Alright so I my 91 civic is still having issues. Whenever I try to start it, hot or cold, it sprays out coolant out of the radiator overflow bottle. I just replaced the thermostat and the Ect sensor, so those weren't the problem. Please help me! Ask any questions if I didn't make anything clear enough.

 

So first things first. I know this sounds stupid but are you sure you put the new thermostat in before bolting on the housing? And if you did, did you put it in facing the correct way? Is your radiator cap defective or not seating correctly so that it maintains pressure in the cooling system?

Incidentally I remove the inner seal of the radiator caps on my 90 and 93 Hondas and run the cooling system unpressurized. This will allow a surge into the overflow tank but I just let it run a little low. Why you might ask? Because it saves blown hoses, old radiator tubes and heater cores. Often if there is a slow leak with the system pressurized it will stop when running unpressurized. I live in Florida where ambient temperature is not a problem with a standard 50 / 50 antifreeze mix. Jim

 

Sounds like you have a blown HG or a cracked sleeve, time for a compression test. 94

 

Yeah I was thinking blown head gasket as well, how would I check if it were a cracked sleeve? and sorry for the noob question, but what exactly does compression test tell you? I know it checks if your compression is good, but if it's not, that tells you that you have a leak somewhere? Or what...

 

A compression test will tell you at what cylinder the leak is at, you will need to pull the head to see if it is the HG or the sleeve.94

 

Alright, Thanks alot for your help man. I don't have the funds to do all that currently though, so it'll be sittin for a while. Thanks to everybody else's answers too, really appreciate it.