Chris350z03

Hello all new to posting but been reading posts on here for a while big help.

Ill try to make this short. I've been reading post after post trying this and that and now I'm at a loss. My car over heated one day to "High" after running warm ( but with in the normal area ) for a couple of weeks. I let it cool down and checked the radiator and noticed it was low. I bought some coolant, it needed about half a gallon. I thought ok that was my problem and went on my way. No luck, it over heated again with out leaking any coolant. So I get on 350z.com to see what you guys thought and I read a lot of bleeding problems on the 350z's. So I bleed and bleed and bleed I feel 80% sure there is not a bubble left over a 5 day period. The car takes a while to overheat now but still works toward the H. I rev 2.5-3.5k the engine and it goes down to about middle stays there for a while then slowly works back up, rev then it goes down a bit then slowly goes back up. takes about 2-3mins to go back up. Can anyone help please.



I would just like to know what or how I could diagnose the problem for sure to bleeding , TS, water pump or head gasket.



No leaking coolant

both fans work and kick on

bottom hose seems never to get hot (car takes a long time to overheat after reaching normal temp stops right at the 1/3 temp spot)

heater works in the car

no white smoke or the tail pipe

doesn't seem to be coolant in the oil

I did the bleeding on an incline using the bleeder and R-cap

Car has 120k miles and I'm pretty sure as never been flushed



Any help would be appreciated.



Thanks!

dcains

iTrader: (15)

You made a nice list of possibilities, but failed to mention the thermostat.

Also, I'd buy one of these for refilling the system:

Chris350z03

TS= thermostat is one of the things I listed. I don't want to change it and have the same problem if at all possible. I was just hoping if someone knew a way to diagnose if its 1 of the 4 for sure.

Thanks!

dcains

iTrader: (15)

Change the TS. Do you want to keep xhaing your tail, or rule this out? Honestly, if I saw my fans were working, the TS would have been the first thing I replaced.

Sleepiedaze

iTrader: (3)

Its 50 bucks to replace the thermostat. or you can test using this method
http://www.wikihow.com/Tell-if-Your-Car's-Thermostat-Is-Stuck-Closed

also does the water boil in the reservoir tank? if so your thermostat might be the issue. depending on the mileage you might need to replace your water pump.

side note. did you replace your radiator cap recently? some people will change there radiator cap to a fancier/shiny looking one and not realize that it will have a great effect on your engine temp if its rated at a higher heat/spring rate.

Chris350z03

The couple of times when its reached the H on the temp I can hear bubbling when I turned the car off but couldn't see any leak and the overflow was almost full but couldn't see it boiling. Not that it wasn't just couldn't tell. But maybe the sound was coming from the overflow.

I'll change the TS I'm sure. But I just wanted to make sure I've tried all the little stuff I could do first. I have read nightmares about guys changing that and it not fixing anything and they run into the air lock problem.

its the same R-cap that the cars always had. I think just as a first step for the price ill get a new cap see what that does.

I really appreciate the help guys thanks. Ill get plugging away.

Justin100

i had this problem recently.

turn the car on let it run with the radiator cap off. then pour some radiator coolant in the reservoir cap. and rev the car up and check for leaks. i found a huge crack in the plastic part on the radiator i saw it leaking out that was basically the smoking gun.

i replaced the radiator and everything myself.and still noticed that it was going to H after i revved it up.

re opened the hood realized that i had to bleed the system and open the bleeder screw to let out all of the bubbles and air. once i did that everything was back to normal.

Justin100

the only time it could be a thermostat problem is if he starts his car at pure cold boot and the engine is sitting at H already. that indicates that the thermostat is not working properly already because the car is completely cold and it shows H.

if the needle is sitting at C on the cold startup and gradually goes up to H as he revs the car up then the thermostat is working properly.

dcains

iTrader: (15)

Man, you've got no f'ing clue what you're talking about.

terrasmak

iTrader: (8)

Still air in the system, simple.

DmanG281

iTrader: (3)

I'd also suggest replacing T-stat. Mine did this intermittently, bled the thing for days and it would always end up back at square one. Changed t-stat, problem went away.

Problem is T-stat was not opening and allowing the coolant to flow to bottom of radiator. After it gets hot, try feeling the lower rad hose to see if its hot or cool. If its cool, you t-stat is borked.

Sleepiedaze

iTrader: (3)

then again, I always trust a guy who tracks there cars on a regular basis. I would probably listen to this guy before anything.

Chris350z03

OK ill go back to bleeding more and see if it works. Changed the cap and no go.

Thanks again.

PP08HR

iTrader: (2)

It doesn't sound like he did anything but add coolant and attempt to bleed.


There has to be a root cause to the overheating. If it ran in the red for even a little bit it could be anything.


But yes t-stat because pretty inexpensive. Maybe if you know someone who can do a block test and see if you're getting hydrocarbons in the coolant.

PP08HR

iTrader: (2)

Yeah dude this is nonsense? WTF

wisniaPl

If your car has 120 k change the t stat nissan oem one is 27$...You have long list to check like collant system pressure test to check for leaks and hg etc etc

Justin100

Shop told me to replace thermostat I called ******** and I was right my problem sounds very similar to this guy

Thermostat imo just measures engine temperature and I think it's pretty obvious when it's not working properly

PP08HR

iTrader: (2)

Thermostats can be stuck open which would cause it to not reach operating temp and possibly overheat cause the coolant doesn't get cooled in the radiator. Usually if hot outside or you're running hard.


They can be stuck closed in which case it would almost always start overheating pretty much right after reaching operating temp.


They can intermittently be stuck open or closed and even half open etc.


If the overheat condition it not obvious it certainly make sense to start there because they're inexpensive.

dcains

iTrader: (15)

No. The temperature gauge (and there's also a temp sensor for the engine management system) measures coolant temp and displays it on the dash.

The thermostat is a variable valve which regulates the flow of engine coolant thru the radiator. It begins to open at a specific temperature and opens wider at higher temps to allow more coolant thru the radiator (or none thru the radiator when the engine is cold). They can fail with age, and the typical failure mode is to stick in the closed position.

grimm66

Air is still in the system. I had to bleed mine like 4 times to get all the air out. So much talk about the T-stat. Take it out, boil it. If it moves, put it back.