911 Diesel Down! No pressure in Cooling system, AGAIN. WHY?

[6 Nebraska IDIs]

I don't understand this. I've had so many cooling system problems its unbelievable. But its doing it again, my brown truck is over heating because of a lack of pressure in the cooling system. I pressure tested the system with my radiator cap on it and everything holds pressure so what would cause it to not build pressure? Did my water pump snap a rotor shaft or what happened. I need to know quickly what you guys think the causes of this problem could be because I am supposed to be driving 2hrs back to Kearney today. I have work tomorrow and I need to know whats wrong. Please help quickly.

 

[DaytonaBill]

I wish I could be better help than this, but it seems to me that if your cooling system can't pressurize, then it has to be going somewhere...

As far as I can visualize, it's leaking either into your engine or outside. A failed water pump would not prevent steam pressure to build up. So, it's either leaking into the engine, or it's turning your motor oil into a tanish goo...

If you don't see either of those, then surely your exhaust is white with a sweet antifreeze smell.

Regardless, you need to find another ride to get where you have to be for tomorrow... Uncle Murphy is back...

 

[6 Nebraska IDIs]

If I pressure test it, which I did, it held 14psi for over an hour so I don't know how it could be leaking anywhere. God this has me so confused it doesn't make any sense.

 

['94IDITurbo7.3]

where did you connect to to pressure test the system?

 

[typ4]

a lack of pressure will not cause overheating unless over the boiling point of coolant. What king of gauge do you have and I have only seen one impeller slip on the shaft and it was not an idi.
Put the pressure tester on it , dont pump it up,and then start it and see if it builds pressure.

 

[Yukon Tyler]

use your pressure gauge and the adapter to pressure check your rad cap.

the rad cap is calibrated to allow a certain pressure in your system, which in turn raises the boiling point and heat carrying capacity of the antifreeze. if your system holds pressure and does not leak down during a pressure test but then fails to do so with the cap installed then it sounds like you've found your variable.

 

[The Warden]

If I pressure test it, which I did, it held 14psi for over an hour so I don't know how it could be leaking anywhere. God this has me so confused it doesn't make any sense.

Was the engine hot or cold when you tested it?

I wonder if it could be some sort of leak that's only becoming apparent with heat expansion? Just a random thought

 

[6 Nebraska IDIs]

It was hot when I tested it. My tester is the Artic Fox Coolant Dam, google it. It has the ability of testing your cap and the system at the same time. I didn't have a fan shroud on this truck so I cut one up to fit around the intercooler and I have it running up against a wall right now to see if it will pull air through it and overheat again.

 

[CurtIDI94turbo]

I hate to say it but I agree with the Warden as I've had a Pinto (NO snickers please) that had the same issues until it became hot and coolant would leak out of a crack in the head. Maybe a retorqe of the heads could help but we need more experienced people here as I'm working off of a gasser and not a diesel.

 

[gingrass179]

hopefully you dont have my problem...i was having issues with over pressurizing. I tested my cooling system and it always held pressure than as I had the system pressurized I turned the engine over by hand til all of a sudden I started losing pressure...i had my first look at block worm at the bottom of a cylinder

 

[Goofyexponent]

Sean, I thought I had a cooling issue as well. My truck would run at *207 according to my mechanical gauge. I thought that was great, but the heater never really put out enough heat for me. I thought myybe my heater core was getting plugged up, so I never really put any more thought into it.

UNTIL just the other day. It was 30*c here...86*F, I was pulling wood out of a skidder path in 4x4 low and my mechanical gauge was showing over 220*....That ain't right!!

So I took my temperature gun and shot the thermostat housing and came up with 170*...I shot the temperature sender(top of the water pump) and came up with 165*...teh rad was no warmer than *120...so I drew the conclusion that my truck will only run up to about *150 - *150 unloaded, whole runnig moderately.

Make sure that it isn't just your sender taking a dump on you making you think it is overheating.

How do you know positively that it's not building pressure? Did you pull the rad cap when she was warm? (put a rag over it and use nice thick work gloves...as soon as you turn it run like the damn blazes and pull that glove off your hand in case it gets soaked in hot coolant!!)

 

[subway]

a safer way to check if its building pressure would be to do what Russ suggested with leaving the tester on the truck and watching the pressure climb. it should be a slow gradual climb as the engine warms up, no need to pull the cap and scar yourself. if the pressure immediatly builds quickly you got a headgasket problem.

i also assume the cap is tested and the seals on it are good

you do not need a water pump to build pressure, my old tractor is water cooled with no waterpump at all. it just uses the thermal siphon method to move the fluid, as the coolent gets hot it rises out of the motor and as it cools it passes down it travels down the radiator. there is not even a thermostat in the system but it can build pressure just fine.

an IR gun can help you out a lot in instances like this, you can check your head temps, verify your sendor and verify the radiator is cooling effectivly. i went through watching my gage peg and come to find out the engine was running 180 the whole time. less than 5 mins to check with a IR gun.

 

[6 Nebraska IDIs]

Apparently its just where my truck is going to run at in the warmer temps outside. I drove it back to Kearney last night and it never got over 180*. I've never seen it get that hot before so it kinda freaked me out. My factory water gauge is useless it will practically wave at me when I'm driving on the interstate going from the hot side to the cold side. Thats why I installed the mechanical mercury filled tube water temp gauge, old school but very accurate. I guess I'll just drive it and see. I know its not building pressure because I can squeeze the radiator hoses. If I let it sit at idle with the pressure tester on it, it does build pressure up to about 10psi but when I start driving it something goes to hell and I lose pressure.

 

[Goofyexponent]

Hmmm....I wonder if you could temporarily plumb in a coolant pressure gauge? Hell, an electric boost gauge might do, but I don't know about the temperature hurting it.

Do you own an IR temperature gun? I bought one a couple years back for like $30 on sale from $120. Best $30 I spent that year on tools. My gauge was showing over 220, but a quick check withthe IR temperature gun showed me I was actually running at about 165* - 170*...Made me breathe a HUGE sigh in relief.

Hell, last fall i was so sure I was overheating I bought a new thermostat and gasket (motorcraft from Rock Auto) and I never installed it. (Cooler temperatures made the engine run evel cooler, like 140* - 150* with that Alum. rad.)

 

[chvycmnslvr68]

Harbor Freight has the thermal guns for $30 new ... I compared one to a snapon gun and it was within one or two degrees all the time ...