devnull420

I've had a problem for a while that is hard to diagnose, and I'm looking for any ideas. My Z always runs at a normal temperature, but if I'm going uphill for long periods of time when it's hot outside (more than 90 degrees), the temperature gauge will start going up and I have to keep the RPMS down to keep the temp in the right range. I'm guessing it's related more to the load of getting the Z uphill rather than the fact the car is tilted, and it only happens on significant sustained uphills, not a short uphill.

My guess is that there is something that leaks under very high pressure, but not sure what it would be. I had my radiator and radiator cap replaced and it didn't help, but I don't know what else would cause it. Would something like a messed up headgasket cause this? Should I try replacing hoses next? They do look a little old as it's a 2003 Z. I'm just not sure what else to try. I don't think it's an air bubble in the system as the car is fine even when it's 100 degrees outside, it's just sustained steep uphills in high heat that causes the problem.

davidv

iTrader: (2)

How hot is too hot? Photo of temperature gage appreciated.

How many miles on the motor?

DB350

is this a srs question? temps go up under load anyways, and put an incline on top of that and the car has to work that much harder, hence the higher temps.

devnull420

Motor has 70k on it. And yes it's a serious question, it starts going up way too much, usually the needle is less than halfway up the gauge, when this starts happening I can keep it around midway up the gauge if I slow down to 70mph, but if I try doing 75 or 80 it will raise up to 3/4 of the way up the gauge (and I'm sure higher if I kept on going). Seeing as how there are civics and SUVs passing me by this point, I don't think it's normal for my car to get to hot. I've never let it get all the way up for obvious reasons, but I don't doubt that would happen if I didn't slow the car down. It's just strange that everything seems to run perfect until a certain breaking point, then it obviously has a problem.

STL 350Z

iTrader: (3)

Flush the radiator or replace it.

If it's stopped up that means it's harder for the antifreeze to flow through the radiator. Since you are going up hill you are putting more of a load on the engine/cooling system. If I were you I would just buy a new radiator, coolant, hoses and oem thermostat.

davidv

iTrader: (2)

My bad for asking for a number degrees. Forgot that the 350Z has no numbers.

A properly working thermostat will give you a reasonably stable temperature. It opens and closes when it is supposed to. A broken thermostat may rise and fall, rise and fall. I recommend that you test the thermostat and replace if necessary.

0jiggy0

iTrader: (13)

90 degrees is really steep, car is probly working real hard.

















Make sure the fans come on. Make sure the coolant is full. If so flush the fluid and put in a new thermostat.

winchman

The car wouldn't be working at all, since there wouldn't be any traction on a 90 degree slope.

I think he was talking about the ambient temperature.

It might be something simple, like cleaning all the dead bugs off the radiator and AC condenser. Is there anything blocking the grill opening? License plate? Does turning the AC off keep the temperature from going up?

0jiggy0

iTrader: (13)

Maybe he had help with a winch.

devnull420

While the grapevine in California is steep, it's not quite 90 degrees. There isn't anything blocking my radiator, in fact I have a stillen series 1 front fascia so if anything there is more airflow than you'd typically have. I'm sure the fans aren't an issue because you don't need them when you're doing 70mph on the freeway. I think I'll replace the thermostat and go get the cooling system pressure tested, then start replacing parts.

Is there any possibility it's a timing issue / something with the engine? I'm running the stock ECU and don't have an aftermarket tune, but for a while there I had weird issues when it was hot, I ended up having to replace the MAF sensor and throttle body. Those issues went away, but it just seems odd that the car runs perfect until a certain threshold, then all of sudden the cooling ability just goes away. I could also see something like a tiny leak in the cooling system that only lets the system lose pressure under extreme circumstances, but I'm not sure how likely that is. I bought that UV dye for the radiator just in case, I'm going to add it to the coolant and then next time it happens I'll check for leaks with a UV light.

Before the last time it happened I had filled the overflow tank to near the top, I checked the level the next morning and it was still near the top. Part of what makes this a pain to diagnose is making the problem happen requires a very hot day and a lot of driving up a steep hill.

SPG350Z

I'm with you devnull420. I too have the same issues with overheating on days near 90 but only while heading uphill. My car is not stock as i am running the Vortech kit a Mishimoto radiator with Mishimoto shroud, 10" Mishi fan and a 14" Spal fan. Car runs super cool at idle and in stop and go traffic or even under boost however, when cruising on the highway past 70MPH as soon and i head uphill the car will start to overheat. The car will overheat even worse with the AC on but still will happen with it off just takes much longer. Any help would be great as i have been dealing and troubleshooting this overheating issue for over a year now. No one seems to know as i have talked with people that have the same mods as me and never have a problem. I also might add that i am using the wiring schematics that punish_her had posted in this thread https://my350z.com/forum/engine-and-...ator-fans.html

Thanks.

SPG350Z

Anyone have any idea what might be causing this problem?

DaveJackson

iTrader: (5)

Devnull: Is it LITERALLY overheating and boiling over, or is it just getting hotter than you "think" it should? It should be getting pretty d@mn hot driving 70+mph up a mountain on a 90°+ day as that is putting a tremendous load on the engine.
Also, I think the fans will be activated by the thermo-switch regardless of vehicle speed if the coolant gets hot enough.

Z1 Performance

iTrader: (564)

when was the last time the coolant was fully flushed and refilled?

are the fans turning on when the a/c is engaged?

m808six

iTrader: (1)

didnt read in full to find out if you solved the issue BUT....

try this... top off all coolant levels and turn your heater on...

im assuming you have air trapped in your coolant lines... well i did anyways.. was having near the same issue as you...

leaving the heater on for like 1 min fixed my issue completely.


HTH

dkgaby

Reviving the dead thread. I'm having the same issue with my Z. When in Idle or cruising, even pedal to the metal it runs at normal temperature. But when going uphil the engine overheated(note: ambient temperature is almost 100deg since I live in the Caaribbean). I went to the track recently and in the first two laps the engine overheated to the line before the "H", and nothing helped cooling it down. We tried with the heater on, turning on the engine so the cooling system pressured out some coolant through the valve in the heater hose and then closing it, hoping it was just an air buble. I don't want to assume its the water pump since the water seems to be flowing and there are no strange sounds coming from the engine. When driving uphil the temperature goes up and down very quickly. The thermostat was eliminated a while ago but I never had this problem in the past. When the issue started, the system was flushed, the radiator cleaned and it seemed to be working great, until I drove an uphil. It really sucks

help please!!!