to make it "click" like the oil fill cap does. It held pressure for a while but after the 1 heat cycle, it worked its way lose.

 

[newshofan]

When I ran my rad cleaner through mine a few weeks ago my cap did the same thing.. I was in a parking lot 30 miles from home at midnight I actually heard mine pop off. Figured I didn't have it on good enough. When I flushed it the next day with fresh fluid and tightened it back up it would just keep twisting off I figured bad thread or something. I replaced it with a new one stant#10238.
So I guess its good to replace every so often just like a traditonal rad cap. Also my old one nor my new one clicks close and if the cap doesn't hold the proper 16psi the fluid doesn't make a complete round through the core and all causing your heat not to work just an interesting bit of info

 

[SHOZ123]

If you cross thread the cap it will ruin the tank and not hold pressure.

 

[newshofan]

Yes I was afraid that the tank thread was bad. But the lady I bought the car from had just replaced the tank with a new one from ford. But she must not have replaced the cap because I believe it was original. I took the cap apart its pretty much a spring type design mine was pretty nasty and seemed almost corroded.

 

[Toolman]

You are speaking of your RES cap, NOT your RAD cap, correct?

 

[SHOZ123]

The reservoir tank is pressurized.

 

[newshofan]

Yes the res cap. I don't believe there is a rad cap on v8 sho. Not like the v6 that has both. And yes the tank has to hold 16psi or the heating and cooling system wont flow right

 

[Toolman]

nm, need to check which section I am in when making a post! Thought we were talking about V6's

 

[newshofan]

Lol hey it happens im sure most of us have done itt