400 sbc dripping antifreeze - The 1947 - Present Chevrolet & GMC Truck Message Board Network

pbzzz · 10-07-2019, 04:07 PM

I built and warmed over up a 76 2bolt main 400 for mild towing duty in my 72 c20. About 2000 miles on motor I notice an antifreeze drip . Crawled under it to try to find leak . Antifreeze is dripping (few drops/minute) off of bottom of starter bolt on the engine/center line side . Any ideas on source of this . Without having pulled starter I am guessing cracked block ? ? ? Any/all thoughts welcome .

**kwmech** · 10-07-2019, 04:20 PM

Rear intake corner, back of head gasket, rear freeze plug. Pressure check and find out

**AussieinNC** · 10-07-2019, 06:43 PM

Sounds like rear freeze plug has sprung a leak....or the rear of the manifold / head where the water jackets meet the manifold....

I assume you drilled the steam holes in the heads if they were replaced....

gearheadperkins · 10-09-2019, 07:59 PM

I am also thinking the Freeze plug, I just had to replace the two under the motor motor mounts on my 400sbc...rusted out..

**AussieinNC** · 10-09-2019, 08:40 PM

I always use brass freeze plugs in a build or in a replacement scenario....seal them up with a little Permatex then forget them forever....

Cost a little more but way better IMO.

Only steel ones I use are cam bore end and lifter gallery plugs...

10-07-2019, 04:07 PM	#1
pbzzz Registered User Join Date: Sep 2018 Location: colorado springs, co. Posts: 15	400 sbc dripping antifreeze I built and warmed over up a 76 2bolt main 400 for mild towing duty in my 72 c20. About 2000 miles on motor I notice an antifreeze drip . Crawled under it to try to find leak . Antifreeze is dripping (few drops/minute) off of bottom of starter bolt on the engine/center line side . Any ideas on source of this . Without having pulled starter I am guessing cracked block ? ? ? Any/all thoughts welcome .

10-07-2019, 04:20 PM	#2
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,596	Re: 400 sbc dripping antifreeze Rear intake corner, back of head gasket, rear freeze plug. Pressure check and find out

10-07-2019, 06:43 PM	#3
AussieinNC Moderator Join Date: Jun 2017 Location: Cherryville, NC Posts: 2,204	Re: 400 sbc dripping antifreeze Sounds like rear freeze plug has sprung a leak....or the rear of the manifold / head where the water jackets meet the manifold.... I assume you drilled the steam holes in the heads if they were replaced.... Attached Images __________________ Family and country before all others... 2006 Chevy Silverado (Daily Driver) 2012 Chevy Equinox

10-09-2019, 07:59 PM	#4
gearheadperkins Registered User Join Date: Jul 2007 Location: Johnson City, TN Posts: 97	Re: 400 sbc dripping antifreeze I am also thinking the Freeze plug, I just had to replace the two under the motor motor mounts on my 400sbc...rusted out.. __________________ 1972 Chevy C10 400sbc 4sp Matthew 4:19 And he saith unto them, Follow me, and I will make you fishers of men.

10-09-2019, 08:40 PM	#5
AussieinNC Moderator Join Date: Jun 2017 Location: Cherryville, NC Posts: 2,204	Re: 400 sbc dripping antifreeze I always use brass freeze plugs in a build or in a replacement scenario....seal them up with a little Permatex then forget them forever.... Cost a little more but way better IMO. Only steel ones I use are cam bore end and lifter gallery plugs... __________________ Family and country before all others... 2006 Chevy Silverado (Daily Driver) 2012 Chevy Equinox

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