on a 89 Cherokee 4.0L, would a bad radiator cap or the cap being on to tight would cause the bottle to over pressurized. I have a coolant leak at the hose underneath the bottle after the engine warms to temp. After I take the cap off and relieve the pressure to leak goes away.

 

Your 89 has a closed cooling system (unless it has been converted) but it sounds like it hasn't. The coolant bottle is a pressurized part of the system and they are very prone to cracking. Sounds like your bottle may just have a hairline crack letting it leak when the system gets warm and builds up pressure. You can replace the bottle or just convert it to an open system (lots of info for that just do a search). Can be done cheap with jy parts.

 

Thanks for the info, that is what I was thinking too, I will convert it over to open system.

 

Is the hose loose, does it need a clamp.

 

I converted mine for like 300 bucks. That was with a new 2 core all metal rad and all new preformed hoses. I got the overflow tank, heater valve and thermostat housing at the jy.