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Radiator Cap: vented vs non vented - what is needed?

Super-Bee-69

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i have a dumb question:

me and my tech had a big discussion about vented vs non vented radiator caps. as we just set in a new 22" us radiator plus fan shroud plus new water pump for my cooling issues of the 69 super bee with no coolant recovery tank, 383 engine and no air condition - this discussion came up!
the car was running on colder days at 205° and on warmer days up to 210° and in stop and go above.

tech said, with the vented cap (stant 10331) the system can't produce any pressure as it immediately goes off and a non vented is needed to build pressure and run cool.
i say, with quickly rising temperature the little vent closes and the system gets pressure and everything is ok.

so, what's the issue with the different caps and what came original with these cars??
 
Pressure only raises the boiling point and has nothing to do with running cooler. Non vented cap? Didn't know you could even get one. What happens if you over pressure the radiator? Something is going to give and you hope a hose does it before you split the radiator. Put a dang douche bag on it and recover your coolant when it expands so it's not always leaving a puddle everywhere you go. Are you running a shroud on the radiator and what type of fan system does it have? Did you know straight water actually cools better than a 50/50 mix of antifreeze? WaterWetter is supposed to do a good job too. I have run straight water before with good results but you had better run a water pump lube and corrosion inhibitor in it. You can buy it as a mix too.
 
You sure he's not thinking of the gas cap? lol Never saw a non vented radiator cap before. They come in different psi ratings but all I know of are vented when the pressure gets to the psi rating of the cap.
 
Yup....questioned that in my 2nd sentence. Never heard of a non vented radiator cap but he's talking about cooling......
 
I remember back in the day, you could buy a radiator cap that had a button on it to press that would (supposedly) let the pressure off. I haven't seen one in years though.
The correct cap for your car should be 1686107. 16 lb. If you want original looking it should look like this.
They are on EBag but pricey ... you may be able to pick up a used one somewhere.
$_12.JPG
 
I remember back in the day, you could buy a radiator cap that had a button on it to press that would (supposedly) let the pressure off. I haven't seen one in years though.
The correct cap for your car should be 1686107. 16 lb. If you want original looking it should look like this.
They are on EBag but pricey ... you may be able to pick up a used one somewhere.
$_12.JPG

The button cap worked best with a coolant recovery system as without...hot coolant sprayed out.
!6 pound cap max on a copper rad...22 on aluminum

I found the best solution is a 6 blade steel fan with clutch...half in a shroud(blades)...50/50 solution and a 4 core copper rad or 2 one inch row aluminum...crossflow rads work best but are not pleasing to look at
 
You can simply order vented or non vented radiator caps. Stant offers them both!
Thinking about a clutch with the six blade steel fan.
With my actual setup I'm running at 195°f on a 68°f day not that cool I'd like to have it!
 
Got it.....always learning.

A ‘Vented’ cap = ‘Closed’ cap – ‘Vented’ means is sucks from the ZERO PRESSURE tank as it cools down. ‘Closed’ means it does not go to the ground.

A ‘Non-Vented’ cap = ‘Open’ cap- ‘Non-vented’ means it does not suck coolant back into the cooling system. ‘Open’ means when the pressure gets too high it dumps onto the ground.
 
Right!
So, why should one use a vented cap without a recovery tank? Or will it do the same job in this situation as a non vented, as we all have a partial pressure cooling sytem?!
 
There is no non vented rad cap. They all have to vent at the psi rating plain and simple. The older ones with no coolant recovery tank would just vent to the ground and if a car was running to hot it could vent (release) at the set psi usually from about 5 to 22 psi and coolant could vent on the ground. Most stock caps are around 12 psi but I see them as low as 5 and as high as 22. The newer cars with a coolant overflow bottle just let the coolant vent to the recovery tank when it hits the psi rating and vents. Then when the cooling system cools down after the car is shut off it goes into a vacum and then the rad caps vacum valve opens and the cooling system can suck the coolant back into the rad. Most cars running normal and not overheating dont usually even reach the venting psi in normal driving but when they do in very hot weather its nice to have an overflow bottle (Recovery tank) to catch the coolant so it can get sucked back into the cooling system and not lost on the ground.

Bottom line is you cant have a non-vented rad cap as the system has to vent at a high enough psi and it also has to have a vacum release valve in the cap or it could suck the hoses shut or even do more damage. Ron
 
A non-vented cap is used on older cars without coolant recovery systems. If the engine overheats or the coolant level in the radiator is too high the cap will push coolant out the overflow tube onto the ground. When they started equipping cars with coolant recovery systems they added a tank connected to the overflow tube plus a vented cap, and the radiator was filled to the top. The vented cap pushed out coolant if the car ran hot like the non vented cap and it went into the tank. The difference is the vented cap allowed a vacuum to be created when the car was shut off, drawing the overflow coolant out of the tank and back into the radiator. I learned this when I added a coolant recovery tank to my 63 Oldsmobile and I will be doing the same on my 67 GTX.
 
No need for a tank. Two-eared 16 pounder as pictured. I don't like seeing the stant caps with the red lever. Stant makes good stuff, just don't like the "modern look of the lever.
 
the only difference in the caps is the rubber seal for the top of the rad neck....the ones without the seal vent coolant to the ground.....the ones with the seal are used with overflow bottles so the fluid can be drawn back into the radiator.

There is no such thing as a "vented" or "non-vented" radiator cap.....that term is for gas caps.....all radiator caps are pressurized to hold the coolant in the system until a certain pressure is reached, then it lets it out the overflow tube
 
ok - that's the usage for these two styles of caps. got it!
stant describes them as "vented" / "non vented".
 
No, no, no - don't mean the lever vented!!


Sorry but 10331 is the part number you posted in the begining..........................................

- - - Updated - - -

What you need is a Stant 10231 or if you want original looks go to Classic Industries .
 
Some very inaccurate information has been posted.

Learn here about the difference between vented and non vented caps.

https://www.coolcatcorp.com/Radiator Caps/Radiatorcaps.html

Sometime the term "partial pressure" is used for a vented cap.

Mopar definitely used a vented cap for many vehicles back in the day, whether the car had a recovery reservoir or not...1968 B-bodies for example. Look it up in the FSM.
 
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