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I have Driven Diesel coolant return lines and o-ringed UCF heads with Motorcraft head gaskets. Even in Texas summer towing never see over 10psi. If I vent it off and start towing again it never creeps back up until I allow the engine to cool then warm it up again. Thermal expansion.
Nose up as best you can, pull a vacuum. With the LS, I have to do both nose and tail up and go through a sequence.
It might be possible to pull a vacuum and pull most of it out. With the heads off, the cavity could be filled before the heads are installed, so the hoses would not be needed. The right type of RTV could do that.
So in looking at the pictures of your heads, it is a air pocket as a result of the head design, and other than pulling the heads to remedy it, one is pretty much stuck with the air pocket. So I guess I'll have to live with the thermal expansion and realize that pulling a load up a big hill at high temps and speed with just cause a brupping of the cap and that is normal for my truck.
One other thing that goes along with the air pocket theory is I am able to pull with high loads, with 20+ pounds of boost in high ambient temps for a hour+ with the coolant below 220 and I stay several pounds below release. So that I guess is the personality of my truck.
It does seem about 221 to 223 ECT with rpm seems to be where I ever see this happening.
I looked through the videos and pictures I have and found some that might show it better for those that are trying to visualize the issue.
When I was cleaning the heads, there was a point where I had the intake ports filled with mineral spirits and also looked if any of the valves leaked (per the Nav service manual). But the heads are held in a position as they are when installed. That port sits above the normal coolant flow paths through the head and dead-ended on the block,
A still grabbed from the video. It's a pretty good trap for air.
Another is from after I cleaned out the rust with Evapo-Rust; you can see the port for the coolant flow. At the front of the motor, this is where the coolant flows out of the heads to the front cover. I rotated the image so it looks more like the installed orientation.
There are two ways of eliminating the pocket; both require drilling and tapping to provide a degassing port. The retailers that provide the kits have you drill and tap the front cover by the thermostat and provide hoses to go there. It doesn't have to be done that way. The hoses or lines can go to any other hoses going to the factory degas bottle, the reservoir. They use a substantial hose diameter; I'm using a smaller amount. Anything such as 3/16" or 1/4" would work. My viewpoint is to minimally detract from the coolant flowing through the head. A line 1/8" in diameter has the possibility of clogging with some of the rust particles that we find in the coolant flow.
The other method is to drill and tap both ends of the head and provide a small line (stainless hardline or hose) to bypass the head, small enough not to disturb the coolant volume to a meaningful degree. This will not hand the heads to right or left.
It should be noted that modifying the heads in this manner will most like void any retailer's warranty on the heads if they have been reworked.
Thanks for the pics, in looking and at the block and head it is just a glitch of design. Unfortunately, I'm stuck with it now. Do you think it will cause an issue, other then an occasional burp?
I don't think so. It's a quirk that seems to influence the psi numbers under some situations, for akblackfoot certainly caused a situation that was worrisome enough to pull heads, but that's very unusual.
To monitor coolant pressure and use pressure as a determining factor for head gasket issues, I think it becomes important to understand how this may alter the methodology and the need to look closer. From my viewpoint, it means that the HG check needs to not only look at how high the pressure gets but, more importantly, what the pressure returns to. If combustion enters the cooling system, there is more probability that there will retain pressure once there is a full cooldown. Depending on the situation, a full cooldown may be longer than overnight.
I don't think so. It's a quirk that seems to influence the psi numbers under some situations, for akblackfoot certainly caused a situation that was worrisome enough to pull heads, but that's very unusual.
To monitor coolant pressure and use pressure as a determining factor for head gasket issues, I think it becomes important to understand how this may alter the methodology and the need to look closer. From my viewpoint, it means that the HG check needs to not only look at how high the pressure gets but, more importantly, what the pressure returns to. If combustion enters the cooling system, there is more probability that there will retain pressure once there is a full cooldown. Depending on the situation, a full cooldown may be longer than overnight.
First thing in the morning my pressure gauge reads zero. After a full warm-up and ten minutes of driving with lots of boost it reads 10-15psi depending on season, higher when it's cold outside, lower when it's hot out. Are you saying it may not be a head gasket after all?
First thing in the morning my pressure gauge reads zero. After a full warm-up and ten minutes of driving with lots of boost it reads 10-15psi depending on season, higher when it's cold outside, lower when it's hot out. Are you saying it may not be a head gasket after all?
I bought my truck about 5 years and 30000mls ago, the head gaskets were replaced at the previous owner, I also have 10-15psi under load (deleted). When the EGR cooler was still installed, I had up to 20psi in the system unter load (in the mountains, heavy camper vehicle). You wrote that you have driven 10 minutes, the engine has not reached operating temperature after such a short time.
I'm watching ECT, EOT and coolant pressure closely. As long as the pressure does not increase, I leave the head gaskets alone. Meanwhile there are some here who could not find any damage to the head gaskets when changing the head gaskets.
First thing in the morning my pressure gauge reads zero. After a full warm-up and ten minutes of driving with lots of boost it reads 10-15psi depending on season, higher when it's cold outside, lower when it's hot out. Are you saying it may not be a head gasket after all?
That is from thermal expansion, that’s why when it’s cooler out your pressure rises more after warm up. Mine still does this after all my fairly extensive rebuild work. Right now it’s about 60 in the morning and starting cold my manual 30psi coolant pressure gauge hits 9-10psi after warm up. If I romp on it the pressure will rise a couple of psi while on the throttle hard but return to 9-10psi when I start driving normal again. The trick to see if it’s truly just thermal expansion is something Jack mentioned in this thread. Once the pressure stabilizes get out and carefully vent the cap and continue driving. If the gauge stays around zero your heads have no combustion gas leaking into the coolant passages. If the pressure rises again you have some leak by.
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