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Mysterious coolant Leak #2859092
12/12/20 08:18 PM
12/12/20 08:18 PM
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cjskotni Offline OP
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I have noticed a very small coolant leak since I pulled my oil pan and have the nose of my car in the air. Engine is a 400 based stroker, oil pan is off the motor...

I have noticed a few drops of coolant per day on the ground right under the pass side rear of the motor (under the rear main seal retainer). I cannot seem to find where this is coming from.

I checked the freeze plugs, heater hoses at firewall, at valve, heater box drain, and water pump housing. When I drained the oil and dropped the pan, there was no sign of antifreeze in the oil.

Anything I am missing? There are no plugs on the back of the motor where coolant could leak, right?

Any ideas of what else I could check??

Re: Mysterious coolant Leak [Re: cjskotni] #2859096
12/12/20 08:24 PM
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Maybe exhaust manifold stud/bolt leaking and running down.

Re: Mysterious coolant Leak [Re: mopars4ever] #2859098
12/12/20 08:31 PM
12/12/20 08:31 PM
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cjskotni Offline OP
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Originally Posted by mopars4ever
Maybe exhaust manifold stud/bolt leaking and running down.


Forgot to mention...this motor has Eddy RPM heads. I seem to recall those not being wet bolts.

Re: Mysterious coolant Leak [Re: cjskotni] #2859143
12/12/20 10:19 PM
12/12/20 10:19 PM
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RapidRobert Offline
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You might use this "tank valve" which is less than $3 at O'reillys. screw it into the 1/8 NPT coolant temp sensor & add some psi from your air chuck & grab your tire psi gauge & pump in 5 or 10 psi. use short blips with the air chuck cuz you can reach a critical psi quick & blow out some coolant hoses real quick (it ain't like airing up a tire). it'll make the leak leak

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Re: Mysterious coolant Leak [Re: RapidRobert] #2859165
12/12/20 11:44 PM
12/12/20 11:44 PM
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cudaman1969 Offline
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Head gasket, I had one that squirted a thin stream under pressure. I used the pump up tool on the radiator, almost 20 psi before I found it. Blue gel-pro gasket, almost new

Re: Mysterious coolant Leak [Re: cudaman1969] #2859207
12/13/20 08:57 AM
12/13/20 08:57 AM
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Originally Posted by cudaman1969
Head gasket, I had one that squirted a thin stream under pressure. I used the pump up tool on the radiator, almost 20 psi before I found it. Blue gel-pro gasket, almost new


This leak is from an engine sitting for three weeks with no oil pan. I can't imagine a blown head gasket would leak like this...especially since I saw no white smoke or lost any appreciable amount of coolant before I tore it down.

Re: Mysterious coolant Leak [Re: cjskotni] #2859376
12/13/20 01:45 PM
12/13/20 01:45 PM
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TJP Offline
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Originally Posted by cjskotni
Originally Posted by cudaman1969
Head gasket, I had one that squirted a thin stream under pressure. I used the pump up tool on the radiator, almost 20 psi before I found it. Blue gel-pro gasket, almost new


This leak is from an engine sitting for three weeks with no oil pan. I can't imagine a blown head gasket would leak like this...especially since I saw no white smoke or lost any appreciable amount of coolant before I tore it down.


So you want to dispute the suggestion ??? argue shake_head

Looking a bare block you don't have many other sources other than a head gasket or bolt.

It's doubtful an exhaust or head bolt leak would find it's way to the center of the motor.
So that leaves intake bolt (if drilled through), a head gasket, or the heater A/c system.

Is the back of the block inside the floor tunnel or in front of it. I might suggest laying under the car and looking straight up to see if their is any coolant hoses, heater /ac box etc. directly above the area of the drip. Leaks typically do not go sideways but rather straight down that is assuming they haven't a ledge or lip to follow.

Another thing to keep in mind, with the car sitting with the front raised up, the heater core, valves, hose connections are under more head pressure. HMMM whistling
Or one could put a camera on it and possibly record the event and capture the source

Myself I agree with the previously suggestion(s) time for a pressure check beer

Re: Mysterious coolant Leak [Re: TJP] #2859392
12/13/20 02:04 PM
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Wh haven’t you pressure checked it?
Dougy

Re: Mysterious coolant Leak [Re: cjskotni] #2859473
12/13/20 04:22 PM
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Freeze plug in the back of block, behind flex plate ?

Re: Mysterious coolant Leak [Re: cjskotni] #2859494
12/13/20 05:14 PM
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cudaman1969 Offline
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Originally Posted by cjskotni
Originally Posted by cudaman1969
Head gasket, I had one that squirted a thin stream under pressure. I used the pump up tool on the radiator, almost 20 psi before I found it. Blue gel-pro gasket, almost new


This leak is from an engine sitting for three weeks with no oil pan. I can't imagine a blown head gasket would leak like this...especially since I saw no white smoke or lost any appreciable amount of coolant before I tore it down.

It wasn’t ‘blown’ it was coming straight out the front from the little hole in the lower corner. Defect in the gasket is the only thing I can figure

Re: Mysterious coolant Leak [Re: Ramtough] #2859496
12/13/20 05:15 PM
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cudaman1969 Offline
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Originally Posted by Ramtough
Freeze plug in the back of block, behind flex plate ?

None there

Re: Mysterious coolant Leak [Re: dvw] #2859707
12/14/20 07:29 AM
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cjskotni Offline OP
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Originally Posted by dvw
Wh haven’t you pressure checked it?
Dougy


Well I got a pressure test kit from a buddy and we pumped the system up to 18 psi. Aside from my lower hose leaking a bit, we were able to replicate the leak coming from the number 8 cylinder - a small drop on the piston skirt. The leak can't be that bad as once the lower hose bled down to about 15 psi, it stopped leaking and the system held pressure.

I was then thinking, maybe head gasket, so I pulled the number eight spark plug and expecting a burst of coolant, I got nothing. Plug looks good. I used my handy borescope and inspected the cylinder. From what we can tell, I might have a casting defect where some of the coolant is weeping through the cylinder wall about an inch below the head gasket. If you look at the pictures you can see the little droplets of coolant on the cylinder wall - but they are all well below the head gasket. We ran the scope around the top of the cylinder/gasket and saw no sings of moisture.

So the verdict is - very small leak through the cylinder wall in the number 8 cylinder.

Since I likely have had this likely going on for years and it isn't diluting the oil from what I can tell (after 2 years/2000 miles), I am going to run it as-is with the plans that eventually I will need to pull the motor and get it re-sleeved.

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Re: Mysterious coolant Leak [Re: cjskotni] #2859803
12/14/20 12:58 PM
12/14/20 12:58 PM
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Not good. I would run these. Stop Leak

Re: Mysterious coolant Leak [Re: NITROUSN] #2859866
12/14/20 03:10 PM
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moparx Offline
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there is a blue bottle of stuff called K-Seal. that stuff seems to work pretty good, and might work for what you are doing.
the "roadkill" guys used a few bottles of this stuff to seal up a smoking head gasket on one of their episodes, and it stopped their severe leak [along with a new radiator cap]
of course they beat on the car severely, which i don't think you are going [or planning] to do.
you might want to try some of that stuff. sorry i don't have a link.
beer

Re: Mysterious coolant Leak [Re: moparx] #2859873
12/14/20 03:23 PM
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The Bars leak pellets work extremely well. GM had a bulletin on using them because of casting porosity issues. I had a pair of ported iron heads that magnafluxing showed cracks and the did leak. I would use the bars leak pellets and the leak would stop and we would race all season. My cracks were in the exhaust ports so no problems in that area. However the poster here should try to see how far up the leak is. If it gets by the rings when the piston is down it is just a time bomb as the cylinder pressures being high may not let the stuff seal. I would use them as a precaution as you do not want coolant in the oil.

Re: Mysterious coolant Leak [Re: NITROUSN] #2859876
12/14/20 03:25 PM
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"milkshake" is NOT good for sure ! laugh2
beer

Re: Mysterious coolant Leak [Re: moparx] #2859931
12/14/20 04:35 PM
12/14/20 04:35 PM
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cjskotni Offline OP
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Originally Posted by moparx
"milkshake" is NOT good for sure ! laugh2
beer


I ordered some of that "K-Seal" and we will see if that helps. The oil in the pan was 2 years old/2000 miles and looked like well-used oil (no milkshake) so I am hoping I have some time to decide what to do for the longer term. thumbs

Re: Mysterious coolant Leak [Re: cjskotni] #2859973
12/14/20 06:07 PM
12/14/20 06:07 PM
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Frankly, that would make me nuts, just waiting for the problem to get catastrophic.
Had a buddy that ran his 351C drag motor a whole season, though, pouring Bars Leaks into the thing until it clogged his radiator.
Looks like there's already a rust ring forming, if I'm analyzing that bore photo correctly, so it's pumping coolant into the bore.

Re: Mysterious coolant Leak [Re: topside] #2859978
12/14/20 06:16 PM
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flush it out real good and use water only... get the temp up to 200 or a little higher like its about to overheat. the reason to do that is it will open the crack real good. if it stops the leak, it will prob. never leak again unless you get it hotter than when you made this repair. there are many products with many issues. this works really well and last. Buy this ! https://www.jegs.com/i/Moroso/710/3...=4579878248437694&utm_content=Moroso

Last edited by ek3; 12/14/20 06:18 PM.
Re: Mysterious coolant Leak [Re: ek3] #2860038
12/14/20 08:23 PM
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cudaman1969 Offline
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Originally Posted by ek3
flush it out real good and use water only... get the temp up to 200 or a little higher like its about to overheat. the reason to do that is it will open the crack real good. if it stops the leak, it will prob. never leak again unless you get it hotter than when you made this repair. there are many products with many issues. this works really well and last. Buy this ! https://www.jegs.com/i/Moroso/710/3...=4579878248437694&utm_content=Moroso

It says not to use with antifreeze, I’m guessing water on first application, once it’s sealed use the mix?

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