Coolant overflow tank pressure question

[Heus33]

I purchased one of those nice aluminum coolant overflow tank to replace my original. After installation I realized that before I solved my cooling issues my truck would boil over and coolant would spout from the overflow tank's snap on cover.

This new tank has a screw on cap that ain't coming off.

My question is am I asking for trouble if my truck does overheat? Or will be 16lb stant radiator cap handle the duty?

 

[Broncobowsher]

That new overflow tank, does it breath at all? it needs to. It cannot be completely sealed. Hopefully the cap does not seal. Try and blow some air into the overflow hose going into it.

 

[backpain]

For most of those alum tanks you need the overflow/refill tube entering the tank at the bottom and a vent at the top. Post pics of the one you have (or from ebay or an ad)

 

[Heus33]

Here's a pic.

I've got it mounted on the inner fender at about a 45 degree angle between the battery and the inner fender.

 

[cgbexec]

Your pressurized radiator cap should not allow coolant past it unless it passes the pressure of your cap. Only then will coolant leave the radiator and travel to the overflow. Then when your radiator cools the pressure drops the coolant is pulled under vacuum from the overflow into the radiator keeping the level full. If your overflow is sealed, then fluit can not travel to and from the overflow and it completely defeats the purpose of having an overflow.

Make sure your radiator cap is working properly. Too little pressure and your engine overheats. Too much pressure and you could damage your radiator or hoses.

 

[NicksTrix]

nice looking tank. you could put a small vent hole in it to get it to breathe.

 

[cgbexec]

It has to have a vent.

 

[Heus33]

So just drilling a small hole in the cap (like a 1/16" bit) should allow it to vent properly?

 

[Broncobowsher]

Looks nice
Look the cap over, there must be a vent or you need to make one.

 

[cracker]

As the commercial for Coors says...."Let's Vent!";D

 

[cgbexec]

It must have been designed with a vent. Without a vent it would not work as a coolant overflow tank. It was designed as a coolant overflow tank wasn't it?

 

[cgbexec]

I was just thinking (which is dangerous). Some Jeeps have closed pressurized coolant systems. They don't use overflow tanks, but they use what is called an expansion tank. These systems usually don't have a radiator cap on the radiator so the expansion tank holds all of the pressure. If your tank was desiged to be an expansion tank, then it would not have a vent.

 

[Heus33]

I'll check it out when I get home - if a vent hole is needed ill make the necessary adjustments.

 

[Broncobowsher]

I was just thinking (which is dangerous). Some Jeeps have closed pressurized coolant systems. They don't use overflow tanks, but they use what is called an expansion tank. These systems usually don't have a radiator cap on the radiator so the expansion tank holds all of the pressure. If your tank was desiged to be an expansion tank, then it would not have a vent.

I know the cooling system you speak of. Not limited to just jeeps. Late model superduty and my grandmothers Taraus were the same way. What looks like an overflow bottle but it is part of the cooling system. It does still vent, there is a pressure cap. the thing is the pressure cap is dry and vents air instead of water.

 

[backpain]

Many(NOT ALL) of these aftermarket Al tanks are modeled after/designed to be catch cans (to meet NHRA rules) for trans, radiator, etc. Many are not designed to recirculate, but merely handle fluid expansion under pressure (and then drain in the parking lot). Properly designed, yes, you can do it fully pressurized. You could buy a vented cap (NOT a pressure release radiator cap, but a vented cap) - but that will be hard to find. Better, drill a small hole (i.e. the closed part of the system ends at the radiator cap), or better yet, drill a hole a route a nice little pice of clear silicone tubing from the hole in the cap to the ground, so if it overflows, it doesn't get on anything you care about.

Is that a 1 pint can? If at least 1 qt, you shouldn't over flow it. It may take some testing to get the right coolant level to keep the engine cool, and not over flow the overflow tank. You will use more of the volume mounted at 90deg instead of 45. But don't change it untill you know you need to. I'll bet you can drill a small vent hole in the cap and be fine.

 

[broncorican]

Here's a question that will bring some laughs. But I have to ask. How tight should the radiator cap be? I’ve tried the 13# and now I’m trying the 16#, because my coolant will overflow into the reservoir and overflow it when the temp reaches 200. The cap shows two arrows that say align with vent hose. If I align them, there is an open-air flow between the radiator and the reserve tank. In other words, I squeeze the top radiator hose and notice that the air will flow into the reservoir. If I tighten the cap all the way, obviously the arrows will not be perfectly align, but when I squeeze the hose it’s tight, no air escapes into the reservoir (even when the engine is warm). Which is correct? . By the way, I’m talking about a 74 EB, recently rebuilt 302 (cut to .40), automatic, fan clutch, all new stuff. Radiator is not in great shape, which is my next item. Thanks

 

[Dan74Bronc]

The cap needs to be all the way on. Push down and turn it clockwise until the tabs on the cap stop against the tabs on the filler neck.

 

[broncorican]

I did this test on my two other cars and found, that when I squeeze the radiator hose it sends air into the reservoir. If I tighten the cap on my EB all the way it does not breath into the reservoir. I've tried it with a 13# and 16# cap. Don't mean to disagree, just want to understand the mechanics behind it. Thanks for your time...
Ed