weird overheating issue-help please
 

car is an 06 with the rev-up and has about 45,000 miles on it. Been boosted with the aps twin kit since 19,000 miles and running 412whp at 8.8lbs boost. About a year ago my car started having overheating issues and I sent it to a few places to get it checked out. The issue it is having is the overheating after even just sitting and not driving. This also happens very fast. After 2 mins past the normal time that it takes to warm up, the needle starts to head to overheating and will peg the top. It also will only blow cold air when I turn the heater on, even when overheating. At first they thought it was the thermostat, and thus replaced my Nismo thermostat with a new one and I still had the issue. Second thought was that since my radiator cap was blowing coolant past it, that it might be that, and thus replaced that with a new one (koyo radiator and cap) but that still didn't work. Now they think that the head gasket is blown but is instead of letting coolant into the combustion chamber (exhaust doesn't smell sweet at all), it is pressurizing the cooling system and hence the coolant spilling out of the cap even after replacing it. Any thoughts, comments (other than I am ****ed), or anything? I am tired of not driving my car (almost a year now mostly due to funding) and would love to enjoy it during the summer while the nice weather here in Seattle exists:suicide:. I don't know what other info you guys may need to help me out here, other than it is still a stock head gasket and head studs, and I am tuned with UTEC. Again, any help is much appreciated.

also, the gauge that is telling me that it is overheating is in fact still working, and the upper radiator hose is scalding hot, while the lower hose is still cold.

ok, found this awesome thread... https://my350z.com/forum/forced-indu...till-cold.html
sounds like they talked about this stuff pretty well. My bleed valve is also gone due to APS kit, and so I just ordered the funnel off amazon that everyone was talking about on there. Hopefully this will work and I can begin to drive my car again. If not, headgasket here I come (although then I can do internals at the same time and push for a bit more power).

I have the same prob just not as severe, as long as I keep the coolant topped off I can run it all the time, I'm on 10 psi 495whp.

Definitely bleed the living hell out of it. Sounds like a huge trapped air bubble not letting coolant flow anywhere. Blown head gaskets at idle don't usually react THAT quickly and overheat... especially at idle. I mean, I would imagine it would have to be REALLY blown to do that. If this is what you ordered, then have at it:
Park it on a slight incline or something to let gravity have a shot at getting the air out as well. See if that helps at all. A LOT of times, it takes quite a while to bleed all the air out.

If that doesn't work, before you go yanking heads, too, do a leakdown test. Pressurize the cylinders REALLY well, and take the radiator cap off. Haven't had this happen to me on a VQ, but on one other motor I was able to see bubbles come through the radiator as the entire coolant system got pressurized. May or may not be the case with a VQ (so I'll let someone else chime in on that) but definitely worth a shot before pulling the heads.

Best of luck to you.

Sounds like air in the system... if it happened out of nowhere then it's probably the headgasket. This is typical failure mode in boosted setups (air pushing into the system under boost instead of coolant into the cylinder during vacuum).

If you do get new headgasket be sure to get the tune fixed up so it doesn't happen again. Timing less aggressive and/or A/F's fixed up.

yeah, that's the same part that I ordered. Hopefully this works and it's not the head gasket. Thanks again for the help!

To me, the key part of the bleeding procedure is the speed of the fill. The instructions call for an EXTREMELY slow fill and I don't think many people follow that.
I think this magic funnel is a fix for that, though.

magic funnel = lulz

Yeah, it allows you to keep fluid dropping back into it every time the system burps. Instead of "burp" then "add fluid," you essentially have a reservoir sitting on top with extra fluid that replaces the air as it comes out without the possibility of extra air making it's way into the system.

Works pretty well, just takes some time to belch all the air out.


djamps has a good point too.... mixture of both issues. Blown head gasket building up pockets of air, then the air gets stuck. So, the blown head gasket may not be THE cause of the overheating, but it could be the cause of the extra air pocket, which is causing the overheating.

It's the headgasket drew ): just went through the same thing on mine a couple month ago. Plus your car has been riff off lol I remember when it was leaking oil into the exhaust and such 2 years ago

Ruff*

yeah, im thinking the same...but I can hope :) just got home and the package containing the funnel is here...gonna go play with it a bit and see if I can get this thing to work for me.

damnit...I think it really is the head gasket :( Got the funnel thing to do its magic, and then took it for a drive. Car did very well for a little bit, then started to climb up. Got to drive for like 5-7 mins before that happened (stayed out of boost). The last little bit on the way home I put the car up to about 4k rpm in 2nd and that is when it started to climb up. Limped it the last 2 blocks home, and parked her again :( Can't say I know a ton about cars (hence asking for help here) but I'm assuming that there is a correlation between the boost and the overheating (head gasket). It didn't overheat even in the garage while idling though...I'm assuming the more I drive it the faster it will overheat again :( Oh well, gonna have to order up some new parts then if I am going to open her up anyway.

Does the car over heat while cruising in the highway by any chance? If you get a chance see if it happens while your moving or only when you stop for a while after cruising.

cold lower hose would lead one to believe the thermostat isnt opening and thus it stays cold. did your thermostat have a little hole in the face with a plunger? if so cut it out that will allow a small amount of coolant to always flow through it and helps bleed the system. i did that and have had 0 overheating issues and didnt even have to use the special funnel. if pressure is leaking in from the head gasket you can pull the radiator cap off and you will see bubbles in the coolant and the gas escapes.

I know this may sound Noob but I've seen so many overlook this simple detail. Start car and turn on AC... check to see that both Fans on Radiator are working... if they are then the problem is a bit more complicated... if one is only working then you may have a faulty Radiator Fan. Lots of 2006 Revups had this defect including mine. Random Overheats... the fan would work and not work at will. Mine occurred at about 14,000 miles. Some others have had this issue later on. Can't hurt to check.

when you bleed the system of air, you have to do it until the thermostat opens or you'll never get all the air out. but like someone said, it sounds like a thermo issue. It may have devolved into a gasket issue but start with the least invasive fix.

I would try and REMOVE the thermostat and then fill up the cooling system and try running like that..I have similar issues..live in Texas and only run a thermostat from nov-feb...

You CAN remove the thermostat from the housing..I actually have two..just use a screwdriver and have some patience and it will come out..