My 2001 Monte Carlo was using antifreeze and blowing white smoke out the exhaust. I had the plenum, upper intake manifold, and lower intake manifold replaced a couple of years ago. I tore into the engine and removed the heads and all of the gaskets looked good. No. 3 piston is considerably "cleaner" than the rest which leads me to believe that was where the anti freeze was leaking. My next move is to buy rebuilt heads or send them off to a machine shop.

Here'* my question! Should I send the heads out to a machine shop and have them repaired or buy some from NAPA for about $300.00 each?? I don't have any idea how much a machine shop charges or if they can deal with a cracked head, if that'* the problem. I can't think what else it could be. I've never bought rebuilt heads before so I don't know about the quality of rebuilt vs.the local machine shop.

Thanks,
Bob

Check on your local craigslist. You may be able to find a set of heads local. Local salvage yards as well. Most of the time coolant gets in to the by the EGR stove pipe. There are 2 small coolant passages right by the EGR. This cracks and leaks in to the LIM. The heads are likely good.

I carefully checked the gaskets on dis-assembly. I couldn't see where the leak was coming from. Also, evidence of the leak was only found in number 3 cylinder.

I've seen the plastic UIM crack and leak. I've seen the gasket for the throttle body leak as well. But if you feel only #3 had coolant in it, then the head may be cracked. Have it magnafluxed to check it for cracks before you invest any money in having them rebuilt.

If the LIM wasn't full of coolant then the issue won't be the UIM. LIM gaskets are kinda common if they are plastic framed. The aluminums don't appear to have any issues. Head gaskets are very unlikely. Heads can crack, but usually it'* only between the valves and not ever noticed.

Please keep us in the loop when you find out what the issue was.

I've checked with the local machine shop and they charge $150.00 per head to clean them up, inspect, and re-seat the valves. It is still a mystery to me what went wrong. I took the heads and poured gas into the ports to see if the gas would leak out. Both intake and exhaust ports held the gas just fine. Maybe if the engine was hot it might make a difference. If the heads check out okay I'm going to put the heads back on and pressurize each cylinder with air to see if it will hold.