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Coolant leak

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green70AMX View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote green70AMX Quote  Post ReplyReply Direct Link To This Post Topic: Coolant leak
    Posted: Jun/21/2021 at 6:27am
Went out to my garage yesterday to work on my 70 AMX when i crawled under the car i found a pool of coolant on the floor under the front of the bell housing. This is a completely new build. So now i suspect that i have a freeze plug leaking on the rear of the block. I restarted the engine and checked for leaks that could be running down but did not find any. when i shut the engine off and looked underneath after about 15 minutes the coolant was again dripping on the floor. Is there anywhere else this could be coming from? Thanks in advance Bob
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2021 at 6:31am
Cracked head at the outer rear corner. There are a few threads on such occurrences. You may use a clean finger and rub around the bolt head and corner for any residue. Being a new build, the fluid leak may not be that noticable over fresh paint.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2021 at 8:52am
The pressure in the coolant system is highest right after shutting down a hot engine. This could be a head gasket, head or freeze plug leak. First thing I'd try is a new rad cap - 13 PSI.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Heavy 488 Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2021 at 10:29am
Heater hose at the rear of the intake could be a less dramatic problem
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Trader Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2021 at 10:47am
Good point. The pipes at the rear of the intake have been know to crack at the threads or get pinhole leaks also.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mopar_guy Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2021 at 10:57am
Originally posted by Trader Trader wrote:

Good point. The pipes at the rear of the intake have been know to crack at the threads or get pinhole leaks also.
Yep. I got burned by once as well. Look for the easy stuff first with a flashlight and a mirror before tearing anything apart. Use a cooling system pressure tester if you can find to borrow.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote green70AMX Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2021 at 11:56am
Thanks for all the good info i am checking everything at least twice or more before i tear anything apart. This has been a 5 year project that i thought i was winding down on put ----- happens. i have tightened all the hoses checked all the fittings. Hopefully will get it started again in the next day and go over it again maybe a different set of eyes over to look also. Thanks again and if anyone has anymore ideas please chim in. Bob
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2021 at 5:30pm
I had lots of issues with core plugs on my most recent build. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bobsterfl Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2021 at 7:53pm
Right rear corner of the intake manifold gasket?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Jun/21/2021 at 8:25pm
Install core plugs with Permatex #2 in the future. 

New head gaskets sometimes seep. I've seen Fel-Pro Permatorque Blue seep down the outside edge of the block. New engines almost always seep from somewhere. There is something to be said for years of rust and gunk sealing stuff up. 

In either case, a few days with a sodium silicate-based stop leak in the coolant will usually fix it. Then you drain and flush it out before it clogs up the radiator and heater core and live happily ever after. I never recommend running stop leak long-term, but running it just long enough to stop the leak then flushing it out has uses. 


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