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Hi,

Some months ago I bought a very nice -66 with a 289 in close to original condition. In the weeks before I put it in winter storage I noticed that the car was loosing coolant. After filling the radiator to about 1 inch below the radiator cap and driving 50-60 miles the car has lost about 1-2 quarts of coolant. There are no obvious leaks, no sign of water in the oil or steam coming out the exhaust. When driving it to winter storage I placed a bottle at the end of the radiator overflow tube to see if coolant were purged through the overflow. I collected about 1/4 of a quart in the 10 mile drive.... When the starting the engine the coolant heats up to about 3/4 of maximum indicated on the gage before the temperature drops to about 1/4 (thermostat opening) and stays there for the remainder of the drive. The oil temperature is low on the indicator (1/4).

Anyone experienced the same thing? Any suggestions?

Thanks,

Roger
 

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Sounds like your thermostat is sticking or may not be opening completely. Hard to know how much silt maybe in your block or radiator if you did not install them but that definitely affects capacity and cooling efficiency, as does the type of fan and the proximity to the radiator as well as the presence of a shroud and whether or not you have air conditioning. So many variables... My recommendation is to do a complete coolant system drain including plugs at the bottom of the block, refill the entire system with white vinegar, let that run two operating temperature and sit 24 hours, drain everything again and fill with tap water, remove the thermostat and use a section of pantyhose for a filter inside the upper radiator hose before the radiator... Run and flush and run and flush until you get nothing but clear water and nothing else gets into the panty hose filter, drain everything again and refill the system with a 50/50 antifreeze and pure distilled water. Choose and test a new thermostat that has a small gas relief hole on the disc, and I recommend a 180° for hot climates and 195 degree for the northern and colder climates.
 

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Sounds like your thermostat is sticking or may not be opening completely. Hard to know how much silt maybe in your block or radiator if you did not install them but that definitely affects capacity and cooling efficiency, as does the type of fan and the proximity to the radiator as well as the presence of a shroud and whether or not you have air conditioning. So many variables... My recommendation is to do a complete coolant system drain including plugs at the bottom of the block, refill the entire system with white vinegar, let that run two operating temperature and sit 24 hours, drain everything again and fill with tap water, remove the thermostat and use a section of pantyhose for a filter inside the upper radiator hose before the radiator... Run and flush and run and flush until you get nothing but clear water and nothing else gets into the panty hose filter, drain everything again and refill the system with a 50/50 antifreeze and pure distilled water. Choose and test a new thermostat that has a small gas relief hole on the disc, and I recommend a 180° for hot climates and 195 degree for the northern and colder climates.
Thank you for the answer. The car has air condition, but I have never used it except from functional check. I can certainly see that silt will affect the cooling efficiency, but would it cause the cooling system to purge that much coolant? I have always refilled coolant, haven't dared to continue driving to see if any more coolant will disappear.

Roger
 

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Depending on if something else is occupying space in the system or preventing coolant from flowing properly that can affect capacity, and the systems are not all exactly alike. One inch below the small ring under the cap, and enough to cover the fins when cold, is all you need.
 

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My car with both the OE radiator and the alum rad will purge quite a bit when topped off after it is parked especially in the summer heat. So I got one of the cylindrical metal overflow cans. It regularly dumps into it and sucks it back out. Highly recommend it! But if you're getting a ton of backup you might have rust & scale in your head and intake water jackets and/or your radiator bends. Do the flush as they outlined above and see what happens. You can also have a radiator shop check your rad flow or just replace it like I did with a better one. I actually didn't need to replace mine. Found out I had a faulty or incorrect temp sensor that was reading WAY too high. Put an OE one in and, oh well, I am forever stuck with better cooling :p
 

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When I bought my car, I found the seller had it stored under a tarp in the back yard. The local mouse population found a nice residence in the heater ductwork where they packed it with seat stuffing.
When opened the duct and cleaned out the stuffing (almost filled my shop vac) I noticed the floor was wet with antifreeze the following morning. It was leaking from the heater core.
Have you opened the heater duct?
 

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What is the actual water temp? Is your radiator cap sealing properly?
 

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Discussion Starter #9
When I bought my car, I found the seller had it stored under a tarp in the back yard. The local mouse population found a nice residence in the heater ductwork where they packed it with seat stuffing.
When opened the duct and cleaned out the stuffing (almost filled my shop vac) I noticed the floor was wet with antifreeze the following morning. It was leaking from the heater core.
Have you opened the heater duct?
Haven't opened the heater duct. Previous experience with leakage from heater core (97 Mustang) is that it is VERY obvious. But, I will take a look.
 

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My car with both the OE radiator and the alum rad will purge quite a bit when topped off after it is parked especially in the summer heat. So I got one of the cylindrical metal overflow cans. It regularly dumps into it and sucks it back out. Highly recommend it! But if you're getting a ton of backup you might have rust & scale in your head and intake water jackets and/or your radiator bends. Do the flush as they outlined above and see what happens. You can also have a radiator shop check your rad flow or just replace it like I did with a better one. I actually didn't need to replace mine. Found out I had a faulty or incorrect temp sensor that was reading WAY too high. Put an OE one in and, oh well, I am forever stuck with better cooling :p
The overflow tank may also need a different radiator cap.
 

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The overflow tank may also need a different radiator cap.
If the extra tank is filling so much that it's overflowing that's another issue. Mine has a pretty tight cap but I don't think it's truly pressurized. Once it's full it would dump out the bottom.

I installed this one. Pretty happy with the install and function.

 

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I believe he is referring to the actual radiator cap, not the cap on the coolant recovery tank. With a similar system, I run a 13 lb. cap. Coolant sits about 1/2" below full (cold) and never requires coolant to be added.
 

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yes, radiator cap.
 

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If the extra tank is filling so much that it's overflowing that's another issue. Mine has a pretty tight cap but I don't think it's truly pressurized. Once it's full it would dump out the bottom.

I installed this one. Pretty happy with the install and function.

Hey Jsbenami,
Got any pics of the tank installed? I've got a 66 (not sure of your year) and trying to decide between a 17" and 15" tank, as they both show on the site as applicable to 65 thru 73..

Unsure if 17" is overall (tubes/cap)or just tank size..

Sent from my SM-G950F using Tapatalk
 

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Watto, a 67 I bought had a 20' tank with the spares when I bought it. Way too long for the 65. Cut it down to 17.5". It fits, but if I was buying one for a 66, I'd get a 15".
Where bouts in Brissy are you?
 

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Watto, a 67 I bought had a 20' tank with the spares when I bought it. Way too long for the 65. Cut it down to 17.5". It fits, but if I was buying one for a 66, I'd get a 15".
Where bouts in Brissy are you?
Ah good, thanks for the info, with my tape measurements I was leaning towards 15" also.
I'm Northside, Wavell Heights.

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On my '66, I was forced to go with a shorter recovery tank to clear the upper A/C line. The actual tank is just under 10" and the diameter is 3". The volume is perfect. I'd suggest looking for a tank with a volume about 30oz.
744900
 

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With a new cap - you should not need a recovery tank. Have a garage use an exhaust sniffer at the radiator opening while running. You may have exhaust gas (cracked head or gasket).
You may even see bubbling as it idles with cap off. Eventually the gas pressure overcomes the cap and it expels coolant. That is why you don't indicate overheating but get overflow.
 

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If it was me trying to evaluate this leak, I would pull out my mity-vac, install it in place of the radiator cap, pump it up to about 10 PSI and see if it held pressure. If it does...you don't have a leak. If it won't hold pressure, either you have an air leak at your tester (easy to look for with soapy water) OR you have a coolant leak. If you have an external coolant leak, you'll be able to see dripping within a couple of minutes and (as the engine is cold) it won't evaporate and (as the engine is cold) you can get your fingers and hands involved without burning yourself.

And...it's $35 on amazon. Absolutely a necessity for this sort of work in my opinion.


Phil
 
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