97 2.2 Overheating - End of My Rope

Have a 97 2.2l Cavalier that started overheating at speed. It idles fine (between 1/4-1/2 on the gauge). Shop did a test of the coolant and found exhaust vapours in it, so the head was done. They confirmed the head was cracked. New head has gone back on with new gasket, everything flushed and new intake gasket, thermostat changed two times (tried both aftermarket and GM original), coolant sensor (fan switch) changed, radiator and heater core flow fine (with garden hose), pump was removed and impeller is still in good shape and has not let go, new reservoir cap. The system has been bled 20 times, is producing good heat in the cabin and will idle for an hour without overheating. As soon as it gets on the road, it overheats within 2-3 minutes. Did another coolant test and there are no exhaust gases in the coolant and the oil looks good so the new head install went well.

At wits end with this car. Anyone have any other ideas of what to look at?

Have a 97 2.2l Cavalier that started overheating at speed. It idles fine (between 1/4-1/2 on the gauge). Shop did a test of the coolant and found exhaust vapours in it, so the head was done. They confirmed the head was cracked. New head has gone back on with new gasket, everything flushed and new intake gasket, thermostat changed two times (tried both aftermarket and GM original), coolant sensor (fan switch) changed, radiator and heater core flow fine (with garden hose), pump was removed and impeller is still in good shape and has not let go, new reservoir cap. The system has been bled 20 times, is producing good heat in the cabin and will idle for an hour without overheating. As soon as it gets on the road, it overheats within 2-3 minutes. Did another coolant test and there are no exhaust gases in the coolant and the oil looks good so the new head install went well.

At wits end with this car. Anyone have any other ideas of what to look at?

Sound like the rad isn't getting any air. Either that ot the thermostat is up the spout but I wouldn't say so as you said it doesn't overheat at idle. I would say try blasting the rad with a pressure washer. You are in Brampton I'm the other side of Toronto near Oshawa so I know how cold it is where you are. Does your car have a bra on it? If so is it covering the rad completely, have you covered the rad with card? Have you tried the rad for ease of flow? What condition is the rad in? Are there a lot of bends in the ally on it as the veins may be blocked from stones hitting and denting! Also, take your oil filler cap off while the motor is running and then see if any steam comes out and then inspect the inside of the cap for a mayo like substance either can mean water in the combustion chamber. This could be from the head before. But it may be that a water jacket has burst aswell as when the head was cracked but they only stopped at the head assuming it was the whole problem!

No bra on the car. The rad flows ok out the bottom with a garden hose stuck in the top of it. It is the original rad, but the fins look ok. My mechanic was thinking the rad as well. The symptoms seem to point to a defective water pump (not pushing the flow through fast enough) but we pulled out the pump and the impeller is in good shape and has not let go. Removing the thermostat and shoving a garden hose in there with it running also produces good flow to the rad inlet and it increases significantly under revs, so the pump appears to be working well. My buddy (mechanic) is thinking there may be a crack in the block. Its actually my brother's car and is up for sale so he just wants to get the problems taken care of before it is up for sale. My mechanic has also had it over to GM for two of his tech friends to look at it and they are stumped as well. They did comment that these cars are a bitch to bleed for air pockets.

Sounds like you might have a cracked block. I had the same overheating issue in a '77 Olds and it turned out the block had a crack in it that was blowing exhaust gases directly into the cooling jacket. I hope this isn't your problem. I assume your compression is good in all cylinders, because aside from a magnaflux, I'm not sure how you could find out for sure.

Don't like the sound of that!

My 92 2.2 has began making a bubbling noise when I start it, the rad is full to the top and the reservior is at the line. How do you bleed the coolant besides revving it and filling it up?

Finally worked out the issue. I replaced the thermostat twice with Canadian Tire thermostats (rated 180). After speaking with GM, they suggested trying the factory stat rated at 190. I still think there was air in the system and whether it was coincidence or not, the car is no longer overheating with the 190 degree stat. The highest it will reach is 3/4 on the gauge in city driving and drop down to half once the thermostat opens up. On highway it runs about 1/4-1/2. I'm still convinced there was some air in the system, but in any case, case closed.