6.0L Cooling System Pressure

[Amarillo_Powerstroker]

A few months back, I started experiencing a low-pitched version of the tea kettle whistle out of the degas bottle immediately after letting out of the throttle. Initially, it occurred every once in a while, but over time it has gotten to the point of happening repeatedly now. I am certain the low-pitches whistle is coming out of the degas cap as it will puke coolant from the reservoir too. It will puke coolant to the point where it levels off, approx. 2 inches below the min. line on the degas bottle. If I refill it to the min line on the bottle, it will puke out again to the same level, approx. 2 inches below the min line. After the coolant level drops to that point, it generally won't puke out any more coolant, but when you pop the hood and listen closely by the degas bottle with the engine off, you can hear pressure escaping from the degas bottle.

I recently got the new updated degas cap from Ford, which in the end, did not solve the problem. It worked for the 1st week, then the same old low-pitched whistle returned, just in a more drowned out version, but it definitely is still there. It will even puke out coolant with the new cap down to the same level as it did with the old cap.

I hooked up a Stant coolant system pressure tester in-line with the return line to the degas bottle and ran it inside the cab. If I manually pressurize the system from 0 psi, it will build pressure and the gauge will level off at approx. 15-16 psi and hold within 1-2 psi. After I release the pressure to start from 0 psi and road test the vehicle with a load(trailer in tow), the gauge will build 15-16 psi fairly quickly(less than 5-10 minutes or so) and then spike to 18-19 psi under a loaded acceleration. I know the cap is only rated at 16 psi, so it must be constantly venting. My only guess is that when the coolant is at the low level in my situation, there is enough empty space in the degas bottle for the pressure to escape without bringing coolant with it.

I am trying to find out what the normal pressures in a 6.0L cooling system are supposed to be. Especially when techs road test a vehicle with a coolant system pressure tester installed, what kind of readings are you getting on a truck that has blown headgaskets versus a truck that has not compromised its headgaskets? Based on my findings and gauge readings, should I have any cause for concern given that I am not overheating nor have any white smoke out of the exhaust.

Thanks in advance...
-Brad

[AFBLUE]

Your HGs are toast. Get it to where the work is going to be done sometime soon so you dont warp a head too bad or wash the cylinder walls and ruin the block.

The coolant system can typically pressurize up to 6psi with good HG after driving for 20+ miles. The cap will only let the coolant system pressurize to 16pis and will vent. You are correct that the system will only puke so much. Once the coolant gets low enough, the air can escape without taking coolant with it. Get it taken care of before too long so you dont make the repairable damage to irreversible damage that cant be fixed with an EGR delete ARPs and a few $$$ on the side to your chosen tech.

[Robsr]

Originally Posted by AFBLUE

Your HGs are toast. Get it to where the work is going to be done sometime soon so you dont warp a head too bad or wash the cylinder walls and ruin the block.

The coolant system can typically pressurize up to 6psi with good HG after driving for 20+ miles. The cap will only let the coolant system pressurize to 16pis and will vent. You are correct that the system will only puke so much. Once the coolant gets low enough, the air can escape without taking coolant with it. Get it taken care of before too long so you dont make the repairable damage to irreversible damage that cant be fixed with an EGR delete ARPs and a few $$$ on the side to your chosen tech.

I concure but...what is 16 pis? Sir, have you been drinking?

[Amarillo_Powerstroker]

Originally Posted by AFBLUE

The coolant system can typically pressurize up to 6psi with good HG after driving for 20+ miles. The cap will only let the coolant system pressurize to 16pis and will vent. You are correct that the system will only puke so much. Once the coolant gets low enough, the air can escape without taking coolant with it.

Thats the info I did not know. If I am understanding that correctly, the coolant system on a 6.0L can only generate 6psi or so on its own. Any excess pressure beyond 6 psi or so in the cooling system would be an indication of combustion/cylinder pressures bleeding into the coolant system(i.e. blown headgaskets)...
I've never tried the pressure tester in another truck yet, so I really didn;t have anything to compare my gauge readings too. ARP's have been sitting at the house just waiting...

Thanks AFBLUE & ROBSR for the advice/info. I appreciate it.

-Brad

[SCUFFY828]

head gaskets would be my guess also , ford spec use to say that anything over 20 lbs was excessive ,but they dont even have to get that high to cause puking , i would wont to know what eot and ect temps are before goin any further first

[Amarillo_Powerstroker]

Techs:

When diagnosing for blown headgaskets, is there a way to "seal" the cooling system(i.e. degas bottle), so it doesn't vent excess pressure when testing for over-pressurization of the cooling system. Therefore, you would be able to get a "true" reading without the system constantly venting...or is this just a bad idea...

-Brad

[Robsr]

A pressure tester is going to "seal" the system. you can do a garage test by running the engine to 2k rpm and watch the gage, if it goes up steadily past 20 psi, there's trouble a brewing.

I did not see an egr delete in your sig., don't rule it out. There is an egr degas line that runs from the intake, to the degas bottle, when the coolant boils, it shoots the coolant right through this line to the bottle and pukes, provided the coolant level is adequate, due to this pressure. get engine to op temp, pull egr valve,engine off, lol, pressurize system and listen with a piece of tubing in the hole for a gurgle or air escaping and moisture in the intake.

You can also use a combustion leak detector which can be purchased at most AP retailers, this method can be inconclusive in the early stages of HG/Headbolt failure because the leak may only reveal under boost/load.

We also use a 5 gas to detect CO, CO2 and HC in the coolant degas bottle. As you can see, there are several methods for detecting HG failure. the early stages can at times be very difficult to detect. hope this helps.

[Galaxie]

Im dealing with the same issues!

[ExtremeFord4x4]

Amarillo_Powerstroker, I am dealing with the same problems on my excursion. Do you know of a dealer that is mod friendly in Metairie? I am under warranty but I know they are going to try and give me s h i t for all the aftermarket stuff I have.

[Amarillo_Powerstroker]

Originally Posted by ExtremeFord4x4

Amarillo_Powerstroker, I am dealing with the same problems on my excursion. Do you know of a dealer that is mod friendly in Metairie? I am under warranty but I know they are going to try and give me s h i t for all the aftermarket stuff I have.

PM sent...