Posted sunday about new radiator cap

[phyl26]

If there is anyone out there that can help me understand why when we put a new radiator cap on cuz old ones spring was stuck inside cap, white smoke started comin out from below engine somewhere and out of muffler. We then decided to put old cap back on and it stopped smoking and started running as usual. Why would a new cap do this to a car? My car had a cracked block, mechanic used K&W Sealer,running straight coolant in it now, but it is still running. We have been putting less coolant in too lately. Just want to see if someone might know why a new rad.cap would make a car do this with a cracked block. Should it not have been better to put new cap on? Or did it create too much pressure on engine and thats why it started smokin'? Tercel GTS,if you read this, give me a clue as to what may be happening. I think its runnin on prayer power right now. Like," Oh, God! Please let it keep runnin' until I can afford to get another car

[NickR]

Oh dear! I think your theory is right. With the old radiator cap, where the spring was stuck inside the cap, the cooling system was not pressurised. Now with a new cap, the cooling system is pressurised, as it should be. Unfortunately, given that you have a cracked block, it sounds as though the pressure was too much, and the pressurised coolant is now leaking into the engine somewhere (through the crack in the block, or headgasket, or wherever), mixing with the combustion gasses, and coming out the tailpipe as steam.

Better put the old cap back on, keep topping it up with coolant when it needs it, keep your fingers crossed, and save your money for a new car (or at least a replacement engine).