Hi All,

I am having an issue with the coolant in my '71 240Z. After I drive it and it warms up I notice coolant in the seam of the radiator, which I've determined it is coming from the overflow spout. I assume it isn't normal that it pushes coolant out after only driving it 10-15 minutes in 50 degree weather? Then yesterday after I drove it I opened up the hood and heard a sizzling sound that seemed to be coming from the thermostat housing, although it was difficult to tell exactly.

The radiator was new last year and I also replaced the radiator cap.

Do I have a head gasket issue?

By the way, the temperature gauge reads as it always has (although from what I understand it doesn't necessarily always work correctly).

Thoughts?

Thanks in advance for any help,

Mike

Hi All,

I am having an issue with the coolant in my '71 240Z. After I drive it and it warms up I notice coolant in the seam of the radiator, which I've determined it is coming from the overflow spout. I assume it isn't normal that it pushes coolant out after only driving it 10-15 minutes in 50 degree weather? Then yesterday after I drove it I opened up the hood and heard a sizzling sound that seemed to be coming from the thermostat housing, although it was difficult to tell exactly.

The radiator was new last year and I also replaced the radiator cap.

Do I have a head gasket issue?

By the way, the temperature gauge reads as it always has (although from what I understand it doesn't necessarily always work correctly).

Thoughts?

Thanks in advance for any help,

Mike

Hi Mike,

Just to get you started, I would try the most obvious first. That would be to replace the thermostat with a "NISSAN" unit. Aftermarket thermostats tend to have a much smaller apurature to pass coolant than the stock unit, adding to an overheating problem. While you have the housing apart it wouldn't hurt to take a look at the temp sending probe also.

Much has been written on this problem in previous posts, a wealth of knowledge if you search with a few key words. Good luck.

Dan

I would determine what the true temperature is before replacing parts. Measure heat if you're concerned about too much of it.

Or, if it's the leaks that concern you, focus on fixing leaks. The overflow tube and the thermostat housing are two separate issues.

But it sounds like what you're really assuming is that you have a head gasket leaking pressure in to the cooling system. There are products available that will tell if you have combustion products in the coolant. I don't know the names but I've seen them referenced. That might be the first thing to do to determine if you have a head gasket problem, along with checking the oil for coolant (typically shown by brown milky goo on the filler cap or dipstick).

Have you "bleeded" the cooling system? I have same kind of problems till i found out that there is air in the system. Take the radiator cap off and let it run until its warm. If it shoots coolant everywhere, you probably have bad head gasket, but if not, only the excess air exits and youre good to go.

Thanks for all the responses so far.

The quick and easy thing to do is re-bleed the system. I'll do that tonight. If I still have the issues I think I'll replace the thermostat like Dan said.

Thanks,

Mike