Coolant loss

[saburai]

Hi Gang!
The mule is running like a champ, pulling the big travel trailer from NY to Florida. With the turbo and the baby moose, it's like a different truck. However, I've been going through a bit of coolant. Maybe a gallon and a half since leaving NY ten days ago. Oil level looks good and the oil looks good too. No real signs of leakage, but I do smell coolant at times when I shut it down... Any ideas or insight would be greatly appreciated!
Edited to add that the coolant temp is pretty consistent at 200-210 except when pushing it, it will approach 230 at which point, if needed I'll back off a bit and it comes right down.

 

[Thewespaul]

Do you smell it coming out of vents when the heater is on? Could just be a slight head gasket leak. I’d test the exhaust for coolant

 

[Macrobb]

Because a lot of leaks won't show up unless you have pressure, you might try pressurizing the system and see what leaks.

The 'easy and expensive' way is to get a cooling system test kit that basically replaces the radiator cap and allows you to put compressed air in(15 psi).

The 'cheap and dirty' way is to just get a tee and piece of hose for the heater core, stick the tee "in-line", and put compressed air into the tee.
You'd probably need a few parts from the local hardware store, and/or harbor freight. a $5 compressed air regulator(with gauge) from there is what I'm using in my test setup.

 

[saburai]

Do you smell it coming out of vents when the heater is on? Could just be a slight head gasket leak. I’d test the exhaust for coolant

How?

 

[saburai]

Because a lot of leaks won't show up unless you have pressure, you might try pressurizing the system and see what leaks.

The 'easy and expensive' way is to get a cooling system test kit that basically replaces the radiator cap and allows you to put compressed air in(15 psi).

The 'cheap and dirty' way is to just get a tee and piece of hose for the heater core, stick the tee "in-line", and put compressed air into the tee.
You'd probably need a few parts from the local hardware store, and/or harbor freight. a $5 compressed air regulator(with gauge) from there is what I'm using in my test setup.

I've got a pretty good Fourny regulator on the little pancake compressor that lives in the truck, I could use that. What would you use fitting wise to tee in? Also, I'd imagine that I might be able to source a radiator cap w/ a pressure fitting. Or perhaps just make one myself - just thinking out loud...

 

[Sidewinded_idi]

I had it happen before where I had the 13 psi cap on and it was pushing coolant past my oil cooler. Oil would look fine but when I.D drain it it would come out the pan. I went to a 7psi cap just until I rebuild the cooler and I haven’t used coolant since

 

[Thewespaul]

give the exhaust a sniff and if you smell a sweet smell like coolant you are burning coolant. you can use something like this to test for co2 in the coolant https://www.amazon.com/dp/B01N2S0DG6/ref=psdc_15706961_t2_B000NPDL76

 

[saburai]

I had it happen before where I had the 13 psi cap on and it was pushing coolant past my oil cooler. Oil would look fine but when I.D drain it it would come out the pan. I went to a 7psi cap just until I rebuild the cooler and I haven’t used coolant since

Thanks! I've got a 15psi cap on there now. Any down side to going to a lower psi cap? Oil level is pretty consistant so I don't suspect it going in it the oil in any quanity.

 

[DaveBen]

The lower cap pressure, the lower boiling point of the coolant. You could get to the boiling point quicker when working the truck. Stay with the 15 psi cap if possible.

 

[Macrobb]

I would seriously recommend pressurizing the system to the recommended 15 psi and seeing what leaks... chances are it's a hose or fitting. If it's leaking now at 15, it'll probably leak sooner or later at 7.

And I was always under the impression that the extra pressure in the cooling system helped to reduce cavitation slightly?
I know that it increases the boiling point too.

 

[Sidewinded_idi]

Thanks! I've got a 15psi cap on there now. Any down side to going to a lower psi cap? Oil level is pretty consistant so I don't suspect it going in it the oil in any quanity.

Go to the 7, if you can’t find one pm me I have a bunch of new ones. Factory cap was 7psi. I work my truck hard even up to 240 degrees and see no I’ll effects

 

[saburai]

Thanks Guys! We're at a friends house near Ocala for another day or three. I've got a five hour drive left to our place down south. I definitely pressurize the system after we settle in a bit. For now, I'll just keep on going as is. I could crawl under and look but I'll ask instead. Where does the tee in the heater hose go to?

 

[chris142]

The truck calls for a 13lb cap. The less pressure without boiling the better.

 

[Thewespaul]

Yep these had a 13 psi cap stock

 

[madpogue]

You should be able to borrow a pressure test kit from the FLAPS. You put down a deposit for the value of the kit (or leave a CC number), and get it back when you return it.

The other thing to test, if you're concerned about a head gasket leak, is for exhaust in the coolant (rather than vice-versa). "Combustion leak test" aka "Block test". You remove the radiator cap and put a tester with a tell-tale fluid in its place, and run the engine. The tester "sniffs" the air space above the coolant in the rad. If there's a coolant-jacket-to-exhast breech in a head gasket, the exhaust gas will eventually end up in the space above the coolant in the rad, and will test fluid will turn color. FLAPS may have this for loan as well, but you'll probably have to buy the test fluid.