5.0 cooling system problems

[yukonstang]

i found a 5.0 when i was looking for transmission for my 2.3L. Needless to say i bought it because it was dirt cheap. This car had been sitting for five some odd years and had a broken window so i just swapped the interior due to black mold. I did a few other things, put a new fuel pump in, a new thermostat and thermostat housing, i also changed all the fluids in the car. the reason i changed the thermostat housing was because the previous on was warped and didn't seal, it was crome colored and cheap so im assuming the previous owner bought it from canadian tire or something. The car seems to have a loss of power when i step on the throttle but only when it is hot. at first i assumed it was because of bad gas from sitting for so long but now realize it is from to much heat. Now today the cars cooling system has started pressuring up and building too much pressure and sending all of the the coolant into thye overflow until it leaks it out. it is not just a little leak either it pours out almost a gallon jug then the coolant is too low in the rad. We took it into our shop pulled the plugs checked them and also put pressure into the system (leak down test) assuming it was combustion air leaking into the cooling system but still nothing. The water pump seems to be pumping also. So i come here to find out what you guys figure. Possibly an airlock? how about a plugged up radiator? Post what your take is on this, thanks guys

 

[1bad67sbf]

so you did do a leak down and all cylinders passed? sounds like a head gasket letting blowby go into the water passage or a cracked head maybe. just my thoughts

 

[f8tlfiveo]

+1 on that

 

[Rick 91GT]

Air can be a pain to get out of a fox, jack up the front end while starting leave the cap off to help get the air burped.

Are you sure the thermos ta t is opening

Are u sure

 

[wiski]

I've never had problems getting air out of my cooling system. I just start the cold car and run it for a few minutes with the radiator cap off, topping off as needed. As for a blocked radiator; its possible; how did the old coolant look when you drained the car? I'd be more concerned about your t-stat though. I'm with Rick91GT, are you sure its opening? Did you put it in correctly? I've put them in backwards (don't work on your car while tired.) Do you have an electric water pump? If so are you sure its working?

One way to tell if coolant is flowing through your engine is to (using gloves cuz it can get HOT) squeeze the upper radiator hose when the car is running at normal temps. When you release the hose you should feel a surge of coolant flowing through the pipe.

Good luck. I battled with cooling problems with my 5.0 and finally swapped out the black"tragic" 5.0 fan for a nicer electric model.

 

[tmoss]

good chance he put the t-stat in backwards. The sensor "bulb" need to go on the engine side.