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: 8,641	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

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.