nismo-kidz33

Hello Ladies and Gentlemen, before I get into any detail. I have, for almost two weeks straight, have constantly search in multiple forums and googling/youtubing, etc, for answers before posting, asking for help. But I still couldn't find the answer.

I have a Base model 2003 350z. Pretty much bone stock other than axis rims and a mishimoto radiator, fan and cooling hose kit.

My problem:
The lower radiator hose never gets warm, so I know the thermostat isn't opening. Causing the temp the shoot up and stay up. Eventually puking coolant from the reservoir.

I know the thermostat hasn't failed because I have done the boiling water test on both, the old one and a new one I bought. They both open by 180ish degrees.

I've pressure tested the radiator to check for cracks or leaks. I even pulled the rad out to see if it was clog and have done the free flow test. I have flushed the cooling system. I've burped the cooling system numerous times, using both the bleeder valve and the spill free funnel method. Bought a new rad cap also.

Cabin heat is almost nonexistent unless the rpms are up. No fluid leaking into the car. So I don't think the heater core is the problem. Checked all the hoses for cracks and leaks and replaced any that was getting stiff. I drained the oil out of curiosity, to see if any coolant had mixed with the oil, in case I blew the head gasket. Oil wasnt milky or watery at all either.

Both of the fans come on at about 203 degree, according to the odb2 reader.

I've done as much troubleshooting as I can think of besides replacing the water pump.

As a college student, funding is quite limited. So if possible, solving my problem, without having to buy more new parts would be much more preferable. This is/was my daily driver and only vehicle.

dynamic21

When you say it's puking from the reservoir, is the coolant literally coming out of the top where the cap is on? Where is it "puking" from?

Also, what steps did you follow to burp the coolant system?

Do you have the OEM radiator to test with, or was that leaking hence why you replaced it?

nismo-kidz33

The coolant is puking from the air hole next to the filler cap. I replaced the radiator because of a previous accident a few years back and opted for a better radiator.

I filled the radiator using a giant funnel until the fluid stopped draining into the rad. Left about 1/3 of excess fluid. Opened the bleeder valve and added coolant until there was coolant coming from the bleeder valve area. Then I reinstalled the valve and poured coolant into the funnel until about 1/3 remained in the funnel. Then I squeezed both, the upper and lower rad hose for bubbles. Added coolant as needed until I had fluid remaining in the funnel. Slowly reopened the bleeder to purge anymore air. Repeated the process until I no longer had anymore bubbles.

Turned the car on and turned the heater on once normal operating temp was achieved. Added a little more coolant and continued to bleed from the valve, until I got a steady small stream from the bleeder.

TT03Z

Sounds to me like you definitely have a water pump issue. Also is the thermostat installed correctly? I have seen people put the t-stat in backwards and will cause the problem you are having. Make sure the spring is facing the engine and not towards the radiator as the coolant flows from the lower hose to the upper hose. But with that being said u sound quite mechanically inclined and I'm doubting the t-stat is in backwards. I would say replace the water pump.

nismo-kidz33

I'll check out the water pump. I'll probably go to Nissan to pick up a water pump gasket, just in case the water pump is functioning properly. As long as it isn't seized/low play, or excessive play(something like a spinning top toy). I should be able to continue using it, at least for the time being, until I can afford to buy a new one.

After the water pump. I'm completely out of ideas.

TT03Z

Once the pump is off grab the pulley and try to spin the propeller. If they spin separately it's junk. Usually when water pumps go bad they will leak from the weep hole but not always.

bealljk

iTrader: (13)

OP, since your mechanically inclined I would (*you're going to have to get crafty - see postscript below) remove the thermostat bi-metalic element and reinstall the thermostat housing without the bi-metallic element...basically you are running the car without a thermostat stopper...

run the car like normal...

*PS - I 'dremmel'd flathead screw-driver slots into the heads of the two small screws that bolt the thermostat element into the thermostat housing as the OEM screws have a proprietary driver-slot...let me know if you need pictures...

nismo-kidz33

After trying basically everything, I decided to go to my last resort. Which is gutting the thermostat and having it open. I've read the thread argument on why and why not to do it. I've been monitoring my temp and engine performance. All seems to be working fine, in fact, it even feels better than before.

I bled the cooling system the same way after switching to open stat. There was a bit of foam in the funnel, which really puzzled me. I thought for sure I had oil in my cooling system, hence a blown gasket. But nope, it went away after a minute. No signs or symptoms of blown HG. Oil still golden brown, as I have changed it during the engine/cooling flush. I still have my heater, even with open t-stat. The only draw back is, it take a few minutes longer to warm up. Car hasn't thrown any codes (engine temp too low). It's still way too early to say I'm in the clear, but at the very least. I'm able to drive her around again and continue my daily tasks.

Thanks everyone for your input. Ill update this thread if anything happens, regarding the overheating issue.

GreyZ

iTrader: (2)

What brand of thermostat were you using

bealljk

iTrader: (13)

Dont do this long term - You'd be surprised on how much your engine temp plays on the (OEM) tuning of the car. run the car like this for a week and if this is your problem then go get a new thermostat.

eZg

iTrader: (5)

and Def use a Nissan Thermostat....not some autozone type.

When you added coolant, did you do it at the rate described in the manual? I forget how the rate was described but it was very slow.

Also raising the front end is said to help.

good luck

rancor

Is it possible to put the thermostat in backwards?

TT03Z

I'm not sure if it is possible on the VQ but I have seen it done in other vehicles.