I have a 1990 300zx NA, and it's been overheating lately. On hot days after driving for 20 minutes or so, the coolant temperature goes up, so I turn the heat on and it solves the problem. I brought it to Z1 and they figured it was a head gasket because the coolant in the radiator was bubbling, even after they flushed the cooling system a couple times. My car doesn't smoke at all when running, and it runs perfectly besides the overheating. Could something else besides a bad head gasket cause the overheating? And how much would a head gasket cost to replace?

 

Bleed all of the air out of the coolant system.

 

Try this: http://www.steelseal.com/?gclid=CMDF...FRwpawodYGdEOw
Another option is Alumi-seal available at most auto part stores for a few bucks.

 

anybody have any luck with steel seal or any of those products in 300zx's? and what other work should be done while replacing a head gasket?

 

or would it be smarter to just replace the whole engine? it only has 108k miles, but I was told that it would save me more in the long run to just replace it with a JDM engine.

 

Have you tried reading the first post in this thread?

 

Yes. When i brought it to z1 they bled the air out a few times, and it didn't change anything.

 

Check to make sure the lower hose isn't collapsing and make sure your fan clutch is engaging when it gets hot.

 

Could the lower hose collapsing cause bubbles in the radiator?? it bubbles more when i rev the engine too

 

I'd say that's a head gasket. The bubbles indicate there is a release of air/pressure at some point in the cooling system, which is typically a blown HG. Guess it could also be a crack in the head or block, but that's assuming far too much.

Do a leakdown test, that will tell you exactly what and where the leak is if there is one.

And no, a collapsing hose wouldn't cause bubbling.

 

thanks. my car and engine only have 108k miles, do you think it would be smarter to just change the head gasket or replace the whole engine? a local engine shop (atlanta engine) told me that it would be better to just change the engine because of possible cracks in the block and the age of it (1990). what do you think?

 

I think if you're a do it yourselfer, you should totally replace the head gasket, but if you are just paying a shop to do work, then it's really whatever you feel like spending money one because either one is going to be incredibly expensive if done by a shop.

Having people work on these cars is NOT cheap.