C2 Small Block Coolant Leak

[George C.]

I have a small coolant leak at the rear of the engine, I have the whole rear suspension, rear end and transmission out for rebuild, clean paint etc. I pulled the flywheel hoping to find a freeze out plug leak. The freeze plugs look very clean and dry and I can't find any signs of a leak. The cam plug looks old and dirty but that would be oil not coolant. There are three allen head set screws in the back of the block, do these enter the oil passage or the water jacket, and what are they for? Do you have any ideas where this cololant may be coming from. I don't know where else to check, and starting the engine to let it warm out is not easy at this point.

Thanks in advance,

George
#36908

[Pat #25912]

Re: C2 Small Block Coolant Leak

Hi George. Maybe you can hookup a radiator pressure tester, pump it up and search for the leak. Just a thought from a guy that can't even spell mekanik. Pat

[Duke W.]

Re: C2 Small Block Coolant Leak

The three allen head plugs are probably the oil galleries. When you have a block "hot tanked" the machine shop usually pulls the oil gallery welsh plugs, threads the holes and replaces the welsh plugs with allen head pipe plugs.

Leaks can be very deceiving. Slight oil or coolant leaks will migrate down to the pan rail, then along the pan rail to the lowest part of the engine,which is at the rear since the engine is typically installed at about a 3 degree angle.

Inspect along the pan rail and search for wetness. If you find any trace, follow it as far forward as it goes and then go up.

Conventional "green" antifreeze usually leaves a white residue from the dissolved salts, so slight coolant leaks are usually easier to trace than slight oil leaks.

Duke

[Joe L.]

Re: C2 Small Block Coolant Leak

George-----

The 3 indented hex head plugs in the back of the block are oil gallery plugs. If they leak, they leak oil and in a BIG way since they are in the PRESSURIZED oil system.

If the rear block cooling system freeze plugs are dry, then I'd say that the leak is most likely coming from the intake manifold. There is no coolant crossover at the rear of the engine, but the cylinder heads still have the coolant passages at the rear which are "blocked off" by the intake manifold and manifold gaskets. So, if a leak develops in this area, you can get a coolant leak at the rear of the engine.

One thing that you might do before doing anything else is to check the intake manifold bolts for proper torque. They may have loosened and this could be what's causing the leak.

[Ed Jennings]

Re: C2 Small Block Coolant Leak

Also, the coolant could be leaking past the threads of the intake manifold bolts if they were installed without sealer. Usually the coolant or oil will puddle on the manifold if this is the case.