Coolant Loss

[rickrat]

I have noticed a strange occurance with my 1983 6.9. Every month I need to add about half a gallon of antifreeze. I have no white smoke coming from the exhaust. Oil looks good. No "milky" stuff on the oil filler cap. No blow by. No leaks from the radiator or the block (I put a pan under it when parked) I have watched the exhaust under load and no smoke at all. The overflow container is good. It runs at the proper temps., no overheating at all. Starts and runs perfect.

Just seems like every month Im a few inches below the filler on the radiator. I have emptied the overflow container, and it will stay empty as the level drops in the radiator.

Any ideas?

 

[argve]

You can pick up some dye at the autoparts store and then use a black light to find the leak - I mean it has to be going somewhere.... Drop the dye in the system wait a couple of days then start playing CSI...

 

[rickrat]

Thats a good idea, thanks. I have been searching for the green antifreeze with no luck. Is it possible to have a head gasket just seep a little and cause just minor coolant loss? I would think that it either goes to leaking big time or not at all.

 

[Agnem]

Yes. The 6.9's are known for leaking coolant externally at the rear corners of the heads, under load. Usually, you can smell it at some point. They have been fooling around with different gasket combinations over the years at the coolant passage locations, and I believe currently the best gasket type has a viton O-ring (ok, I know it's not really a round circle, but you know what I mean). Usually, when a 6.9's head bolts get tired, this is the first problem to show up, especially if it has an older head gasket design without the O-ring. you can track this problem by throwing some baby powder on the back of the head and block (already cleaned). The coolant leak will streak the powder. They decided to eliminate these water passages on the 7.3, which (in my opionion) is why 7.3's are known to overheat more than 6.9's.

 

[rickrat]

Is this something that I can live with for a while? Or is this an indication that it needs to be fixed now or it will end up blowing on me at the worst possible time?

Thanks!

 

[2manydsls]

The 6.9 that was in my 84 camper van went through a lot of coolant and used a lot of oil before I removed it. Most of the coolant came out of the area near the block heater. It had the dreaded crack by the block heater. It never dripped on the ground. It seeped out from under the starter when it was running. I put enough various types of stop leaks in it to plug a ****. Some worked for a short while. I finally weighed the cost of antifreeze and oil against changing out the engine, and the changeout won.
Ross

 

[riotwarrior]

Mel, not sure if this is the correct area but here is a pic of the 6.9 in the ole F250 I am scrapping out. You can see there appears to be a coolant leak down the back of the engine.

 

[Robert Davis]

I came to this forum thinking that I could be helpful but Ive got to say theres a lot of good tecks here.I agree there bad at leaking at the corners of the head front and back.Im sure you would have noticed by now but you dont have a sweat smell in the cab from a heater core leak do ya?If it was burning the coolant I would believe it would build pressure and push coolant back into overflow resavoir or have got a lot worse.I would pressure test my radiater after eng is warm it might even be somthing as simple as a hose leaking.

 

[Diesel JD]

Yep the back and front corners is where they fail on the 6.9s. My truck actually had the external leak plus it was blown in several places close to the firing ring. I was probably pretty close to having some real problems right before I pulled the heads, but still there was NO swapping between the coolant and oil. The really correct way to do this is to pressure test the cooling system, usually if it isn't the head gaskets it is a loose hose clamp or a bad hose. Also don't expect the water pumps to last forever, however they are pretty durable. The heater core always leaves you with that sickening sweet smell in the cab when they fail. Easy fix.

 

[rickrat]

No sweet smell in the cab at all. It has a relatively new heater core in it. I have used a mirror and cant find any seapage anywhere. I may try some Bars-Leaks and see if that helps.

 

[f-two-fiddy]

NOOOO, stay away from temporary fixes. Find the leak, and repair it.

 

[fuzzy1626]

NOOOO, stay away from temporary fixes. Find the leak, and repair it.

Stop leak can stop up things you don't want stopped up.
In an on the road emergency, maybe.

 

[Agnem]

Mel, not sure if this is the correct area but here is a pic of the 6.9 in the ole F250 I am scrapping out. You can see there appears to be a coolant leak down the back of the engine.

Yup that's a good example there.

 

[rickrat]

I have heard several people comment positively on the Bars Leaks. I have never used it. Someone told me that the factory actually uses it in their new vehicles now to ensure no future seepage. Not sure how true that it either.