I just got a 94z and it's overheating. i thought it was a stuck thermostat, cause temps would peak then spike back down to normal fairly quickly and stay there for say 30 minutes just fine. However, I knew it had a crack at the top of radiator and it's spewing a little coolant (actually quite a bit now) and it overheated again after putting a new thermostate in this morning. I also changed the cap. I'm pretty sure all the air was bled out and it had plenty of coolant. it seems to run great other than this problem, and yesterday it would run great for 20 min then almost overheat and finally cool back down. seems to me like maybe the leaky rad is causing system pressure issues.

So hopefully a new radiator will cure the problem. My real question is, would a crack at the top of the radiator tank cause the overheating and WHY? I don't understand the cooling sytem all that well... particularly what maintaining the approx 18 psi in the system is good for? just trying to get an understanding of this.

thanks!

 

The cooling system is a closed system and when the pressure exceeds 18 lbs water or coolant is discharged to the fill tank. when the radiator cools it creats a vacume that sucks the coolant back in to the system from the fill tank. You have a crack in the radiator so the coolant is discharged to the street and when it cools down your radiator is sucking air. problem is your loosing coolant.

 

The higher pressure allows higher temperatures before boiling. As with any cooling system, if you have a leak in the radiator you need to fix it.

 

PV=nRT is the appropriate formula, therefore the higher the pressure (P), the higher the temperature (T) can be to be at equalibrum.

 

i see. as a follow-up i did replace the radiator (Ready Rad model $173 @ Advance Auto) and overheating problems solved. it runs around 200* now pretty much all the time. below halfway point on gauge. still think it has a clogged heater core though.

i was afraid the radiator might not fix the problem since it did have plenty of fluid even though it had a leak in the rad.

just FYI, the radiator comes out the top the easiest, not the bottom as i saw some posts reference. took me maybe an hour and half start to finish.