Guys on my 92 F-150 my antifreeze that is in the overfill container always ends up going somewhere and the container doesn't leak anywhere. What's weird is that it's not burning antifreeze and it is not showing up in the oil what could be going on? 302EFI motor if that helps...

 

Do a pressure check. Then do a visual check making sure to check your freeze plugs on the block especially the ones hidden by the engine mounts, the rear of your intake and your heater core.

 

Weak radiator cap spring is causing the release of coolant and it is overflowing from the resevoir and then when the engine is turned off--the coolant is drawn back into the radiator. The resevoir is empty or low--and the coolant gets lower and lower .

Probably need a new radiator cap. Have it tested. Very common with these Fords. Every one that I looked at when shopping for mine had this same apparent problem.

 

I believe that is the way it is suppose to work.
If the rubber on the vacuum check valve and the lower seal are OK the cap will come off the lower seal at whatever pound cap you have.
If the coolant level is at the mark in the reservoir when the engine is cold the coolant will not overflow the reservoir when hot. Coolant will only expand so much from hot to cold and the spring will not make any difference.
The job of the spring is to raise the boiling point of the coolant, the higher the spring tension the higher the boiling point.

 

You have a leak someplace. It may be in your heater, radiator, hoses, crack in the engine or a gasket.
You will just have to put a pressure tester on the radiator and see if you can find it.
Cooling System Tester:

If that does not find it put air pressure in each spark plug hole while that piston is at the top of its stroke and listen at the tail pipe, where you put the oil in and check for bubbles in the radiator.
Air tester:

Also check the hose between the radiator and the reservoir. Also check the upper seal of the radiator cap to see if it makes a good seal to the radiator.

 

It is supposed to do what it is doing. Water and antifreeze expands when it is heated - a significant amount actually, and by doing so it takes up more space. Since it expands when heated it has to go somewhere - so they put a little tube to the radiator "overflow" tank to catch the fluid. As the truck cools off the fluid shrinks a bit and creates a slight vacuum and sucks most of it back into the radiator. Now, if you are adding coolant weekly, daily, and for god's sakes hourly, you definitaly have a leak and need to repair it. But if you aren't adding any cooling to this thing you have nothing to worry about. It is functioning just the way it was designed to.

 

Yeah--the cap should release coolant and pressure at 13 PSI.But if the spring is weak--it will release at a lower pressure and actually cause the coolant to boil--because the boiling point is lowered when the pressure is lowered.

A weak cap spring will cause the reservoir to overflow when the truck is operated. Then the cooling coolant when be drawn back into the radiator when the truck is turned off. One will lose coolant and the reservoir will be empty or low.

Pressure check the cooling system and then the cap. I saw dozens of F150s of this vintage that had this problem.All had empty reservoirs and the coolant was about two inches down in the radiator. None had apparent external coolant leaks and none were leaking into the oil.

If your reservoir is full when the truck is hot --and it is empty when the truck is cold--I really would suspect that the cap is bad--especially if there is no signs of leakage on the outside of the block nor in the oil--as you have already stated.

 

Yes it will in Colorado, but he lives in Kansas and without pressure it boils at a higher temp. in Kansas.
No it will not. Why would it lose coolant?

Somebody is not checking their coolant system.

This is what it is supposed to do. It will drop down to the cold mark on the reservoir and will not overflow when hot.
You do not fully understand coolant systems do you?
Please reread what T.R.Bauer posted and I posted above.

 

Subford:

We are getting a little personal here--aren't we??

The altitude of the location that the truck is located shouldnt have an effect on the trucks cooling system if the pressure of the cooling system is maintained at the correct pressure. You are making my point here--that the cap or the system isnt maintaining the correct pressure. With no apparent leakage--the cap is suspect.

The cap should permit the coolant to expand and should release pressure when necessary--it loses coolant when it is working correctly--that is how the reservoir fills. But coolant will be totally lost if the coolant overflows from the reservoir onto the ground--if the cap doesnt control the amount of coolant that expands thru the cap into the reservoir. And a weak pressure spring will cause an abnormal amount of coolant to past thru the cap into to the reservoir and then onto the ground. And when the truck is stopped and the engine is turned off--there is no overflow from the reservoir to the ground--because the pressure and expansion of the coolant decreases and causes contraction of the coolant in the radiator--and thereby `causes a vacuum that draws the reservoir coolant back into the radiator.

It is unlikely that all of these trucks were just low on coolant--when the inside of the reservoir was still damp--right up to the top of the reservoir!! Not normal-and only a pressure loss (without overheating being involved) would cause this situation. Abnormal expansion of coolant is caused by overheating or low pressure in the coolant system in my experience--that predates overflow bottles by the way(pre 1968).


And no--it isnt normal for the reservoir to be completely full when the truck is at operating temperature--that isnt normal. And no--it isnt normal for the reservoir to ever be completely empty. The operative word is "COMPLETELY".

I do think that I understand cooling systems--and am willing to learn more--but I cant follow your points.

The point I am trying to make--and not to denigrate your point of view--is that this happened on my truck--loss of coolant,no apparent leaks, no overheating,empty reservoir/engine cold and full reservoir/engine at operating temperature. And a new cap fixed this problem on my truck.

Again--pressure check the coolant system--and then check the cap.

 

There is no question in my mind that cooling systems need a good cap in order to function properly. And the cap, because of the pressure that it holds, is a very important part of the cooling system because this pressure does significantly raise the boiling point of the coolant. If the cap isn't holding the pressure it can cause all kinds of problems - no matter if you're a mile high or in Death Valley. However, with this kind of cap failure, one would most likely find that the radiator is filling the coolant overflow beyond its capacity and it wouldn't take much time for the radiator to be significantly low on coolant too. Although, I doesn't necessarily have to be the case. So, I wouldn't hesitate to say that both of you are correct in your statements.

 

I would add just one more point, the pressure cap only holds the pressure that it is rated for above the atmospheric pressure where it is at.
So where a 13 LB cap is good in Texas and to get the same boiling point in Colorado you would need a 15 or 17 LB Cap and that may not be enough if you go high in the Mountains. You will boil a lot more water off in Colorado than in Kansas with the same cap.

phoneman91
I did not mean to get personal but I like to correct the information where I can so we do not put out bad information. That way we can help the Posters.
Of course I have no idea of your expertise or experience in these matters but I have worked in and around these cars and trucks for over forty years.

 

Indeed. You're not in Kansas anymore