Radiator fluid level

[militarypotts]

My truck operates at about 190 degrees all the time. My question is this, when I look into the radiator, the cooling fins are always visible and not covered with fluid. If I add any water, (to cover fins) its only a matter of a short drive before its down to the fins again. It appears to boil out the overflow tube. Never any leaking under the truck when it sits for awhile. No signs in the crankcase oil. Just seems like the truck doesn't want the radiator topped off. Any suggestions?

[kwai]

Your cap might need to be replaced.

[maskale]

You could replace the cap out of peace of mind.

But, radiator basics.

You fill it cold. As the fuid heats it expands and what ever that expansion is the excess fluid gets pushed into the reservoir. As the fluid cools back down it will not necessarly draw all that fluid back in because of the cap and its pressure rating.

If ur not over heating, and the level stays constant, dont worry about it. You technically dont even need a reservoir, its only a catch can and only tops off the rad if there is a leak, and that only buys u time before you run out of coolant and over heat if you never watch the gauge or your check driveway once in a while for a leak or dont pay attention to that sweat smell as u get out of the truck.

[Tyson]

Does your truck have a catch can? If not you could always add one to give you peace of mind. I've seen some guys make there own out of a military canteen which is a pretty neat idea. Or you could always buy a universal one from summit. I think there selling them for about $20 bucks.

Sent from my DROID2 using Tapatalk

[randyscycle]

You could replace the cap out of peace of mind.

But, radiator basics.

You fill it cold. As the fuid heats it expands and what ever that expansion is the excess fluid gets pushed into the reservoir. As the fluid cools back down it will not necessarly draw all that fluid back in because of the cap and its pressure rating.

If ur not over heating, and the level stays constant, dont worry about it. You technically dont even need a reservoir, its only a catch can and only tops off the rad if there is a leak, and that only buys u time before you run out of coolant and over heat if you never watch the gauge or your check driveway once in a while for a leak or dont pay attention to that sweat smell as u get out of the truck.

Not exactly.

There are sealed systems and non-sealed systems.

The M715 isn't a sealed system, so if the pressure and temperature gets over a certain point it will push out whatever coolant isn't needed via the overflow. The stock radiator cap design doesn't have a valve that allows it to pull any coolant back into the system as a sealed system (i.e. one with a separate reservoir) when the temperature drops and the system goes into a vacuum when it cools off.

You'll find that the M715 in stock form has a self-correcting sort of coolant level. Top it off, let it purge what it doesn't need and it will be happy there. Keep topping it off, and it will keep pushing out the excess. Just the nature of the old beast.

[kwai]

And if the spring in the cap is wore out it will vent at a lower pressure thus lowering your water below the top of the core. A normal system will have water just covering the core.

[militarypotts]

Well Randy, my truck seems to have this so called "self-correcting" fluid level. It's absolutely for sure, that once I top it off to cover the core, I can drive it for 1/2 an hour and when I get to where I'm going it will develope a small puddle of fluid under truck. Happens everytime. I ordered a new radiator cap some time ago because I thought that was the problem, but was never able to use it because the one they sent was to large. Will an auto parts store pressure test it for me, and can I pick up a replacement at the local parts store? Thanks.

[kwai]

As per the manuals:

1. Fill the radiator to within 2" of the filler neck opening.
2. The radiator uses a 15 psi cap. You can test the cap with a radiator cap pressure tester.

[Barrman]

Once you get everything right. Such as the cap and fluid level. Just check it every so often to make sure it is staying at it "happy level." One of my Dueces stays right up next to the cap and the other is so for down the neck I can feel, but not see coolant. Both self correct back to those spots if I add more.

[MJCougler]

I added an overflow tank to mine, and the clear overflow hose will never be full of coolant; it has an air pocket. Possibly I need to put a small hose clamp on the connections. But if it overflows, I assume I am catching it.

So, I guess based on these posts, I need a radiator cap designed for overflow tanks? How do I go to AAP and ask for one of these type of radiator caps?

Thanks in advance,