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Radiator Overflow Bottle

7026 Views 33 Replies 13 Participants Last post by  David McCollam
I've been thinking about adding a radaitor coolant overflow bottle. I've looked at those cheap Interdynamic "vehicle coolant return systems". The small one's bottle is 1.5 quarts. Sizing it up under the hood I can't really find a decent place to locate it. A few questions to anyone who would like to reply:

1) Is this really a good idea? The radiator cap will have to be replaced or modified to allow the coolant to flow back and forth from the bottle via the overflow tube on the radiator filler neck. Isn't this messing with the operational pressure the coolant system is running at? Is there a draw back doing this?

2) If anyone has made this change, just how big a bottle is really needed? What's the approximate volume differential between cold and hot? The cooling system is suppose to hold 6 quarts. Is a 1.5 quart bottle really needed, or could I get away with a smaller bottle?
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I added one last year. I didn't do this to change anything, but more for a catch tank, like SCCA recommends to keeps drips off the course. I got a cheap small one from the local auto parts and mounted it in dead center in front of the radiator. I did not change the cap, but it does seem to move some fluid back and forth.
I would recomend at least 2 quarts. Almost all auto makers use even larger. No modifications are needed to the radiator or the overflow tube. You MUST use the proper cap for a coolant recovery system. The right cap will have 2 rubber seals on it, and a small spring loaded valve on the coolant side. They make caps that have this valve hanging down with no spring on it, you dont want that one. I use a Stant # 329 wich is a lever cap rated at 13 PSI. The best reason to use this system is to keep all air out of the cooling system. No air means better cooling and less corrosion. But for the system to work right the rest of the system must be totally leak free. As the coolant warms up some is forced out the cap into the bottle, when the engine/coolant cools back down a vacuume is created which draws coolant from the bottle back into the radiator. With everything working right you only need to check the level of coolant in the bottle. I hope this was not too long...
Here is a photo of an expansion tank from a VW Jetta installed in a GT.


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Hey OPELMUTT nice photo, I bet the VW bottle would fit in a lot of places. My question is did you modify the bottle in any way? I ask because on the Jetta this bottle is part of the pressurized cooling system and uses a pressure cap on it. Most overflow systems do not use a pressure cap on the bottle, then you would have 2 pressure caps on your cooling system, the one on the rad and the one on the bottle. Does it seem to work for you?
OK - I got caught posting a picture of someone else's installation. Yes, it works well. but I don't know if the pressure cap was modifiedto allow it to act as strictly an overflow tank. The car belongs to Mike in San Diego and he drives it on a regular basis so I'm sure it is totally functional. There is no problem disabling the pressurization feature ishould that be necessary. I picked one up for the FrankenOpel but haven't gotten around to installing it yet. Arizona summers are killers on the cooling systems in the best of times, so I figured this might just provide a tad more efficiency for the system. It's a neat option for the creative modifier and looks just like it should have come that way from the factory.

Bill and the FrankenOpel
Well, cover the VW logo and no one will ever know.
I installed one from Auto zone ( ~ $7.50) before we went to Carlisle in both mine and Vickie's cars. They worked great. I mounted them in the driver side lower corner of the nose of our GTs, directly across from the battery.

Installation took about 1/2 hour for each car. I just really prefer not to have more fluids than necessary leakig out into our envorinment. MHO

Allen Gage :cool:
my overflow bottle i put in my GT is not even a overflow can. its a windshield resivoir off from a 69 bel-air. it has a rubber tube running from the cap to the bottom of the can, and it does catch the coolant, but not always recover it. i think i need to change the cap now i that i remember you need a different type if you have a recovery tank. i had some breather assembly's from part cars, and i cut the snorkle off one of them, and mounted the overflow can right infront of where the snorkel stuck out of the radiator support. had thoughts of building a box to draw air in from the "scoops" in the hood but i dough i'll ever get around to it.
Thanks everyone for the info. I rigged up my own bottle using a 32 ounce Nalgene screw top container that I used for backpacking. They sell them at www.campmor.com for $3.99. Some plastic hose, a hose clamp and a barbed hose connector fitting...done. I was able to fit it right along side the radiator. New radiator cap (thanks for the info on that) and I was done. After it burped out all the air I was amazed at how firm the upper radiator hose was when squeezed, no more sloshing and bubbling noises.


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Picture of new radiator cap and hose to overflow bottle.


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looks great, better than my set up.
sloshy and gergerly noises bt radiator

what causes "celeste" to make those noises as she sits?It gurgles...
hoses look fine

how do I fix her? Did I read Jimsky correct that "If I install a catch bottle it will quit?"

I meant that prior to having the overflow bottle installed, when I squeezed the upper radiator hose it would deform and you could hear coolant and air sloshing around. My GT never made noises just sitting there, like you has described. Anyone have any clues?

It was mentioned in this thread that using an overflow bottle will allow all the air to be purged out of the coolant system. From what I can see that's true. I've now got firm radiator hoses, and no noises when squeezed.
what is a franken opel?

don't take this the wrong way... but I don't know what a franken opel is?

I think I have seen that description somewhere else ..but I don't know where.

gurgle noise

that gurglenoise could be caused by the thermostat and the coolant is beign still circulated by the presure in the system even after the car is stopped ill find out this afternoon.
The Frankenstein Monster - as you recall from Mary Shelley's story - was made of parts scrounged from here and there. It was a creature more or less resurrected from the dead and jumpstarted with a lightning strike. Unfortunately, an evil brain was inserted by mistake and the creature made life miserable for its creator. This pretty well describes my '73 FrankenOpel GT, made to run with pieces acquired in the dead of night, so to speak.

Bill and the FrankenOpel
What's that you say, Igor? I can't hear you over the rattles.
frankenopel is way cool

It makes perfect sense to me now.Thank you for taking time to explain that to me.:D
overflow bottle

has anyone used a mercedes over flow bottels like from a 95 or 97 or so they look like they would work nicely. also about the nalgene bottel how were u able to keep pressure in the bottle since u had to drill a hole in the side how did u keep a good seal. also any more info on the nalgene or any other pressurized overflow bottle would be helpfull.
The Nalgene bottle in my setup isn't presurized. The top of the bottle is open to the atmosphere. As the coolant expands is flows out of the radiator and into the bottle (fed to the bottom with ample extra fluid in bottle). Engine off, coolant cools down and is sucked back into the radiator.

I didn't drill any holes in the bottle to mount it, I used a large hose clamp (that I pop riveted to the car body) to hold the top of the bottle. Mounting a second lower clamp was difficult, so I used some shock cord to secure the bottom of the bottle.

I drilled one hole in the bottle to feed the hose to the bottle's bottom. A second small hole was drilled in the top screw cap to assure the bottle stays at atmosphere, and to provide overflow ability if required.
Stainless Steel Overflow Tanks

Having just reinstalled the stock air filter housing and snorkel I need to relocate my overflow container, in fact I need to find a new tank as the current one is oddly shaped and doesn't seem to fit anywhere else.....well maybe in front of the radiator but due to summers here I'm not keen on having any part of the radiator covered.

My question is...does anyone have experience with these new cool stainless steel overflow tanks (tubes) I've seen on ebay...i.e.2x10 or 2x13 or 2x15.....or maybe even a 3x10. Not only do they look good they are very sleek and could be mounted in one of several locations. They have a cap for filling and two tubes on the bottom....one in from the radiator and one for extreme overflow.


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