I think I've got a leak... I went to DEQ today and noticed coolant coming out of the overflow... the temp was also pretty hot, although not hot enough to worry about... I also noticed bubbles coming up in the overflow tank..... so air is obviously in the system... I checked the radiator hoses and it appeared nothing was leaking... drove for a block and the temp was steadily increasing so I parked it for an hour, had lunch and came back with distilled water. She drank about a quart, I then drove home... on the way home (approx. 12 miles all highway) temp stayed where it should... and I noticed no visible exhaust or smell. Upon getting home the overflow was once again boiling over... I *think* I see a little bit of oil when I open up the radiator... but I can't be sure... so what's the best way to determine if it's my head gasket? Will compression alone tell me? Should I get a Q-tip and attatch it firmly to something to see if there's water in the cylindar?

If it is the head gasket, what's a good replacement? how thick is still safe to go with?

it could be, it is hard to tell, do a compression test to see if that could narrow it down. you could just have junk in the motor that looks like oil, so don't get too worried, but don't shrug it off like it is nothing too, you could have a very small hole in your gasket. drain your oil to see if there is water in there too. it should be more obvious than looking for oil in antifreeze, water and oil don't mix too well.

Like I already told you...
check your thermostat, radiator cap, timing, fan and all of it's wiring connections...
my sentra did the same damn thing... freaked me out, was a combination of a dirty fan connection and a bad thermostat...

good luck ;)

Check your engine oil. If there is white gunk in your oil, that means coolent is entering your engine, therefore head gasket.

Good Luck

I drained the oil, it looked normal coming out, still draining, then I'll put it in a clear jug...

In the meantime I pulled all my plugs and all of them (all 4!) were white... so what do I check from here? timing? I would think this pretty much rules out the head gasket (?)....

Well, looks like there's no water in the oil, it's all clean... so is it possible I have a problem with the water pump, thermostat or radiator cap, and in turn it overflowed the fluids, which made the engine run very warm for a period of time, and the plugs turned white?

Q-tip in each cylindar came up dry if that helps any... =\

*AHEM*

trust me dammit! check your thermostat, rad cap, and flush the system.
Check the damn fans too! It can work at idle.. it can work at driving speed.. and it can also not work for 30 mins while dirving, but when you hit a bump as you pull to stop to look at the fans it can bump it and make it work again...
check it :P dammit!

like the man said , you're over heating. mine did the same thing. my fans weren't turning on. it was a bad relay for me 18 bucks. check to see if the fans come on if they do flush your radiator and get anew thermostat and while you're at it get a 96 300zx tt radiator cap, from nissan though!it will keep your ride cooler and you'll be cool!:cool:

Supposing it was my radiator cap, fan, or thermostat... how would that ever allow things to get hot enough to cause my spark plugs to be white? Should I be focusing on timing and fuel?

somebody on here has to have an idea of what's going on, or how to narrow it down quickly... come on, don't make me talk to those ingrates on the Supra forums.

listen here buddy!:D
lol

You have not driven it since you replaced the cap.. or the thermostat...(cause you have not done either yet)
You are running the right plugs.. but you are running or/wa gas... which they screw with during the winter.. and you are running a decent amount of boost on shitty pump gas...
what do you expect?
get new plugs, replace the cap and thermostat... flush the coolant... drive it on a lower boost setting.. see what it does... then if you run lean again.. we'll fix it *then* :p x

well, how old is the cap, thermostat, ect, ect. I would guess that you are pretty up and up on your tuneups, the white is from the cylinder running waaaaaaay hot. do you have an ignition on your car? (aftermarket) if you don't see oil in your water, or water in your oil, it might not be your head gasket. it could be a messed up water temp sensor, but it is something that is beyond internet diagnosis unfortunately as far as I go.

put your thermostat in boiling water and see if it opens up. might as well put a new one in while you're there. oh, and a new radiator cap too, get one for a twin turbo z. not sure which year, i'm sure somebody here knows. Someone like Brian at courtesy!

Thanks for the help guys... I'm waiting for a 300Z cap to arrive still... they're actually the same between turbo and na from 90-96... I have a thermostat waiting, I'll put it in Sunday... but I'm still confused how I'll figure out why it is running lean... =\

have you monitored your fuel pressure?