G35 Coupe V35 2003 - 07 Discussion about the 1st Generation V35 G35 Coupe

Overheating but not thermostat

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Old 01-24-2011, 12:31 AM
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Overheating but not thermostat

Howdy. 2004 automatic coupe here and haven't had it long. The car is overheating at idle. I changed the t-stat today (oh what fun). Here is what I know:

1) No cabin heat at all
2) Cabin heat used to be nearly useless anyway, but was at least a little.
3) The reservoir is nearly full, just noticed that.
4) There is a short screech starting up, belt slip I'd guess, but it's gone quickly.
5) The power steering pump(?) sounds really bad/noisy idling...If it is the topmost left driven one while facing the engine.
6) The engine warms up to mid guage, rpms drop, the fans kick on, then a minute or so later the temp starts jumping up and up.

I am doing a proper flushing tomorrow hoping that this is all just gunk.

Anyone have other wisdom? I am really hoping it is not the water pump.

Thanks!
 
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Old 01-24-2011, 06:12 PM
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Athens Blue G35 Coupe 6MT
Is it cold where you live? Cold + mostly water in radiator = frozen and/or broken waterpump = overheat.

Best guess, good luck!
 
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Old 01-24-2011, 06:13 PM
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checked your oil?
 
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Old 01-24-2011, 06:37 PM
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check your hoses, the screech you hear could be the belts getting wet from the antifreeze.
 
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Old 01-24-2011, 06:48 PM
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The FSM says that a deterioated/squeaky belt could be cause by a bad water pump, but our cars are driven by the timing chain... so unlikely but worth checking I suppose.

I'm not sure where the weep hole is for the water pump, but I think it's on the bottom side of the block *someone please confirm this.

I'd say you should check that powersteering unit out. If the pump is bad then perhpas it's the reason why your belt is loose and screeching.

Did you bleed it after the T-stat change? Maybe you just have air in the system, as you did before. No heat at idle is a classic sign of air in the cooling system.
 
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Old 01-24-2011, 06:53 PM
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coolant fans were replaced on my 06, service guy said they had a problem with that year and extended the warranty to 100k for the repair, i know you said an 04 but might be worth checking
 
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Old 01-25-2011, 12:34 PM
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Sounds like the system is either air-locked or the water pump is dead.
 
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Old 01-25-2011, 04:51 PM
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Almost definitely the water pump.
 
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Old 01-25-2011, 05:55 PM
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Good posibility of air in the system as our cars are a real pita to bleed it out.
 
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Old 01-25-2011, 10:40 PM
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Originally Posted by superchargedg
Good posibility of air in the system as our cars are a real pita to bleed it out.
The key is to fill it real slowly after doing a coolant flush and bounce the car up and down every once in a while while filling it so that the bubbles work their way out... then you don't even have to bleed the system at all.
 
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Old 01-26-2011, 01:45 AM
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Originally Posted by partyman66
The key is to fill it real slowly after doing a coolant flush and bounce the car up and down every once in a while while filling it so that the bubbles work their way out... then you don't even have to bleed the system at all.
Thank you for the feedback. I flushed it tonight twice. The first time, right away I could feel heat coming out of the vents again and no overheating. Same thing the second time.

I think I got anxious the final fill and went too fast as I had the overheating engine again! I opened the radiator plug and got air out and heard lots of gurgling. That did it but only for a quick trip around the block, then the heat went out while driving! I tried the bleeder near the heater core and got air out..but no luck still overheated after.

Now, there appears to be no coolant flow at all. I am tempted to drain it again. Is there any other way to get this air out without draining again? Should I leave the bleeder by the core open for many minutes?

Also, is it odd that each of the 3 drainings I only got 5-6 qts of the 9 out?

Thanks for the help.
 
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Old 01-26-2011, 04:56 AM
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When i bleed a cooling system i always leave the rad cap off with the engine running, until it reaches near/normal temp, that way the thermostat will open and this helps with eradicating air, although the VQ motors all have a bypass hose for quick warm up.

But anyway try it this way and see if that helps, if not i suspect your water pump.
 
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Old 01-26-2011, 11:45 AM
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Originally Posted by Matthew McGrew

Also, is it odd that each of the 3 drainings I only got 5-6 qts of the 9 out?

Thanks for the help.
You won't get the entire amount out of the car when you drain it. If you want to get more out, there is also a drain on the block which will allow you to get all the remaining coolant out of the block itself and not just the radiator.

Then there will also be some coolant in the heater core that is probably not going to come out when you drain the system.

Personally, I don't even bother draining the block. I just drain the radiator, refill with pure distilled water(no coolant), warm the car up with the radiator cap off and the heat on full blast, and then shut it down and drain it again. I do this like 2 or 3 times until the coolant that I drain out of the radiator is clear..... then I refill the radiator with like a 65% coolant, 35% water mixture(so that it will hopefully eventually mix in with the leftover pure water portion in the heater core and block, resulting in about a 50/50 mixture in the whole system), and fill the coolant reservoir with a 50/50 mix.

Of course, whenever I fill the system while doing the steps mentioned above, I try to fill it slowly like I mentioned before and bounce the car up and down a bit to shake out air bubbles.
 
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Old 01-26-2011, 11:43 PM
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Done & done.

Thank you for all the helpful suggestions & feedback. This really saved me $ and trouble. I think I've got all the air out after repeatedly using suggestions made.

Parked on inclined driveway. Cap off. Squeezed hoses. Turned on. Waited for fluid to hit the top and recap. Bleed near core. Drive. Cool the engine. Repeat. All seems to be great now!

Thanks to a friendly community. It is great to have my new-used car back.

Now to tackle power steer pump <sigh>.
 
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Old 01-27-2011, 08:16 AM
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Glad its OK now and you don't need a water pump.
 
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