Radiator hose routing (overpressure version)

[DAVID_T]

In my radiator setup I have two overpressure valves. They are both on the upper side caps (one cap is on the radiator, then I have a remote cap for accessibility).

Is it OK to hook these hoses up to the overflow tank as they are? When I look at diagrams online I see some that have an overflow connected to the top, and the bottom of the radiator, and some not.

And is there a specific way to connect them to the overflow tank? I notice one hose connection is deeper in the tank than the other.
Thank you!
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[michael everson]

You can put a T on them and hook them together tot he lower tube on the overflow. Or buy a higher pressure cap for the radiator and it will probably never open.
Mike

[egchewy79]

What mike said. Put a #16 cap on the more accessible one and hook that up to your overflow tank. Put a #20 cap on the other one and you shouldn't need to worry about hooking it up to anything since the #16 cap will pop open first.

[CraigS]

I agree w/ chewy. Also cap the nipple on the radiator. Both caps, regardless of pressure rating, are set to allow coolant to be sucked back into the rad through that nipple. But air is easier to suck than coolant, so you will be sucking air back into the radiator rather than sucking coolant back from the tank. I usually use a piece of fuel hose w/ a bolt in one end, and two mini-clamps.

[rich grsc]

I agree w/ chewy. Also cap the nipple on the radiator. Both caps, regardless of pressure rating, are set to allow coolant to be sucked back into the rad through that nipple. But air is easier to suck than coolant, so you will be sucking air back into the radiator rather than sucking coolant back from the tank. I usually use a piece of fuel hose w/ a bolt in one end, and two mini-clamps.

This is very important to understand, just a higher psi rated cap won't solve the problem.

[seagull81]

I have the same radiator with the 19 lb. cap. I put a rubber cap over the outlet on the radiator and a 16 lb. radiator cap on the remote tee fitting and plumbed that one to the overflow. It seems to work fine for me.

[narly1]

While we're on the subject of rad hoses and caps a question.

If using the CobraEarl style of thermostat housing & filler neck/rad cap, can you do away with the inline rad cap in the upper hose?

Earl

[Hoooper]

Just put a cap on the radiator and use a plug instead of the nipple. If you go with a higher pressure cap there you arent evacuating that little bit of air thats trapped in that spot anyway, might as well just cap it up and reduce complications

[DAVID_T]

Great! So I'll cap off the radiator vent and use a #20 cap. Connect the remote vent to the lower tube on the overflow. What connects to the higher tube on the overflow? Thank you, again.

[egchewy79]

put a length of fuel line to the nipple connected to the higher tube. this will allow your system to puke out any excessive coolant in the system when the engine gets warm. I zip tied this tube to my X member so it's directed directly under the car. When the car/coolant has cooled off, you just want to make sure the fluid level in the overflow tank is above the bottom nipple fitting otherwise you'll be sucking air back in the system when it cools down.

[DAVID_T]

The higher tube is still lower than about half of the radiator system, is that going to be a problem? Do I want to run that hose up a little bit so it doesn't drain the system straight out, or is it pressured enough that it won't do that on its own?

I also discovered that my two radiator caps are rated at 19 and 22-24 PSI. Would I be alright swapping those two? The important part is making it so the one gives before the other, correct?

[CraigS]

I think 19 on the filler and the 22 on the rad will be fine. Can you show us a pic of your overflow tank please.

[rich grsc]

A 19# cap may blow the hoses off that corrugated tube.

[DAVID_T]

I installed it based on some other photos I saw of placement.

*Well, I'm not sure why the photos are sideways in the post, they are oriented properly on my phone. Oh well.

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[egchewy79]

The higher tube is still lower than about half of the radiator system, is that going to be a problem? Do I want to run that hose up a little bit so it doesn't drain the system straight out, or is it pressured enough that it won't do that on its own?

I also discovered that my two radiator caps are rated at 19 and 22-24 PSI. Would I be alright swapping those two? The important part is making it so the one gives before the other, correct?

you'll be fine. the fluid only flows when the coolant temp reaches a certain temp, opening up your valve in your T neck. This pushed the hot fluid into the overflow. If too much fluid enters, it'll dump out of the higher tube inside the canister onto the ground. When the engine cools off, the vacuum in the system will pull the fluid back into the system through the lower tube in the canister. Since there's a valve that opens and closes, this system is not subject to the regular hydraulic forces in the rest of the coolant system.

[DAVID_T]

Thank you all, very much!!

[NAZ]

There are caps called Blanking Caps that will close the fill neck that do not have a pressure relief function. You will have to block off the overflow fitting. There are also caps that do not have the vacuum valve, they're called non vented like this one: https://www.summitracing.com/parts/aaf-all30134 Neither of these caps will suck air into the system when the system cools.

Regardless of what cap you use, you should familiarize yourself with cap sizes and how to measure to determine which size you have.

The pressure relief (lowest pressure radiator cap in this context) should be at the highest point in the system.

Good luck, and have fun with your car.