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Discussion Starter #1
i have been having a coolant leak for a while and cannot figure it out. every time i put coolant in the reservoir it leaks onto the floor through what looks like the back of the engine block. if you guys have any idea of what to look at please let me know. thanks
 

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freeze out plug? get a pressure tester from a box auto part store and check it
 

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freeze out plug? get a pressure tester from a box auto part store and check it
Yeah I'd have to agree here. Freeze plugs are notorious for rusting through. Could be a cracked block or even a blown head gasket. Check the bypass hose to make sure the coolant isn't running down the block to the back.
 

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Discussion Starter #4
yea thats what im thinking. it only leaks when i put coolant in the reservoir. it does not leak coolant through the radiator though. correct me if im wrong, but i thought the coolant reservoir just add coolant to the radiator when it runs low?
 

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Discussion Starter #5
nevadagary, you are scaring the h*ll out of me. the car runs great, with the exception of this coolant leak and a small oil leak coming from the oil pan, i dont think it is a head gasket because there is no white smoke being emitted from the tail pipe, therefore the coolant is not mixing with the oil, no overheating at all. just a pretty big coolant leak whenever i put coolant into the coolant reservoir. do the symptoms really sound like a head gasket problem or a cracked block?
 

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yea thats what im thinking. it only leaks when i put coolant in the reservoir. it does not leak coolant through the radiator though. correct me if im wrong, but i thought the coolant reservoir just add coolant to the radiator when it runs low?
Did you check for a coolant trail down on the frame and on back. Does all the coolant leak out of the reservoir?? Go to a JY and get a reservoir and change that first. I got one for $5.00 and the guy threw in a scale weighing for my Brocno:toothless
 

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nevadagary, you are scaring the h*ll out of me. the car runs great, with the exception of this coolant leak and a small oil leak coming from the oil pan.
HAHAHAHA sorry didn't mean to scare you. If you have a 351 the oil leak is probably the rear main seal. They all leak...good Ford design.:toothless

How's temperature? Normal??? Let the coolant res run dry and see if that clears up the leak. Drive it for a day or so with the tank dry and check then for leaks.
 

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Another thing you can try is to park in your driveway backwards or point the front down a slope and see it the leak is still there or coming from the back of the block or maybe the front.
 

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FSB's Dirty Jersian
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Is the heater on? It is likely that it is the heater core or the rubber hoses leading to the heater core, or also I will 2nd the possibility of a freeze plug rotted away. Keep in mind, there is also a coolant line that runs through the throttle body (it runs all around the rear of the truck too, to a couple of other things), so that is also a possibility too. I would get under the truck or stick your face as close to the rear of the engine as possible without burning yourself or cooking your face at all, and buy yourself an LED flash light purely for the clear brightness (not that off-yellowish white from regular bulbs) LED lights have helped me find all but the tiniest leaks & problems
 

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Discussion Starter #10
yea the temperature is normal, no white smoke out of the tail pipe and the oil is not milky. just a bad coolant leak. its no coming from the actual reservoir. however, i only see the leak when i put coolant into the coolant reservoir. where does the reservoir deliver coolant to anyways?
 

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FSB's Dirty Jersian
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yea the temperature is normal, no white smoke out of the tail pipe and the oil is not milky. just a bad coolant leak. its no coming from the actual reservoir. however, i only see the leak when i put coolant into the coolant reservoir. where does the reservoir deliver coolant to anyways?
The radiator only. There is a thin rubber tube that leads to the top of the rad.


**edit**
I'm not sure why it only leaks with coolant in the reservoir though, that doesn't make sense. Unless that's where it's leaking from. Something is wrong here. The only reason why that would make sense is if you didn't have any coolant in the system at all, and only leaked when you did (obviously it can only leak whatever it has) but your truck would be overheating if that was the case...

Are you sure about that?
 

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First put a pressure gauge on the radiator neck and stop guessing, where ever it's coming from building up pressure will tell you "exactly" where it's coming from immediately.
Make sure all "clamps" are snugged and inspect hoses, freeze plugs for as many as you can see especially the ones on the back of the cylinder heads they ALL have a tendancy to get soft from rust over time and start to "bleed" slowly" but in most cases can be repaired either with the OEM metal or "brass" ones. Napa has "expandable rubber freeze plugs" that has washers on each side with a bolt in the center and expands in the bolt hole when tightened, many here have said they can last a very long time and costs is around $7.00 with all different sizes last time I bought one.

It could also be coming from the back of the lower intake manifold so check/tighten as many bolts as you can or pull off the upper FI plenum and do them all....PITA

Last, once this is resolved I would "backflush" the cooling system with plain tap water until it flushes out clean, check the T-stat and radiator cap and replace if necessary, wash any reusable radiator/bypass/heater hoses in detergent, wash out the over flow tank then top off with a good quality anti-freeze, add some Redline "water wetter" to help prevent corrosion and reduce ambient tempertature around the cylinders then you're good to go for awhile AND have really nice heat in the winter time if region climate dictates.

Good Luck ~ :thumbup
 

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This happened to me. It was my coolant bypass hose. It runs into the therm. I had a crack in it. It cost me 6 bucks at oreilys and about 1 hr of time.

The coolant leaks thru a bunch of your frame rails and parts so its hard to actually trace it. You should take a look at yours. Keep us posted
 

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Discussion Starter #14
jon722, coolant only leaked for you only when you filled up the reserve coolant reservoir? what you said fits the description of whats happening. its very difficult to trace the exact location of the leak.
 

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FullSizeBronco1990:

A. Get a good bright flashlight and a friend to help

B. Put the pressure guage on the radiator neck, max 12lbs pressure.

C. Pump the guage and shine the light around in the areas you think it's leaking, you indicated it might be coming from the back of the engine, shine the light on those 2 freeze plugs in the cylinder heads at the back.

D. Keep pumping the guage until you find "exactly" where the leak is coming from, look for fresh liquid on the floor.

E. Fix or repair the leak.....DONE

Any leaks at the front of the engine are going to be visible, easily detectable with tell tale liquid stains/trails on the metal as it leeches downward......SO!


Good Luck ~ :thumbup
 

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Former owner of Shadofax
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my '95 has leaked just a little coolant for years now. Summer it pretty much stops, winter I get a little leaking again. But, long ago I realized that for whatever reason my motor does not like the overflow with fluid in it. so I run it empty. It might put some coolant into the overflow when I go up into the mountains wheeling and it's hot. and when I come back down it's dry again. So don't put any fluid in the overflow if your system is cooling fine.
 

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Yeah I think these coolant reservoirs suck. Mine just spits coolant out whenever I hit a bump ro turn a corner. I think it needs a baffle inside.
 

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just don't leave much of anything in it. You probably could make a little baffle right inside the filler if you wanted.
 

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Discussion Starter #19
yea, i figured its not hurting anything might as well just run it dry. its runs fine with no leaks. the reservoir usually runs dry after an hour or two after putting coolant in it. thanks alot guys, i have been involved in alot of forums and i have to say this has the most informative and helpful members.
 

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Yea dude. Everytime i filled it it would jus pour out. i thought it was my water pump and when i went to replace it i was like "Damn! I could have just replaced this hose."
 
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