coolant leak

[waf8607]

1971 C10 with the 307 engine and all stock.
I have a small coolant leak in the rear of the motor. Were the transmission joins the motor, there is a plastic cover, and if you remove that plastic cover you will see the coolant dripping from the top of the oil pan and down onto the 'thing' that the flywheel connects to. I am sorry I don't know the part names but from what I have described does anyone know what this might be.

Thank you!

[Fldawg]

sounds like a freeze plug at the back of the block

[FirstOwner69]

GM sells some stop leak tablets that are required to be added when replacing the coolant in Northstar engines. As i recall, a pack of 4 is less than $7.00. Crush 2 and put them in the coolant. I did that in a brand new GMPP 350 crate engine with one of those freeze plugs leaking at their suggestion. No problems since. I THINK it may be similar to the Bars Leak powder.

[leftybass209]

I'm a firm believer in quick fixes when needed, but I can't help but think, all those stop leak products do is plug things up, literally. When time permits, it really should be fixed correctly. Coolant leaking is only going to corrode the input shaft and flywheel making for a more expensive fix down the road, not to mention the coolant flush you'll need after using that stop leak stuff.

[NoNeck]

I'm not sure about the GM tablets, but I have seen the inside of a small block Chevy after using Bars Leak. It is not a pretty sight. The coolant passages in the heads were almost completely blocked and the water pump impellers were transformed into a single block of gunk. Also, the inlet side of the thermostat was 90% blocked. No wonder the truck was overheating. Just my 2¢.

You might want to check the back of the intake manifold. I have had several V-8s that leaked on the rear driver side. Especially if it's the stock intake and maybe has been on there since 1967. I think some stock intake gaskets were mismatched to the block flange right at that rear corner where the head/block/intake make contact.

POP

[FirstOwner69]

Originally Posted by NoNeck

I'm not sure about the GM tablets, but I have seen the inside of a small block Chevy after using Bars Leak. It is not a pretty sight. The coolant passages in the heads were almost completely blocked and the water pump impellers were transformed into a single block of gunk. Also, the inlet side of the thermostat was 90% blocked. No wonder the truck was overheating. Just my 2¢.

You might want to check the back of the intake manifold. I have had several V-8s that leaked on the rear driver side. Especially if it's the stock intake and maybe has been on there since 1967. I think some stock intake gaskets were mismatched to the block flange right at that rear corner where the head/block/intake make contact.

POP

I believe there are a couple different Bars Leak versions and that one is an organic powder. It might be similar to the GM tablets. There is no gunk with the GM tablets, and it's not visually obvious. I would not want to use the liquid versions either. As I said in my post above, GM says to use the tablets in the Northstars. GMPP also recommended their use. Of course, I'd also prefer nothing but coolant, but this beats dropping the transmission or pulling the engine to replace one of those rear freeze plugs. At least it's worth a try. In retrospect, I think I may have only used one tablet.