I just bought a 98 Civic DX and it overheats. It doesn't have water in the oil. Has new radiator it builds pressuer in the radiator and sprays the coolant out of the radiator cap almost instantly when you receive the engine but it won't when it sits at idle. I have never ran into this problem before so I'm wondering if the head gasket is blown differently.? Just want to know before I tear the engine apart. I already took the thermostat out and tried that but did not do anything. In anyone could tell me why it is doing this I would greatly appreciate it thanx

 

So, running engine or revving would work the engine harder
And when sitting at idle, engine isn't working so hard
Working harder makes for more heat
If coolant isn't flowing then engine may not be cooling fast enough to prevent overheating
At idle, engine is not producing as much heat as when running or revving higher
So moderate coolant flow could be enough to keep engine cool

I would check thermostat and then see if the coolant is flowing.
Try turning on the cabin heater to see if that will cool down engine.
If not check coolant level and check for flow.
My suspect would be a weak water pump
But, this is only a guess.

 

 

Head gasket is definitely blown.
When you rev the engine, the compression raises and forces air out of cylinders, past the head gasket and into the radiator.
That is the reason for the gusher.
I know, I just replaced a head gasket, water pump and timing belt in an 01 Civic.