OK you are on the right track with the troubleshooting process. You have flushed the system and filled it with the proper coolant and put in a thermostat that wasn't there before. I am going to BET dollars to donut holes that your problem right now is two fold. #1 you definetly need to get a new radiator cap. I believe the prober cap is a 13 pound cap which means that it takes 13 pounds of pressure inside the radiator to compress the spring to let the radiator overflow into the overflow tube. the second problem is yes that pinhole leak that you menationed can cause problems because the radiator isn't going to build the proper pressure inside to keep everything flowing and not boiling. A radiator works on the same principle as a pressure cooker. The higher the pressure inside the higher the temperature is allowed to get before it boils over. So basically water poils @212 degrees Farenhieght at sea level. The lower the pressure (higher the altitude) the lower the boiling point is. The higher the pressure the higher the boiling point. Does your radiator cap look like this because if someone has put a more modern radiator cap on your Maverick it may not have the correct pressure spring and or size seal. So get that pin hole patched up and get a new radiator cap and I think you will be good to go
Milkey coolant could be from a bad head gasket as scooper stated.It could also be milkey due to the flush agent you poured in.That said:Was it milkey before you did the flush??? if so the probability of a bad head gasket is unfortunately high.If it was only milkey during the flush process I would say its due to the flush agent.Do you have little brown poop looking floaties in the radiator now?with the fresh coolant??As I stated before:When you did the flush did you flush it till the water ran clear and clean??If not you may still have residue in the system which will give you a false positive as far as the head gasket is concerned.It sounds like your water pump may be fine from your diagnostic proceedures you mentioned above.Keep plugging away at it!! your getting there!!As for the head gasket.If it is bad,its not the end of the world.You can do it yourself.It isnt that big a job(not rocket science)Hope it doesnt come to that but if it does.We can walk you through it,no biggie.Good luck.Dont let the horse powers tell you to give up.
A bad head gasket isn't the end of the world. $20 for new gaskets and a few hours of your time and it's fixed. If your top hose gets hard right after you start the car or you see alot of bubbles coming up in the rad that could be a bad head gasket or cracked block/head. If you have a crack, you will need to track it down. With duffus running straight water in the engine, depending on how cold it gets there, a crack is possible... Another possibility, as mentioned before, is a bad water pump. My 76 had straight water in it for years, apparently, (before I owned it) and the water pump was corroded to hell. If you suspect a head gasket, try doing a compression test.
In from the cold, but this time a feel a lot happier, after fixing everything you said and after using so much coolant that my gas station is starting to wonder if I´m hooked on that stuff. Everything (well not everything) runs smooth, no more boiling over, no more hissing noice, I patched up the pinhole with som goooey metal stuff and that seemed to do the trick... New problems are heading my way, but this one is over and done with thanks to you all... Strenght and faith to you all and thank you over and over again!!!!!
