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Manufacturing antifreeze

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scottyz

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"Hi. After doing extensive wo

"Hi. After doing extensive work to alleviate an overheat problem at low RPMs, I noticed that the plastic overlow bottle of antifreeze connected to my heat exchanger is filling up and squirting out the top, while one of my 5.7 Captains Choices are running. I replaced both raw and fresh water pumps, thermostat and flushied out the complete cooling system, including the heat exchanger. Not being a tech, I don't think this new problem is a good thing. Any thoughts? Thanks
Scotty"
 
"What year are the engines? E

"What year are the engines? Early models used a vented cap on the overflow bottle that merely captured the expanding mass of coolant created by the increased temperature. The newer models use a pressurized container similar to your car. This cap is not vented and if coolant is squirting out, the cap needs to be replaced.

There is a chance you have not yet cured your overheat problem.

Note: you will find that once the engine cools down your bottle is now empty since you're not actually manufacturing antifreeze, you're just expanding it beyond the capacity of the cooling system then dumping it in the bilge."
 
"2003 engines with 425 hours.

"2003 engines with 425 hours. The overheat problem seems to have been repaired, but then again, I have only put on 1 hour since the fix. Thanks"
 
"'03 was the last year of

"'03 was the last year of the unpressurized recovery bottle.

This cap is vented so any overage of coolant will squirt out. With only an hour of running after all that work, is it possible you had the bottle overfull to start with?

If the bottle is within the marks cold, overflows when hot, then returns to the original marks you need to revisit that heat exchanger. You have raw water entering the system. Unless you have the pressure cap loose, this is not possible as the pressure in the closed system is greater than the pressure in the raw system.

The cap on the exchanger may well be bad allowing coolant to blow off and into the bottle at too low a pressure.

I would swap the cap with the known good one from the other engine, adjust coolant in the overflow to the proper lever (not full) and retry the engine.

If the engine is not overheating, yet the bottle is blowing off, the cap is bad.

Rick"
 
"Rick, the level in the bottle

"Rick, the level in the bottle was to the full line...not above. When you say "cap", do you mean the plastic cap on the overfill bottle? All that has is a pin hole bleed off. Thaks again
Scotty"
 
"The plastic cap on the overfl

"The plastic cap on the overflow bottle will have a bleed hole in it as you can see. The "Radiator" cap on the heat exchanger is a pressure cap. This is the one I suspect may be your problem. When the pressure in the system reaches a preset amount, the relief valve in the cap opens and allows coolant to flow through the black rubber hose and into the overflow bottle.

When the engine is shut down and starts to cool, the volume of coolant decreases (we call it shrinkage) and is drawn back into the engine by the vacuum created by the cooling. That's why the bottle can not be filled too high when cool, otherwise it will overflow when hot.

Swap this cap with the other engine and see what happens."
 
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