Plumbing a radiator without a cap?

-
purplehazenils

purplehazenils

Well-Known Member
Joined
Aug 11, 2013
Messages
269
Reaction score
162
Location
Sweden
Hey guys, I got ahold of this used junkyard aluminium radiator for my dart to solve the cooling issues. Only thing is Im not sure how it should be installed.
It has no radiator cap, no problem I thought Ill just use an external one or an "inline filler neck" like pictured below. But whats with the hose? Its not an ATF cooler, there is only one opening.
Is this for some sort of pressure guage or is it for an overflow system? From what I understand the overflow hose should be "outside" the pressure release valve like in the second picture.
Any info would be great.
 

Attachments

  • WP_20140821_15_27_25_Pro.jpg
    52.4 KB · Views: 778
  • CBR-Inlettee.jpg
    24.6 KB · Views: 894
Is that where the draining petcock goes? What is that other thing above the hose? Could that be the other ATF line that has been plugged?
 
As above... remove the hose and see if it is a drain point. Then see if it connected to the port above, in which case it is a cooler.
 
The hose just leads into the water reservoir, the thing above it is a mounting bracket. The drain plug as at the top left in the picture. So there is just the inlet, outlet, drainplug and this hose opening.
I could just plug it and go but I'm curious and if its for a clever recirculation system id like to use it.
 
Maybe a return from the heater. Water pump may feed the core and it returns there.
 
It's most likely a line to the fill/expansion tank. My bmw uses a cap-less radiator and my dads mustang as well. Both of those vehicles use a pressurized expansion tank.
 
1994redram said:
It's most likely a line to the fill/expansion tank. My bmw uses a cap-less radiator and my dads mustang as well. Both of those vehicles use a pressurized expansion tank.
Click to expand...

Aha thought it could be that. But in this case is there a radiator cap on the expansion tank?
Anyone know if the tank size is very important and specific to the application?
 
Back in the day, some FE block Fords used expansion tanks that had a pressure relief cap (radiator cap) on them. IIRC, the tank held about 1½ qts. The tank was the highest point of the cooling system. This was before the days of coolant recovery systems and double sealed caps.
 
Yes. The expansion tank will have the cap. I know that on my bmw the radiator sits a bit lower than the motor and the heater core. So the expansion tank is used to fill and bleed the system.

If you cap the line off and use the in-line fill cap that you posted, in your upper hose. You should be fine. That'll definately be the highest point in the cooling system. I'm not an engineer by any means but I HATE the expansion tank design. It's extremely problematic on the BMW's. It's considered a basic maintenance item.
 
Done well and done right the expansion tank design is excellent for getting the air out of the coolant and keeping it out. It should have the pressure cap and the cap should be the highest point in the system. When possible most water pumps will benefit from having the bottom of the tank feed the center of the pump impeller. All localized high points should have a small bleed hose or tube that goes to the top of the tank.

The inline cap design is a bad one. The coolant flow acts to reduce the effective pressure below what the cap is rated. To get the pressure that you want you'll have to run a racing type cap with a higher pressure. I can't predict how much higher, you'd have to experiment.
 
Turn the rad upside down and I think it'd be a purge to get the air outta the rad.. to the expansion tank/filler..??
 
nm9stheham said:
Not getting this.... can you 'splain more?
Click to expand...
The coolant flow apparently is enough to pull a vacuum on the bottom of the cap, depressing the point where it will vent to some pressure below it's actual rating. Mr. Bernoulli at work. That is the real reason why those Ford FE engines had that mid-hose "expansion" tanks. Not for more capacity or to act as a reservoir, but to create a volume where the flow was so slow that this didn't happen.
 
corvettes used a remote cap / tank deal too. not even in the main hose

64-corvette-022.jpg
 
I'd mount a small fill/expansion tank on the inner fender,, run a heater hose in and out,, with that small rad hose to a fitting at the top of the fill tank,,.. not the overflow..

LOL,, outposted again.. just like pic above,, tank can be smaller of any design..
 
Great info here, thanks everyone. Im going to try go with the expansion tank route. Just one thing Im wondering about.

When filling a system like this with a cross flow radiator from empty you wont be able to fill the radiator 100%. There might be around 1" of air left at the top. Will the rest of the coolant expand enough to push this air out and later suck coolant back from the reservoir and fill the radiator 100%?

Maybe its not that important, its a big rad for a pretty mild 360. Any thoughts?
 
Why not take it to a rad shop and have a neck welded on? It seems like that would cost around the same as running an expansion tank setup. It would probably look cleaner too.
 
If the radiator has an epoxied core then welding is a dicey option.

purplehazenils said:
Great info here, thanks everyone. Im going to try go with the expansion tank route. Just one thing Im wondering about.

When filling a system like this with a cross flow radiator from empty you wont be able to fill the radiator 100%. There might be around 1" of air left at the top. Will the rest of the coolant expand enough to push this air out and later suck coolant back from the reservoir and fill the radiator 100%?

Maybe its not that important, its a big rad for a pretty mild 360. Any thoughts?
Click to expand...
There needs to be a bleed hose from the top of the radiator to the expansion tank. These are necessary at any localized high point in the system. Then it will self-purge the air out of the system. This hose need not be very big. ~6mm should do it.
 
ntsqd said:
If the radiator has an epoxied core then welding is a dicey option.


There needs to be a bleed hose from the top of the radiator to the expansion tank. These are necessary at any localized high point in the system. Then it will self-purge the air out of the system. This hose need not be very big. ~6mm should do it.
Click to expand...

Good stuff, I seem to be all set then. Going to go with this tank pictured below and place it over the inner fender as high up as possible.
Thanks for the help!
 

Attachments

  • 04186_1.jpg
    12.3 KB · Views: 285
You must log in or register to reply here.
-

Back
Top