I have a 98 Neon DOHC 2.0L engine that overheats after about 20 to 30 minutes of perfect driving. I have replaced the water pump and radiator with new, not rebuilt, parts. I have removed the thermostat all together and bought a new radiator cap with pressure release.

What is happening is the cooling system is building up a lot of pressure and forcing water out of the reservoir. The car then overheats and I have to stop and flip the pressure release on the radiator cap because there is so much back pressure. Once the water blows out of the cap release, I refill the cooling system with water and it will again run cool until the pressure gets so great and the heat gauge is all the way up and I start all over again.

I carry 2 full bottles of water if I am going to drive any distance and as long as I relieve the pressure and put in fresh water it will run perfect. But the built up pressure is so great that it blew up my previous radiator, which is what forced me to buy the new one.

I don't have any water in the oil or any smoke coming out of the exhaust. The car runs like a dream until it starts to overheat.

Any help or suggestions with what you think might be the problem will be appreciated.

 

It's either lack of cirulation or head gasket. Since you've got a new radiator, only hte water pump and thermostat could be suspect on the circulation end. And I've never seen a Neon loose the propeller (very common VW problem).

Go to Napa and get a block test kit. Follow the instructions and you'll know quickly whether it is the head gasket or not.

 

Possible head gasket. Are there ANY puddles of coolant under your car ever? Check in the morning before leaving and after you get where you are going.

 

I heard that some vehicles if you take out thermostate then to much pressure will build. Don't know if this helps, just what i've heard..

 

You ever take shop class? The system works at a certain psi for a reason. Mess with that and you are going to have some problems.

 

system pis is maintained by the rad cap. thermostat allows coolant to flow thru the radiator, removingit will only allow more wear on your engine.

its the head gaskit, once air is introduced into the systemthe water boils, makes steam and pressure goes up.Also using just water as the coolant is bad for the gaskits and froms deposits in the cooling system. TRy adding anitfreeze and that sould lower the refill time unit you get the HG fixed.

Agood idea is to have the cooling system pressure tested if you fell bad about not knowing for sure.