Coolant leaking from...somewhere

RSchanz

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2 of my 6.9s leaked at rear passenger head & 1 at passenger head top front corner when head gaskets had leaked. You may try re-torquing head bolts (they may break), I chose to replace. I think age got to them more than anything else. I visually checked the heads, no milling, cleaned up with brush on a drill, lapped the valves & new seals. I did replace the lifters, pushrods and 7.3 rocker arm assys since they were cheap for good new ones on eBay when eBay was thrifty for US Made engine parts. Studs were not the 'thing' at the time for the first 2 trucks or I would have used them as I did on #3. No trouble afterwards.

Guess re-torquing the headbolts isn't too much work and worth trying before replacing the entire head gasket right? UV dye and flashlight come today in the mail.

The leak I struggled to locate was
AF from a barely leaking radiator being flung into the engine by the fan. Not until the leak became greater did I finally see droplets jumping from the fan to the block.

Radiator is new and I think it's pretty solid.
 

RSchanz

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Unless you snap the head bolt and find out it’s not leaking there anyway. Identify where it’s coming from and fix that problem. If it is leaking from head gasket then it may be worth a try to retorque before pulling heads.


A friend mentioned that sometimes pressure builds up because certain check valves get stuck etc. He isn’t speaking directly to 6.9’s but just in general but idk if our systems work that way. I will say I just took the rad cap off and some fluid spilled over and it seemed pressurized. I also heard it kind of allow some fluid to go into the overflow tank. Truck hasn’t run since Thursday.

Is it possible it’s some kind of excess pressure build up that is making it leak somewhere? It’s probably also worth pointing out that the coolant doesn’t look contaminated with oil so it makes me hope it’s less likely that it’s the head gasket.
 
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gnathv

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It is odd that it would hold pressure since Thursday if you have a leak. It may only leak at pressure. The valve you have in the system is your radiator cap, seems to be sealing. If combustion was getting into coolant system normally your radiator cap would vent and overflow your coolant reservoir. Are you sure it’s coolant your seeing leak?
 

gnathv

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I’ve read it all and I don’t see where you say you’re having trouble with overheating. You do say you had to loosen a hose clamp to adjust ip. I’d look at that hose very closely.
 

david85

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I'd look around the thermostat housing, and engine side of the upper rad hose. It's too much of a coincidence that it would start leaking after recent work on the injection pump, which is right next to it. There is also a coolant temperature switch nearby. There is also the heater core hose on the passenger side head. I'd make absolutely sure the source of the leak is not these minor locations before taking drastic measures and retorquing the head bolts.

I had a slight leak at the top of the rad hose that would run down the hidden side of the thermostat (goose neck) housing, down the side of the engine and then follow the head gasket edge to the rear of the block. Caused quite a scare until I realized it was just hose leak from the top of the engine. But at first glance, it looked like a head gasket leak.
 
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IDIBRONCO

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Identify where it’s coming from and fix that problem.
YES! This is the solution right here. It sounds to me like you've almost got yourself convinced that it's a leaking head gasket, but have you actually checked? Don't assume anything from anybody else's experiences. Do the checking and find your leak. Don't worry about where theirs was at. Yours may be simple to fix and then again, it may not be. You won't know until you find out where your leak is at.
 

RSchanz

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It is odd that it would hold pressure since Thursday if you have a leak. It may only leak at pressure. The valve you have in the system is your radiator cap, seems to be sealing. If combustion was getting into coolant system normally your radiator cap would vent and overflow your coolant reservoir. Are you sure it’s coolant your seeing leak?

It does only seem to leak when the engine is running so under pressure. Pretty sure it's coolant because its clear and it doesn't smell like diesel.

YES! This is the solution right here. It sounds to me like you've almost got yourself convinced that it's a leaking head gasket, but have you actually checked? Don't assume anything from anybody else's experiences. Do the checking and find your leak. Don't worry about where theirs was at. Yours may be simple to fix and then again, it may not be. You won't know until you find out where your leak is at.

I'm definitely not doing anything drastic until I check the basics. The UV test should clearly indicate where it's coming from which I'm excited about.
 

RSchanz

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Be sure to let us know what you find, I’m curious now.

UV dye and flashlight didn't get delivered today so now expected to arrive tomorrow or the day after. Stand by...

I did replace the radiator with a champion rad and I decided to keep the old rad cap instead of using the champion one. Depending on what I find and maybe regardless I wonder if I should switch to the one that came with the Rad. Maybe that would help with the pressure relief. As stated I've probably driven over 300 miles since replacing.
 
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Kurt_M

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My mysterious coolant leak that showed up about the same place as yours was the heater hose where it attaches to the right side head. It was leaking when cold but hard to find it as after it ran a while the manifold heat boiled all the signs away.
 

Big Bart

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Thoughts about your issue.

1) Don't asssume (You know the saying), test and conclude. Borrow or buy a decent video scope, they are $100-150 for a decent one. (Less used on Offer up or CL.) Then you can see in the tight spaces.
2) I agree with a couple others, you likely when taking off or loosening the upper radiator hose at the thermostat housing caused the hose, housing, or housing to block gasket to give up the ghost and leak. The housing to block gasket area is hard to see with the alt in place. So take your time and get a close look. The silver linning in this is it leaks when running, VS only when driving or very hot. That housing is about 10" long if you have not removed it before.
3) It could be coincedental you found somehting that was leaking prior. So look closely at the freeze plugs, block heater (If yours is on the passenger side.), head gasket, and head for a crack. But keep in mind that head to block gap/line could be just the path the leak is traveling down then dropping mid engine but coming from something simple.
4) How I always try to determine a leak is to look at the coolant overflow tank and then open the radiator. (When cool) to see if the coolant is down. Then you can conclude a coolant leak. (You mentioned you are not 100% sure.)
5) As stated above add coolant dye and do some testing.
a) Do you see water or dye in the oil. (Milky white on oil cap or on dipstick. If so head gasket, water pump bolts, or oil cooler seals. May be a seperate issue, don't assume.)
b) Do you get instant pressure build up in the radiator with your hand over the radiator opening when the truck is running? (Do it when cool, don't burn yourself on 200 degree coolant.) This points to a head gasket, so pick up a test kit and test for gases at the radiator cap hole to confirm. Yes on gasses, then clearly head gasket.
c) Do a radiator pressure test. (Autoparts store will likely loan or rent you one.) Start at 10psi and see if you can find the leak. If not go to 13psi. Go to zero PSI and start the truck if pressure builds again points to a head gasked. But I would not go higher than 13psi as these engines are all aging. You can make it leak, but without the engine running or getting hotter. Now with the die and flashlight you can see where the leak originates from. Remove what is needed if you cannot see the start of the leak and find where it is coming from. (IE could be the thermostat housing (But you cannot see that area with the alt in place, but running along the block, to the head, down the head gasket, and dripping mid engine.)

Wishing all the best and that it is something simple!
 

coffeerich44

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I went through the same thing your going through now. Coolant leak on the passenger side of the engine. It was hard to tell because the fan blows it all over the place but my first thought was "oh no its the head gasket" because apparently they do that after awhile. I dried everything up as best I could and then pressurized the the cooling system with a stant pressure tester and to my surprise, and relief it was the thermostat housing. Its hard to see it due to the location but I got lucky it was able to se. They are pretty tricky to seal right so you have to be careful cleaning it up good before you reinstall it. I've done a lot of thermostats in my day on all different cars and trucks and this was the only one that gave me trouble. Hopefully that's your problem too since its the cheapest option to repair.
 

RSchanz

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Well, I'm pretty much lost now. I got the UV dye and the radiator was so full I couldn't add it so I just poured as much as I could in and I'm almost sure that it all just ended up in the overflow tank. Also, there was no dripping leak! That said I haven't really figured out anything. I tried to hold my hand over the rad with the cap off as suggested by Brad but of course the fluid just starts to burp up.

What is concerning me the most now is that the last 3 times that I've removed the radiator cap when the engine is cold fluid will overflow out of the cap as soon as I loosen it. In other words the radiator is getting pressurized when the truck hasn't been run for like 5 days. Does this point to head gasket?? My research shows that pressure from the cylinders might be getting into the cooling system.
 
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