Coolant indigestion

[tmcalavy]

Heh heh it'll happen, miles from home when you don't have your phone or it's dead...shoot it after you kill it, don't leave it lying there wounded.

 

[acceleracion]

Overflow tank is a bit of a misnomer(wrong name) as it sounds like if it is used something is wrong, i.e. it overflowed!!!, lol

When you heat up a fluid, like coolant(or water), it expands with temperature.

As the engine/rad coolant heats up it expands, this puts pressure in the system, rad cap is usually rated for 16psi of pressure, when the pressure in the system reaches 17psi the rad cap's large spring is pushed up and the now "extra" coolant is pushed out thru the overflow hose and into the overflow tank.
When pressure is relieved and drops to 15psi rad cap spring closes to maintain the 16psi.

The other part of this system involves the smaller spring/valve in the rad cap, yes there are TWO valves in a rad cap.
As engine cools off the coolant shrinks, when engine/rad pressure reaches -1psi the smaller spring in the rad cap is sucked open and coolant in the overflow tank is sucked back in.

For this system to work right the overflow tank must ALWAYS have coolant in it(which is why there is a COLD line on the tank), and the overflow hose must not leak.
If overflow tank is empty, then when engine cools off it will suck air into the rad instead of coolant.
It is easier to suck air than fluid, if there is a leak in the overflow hose OR anywhere in the engine/rad/hoses it will suck air from that leak point because it is easier to move the air than the coolant in the overflow tank.

If you are losing coolant slowly then you do have a leak, most likely in a place where coolant evaporates on hot parts before reaching the ground.

Best place to start is to make sure overflow system is working.
Cold engine, top up rad and fill overflow tank to COLD line, if tank level is hard to see get a straw or short stick and mark it with fluid level, put it in the cab and check fluid level the next time engine is cold, this will tell you how much coolant you are losing.

Also clean out the overflow tank next time you do a flush, any debris in the overflow tank will settle at the bottom, which is where the overflow hose is, this can block coolant from being sucked back into the rad on cool down

Hi I'm having a problem with my truck. I see that if you have this much knowledge, spot on, about the cooling system; you could probably answer this for me.

The new cap that I got is stamped steel. Got it from autozone. No clamp on top of it. When I lock it on it twists on past the locking cam 3/4 turn thread with very little effort.

I've worked on a few different cars, Japanese, korean, german, and american cars. I've seen plastic thread on caps, I've seen the ones like ours 3/4 turn with locking cam, but every single radiator cap I've ever dealt with required a slight amount of effort to twist/lock on.

My radiator is aftermarket could there have been a different year chosen where the cap is different from the stamped steel one that I have. I've seen a black plastic one for sale too could that be the one?

Eddie

 

[acceleracion]

So yeah brand new cap leaks.

 

[acceleracion]

That's the one I got

The one I think is correct. My overflow line comes out like the one in this picture.

 

[acceleracion]

Well found my answer had the wrong cap on there for years. Correct cap is http://www.fordparts.com/Commerce/PartDetail.aspx?n=qPHKQgBo7JbfsrQSWdYdfQ%3d%3d&id=331879852&m=2&search=true&year=1994&make=Ford&model=Ranger

Rs-76

 

[Mark_88]

Looks like you have it figured out~!

Good to get there on your own with just a bit of help...

 

[acceleracion]

Just wanted to add that I purchased the ford part at the dealership only 13 dollars and solved the problem. by the way the cap I found online is totally different from the one the dealer gave me.