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Discussion Starter · #1 ·
Have had an issue since I rebuilt motor ...coolant blowing out the overflow. System always holds pressure because when I take the cap off it fills the tank immediately. I have burped it a couple of times with the front end up on milk crates ...I am wondering if maybe the crates are not high enough...read somewhere that in order to burp it properly it has to be 24 " off the ground ???

Thanks for any help guys

Also there are not any leaks anywhere else as the coolant is aways just out the overflow...no oil residue in the coolant either ...which would rule out a head gasket leak.
 

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Leave it be, It ll find its sweet spot. Mine stays just below the half mark.

Do a quick search and you'll see quite a few post regarding this.
 

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Fingers crossed it's something simple, but repeated coolant out the overflow is most often indicative of a leak from combustion to coolant. A couple of heat cycles and the level should surely normalize.
 

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Are you always adding coolant back? If so, don't for a while.

Is it blowing enough out the bottle is empty?

Typically cold mine will be below the half mark as well, but I have seen it almost full too. After a couple cycles it should normalize as stated already. As long as there is green in the bottle your good, don't feel you have to have it full.
 

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Discussion Starter · #5 ·
I have been adding coolant It shows just abut of coolant in the bottom of the jug. If it was leaking into the motor would it not cook the motor or foul the plugs ???
 

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Plugs surely would be white, so would the inside of your exhaust, if it's leaking from the head into the jugs of course.
 

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Cylinder pressure is much higher than cooling system pressure. A marginally "sealed" head gasket can leak one way.

Simply put when you warm up the coolant expands and builds pressure. When that pressure exceeds the cap pressure it expels to the overflow. Ideally, any air will collect in the cap/fill neck sending the air to the tank first.

If you have a dribble in the tank and it's overflowing when it warms up, it sounds like you are "making" air in the system.
 

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Discussion Starter · #11 ·
Inside of y pipe when I take the pipe off is evenly tan brown along with the plugs. No white
 

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Thermal cycle it several times. If the coolant tank gains it's "adding air" to the system. If the coolant recedes it's expelling air and replacing it with coolant. It's that simple.

As stted earlier it CAN leak one way. Combustion pressure is several hundred psi or more. Cooling system pressure is <15psi.
 

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Cylinder pressure is much higher than cooling system pressure. A marginally "sealed" head gasket can leak one way.

Simply put when you warm up the coolant expands and builds pressure. When that pressure exceeds the cap pressure it expels to the overflow. Ideally, any air will collect in the cap/fill neck sending the air to the tank first.

If you have a dribble in the tank and it's overflowing when it warms up, it sounds like you are "making" air in the system.
and sir what will happen as the sled is shut down and to the pressure in the cooling system?
 

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Contraction will occur. Depending on volume of liquid and "air" it could maintain some pressure, it could zero out, it could go negative and draw coolant back in.

If it's been thermal cycled and it pukes it's likely a head gasket. If you simply overfilled the expansion tank it would overflow but then settle into a normal level.

I wish they'd go back to a pressurized bottle.
 
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Discussion Starter · #17 ·
It does not matter how long I let it sit ...it maintains pressure in the system ...That's why I can't believe it is leaking into motor
 

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It does not matter how long I let it sit ...it maintains pressure in the system ...That's why I can't believe it is leaking into motor
That my friend is your smoking gun. Making pressure without expansion or maintaining pressure after contraction tells me you have a head gasket issue. Combustion pressure adds "air" to the cooling system. When it hits the relief pressure of the cap it expels to the tank. It expels whatever is at the high point under the cap which is often part liquid hence the overflow.

Again, cylinder pressure is in the hundreds to even thousands of psi. Cooling system is <15psi. The gasket or oring or whatever is able to hold back the liquid, but not the gas.
 
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Discussion Starter · #20 ·
Unscrewed the Rad cap last night and you can smell exhaust on the rad cap ...like I said pulling the head tonight to have a look...
 
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