350 overheat damage?

[Mike F.]

Installed a freshly rebuilt L-46 yesterday. Engine wouldn't start or attempt to fire. During trouble shooting, removed the temp sending unit wire to access #1 plug for timing/compression varification etc..

Get engine started, adjust idle, watching for leaks, etc., after running about 10 minutes I go to shutoff the ignition and it diesels like crazy. Had to put it in gear and release the clutch to shut it down. Stick the temp wire back on and it's pegged full right (way past hot). Check radiator hoses, ones hot, ones cold. Pop the radiator cap, avoid the spray, and start adding fresh anti-freeze. When temp eventually gets down to 210F, I restart and thermostat/water pump work fine. Apparently had an air bubble and the inadvertant leaving off of the temp wire added up to bigger problems than needed.

So, how much damage did I do to a new engine?

TIA,
Mike

[Shane F.]

Re: 350 overheat damage?

Mike, I am new to the discussion board but as an ex mechanic I will give you my recommendations.

First of all, "pre ignition" after an engine is switched of indicates an extremely high combustion temp to cause the engine to "run on". I would remove all the plugs for inspection and do a compression test on all cylinders. If all appears ok then run up the engine with the radiator cap removed, checking for continuous air bubbles in the header tank. This would indicate a cracked head or leaking head gasket. If all checks out you should be good to go.

Regards
Shane Fever

[Jim T.]

Re: 350 overheat damage?

A 350 engine alone holds over 6 quarts of coolant.

[Duke W.]

Re: 350 overheat damage?

I doubt if there is any engine damage. Cast iron is very forgiving of significant overheating. Aluminum is not.

When installing new coolant, leave the cap off the system and monitor temperature closely. When the thermostat opens the level will usually drop. Add coolant as necessary and install the cap.

It may take several more heat cycles to purge all the air, so the coolant level should be checked frequently until it stabilizes.

Duke

[Larry B.]

Re: 350 overheat damage?

When a engine gets overheated badly the best thing you can do is retorque the heads.When the motor got overly hot the heads swelled more than normal then when cooled the torque will be loose. If you retorque you can save the gasket from blowing. The dieseling could have been caused from idleing to fast during cam break in.Watch for bubbles in radiator.There is also P&G block which is a solution that will change color if exhaust gases are in the radiator water.