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'80 I-6 Cooling

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'80 I-6 Cooling
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Flundertaker

Jeeper
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Location
Oklahoma City
Vehicle(s)
'86 CJ7, 258, T5, D300, D30/D44 Pretty Much Stock
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Should my 1980 CJ7 with AMC 258 i6 / 4.2l I-6 have an overflow coolant tank? The Chilton manual I looked at doesnt show one for the 6 banger but does for the AMC 304 . I just picked up this jeep and have only driven it a few miles but its blowing coolant out the hose coming off just below the radiator fill cap.
 
I've got a hose running into a pop bottle zip tired to the radiator. Actually works really well.

DrDoc
 
My 1980 CJ5 with the AMC 258 i6 / 4.2l does NOT have a coolant recovery tank. I'm not sure if at one time it had one or not. It also doesn't have a radiator shroud.
So far I haven't had any overheating problems but I have only made short trips with it.
 
TnCJ said:
My 1980 CJ5 with the AMC 258 i6 / 4.2l does NOT have a coolant recovery tank. I'm not sure if at one time it had one or not. It also doesn't have a radiator shroud.

So far I haven't had any overheating problems but I have only made short trips with it.
Click to expand...



Yeah no shroud with a small 4 blade fan. I saw somewhere online that the radiator isn’t supposed to be completely full. Maybe that’s what was dripping out. I may run it and see if it drops a bit and then stops overflowing but keeps the temp ok.
The overflow tank for an ‘81 is available for less then $30. It seems like cheap insurance without having to go with a soda bottle and a few zip ties


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I bought a generic overflow tank from Summit and put it in there. It's great and I have the AMC 258 i6 / 4.2l with a big 4-core aluminum radiator and it overflows into the tank and sucks back in as it cools just like it should. I would recommend it.
 
Scotch bottle, rubber pad underneath it (self adhesive stuck to the bottle, zip ties, hose, and drill a hole through the cap/cork.
Then I can see what level the overflow is at. Coolant gets drawn up the hose when rad cools too don't forget. (Run the hose to the bottom of the bottle).
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It appears coolant tanks were installed after 1980. No sure if all models came with one thought. Mine has a Crown coolant tank, which is mounted on the left front fender in the back under the master brake cylinder. With the SBC radiator, the radiator cap is on the right side, which makes for a long coolant hose. Most caps these days are designed to vent back and forth into tank. If you don't have a tank I would install one, one reason is to keep your antifreeze mix from dumping onto environment.
 
Gentlemen, let me step in and help you with this discussion. Let’s all agree with the purpose for this tank and how it works. It’s main purpose is to keep air from entering the cooling system and thereby avoiding rust which causes components and seals to fail.

Here’s how it works. In a healthy cooling system, the coolant will expand as the engine reaches operating temperature. The thermostat will open at its set point and coolant will start to flow and remove excess heat from the engine. The sealed system will eventually not be big enough to contain the coolant’s volume due to thermal expansion and must be relieved somehow. Normally, in our old design vehicles, the relief is through the radiator cap which is designed to do this at a preset pressure point. The relieved coolant will be routed past the cap seal to the bottom of this famous recovery tank which is normally at atmospheric pressure.

When the engine is shut off, coolant temperature drops and starts to contract. The contraction is the critical point, it will have a suck back in effect and draw back the coolant from the tank. Therefore, it is very important that the hose end be at the bottom of the tank to avoid air induction, and the tank kept at atmospheric pressure.
 
More to the point would be why the coolant is blowing out to begin with?
After cleaning my system this past summer and filling radiator to correct level ~1" under full I have yet to get any overflow into my reservoir.

If you're constantly blowing coolant I'd suspect a head gasket failure or it's overfilled.
 
Basod said:
More to the point would be why the coolant is blowing out to begin with?
After cleaning my system this past summer and filling radiator to correct level ~1" under full I have yet to get any overflow into my reservoir.

If you're constantly blowing coolant I'd suspect a head gasket failure or it's overfilled.
Click to expand...

This maybe the best question. If the factory didnt install an overflow tank there was a reason and may be in line with my previous post that the rdiator isnt designed to be slap full. If I had more confidence (which I dont unfortunetly) in my temp gauge I would just keep driving it and just watch what happens with overflow and coolant temp. If the overflow stops and the temp remains in the safe zone than I would say all is well.
 
I have an 80 as well. No overflow tank but I have a small shroud and the fan is 6 blades I believe.
 
Basod said:
More to the point would be why the coolant is blowing out to begin with?

After cleaning my system this past summer and filling radiator to correct level ~1" under full I have yet to get any overflow into my reservoir.



If you're constantly blowing coolant I'd suspect a head gasket failure or it's overfilled.
Click to expand...
Running without a fan shroud?
No fan clutch or fan clutch blown.
Belts loose and slipping?
Coolant pump shot?
Electric aftermarket fan, relay, or thermostat not working?
P.O. re- routed the coolant lines wrong?
High coolant line causing an air-lock?
Aftermarket coolant circulator installed incorrectly?
Wrong/Failed thermostat?
Cold zone on the rad (running a rad blanket or cover?) freezing a small section?
Scaling from hard water?

Engine original or rebuilt? Cylinders bored much larger? Aftermarket Headers?
Elevation?

Coolant premixed or concentrated?
Using tap water or ionized water?

A few other things that might contribute to a boil over.

My rebuild is fresh, all new plumbing, heater core, rad, etc.
Still pukes a little now and then. That's what the reservoir is for. If your running hot from time to time ( heavy foot?) the overflow does its job.

If it's everytime you drive or even more often than not I agree you should eliminate potential problems.




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I would be worried if my vehicle didn’t “blow out” the coolant through this recovery tank method. That tells me that pressure is building up and is displacing air as much as possible and is relieved correctly. Many of us associate this relief with overheating and freak out. Keep in mind that air in the cooling system invites trouble. Air speeds up rust, causes coolant to boil at a lower temperature, and can wreak havoc with your pump. It can also cause detonations in severe cases.

Don’t be afraid to fill your radiator to the top (you really can’t) with this recovery tank system. Every little space of coolant to radiator contact helps. Ah, and refill your radiator through this recovery tank per the hot and cold marks, not through the radiator cap.

On another note, here’s some advise for those of you with carbureted engines. Use 190 degree thermostats in any weather. Get a shroud for your fans or go electric with a properly sized and shrouded fan. Good luck.
 
Patrick said:
I would be worried if my vehicle didn’t “blow out” the coolant through this recovery tank method. That tells me that pressure is building up and is displacing air as much as possible and is relieved correctly. Many of us associate this relief with overheating and freak out. Keep in mind that air in the cooling system invites trouble. Air speeds up rust, causes coolant to boil at a lower temperature, and can wreak havoc with your pump. It can also cause detonations in severe cases.



Don’t be afraid to fill your radiator to the top (you really can’t) with this recovery tank system. Every little space of coolant to radiator contact helps. Ah, and refill your radiator through this recovery tank per the hot and cold marks, not through the radiator cap.



On another note, here’s some advise for those of you with carbureted engines. Use 190 degree thermostats in any weather. Get a shroud for your fans or go electric with a properly sized and shrouded fan. Good luck.
Click to expand...
I agree.

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If you’ve only driven it a few miles since getting it home might be a good idea to do a coolant flush. CLR or muriatic acid is stronger than the Prestone flush stuff might take a few cycles and advisable to run a baking soda rinse afterwards. You don’t want to leave any of them sitting in the engine for long periods of time.

If it’s “blowing” coolant after you shut it off that is normal the engine is heat soaked and the coolant is no longer circulating so flashing does occur near the block.


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