Blown Seal?
 

ok so my 87 TII started erratically bucking randomly throughout the rpm band. so i checked grounds and cleaned injectors and replaced fuel filter. It then began to overheat so i checked coolant, replaced thermostat and checked water pump. when i drained the coolant for the thermostat replacement, i noticed there was olny like 1-2 quarts of coolant, if that. finally, i was removing emissions while i had down time and everything was apart and i noticed coolant residue in the oil filler neck. Blown coolant seal?

p.s. i havent put everyrthing back together yet to fill coolant, crank and check overflow because i would hate to put it all back together just to take it apart for the umpteenth time, if its obviously blown. thanks in advance for any help.

OEM Thermostat? Or did you get a shitty parts-store thermostat?

I would trust a broken OEM thermostat over a "working" autozone one.

Buy an OEM mazda "nsk" thermostat.

yes it was oem, did i forget to mention that after the thermostat replacement, the upper rad hose was hot untill about 6" down from the filler where it was cold. this is why i thought the pump was bad but it looked ok, (blades in good shape no coolant from weep hole). i am pretty sure i blew the coolant seal but i would just like imput from someone who knows more than i do. (which isn't a whole lot).:wallbash:

nobody else huh? i guess i will throw it all back together then

if the oil is milky the coolant seal is blown.

Check your heater hoses and heater core. The lines going to the throttle body also. Try pressure testing it. If not, fill it back up with water and warm it up andf look for leaks. Hopefully there is no coolant in your oil