OK Team what could possibly be causing this, as I've posted in the past.

1. I'm losing coolant at what seems to be a sudden loss that is every now and then. I originally thought I was losing about 1-2 gallons every 400-500 miles, but after closly monitoring and not seeing too much of a loss untill all of a sudden it's gone. Leads me to believe that I lose alittle and then bamm, A bunch.

2. I pressure tested, all ok.

3. No coolant in oil and no Oil in Coolant.

4. All hoses checked and double checked.

5. Drained and flushed Heater Core, all good.

6. One visible sign of water damage in engine compartment, is Rust, redish-orange rust on the steel injector lines and some surface rust on the valve covers.

7. Overflow Res looks fine.

8. No visible leakage, compression test looks good and averages the same across all 8

9. Got a new T-Stat (International) and New Rad Cap (13PSI)

10. I'm going broke buying coolant and additive and cannot manage the addditve mixture with a loss rate like this.


TOP Question: Could the Cab Heater have something to do with the flow/pressure of the coolant and where other than the Htr Core would I see a prob.

Second Question: My dry Bottle for the AC frosts over pretty good every now and then, so much frost forms up the suction line, could this have an immpact on Coolant flow? Is there a tie between AC and Coolant Flow?

 

There are two coolant passages in each head that are very close to the end of the head. If they are leaking on the back you would have a hard time seeing the coolant between the cab and motor. My 86 6.9 would do something like what you are describing. Periodically it would fill the back intake manifold web up to the top of the glow plug. It would do that for a day or two and then not leak for a week or month or three months. Never knew when, nothing in common with when, it just did it. There are no coolant passages in the intake manifold. Closest passage is the head to block passage through the head gasket. Do you ever see a steam trail out the exhaust? Do you ever see puddles under the truck engine?

There is no connection between the AC and the coolant other than both have coils in the heater.

AC compressor will run when the defroster is turned on if the cab temp exceeds the heater / AC thermostat setting. When it runs frost will build up on the suction line even in the winter as long as there is enough moisture in the air to condense on the lines.

 

No steam or smoke at all, I will crawl under the hood and take a close look at the rear of the engine. I hope I don't have to do a head gasket job. Just finished a valve job and now wonder if I screwed up aligning the headd gasket. Hmmmm No visible leakage on the ground either. Figured, I would have a visble smoke trail if I was leaking out the head gasket into the exhaust or milky oil if it was leaking back into the engine from the gasket. I have neither signs.

 

I would imagine if it were going to the cylinders (bad head gasket) you would be able to smell the anti freeze in the tail pipe if you are loosing as much as you describe.
Why dont you get an oil sample and take it to a CAT dealer and get it done now. If it were the heater core, you would be getting anti freeze in the cabin and start your own car pool. Maybe these few thoughts may help you out. A $20 oil sample would save the engine if you tried cranking and had a cylinder full of coolant.

 

yeah, I'm gonna do the oil sample, but the oil is not milky?

 

i took an oil sample this morning and will send it in monday.mine seems to use more when it gets worked hard.when pushing this heavy,wet snow you can smell anti freeze but cant see it anywere.im thinking a small head gaskit leak or maybe a small crack in the head that opens up when the engine gets hotter than normal.might cap off the heater core and try some bars leaks to see what happens.what do you guys think?

 

I'm in hopes that I do not have to pull the engine again right now, so what exactly would coolant coming out the exhaust smell like. i like to eat, can we relate it to food. HA?HA, I'm serious in that my nose sux, everyone say smell this smell that, I just cannot tell a smell, unless it's bad fish. I relate to sight, and I do not see smoke coming from the exhaust at all, every now and then a burst of white at cold start up, but I believe that is normal for diesels. Everyone I know here with Diesels are proud of how easy mine starts when it gets colde here, and It is not really that cold, say 20 degrees. I cannot wait to see how the truck does when I move back north. But want it ready.

This site has helped out so much, and am collecting so much data, in hope to post a web site dedicated to my last 6 month's of work on this truck.

Thanx All

 

We had a similar problem with our 86 6.9. It would be fine for a month,(checked everyday), then all of a sudden, overflow would empty out.

Finally found it when plowing. I worked the motor and waited until the temp got a little higher than normal, and the clutch fan would kick in. Figuring that's when the engine was hottest and the cooling system pressure was at it's highest, I would get out and smell the exhaust. Very VERY faint smell of antifreeze, not enough to make steam, but enough to smell it. If the motor wasn't working hard, it didn't smell, but when we got to working it, the smell was there, and the next day, the overflow would be empty. This all started after a head removal to retrieve broken glow plug tips,( damn autolights)

So off come the heads again, but this time instead of working my was up to 80 ft/lb's, I brought it up to 70, then waited till next morning, then brought the bolts up to 80. Gives the new head gaskets all night to compress. 30K miles later, no leaks.

Learned that back in the race engine days, when we'd blow out $200.00 copper head gaskets after 2 runs on an 800horse BBC.

Put a cloth glove on na hold it over the tailpipe, this sort of concentrates any odors into the glove, may help detect the sweet smell of antifreeze.

 

If you can, get your hands on a cooling system pressure tester.(Rent one from parts store, rental joint, etc.)I wonder if it is possibly a cold water leak? Park the truck on a big clean piece of cardboard and pressurize the cooling system up to 12-15 psi. with rented tool. Leave system pressurized for at least 1 hour. Check for anti freeze on cardboard. Make sure that gauge on tester reads same pressure as before. If no leaks, release pressure on cooling system, run engine and get fully up to temp. Pressurize system again for at least 1 hr. If cooling system is leaking externally it will show on this test. If that much coolant were leaking internally your engine oil would definatly be mikly. That leaves the exhaust. Have a friend follow you while driving, watching the tailpipes. The coolant can only go so many places.

 

Man, I gotta a niece pressure tester thanx to the Army Supply System and did a basic, test which came up good, but I'm gonna run out do a bit more like you said. Thats a real good ideal, has for the buddy following; done that been there. No Smoke and No liquid. It's like a big trick being played.

 

What kind of antifreeze are you running now? If it has a leak guard / stop type of formula it may be sealing the leak till you get it in a particular condition. Then it leaks for a while and stops again. Till the next time it is stressed. Then it breaks loose and dumps a bunch till it seals again.

 

Interesting, I was using some Fleet from the International shop here in town but turned to NAPA because they are closer to the house and well I'm replacing too often. I would like to hear more on your theory. The NAPA brand is I believe calle FleetCharge, it's pre-charged with the CSAs. Tommorrow I pick up a new upper and lower hose and my buddy is bringing back my pressure tester. I am gonna try and get some dye and do some more diagnostics. Next after that I guess will be another compression test. Should be able to drop an Oil sample off at the Cat Shop here, I need to call them an see if they can do that for me. I would settle for a blown head gasket but with the NO SMOKE situation I don' think that the problem, the power is good, the same has always anyhow, along with no milky Oil or Coolant, I'm just in Awe. I hoipe and Pray it's not the C-word.

 

You should be able to get some dye that you can use an ultraviolet light and see it even after it is evaporated.
I do not know if it will work if it is going through your cylinders but it will show up if it is going external.

I never did find mine, it was very intermittent just like yours, the day I took mine to the shop to change the engine a head gasket blew out completely on the number 2 piston. I had seen antifreeze form time to time in the intake manifold web by number 7 intake for a couple of years. It only leaked every three or four months, a gallon or so, then it quit till three or four months later. Strange kind of leak. Never did figure out how it got up there cause there is no antifreeze in the intake manifold.

If you had cavitation you should be getting compression pressure in the radiator.

I just blew a head gasket, cracked block. When the engine started it took 25 seconds of idle to build 15 pounds in the radiator. I also do not think cavitation would be so intermittent.

If you use a block sealer it seals when the pressure is inside the cooling system. When you reverse the pressure by letting the motor cool after being hot, it blows the patch off the hole, letting the leak start again. It will reseal after some time running the engine and building pressure again, but how much leaked out over night?

Cooling system leaks are funny sometimes, the smaller they are, the harder they are to find, and the stranger they can act.

Personally I like the lower radiator hose blowing, no questions, no guessing, plain and simple to find and fix.

 

Just a thought their is a sending unit or possibly it might be the block heater but it is behind the stater you cant see it unless you take the starter out .

 

I'll check that spot, I am picking up the Oil Sample kit today. When I did the Pressure test, I pressurized up to 15 with the kit and it held, then started the truck and ran it for about one minute or so and it held steady, I'm no certifified mechanic and can do the test again, but these results prove good to me, what do you think.