After a 3.5 hour drive last weekend I noticed around the Degas bottle the dreaded "white residue" indicating the coolant cap might be letting lose some pressure. I replaced the cap with the updated version when I bought the truck about 3 years ago.
I rigged up a pressure gauge to the degas bottle. Took the truck for an hour drive down the highway averaging about 70mph with a WOT romp every 5 minutes or so. Pressure built up to about 12-13psi and never really increased or decreased from there. I know the relief point is 16psi. Keep in mind this was an empty truck flat highway. Coolant temp was 182-185(via edge cts)

What does a "healthy" coolant system pressure run at? Should I start saving for HG's or are my numbers normal...

Truck is deleted(EGR) so I know its not that. ECT/EOT spread is about 10-12. truck does have a SCT tuner running the tow tune.

I plan on maybe making a permanent pressure gauge so I can see what is really going on during these longer trips

thanks for any replies

 

I can't really comment on what a normal degas pressure is, some people just run different numbers, coolant pressure is usually higher depending on temperature, when my truck is at 182-185 F on Coolant the pressure is usually between 5-8

 

it was a brisk morning...about 45 degrees out

 

Kinda hard to say what normal is. Seems like everyone with a 6.0 I've talked to that monitor coolant pressure have different readings. I just bought the universal sensor add on for my Edge CTS for monitoring coolant pressure. I bought a 30PSI transducer and an Fuel Pressure Gauge Fitting 3/8" Barb to Gauge Port to 3/8" Barb from ebay. I plumbed the fitting in the hose from the radiator to the degas bottle. cr38er has a good YouTube video on setting up the Edge CTS for the transducer.

 

I'm looking into doing the same with my CTS. Have you installed it yet? what are you seeing for numbers?

 

I haven't had a chance to drive it. The parts came in shortly before I had to catch a flight for work. So, all I had a chance to do is install it and start it up to make sure it was reading pressure. For what it is worth, I revved it up a couple times and I was seeing 5-6 psi.

 

Normally you will go from zero to 7 or 8 going from dead cold to normal operating temps.
It is a direct correlation to temperature assuming you have no leaks in the system or any combustion gasses entering the system.

There are 3 variables that directly correlate:
1- Temperature
2- Pressure
3- Volume

Change any one of the 3 variables in a closed system and the other 2 change also. So as temperature increases in your coolant system, pressure increases while volume decreases(heat expansion).

Now one thing you have to account for is baseline temperature and barometric pressure. In a perfect system with no leaks, say you open your coolant cap at 70degF. Then seal it again. Your zero PSI point should technically only occur at 70deg with the same barometric presure(Credit to Ian for this idea). Say you have done this and park overnight and start at 40degF in the morning, You should technically have a vacume on the system since you have fallen before the zero point.

Most people have small leaks and by the time the next morning rolls around your coolant system has equalized with atmosphere and temp which basically resets your zero point to whatever temp it was on first start.

So to make a long story short. Crack your degas bottle before you start and you should get up to around 7 or 8 by the time you reach full operating temp.

If you are getting over 10PSI, you are pulling heavy up a hill and your temps are climbing with pressure. You should never see over 10 in any daily driver condition.

I've pulled trailers all over the USA and Canada for a living watching degas pressure the whole time.

 

So that's the kind of answer I was looking for. I feel that 12-13 is excessive especially with little to no load on the truck. I guess I need to start depositing more money into my head gasket fund(still stock). Although I'm trying to hold off until the spring. I might try to put in a permanent gauge in the mean time.

 

Try a different gauge also. Transducers especially tend to start reading off very quickly.

I think a lot more people have small head gasket leaks on their 6.0L than they realize.

I knowingly pulled trailers with blown head gaskets for a year before I did my first rebuild(monitoring presource aND temployees the whole time). It's actually not that big a deal with a small leak. I wouldn't worry about it until you start puking out the degas lid, or overheating.

 

With healthy gaskets, my truck was 6-8 psi normal/9-11 towing when I had my 6.0.

 

Well just ordered this gauge so I can keep an eye on things while i'm driving the truck, I guess well see what happens...I got in contact with a guy who works at a ford dealership and does head gasket on the side at his house gauge.

 

I have a coolant pressure gauge on the windshield pillar that I can monitor at all times. As engine warms up to T-stat opening point of 192deg it slowly climbs to around 12 psi and stays there pretty much all the time. That's just running around town (no towing). When towing, my coolant temps run anywhere from 192 - 215 and coolant pressure climbs up and down w pressure.... from 12 psi at 192 to a max of 16psi at around 215 degrees. Hope that helps..................

 

Mind me asking how you plumbed in the gauge? The one i'm buying is a mechanical with 1/8" ntp fitting...

 

The easiest way to plumb in for a pressure reading is at the vent tube between the radiator and the degas bottle. Fit up a tee with hose barbs for the straight through ports and whatever size you need at the 90 port. Cut the tube a few inches from the degas and install with hose clamps.

The problem with a "spec" is the calibration of the gauge or sensor itself. All reading devices have a tolerance and its closest tolerance will be in the center of the range. Take a look at pressure garages at McMaster and compare prices to a gauges precision.

After installing a gauge or sensor you need to find what your gauge is going to read. It may be 7 psi or it may be 12, depending on its zero point and its tolerance. Honestly, if you have combustion pressure creeping past a head gasket it's not a situation where it's going to climb from 7 psi and then stay at 14 psi, just below the cap release. If you have gases escaping it will be much higher then 16 psi. The volume of the leak is what will determine how much fluid gets blown out the cap. IMO, you're better off checking at the degas bottle for released fluid or drop in level then monitoring the pressure in the system on a routine basis.

 

Good point on the gauge cal Toomanytoys. Luckily I do work as a testing engineer, and it would be a cold day in hell if I let an out of cal instrument get the best of me. I have a quick n easy nitrogen test rig I can give a baseline calibration(certainly not ISO9001 cert) to the autometer gauge when it comes in. I did check the gauge(a well pump gauge, 0-30psi) I used originally against the one on my air compressor and they were within +/- 1/2 psi of each other. My plan is to see the trend analysis of the coolant pressure under different driving conditions. If it starts climbing to 16+ psi and there is coolant residue around the cap, shes certainly in need of repair. If day to day driving only produces <12psi I might be in the clear. I feel I need a "real deal" indication of whats going on in there.