v8 Overheated, now losing coolant. Are my heads gone?

[duffdog]

Long story short,

A few years ago I was experimenting with electric fans and installed a temperature sensor in the top of the radiator. Electric fan crap is removed, but the sensor was left in. Yesterday when heading up Donner Summit, the truck went from normal temp to overheating in less than 30 seconds. I pulled over to find that the sensor had blown out of the top of the radiator and all the coolant had boiled out. I put a bolt in the hole and refilled the coolant at a gas station, but noted that the coolant visually overflows the expansion tank even at idle. I drove back down the summit to my house and found that the same problem happens every 50 miles. The radiator has no coolant and the engine is overheating. My instinct tells me that I have warped the heads and blew the cylinder to coolant passage of the head gasket, but I would like some opinions about any experience people have with this problem not being the heads. I performed a compression test after the engine cooled off and came back with really low numbers, highest cylinder was 170, lowest was 135.

Any advise from experienced techs welcomed.

 

[rdruss]

You may need to get a cooling system pressurizing tool and perform the test to confirm ( or take to a shop and have them test it), but my guess is you've warped head/blown gasket and compression is going into cooling system forcing coolant out the overflow tank.

 

[duffdog]

I'm taking the whole engine apart again. While im in there I think ill do all the maintenance that I have been putting off for so long. new timing belt, weld up the ticking exhaust manifolds. Engine should be bulletproof when I'm all done.