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Discussion Starter #1
Got too many irons in the fire right now, so I haven't gone over the engine for myself or been able to check things over with him but Dad has been loosing coolant, having to add anywhere from a 1/4 to a 1/2 gallon each time he's driving it. He's not seeing any signs of leakage anywhere under the rig or in the engine bay. Even gone to the extent of slipping a large piece of cardboard under it overnight, etc. His coolant overflow has no recovery tank, so I had him tape up a plastic pop bottle to the line, to see if maybe it was overheating and spilling out while he was driving. Nothing was caught. It "appears" to be evaporating or burning off. Not really sure at this point. I'm concerned he may have an internal leak and it's going wherever it would be burnt off.

Looking for tips and tricks to help me figure this out with him when I get the time. Appreciate any help you guys can offer and will answer whatever questions I can but as noted, I haven't been able to dig around yet.

Dad's '78 FSB w/a rebuilt 400 from his old Lincoln. He says he pays more for insurance than gas, so it's not getting a lot of mileage. :doh0715:
 

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Yo Pepe`,
Possible suspects are:
t'stat, water pump, heater core, hoses, intake manifold, head gasket, freeze plug(s).
...

Using a Radiator/Cap Pressure Tester to pressurize cooling system and maker it somewhat easier to find the source.
Some parts stores may provide you one under their loan a tool program.

CHECK COOLANT FOR INTERNAL LEAKAGE
Visually inspect coolant in radiator for signs of transmission or engine oil.

If engine oil is evident on vehicles with an engine oil cooler, remove engine oil cooler and INSPECT for damage. replace if damaged.

If engine oil is evident on vehicles without engine oil cooler or if oil cooler checks out OK, REMOVE cylinder head
INSPECT for leaking head gasket and head or block cracks.

If transmission oil is evident, replace transmission oil cooler, if equipped and check condition of transmission oil.

GL!
 

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Discussion Starter #5
I will be taking all these suggestions to heart. Dad says he's checked the oil and there's no sign of the dreaded milkshake. I was hoping I could have him running it and stick my head around, while he gives it some throttle to stimulate pressure. I can get a hold of a pressure tester from the local O'Really's, if that doesn't yield any results. There are no visible signs of leakage in the regular spots () but if it's only happening under a highway load, it could be blowing off... still, he sees no drips when parking immediately after a drive, so chances are slim. No oil cooler on the '78 but the transmission cooler could be built into the radiator. Not sure yet. I'll get back with more details when I get the free time to dig around it with pops. Thanks guys! :beer
 

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If the head gasket is going out there are a few things that could happen. Coolant could get into the combustion chamber and be burning off causing steam out the tailpipe, coolant could be getting into the oil and give you that lovely milkshake in the oil pan, and the compression from the combustion chamber could actually be pressurizing the coolant which will cause tiiiiiny bubbles to appear in your coolant if you leave the engine running with the radiator cap off and watch.






Or, maybe your pops is just making things up so he can spend some more time with you?
 

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Yo,
A little more on colors;
CHECK COOLANT FOR INTERNAL LEAKAGE
Visually inspect coolant in radiator coolant recovery reservoir for signs of transmission or engine oil.

Inspect coolant in both radiator and radiator coolant recovery reservoir. Coolant should be a green or blue color (depending on brand of antifreeze used).

Clear coolant or coolant only a very light green or blue indicates that there is only water or a very weak antifreeze mixture in the system. Advise the owner of the need for the correct 50/50 coolant mixture.

A very muddy brown color indicates an unauthorized brand of stop-leak has been used. This may eventually plug the system, causing overheating. Advise the owner that the best course would be to drain the system and repair the original concern, flush the system, and refill with correct 50/50 coolant mixture and, if necessary, Cooling System Stop Leak Pellet D9AZ-19558-A or Cooling System Stop Leak Powder E6AZ-19558-A or equivalent meeting specification ESE-M99B170-A.

Make clear to the customer that any stop-leak material is not a satisfactory repair for a serious cooling system concern such as a leaking water pump, gasket, or radiator.

A reddish brown color indicates rust in the cooling system. Advise the customer that the best course would be to flush the cooling system and refill with the correct 50/50 coolant mixture. In addition, add 1.4 liters (1.5 qts.) of Heavy-Duty Cooling System Additive FW-15 or equivalent meeting Ford specification ESN-M99B169-A.

An iridescent sheen on the top of the coolant indicates a small amount of oil entering the coolant. This is common in high-mileage vehicles.

CAUTION: If there is coolant in the engine oil, the cause must be corrected and the oil changed or engine damage will occur.

Check the engine oil on the engine oil level dipstick to see if any coolant is entering the engine oil as indicated by drops of coolant visible in the oil or a milky appearance to the oil. If the oil checks out OK, inform the customer that, while not an immediate problem, the situation should be closely monitored during routine maintenance.

CAUTION: Severe oil leakage to the engine coolant, as indicated by a milky appearance to the coolant, must be corrected or severe engine damage will occur.

If the coolant is a milky brown color (like coffee with heavy cream) engine oil is entering the coolant. On 7.3L diesel and 7.5L gasoline engines the most probable cause is a leak in the engine oil cooler. Remove and inspect to find the problem.

If the oil cooler checks out OK, the head gasket may be leaking around the oil passageway to the cylinder head. It will be necessary to remove the cylinder head, inspect for the problem, and replace the head gasket. If the head gasket checks out OK, then a crack between an engine oil gallery and the cooling passageways could be the cause. Inspect the cylinder block and cylinder head.

A reddish milky appearance to the coolant indicates that transmission oil is leaking into the coolant indicating a leaking transmission fluid cooler, if equipped.

CAUTION: If coolant is found to be entering ,the transmission fluid, the cause must be corrected or transmission damage will occur.

Check transmission fluid to make sure coolant has not mixed into transmission fluid as indicated by a milky appearance. If it has, it will be necessary to flush transmission (7003) and replace filter outlined in the appropriate section. Replace radiator assembly, flush cooling system, refill transmission, and refill cooling system with correct 50/50 coolant and antifreeze mixture.

If chunks of rust are visible on top of the tubes in downflow radiators or in the inlet tank in crossflow radiators, flush the cooling system.

If there is puffy white corrosion around the tubes where they are attached to the core headers, flush the system. If there is corrosion on aluminum radiator parts, there is going to be corrosion on aluminum engine parts that come in contact with coolant.

Advise the owner of the importance of using the proper 50/50 mixture of water and Ford E2FZ-19549-AA Premium Cooling System Fluid or equivalent meeting specification ESE-M97B44-A that contains corrosion inhibitors. In addition, add 1.4 liters (1.5 quarts) of Heavy-Duty Cooling System Additive FW-15 or equivalent meeting Ford specification ESN-M99B169-A.

If the appearance of the coolant is OK, use a hand-held refractometer, such as Rotunda Battery/Antifreeze Tester 021-00046 or equivalent to verify proper coolant concentration. The range is: (minimum) 45/55, (maximum) 60/40.

If the cooling system is found to be low on coolant, top off only from a premixed solution.

If a weak concentration is found, add straight coolant sparingly until concentration readings are within acceptable levels.

If too strong a concentration is found, remove a small volume of coolant and add water sparingly until coolant readings again fall within the specified levels.

NOTE: Make sure coolant is thoroughly mixed before taking readings. This is accomplished by running the engine until the water thermostat opens.

Recheck coolant concentration to make sure the coolant has been brought into the proper concentration.
 

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My vote is to pressure test the cooling system. A common leak source is the heater core with an aged vehicle and could be leaking inside the vehicle. I had some coolant loss myself and, after a pressure test, found a loose clamp on one of the heater hose connections to the heater core. Good luck.
 

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Put two tablets in the drivers side of the radiator fill hole (I say drivers side that way it flows into the engine directly). Just crunch them up till they are powder and pour it in. Did this on my daily drivers and had no problems years now later. No worries about sludging up my radiator or heater core as these dont do that. If you do research on the GM stop leak tablets they were put in various GM vehicles from the factory (2 tablets) to prevent warranty claims for coolant leaks. This is for external coolant leaks; not bad head gaskets; blocks; heads etc. if 2 tablets of these dont work you need to do a repair to fix it.

https://shop.advanceautoparts.com/p/bars-leak-radiator-stop-leak-tablets-3-oz-hdc/89012946-P

Dont forget the 25% coupon code and free instore pickup!
 

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check all hose clamps, a loose clamp could allow just enough coolant to steam its way out and go undetected or even a pinhole in a rad opening up under pressure ,my 78 did that a couple yrs back,hard to find the leak cold,same as rad core , and usually you will smell a heater core


had a leak in inner hose liner and was leaking out the end of the upper rad hose between the inner and outer layer in cord

cooling system pressure test when hot is a good idea,but warm up unit with rad cap off so you don't go burning yourself when you take cap off pressurized system:whiteflag

also check for a bad rad cap, check over flow hose to see if wet inside,could be puking it out there
maybe add an overllow bottle if it doesn't have one
I used a Gatorade bottle on mine for years
 

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I had one years ago that about drove me over the edge. I could smell the antifreeze outside the car, lost about 1/2 gal per week. No wet spots, no drips, no milkshake oil. Turned out to be a pinhole leak in a heater hose that sprayed directly on the exhaust manifold once the engine got hot. It didn't leak when the hose was cold.

All the leaking coolant was boiling off on the manifold, hence no drips or wet spots.
 

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A cheap UV dye test kit can do wonders for finding those annoying leaks. I forget which stores you have on your side of the hill but you can get them at most...NAPA carries dye refills for all automotive fluid types.

 

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Discussion Starter #17
Not a bad idea. Hopefully, it won't get to that point. I'm still running around like a chicken with my head cut-off but I spent some time yappin' with Pop and we went through the list of potentials, again. He's going through about 1 gal. of water for 2 hours highway driving. He's so thinned out now, it's most likely just water running through and I warned him about rust potential. He rolled his eyes, as expected. :toothless

Says he had everything to change his oil ready since winter but hasn't gotten around to it. I told him he needs to at least loosen the oil drain plug and verify that he gets oil and not water, recalling my never resolved search for coolant drip on my last 351W. Verifying no water in the oil pan (milkshake never occurred on mine but pure, clean coolant was in there) should at least eliminate one serious potential problem but still isn't likely a culprit. I also told him checking the plugs may yield some sign he hasn't looked for. Both of these are simple things he can do in the driveway and if no results, I told him we'll need to go to O'Really's and rent the pressure tester. I also told him we need to restore his original, 13 lb. radiator cap and reservoir system, as he's currently running a 16 lb. cap with no reservoir. Shouldn't really matter but it is limiting the system capacity. He rolled his eyes again. :rolleyes:
 

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(milkshake never occurred on mine but pure, clean coolant was in there)
It was weird but I had the same issue during an oil change, pure, clean coolant came out as I loosened the drain plug followed by "uncontaminated" black oil. What did you attribute that to?

Did he look at the radiator cap? How is the gasket? Bad cap would explain why nothing is leaking when it's stationary..
 

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Discussion Starter #19
It was weird but I had the same issue during an oil change, pure, clean coolant came out as I loosened the drain plug followed by "uncontaminated" black oil. What did you attribute that to?
Never did figure out exactly what went wrong but likely something to do with some mistake of mine when I pulled the engine to deal with a leaky rear main, gave it some other love and put it back in... only to find bigger problems arise within a few hundred miles. :shrug After seeing the signs I shared, a rebuild was clearly in order, regardless... so I got busy on making that happen. :doh0715:

PICS FROM MY '95 351W BEFORE REBUILD:



He did check the cap and says it's solid. :shrug
 

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Discussion Starter #20
Rented pressure test yielded exactly NO results. Held pressure with a very slow drain but easily passable. Pumped up to 13-14 and couldn't find any sign of external leakage. Pumped up to 15-16 and still... no visible results crawling all over/under, checking all the hoses, pump, manifold, etc., etc. Not a damn drop.

Compression test will be the next shot... and checking the plugs. You would think that if it was leaking internally and burning that much, there'd be more moisture or even some moisture at the exhaust pipe. :shrug
 
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