Degas cap pukes coolant sometimes

Diesel625

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My 06 sometimes pukes coolant out the degas cap. It has a kdd stage 1 long block, Kc stage 1, oringed heads and oem gaskets with arp studs, and 175/stock injectors. I used to run an atlas 40 as well. I have tried the atlas 80, but I dont like the extra egts that come with it. I’m going to hook a gauge and see where I’m at pressure wise soon, just trying to gather some thoughts. I run tunes from Wdi, tsd, and Quicktricks. I can run a wdi tow tune, and never have an issue. I tow 20k with not a single problem. At first, I was thinking my fan was not working correctly, so I put my bpd manual 7.3 clutch back on, and the ect stays at 190-200 at all times. Before I could hit 220, and still never puked. If I run my tsd tow, or 1.6mpd, it won’t puke for a good while on a very hot day. The spd will puke sooner, but I have to be running kind of hard. My oem water pump went out a while back, so I replaced it with another motorcraft too. The thermostat was not replaced, but it is a motorcraft as well. The deltas are very good. Usually within 10 degrees towing heavy. I stopped at an Oreillys and bought a cap there. They only had aftermarket caps. It lasted a few days, until my motorcraft caps came in. With the 1.6mpd, it puked after a few months. The highest egt I’ve hit was around 1300, and that was for a very short time. Usually when it starts to bog down, I hit the tow haul, and after the downshift, it cools down to 1000-1100 in a hurry. The coolant level is just below the minimum. The highest ect I’ve hit is 225-230, and the highest eot has been around 230 as well. I’m hoping I’m flash boiling coolant somehow. It also has a coolant filter kit and I have elc coolant as well. Any thoughts? I doubt it’s the head gaskets or heads, but you never know. Other than reading pressure at the degas bottle, what else can I test? I don’t have a way of testing the degas caps. Thanks.
 

DEEZUZ

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New Motorcraft caps are popping off almost at 17 psi from my testing in the last few years, so if you are popping those off I'm suspecting a gasket issue.

You need to get a cheapo air pressure regulator and t it into one of the top smaller degas bottle lines and walk the pressure up(by reading a gauge on the regulator) and see if the caps are Bleeding off premature which I doubt.

How hard is upper hose getting?
 

DEEZUZ

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Also pick up a combustion gas tester from like a Napa. It will tell us if there are gases in the system
 

Diesel625

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I haven’t checked the upper hose recently, but it wasn’t hard when I last remember checking it several months ago.
 

Diesel625

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Hooked a gauge up yesterday. After truck is warmed up, it will reach 14-16psi. Tried a few different tunes, same thing. Never puked though. On a hard run going uphill, it will hit 17-18psi, then back down to around 14psi. Egts 1000, eot 195, ect 200. Upper radiator hose is hard as well. I am going to replace the thermostat, then see what it does. The return line to degas bottle from radiator hardly has any flow. Opened the degas bottle to check for bubbles, and didn’t have any.
 

DEEZUZ

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Combustion gas checker.

Run the truck super hard. Slowly remove degas bottle cap. Set tool in bottle and have someone vary the rpms while squeezing the bulb on the tool. If it turns color you have combustion present.
 

DEEZUZ

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Does it get to the 14-16 while Idling or aggressive driving or what
 

Diesel625

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Idling it’s fine. It stays low. You have to get hard on it to hit 14psi+. Local parts store didn’t have an indicator. I have to order one.
 

Diesel625

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Little update, maybe. My motorcraft thermostat came in, but I decided to try something before changing it out. I have a digital combustible gas indicator I carry in my welding truck. Before opening the degas cap, it still had 7psi, and had been sitting for a couple days. I turned on the truck, let it warm up to 175f, then opened the cap. My meter picked up 25ppm CO. I checked the tailpipe, and it picked up CO as well, as it should. Sounds like I definitely have combustion gasses in the coolant. Is this an accurate test?
 

Diesel625

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The degas psi fluctuates when it shifts at high rpms. Taking it in. The long block has a 3yr unlimited mileage warranty.
 

Hartwig

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If you don´t want to read the complete thread, start at post #120
 

DEEZUZ

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If you don´t want to read the complete thread, start at post #120
Sweet. You should start a introduction thread here. I browsed your YouTube catalog
 

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