changing out thermostat

[ScubaDive]

3.0L 2008
is the thermostat in there with an 'O' ring or gasket and do you get a new one with a new thermostat?
+
do you change them out just on spec. or wait till there is an issue, not getting to temp or temp getting to high?

 

[RonD]

Gasket or O-ring will usually come in the box with new thermostat.....usually being the key word there.
Use a 192 or 195degF thermostat, with a "jiggle valve", yes that sounds made up but it is real, if there is a small hole in the thermostat plate with a metal pin in it loosely fitted, that is a Jiggle Valve, the jiggle valve should be mounted at the 12:00 position, it allows air to escape when you are refilling the cooling system, or is air gets in from a leak, the metal pin "jiggles" with coolant flow keeping the small hole open and clear of debris.

Just like the rad cap, I change my thermostat when I change the coolant, but it really depends on how hard it is to get too and any other work you may be doing on the engine.
Thermostat is not a common failure, coolant leaks are more common and when repairing a leak thermostat is often changed when doing that work.

I have an older model so I change my coolant every 2 years, new coolant types are often 5 years between changes.
Lifetime coolant is the hamster or arctic fox of coolant, 5 years and you are on borrowed time, lol, lifetime being "who's lifetime"

 

[ScubaDive]

Thanks RonD for the feedback, is this "jiggle valve" a special order thing or a common item something I may find at a auto parts store?
I never really heard of people changing there rad cap, well ever.
Just changed the coolant and tend to do that every 2 years maybe 3 at the most. But I have never done the thermostat, I do keep and eye on eng. temp. and my Rangers running temp sits around 89 / 90degC I was just wondering. I have had the ranger since new 2008.

 

[RonD]

Unless it is a very inexpensive t-stat it will have a jiggle valve.
I drilled a hole in the t-stat plates for many years prior to the jiggle valve becoming more standard.

Yes, rad cap failure is not common either, but again it is not an expensive part.
Rad caps have 2 valves inside
The larger one uses the large spring you see when cap is removed, that valve is the pressure rated valve, it holds 12 to 16psi of pressure in the cooling system, as engine warms up the coolant expands(like in a pressure cooker), thats were the pressure comes from, so as coolant gets warmer and pressure gets to 16psi, for example, a 15psi caps large valve will open and allow coolant to flow out and into the "recovery tank"/overflow tank, until pressure is back down to 15psi.
Having the system pressurized raises the boiling point of the coolant or water, water boils at 212degF, 50/50 coolant boils at 230degF, pressure adds about 2degF to boiling point for each pound of pressure, so 15psi pressure adds 30degF to boiling point of water or 50/50 coolant mix
Engines should run 195 to 220degF, but on hot days or pulling loads or long uphill grades temp can climb to 250degF.
Ford temp gauge usually has 210-220degF as center line.

If larger valve should no longer hold pressure you probably wouldn't notice it, UNTIL engine needed to generate some extra heat because of a load, then you would get boil over, coolant flashes to steam in the head and spits out lots of liquid coolant from rad into overflow tank and then engine temp gauge shoots up to HOT very fast, head gasket failure possible.

The smaller valve in the rad cap(center) allows coolant back into the rad as engine cools down.
As coolant cools it shrinks back to its cold volume so pressure in the system goes down to 0psi, and then -1psi, this pulls open the smaller valve and coolant is sucked out of overflow tank and back into radiator, keeping system "topped up".

If this valve fails you would notice collapsed upper rad hose as pressure in the system is -1 to -5, so outside air pressure is pushing the hose in.
Over time this will cause air to be sucked in so you can get random over heating or no heater as air in the system causes air blocks in passages that temporarily blocks coolant flow in the engine or heater core.

Caps are cheap

 

[ScubaDive]

Wow thanks for the write up, I learned something.
Off to the auto parts store to change my cap and get a t-stat.....