300z

no, but a leaky overflow tank will eventually lower the level of coolant in the engine, which is not a Good Thing (tm.) when the engine gets hot it will force coolant out into the bottle but will suck air back in when it cools. so you should repair/replace that at your first opportunity. I assume that you are filling the system through the cap on the radiator (if it has one) upper hose, etc. and that you are just posting re: the overflow tank as a separate issue, and are not trying to completely fill the system through the bottle? (I know, I know, but you have to ask...) might want to wait for a response from someone more knowledgeable about your car, it might require a special bleeding procedure to keep the system from getting air locked? other than that, yes, pretty much you're down to a defective thermostat or water pump.

good luck

nate

No, I did not try to fill the sys from the tank. I filled it at the rad. cap. What started the problem was the top rad. hose blew off from the pressure build up in the sys. I replaced the hose and filled the sys. with water. However, I tightened the clamp to tight and broke the connector port. So I decided to replace the rad. and the therostat. I put in a fail safe thermostat and thought all should be good. However, the return hose to the engine still does not have any flow back into the engine. ???????????

was it working OK before? if the top hose blew off sounds like the radiator was plugged so replacing/refilling should correct the fault. I'm still thinking air lock, or you really did cash in your water pump (impeller now spinning on shaft?) I'd ask in a Nissan-specific NG or forum, but in the meantime, have you tried filling it with the front of the car up on ramps? generally that will get the air out of all but the most stubborn systems.

nate

Thanks for trying to help Nate. I don't know what other site or forum to try, in order to get a professionals opinion. I really don't understand why it would have happened in the first place. Wouldn't an air lock happen right after replacing the rad. and hoses? I drove the car for a few months after getting it back from the dealers repair of the timing belt.

Where did it run out?

No. It might allow all the coolant to run out, though. Check the water pump. Make sure the block isn't plugged, also.

--scott