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BrandonOlsen

Did coolant pressure test. Found coolant leak from clamps being loose around hose from thermostat housing. Tighten them up and leak went away. I had it at 15 psi. It never came down from 15. What would cause it to not release pressure? Also tested CAC and found a leak there. Not sure if that’s relevant to pressure not releasing

tree98

The cap is what let's the pressure out if it gets to high. You replaced the cap with a pressure tester that's designed to hold pressure.

No the cac and radiator are not connected

BrandonOlsen

(12-05-2022 )tree98 Wrote: The cap is what let's the pressure out if it gets to high. You replaced the cap with a pressure tester that's designed to hold pressure.

No the cac and radiator are not connected

The release cap was on. I pressurize it from the back of the coolant tank that goes to the radiator and blocked that hose off so pressure would be the same. I pressurized it to 14.5 - 15 psi. It stayed at 14.5-15 psi for over 20 minutes until I released the pressure from the gauge. I disconnected the air hose immediately after pressurizing it. I’ve noticed last few weeks that when the truck is sitting for a few days that when you open the coolant reservoir it has a little pressure. Release it and go check again in a few hours and has a little pressure again. Parked in a shop that’s heated it does it. Park outside it does it. Had oil sample done last week with good results. Coolant doesn’t look mixed. Fuel doesn’t look mixed. 2 days ago valve cover just started leaking on both sides and the front. 60 K miles on valve cover gasket at the time of overhaul. Everything but the head was done as it was to cummins specs .

Bengy88

I would say your coolant system is sealed near perfectly. You dont want it to release pressure unless it is higher than your caps specifications. A coolant system is designed to hold pressure to prevent the coolant from boiling. The higher the pressure the higher the boiling point.

tree98

I think the caps are around 18 psi so you probably just didn't put enough pressure in.

BrandonOlsen

I think what was going on in my head was that I put the pressure in the system and it wouldn’t release. I was thinking when you drive and shut the truck off the pressure releases so it has to release somewhere. The difference is when driving the truck is heating up the coolant which builds pressure and shut it off it gets cold and relieves pressure. I don’t always put 2 and 2 together. I just remember watching a video that you pressurize it and wait 5 minutes to see if it drops. I just assumed after 5 minutes it would start dropping. Thanks fellas

Rawze

Acually, checking the coolant system on a big truck should be done at 20-psi, not 15 psi. This is done by applying the test kit in place of the pressure regulator cap and not the fill cap. This ensures that you will find any leaks that may only occur when pulling a hill and working the engine really hard. -= You know... that area of engine operation where it would count the most,., like pulling a steep mountain at 80,000lbs, and its 120-F outside, and at 6,000 feet altitude.. when you need it not to fail because your in the middle of nowhere.

next: checking for coolant leaks does not involve watching the air pressure gauge except to ensure it is kept at full pressure. It is actually is quite normal for some of the pressure it to fall off a bit as the truck and engine cools down, or sits over and entire night while testing it. -= and if it falls off, just top it off again, no big deal. 15+ gallons of coolant will contract b y a lot as it cools down, making it seem as if it lost pressure somewhere.

It is not "AIR" your checking for leaking.. it is COOLANT. -= SO WHAT YOU LOOK FOR AND WATCH FOR IS actual COOLANT leaks, both externally, and internally to the engine if necessary.

Lastly, coolant leaks tend to almost always get worse and easier to find as "cold leaks" too. This means that any leaks will show up more when the engine has cooled off and has sat all night with a pressure test kit on it. Hot seals are soft, but as they cool, they stiffen. So ... because metal components will shrink slightly and seals will get stiff, that is why the leaks show up more after, or as the engine has cools off during the night.

This means that you mentioning a simple "5 minute test", and at only 15 psi .. is only a simple quick check. This if fine if you have an immediate issue, but if you want to test the system properly.. it has to be done over night.. over several hours, and at 20-PSI. This is important to do every so often for someone who has to make their living with the truck every day.

Hauling freight for hours on end with heavy loads and working that engine and truck hard is nothing to skimp about. Running up and down the roads day after day.. across god knows where and at what altitudes.. at god knows how much weights... an over-night test is the proper way to test the coolant system if you want to stay on top of any future coolant leak issues or potential failures.

AND ... if your loosing a gallon every here and there. .. and you do a coolant leak test over night and find zero leaks.. then it is time to drop the oil pan, open up the EGR cooler exhaust piping .. and find the issue, because it is most likely an internal leak and those are the most damaging.

BrandonOlsen

(12-06-2022 )Rawze Wrote: Acually, checking the coolant system on a big truck should be done at 20-psi, not 15 psi. This is done by applying the test kit in place of the pressure regulator cap and not the fill cap. This ensures that you will find any leaks that may only occur when pulling a hill and working the engine really hard. -= You know... that area of engine operation where it would count the most,., like pulling a steep mountain at 80,000lbs, and its 120-F outside, and at 6,000 feet altitude.. when you need it not to fail because your in the middle of nowhere.

next: checking for coolant leaks does not involve watching the air pressure gauge except to ensure it is kept at full pressure. It is actually is quite normal for some of the pressure it to fall off a bit as the truck and engine cools down, or sits over and entire night while testing it. -= and if it falls off, just top it off again, no big deal. 15+ gallons of coolant will contract b y a lot as it cools down, making it seem as if it lost pressure somewhere.

It is not "AIR" your checking for leaking.. it is COOLANT. -= SO WHAT YOU LOOK FOR AND WATCH FOR IS actual COOLANT leaks, both externally, and internally to the engine if necessary.

Lastly, coolant leaks tend to almost always get worse and easier to find as "cold leaks" too. This means that any leaks will show up more when the engine has cooled off and has sat all night with a pressure test kit on it. Hot seals are soft, but as they cool, they stiffen. So ... because metal components will shrink slightly and seals will get stiff, that is why the leaks show up more after, or as the engine has cools off during the night.

This means that you mentioning a simple "5 minute test", and at only 15 psi .. is only a simple quick check. This if fine if you have an immediate issue, but if you want to test the system properly.. it has to be done over night.. over several hours, and at 20-PSI. This is important to do every so often for someone who has to make their living with the truck every day.

Hauling freight for hours on end with heavy loads and working that engine and truck hard is nothing to skimp about. Running up and down the roads day after day.. across god knows where and at what altitudes.. at god knows how much weights... an over-night test is the proper way to test the coolant system if you want to stay on top of any future coolant leak issues or potential failures.

AND ... if your loosing a gallon every here and there. .. and you do a coolant leak test over night and find zero leaks.. then it is time to drop the oil pan, open up the EGR cooler exhaust piping .. and find the issue, because it is most likely an internal leak and those are the most damaging.

Rawze,

Many thanks for taking your time to respond with a detailed post. Let me tell explain what caused me to pressure test it to begin with.

Fuel mileage had gone down roughly 1mpg in the last month and a half. Never saw any drop in performance or boost just bad fuel mileage. Couple weeks ago I made a post about my turbo spooling at idle which it’s never done. Thought maybe it started doing it because it was cold out. Sitting next to another truck same exact year same engine, same setup and their truck doesn’t do it at all. Did EGR tune up and that had no change. Did a forced regen after the tuneup and that made the turbo spooling at idle significantly less but is still slightly there. This last week I started to pull some hills and it was 5 degrees (Iowa) and I could see in my driver side mirror what seems to be smoke or stem and puffing away. Stack tip was white and had white stuff on the back of the cab from the smoke. Noticed my coolant was a little lower than what it normally when I stopped to check it. I keep coolant at the full line. When truck gets up to temp the coolant rises past the full line and stays there. Shut truck off it goes back down to full line. So day before yesterday I pressure test the coolant system and found a leak off the hose from thermostat housing and tighten the clamps and pressurized it again to make sure leak was solved. Left it for 30 minutes and didn’t lose any air. I will today pressurize it to your recommendation and let it sit tonight. My spot load ever since owning this truck has stayed between 0-2% once in awhile got to 3%. In the last week it went from 2% up to 22%. Regen history on insite looks good. Shows “normal” and all recent regens. I pressurized the air to air intercooler and found a good size leak. I’m curious if the air to air cooler could be the one causing these issues ? I asked my father in law and he says no. But he’s never dealt with these newer trucks. His newest truck is a 2007. Mine is 2018. The air compressor is a little bit noisy as well. It builds and maintained pressure fine but when compressor kicks on it makes the air intake have a continuous “popping” noise while it runs . It also does It going down the road constantly at high rpm’s . I noticed this week when I pulled the truck into the shop that my valve cover gasket started to leak on both sides. Not bad but still leaking reguardless. Don’t really think I have excessive blow by through the breather or oil fill tube. I’ve talked to a few shops and all they want is to throw parts at the truck. I can tell they just simply don’t understand this engines. They can replace parts but that seems like that’s it. I’m capable of doing a good portion of everything myself.

Sorry for the long post!

ahub86

Not sure if it fits in with all your symptoms but could the steam/smoke be DEF? I had a DEF doser go bad and drizzle the DEF into the pipe rather than spray. It “steamed” for sure. I just was noticing that your stack looks similar to a DEF stain.

Not pertaining to your situation but a learning story: My doser was drizzling through and I didn’t know it. I was in a job in the morning and left my key on (engine off) listening to the radio while I waited my turn to unload (pressurizing the DEF system, oops). It pumped like 2 gallons into the system. When I fired that up and took off STEAM was an understatement. I learned that the DEF system is pressurized with the key in the run position and if I want to listen to the radio with the truck off now I turn it back to accessory position. Lol