Hello, I'm having issues with the cooling system on my 2003 G35 with 6mt. I bought the car almost 3 months ago, and everything was working okay on it. After i bought it, due to some personal issues, i left the car sitting in my garage for about a month until i started driving it. Right away i noticed that the heating would only work while driving, or if i revved at high rpms while stopped, and cold air would come out while on idle. I would also hear the sound of gushing water behind the dash. I figured i had air in the system so i tried bleeding the air out. I was out in the cold for over 2 hours trying to get hot air on idle but i was only able to get some warm air only. Due to me freezing outside with this cold weather here in Chicago, i gave up and left it at that and decided to try again later on some other day when i had time. After a couple days i noticed that no hot air would come out at all not even while driving. I was freezing inside my car so i decided to rev my engine to see if i got some hot air, but instead, as i held the rpms at about 3000 at some point they plummeted straight down. Once that happened i let go of the gas. I then tried to rev the engine again and it would not let the rpms go any higher than 2000 they kept dropping by itself even while i tried to hold the rpms in a certain spot. Right after this i noticed my car over heating and my "service engine soon" light came on. I opened the hood and inspected the engine bay; i noticed the coolant reservoir tank was overflowing and the top hose of the radiator was hot and the bottom hose of the radiator was cold. I let the car cool down and after the **rpms dropping** issue stopped but the car was still overheating. I plugged in my obd2 scanner and got the code p1217. I read that the issue for this code is usually the thermostat so i swapped it for a new one the next day. I also noticed the top radiator hose was "flattening" (being sucked flat in other words) so i also swapped the radiator cap, but the issue remained the car was still overheating and top hose would get hot while bottom one remained cold. After i was done switching the t-stat and had realized that the problem wasn't resolved i noticed a small coolant leak on the corner of the radiator. I am ordering a new one to replace it. I'm hoping this resolves the issue. Any feedback from you guys would be greatly appreciated. Thanks you!

 

 

Sadly, that might be the next culprit. I'm really hoping for the radiator to be the issue and not the water pump. Fingers crossed!

 

 

Im thinking maybe it's clogged?

 

 

I'll give that a shot tomorrow. How about the coolant leak on the radiator I mentioned? Wouldn't that cause the overheating too ?

 

 

 

I top it off but when i go back and open the radiator the coolant level has gone down a lot. Im not sure exactly why? Plus the reservoir coolant tank is overflowed, almost dripping out of the tank.

 

 

Probably worth a pressure test on the system!

 

Sucking hoses is usually just a bad cap. The system needs to be able to build up pressure to compensate for the vacuum created on the line side of the pump.

Like the previous post, pressure test the system to find the leak.

 

Couldn't getting anything figured out. I changed the radiator cap, the hoses aren't being sucked anymore and the reservoir tank doesn't seem to be overflowing anymore. I had a mechanic come in he said the radiator didn't have any leaks after all, he tried bleeding the air out but it was no help. He unplugged the fans to see if coolant ran through the bottom hose of the radiator and opened the thermostat since the bottom hose remained cold. He got the the bottom hose of the radiator to warm up. He then turned the heater on to see if hot air would come out of the vents, and it did for about 5 seconds then it started blowing cold again. The bottom hose of the radiator got cold again and he then noticed that half the radiator was also cold while the other half was hot. I took it to a shop i cant trust, they're gonna replace the waterpump. I'm hoping this fixes the problem. If it doesn't what can else can it be? Bad headgasket??

 

No I think the original culprit was already fixed, a stuck thermostat. However burping ALL the air from this motor is tricky, first you open the heater core purge valve up near the firewall while filling the radiator until coolant spills out the purge, then screw the valve closed, continue to add coolant to the radiator until full. (Option and HIGHLY recommended is to get a Lisle spill-free funnel that screws onto the radiator cap). Next fill the reservoir, jack up the front of the vehicle and place it on stands, start the engine and run with the heater on HIGH and temp set to MAX, once it starts to warm up a little vary the rpm's by bliping the throttle to 2-3k until it reaches operating temp but BE CAREFUL IT WILL OVERHEAT, there is still a lot of air trapped in the system. Turn off the vehicle when it's at operating temp, take it down off the front jackstands, refill the coolant reservoir, grab a spare bottle of coolant and go for a short drive, be agressive on the throttle and try to get rpm's to 4-5k a few times, watch your temp like a hawk and pull over when it starts to get a little warm. Check the reservoir level every few blocks and make your way back to home/shop, once back check reservoir level again, jack up the front AGAIN, start and run vehicle to operating temp AGAIN and hopefully by then you have all the air out of the system. You will hear the heater core gurgle loudly when it finally purges air from it and it will immediately suck up about a half gallon of coolant, once that happens you're basically good to go but do check the coolant reservoir for a couple days for any residual coolant ingestion from those last few bubbles.

EDIT: Let to engine cool after the initial burp (before road test) and again after the road test.