Passenger side Coolant leak

[newguy11]

Just an fyi.

I rebuilt a 350 taken from a 1989 TBI and installed it in my 1985 pickup. When rebuilding the engine, I removed the knock sensor and observed what I thought to be a blind hole threaded in 1/4 x 18. I thought nothing of it for the past 18 months and maybe 3000 miles on the engine until I sprung a very small coolant leak.

My starter was giving me trouble and I found it was dripping coolant. I suspected a freeze plug but found a small threaded hole weeping a drip every 10 min or so. I installed a 1/4 x 18 npt plug and problem is solved.

Hope this problem helps the next guy .
-Plug that knock sensor hole -

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[fast 99]

Lucky, have seen engines dump coolant so fast it didn't show on the gauge, result, burnt up.

If that opened up under pressure all coolant would be gone in seconds.

 

[newguy11]

Lucky, have seen engines dump coolant so fast it didn't show on the gauge, result, burnt up.

If that opened up under pressure all coolant would be gone in seconds.

About 20 years ago I had built a very expensive engine for my Lincoln mk VII that had the oil pressure sensor give out on this very first road trip… that’s a quarter inch hole at 60 pounds pressure or so. That hurt the number eight cylinder and necessitated a bearings change.

 

[Bextreme04]

The really concerning thing is what kind of junk is in the bottom of your coolant passages. The SBC use coolant drain holes for the knock sensors... that is an actual open hole to drain the coolant. I'm amazed that the first time the cooling system pressurized it didn't blow whatever is plugging that hole clean out and dump all your coolant.

The BBC fuel injected engines use blind holes to mount the knock sensors, so they don't have that issue.