G35 overheat - ds radiator fan not working

[flyhighusa]

hey guys,

have a G35 with a major overheat problem

I can only keep it from max. heat all the way pegged up. when I drive on the interstate if I hit any traffic it will spit out the coolant from the boiling reservoir. so far I can't detect a radiator leack. I shut the car down in time

- driverside radiator fan not working (checked the 40a fuse ok)- passenger side radiator fan works accordingly- ac is kept off and cabin temp full hot with windows open to relieve engne strain however the ac doesn't blow cold air anyways and cabin full hot just blows lukewarm air

what could my prblem be? can't find the temp sensor that controls the radiator fans.

- where do I find those sensors?- is my waterpump faulty?- faulty engine thermostat?

it takes about 10min to overheat real quickly and gives the people drivng behind me a nice cloud of coolant vapor.

thanks a million for any suggestions. !!!

- Sander

G35 coupe

[pfarmer]

hey guys,

have a G35 with a major overheat problem

I can only keep it from max. heat all the way pegged up. when I drive on the interstate if I hit any traffic it will spit out the coolant from the boiling reservoir. so far I can't detect a radiator leack. I shut the car down in time

- driverside radiator fan not working (checked the 40a fuse ok)- passenger side radiator fan works accordingly- ac is kept off and cabin temp full hot with windows open to relieve engne strain however the ac doesn't blow cold air anyways and cabin full hot just blows lukewarm air

what could my prblem be? can't find the temp sensor that controls the radiator fans.

- where do I find those sensors?- is my waterpump faulty?- faulty engine thermostat?

it takes about 10min to overheat real quickly and gives the people drivng behind me a nice cloud of coolant vapor.

thanks a million for any suggestions. !!!

- Sander

G35 coupe

If the cloud is out of the exhaust then it could be a head gasket or even a cracked head. Need to fix what you know is wrong and hope for the best.

Perry

[flyhighusa]

If the cloud is out of the exhaust then it could be a head gasket or even a cracked head. Need to fix what you know is wrong and hope for the best.

Perry

cloud is from overboiling coolant reservoir. smells great thanks for reading. I appreciate all the help.

[tollboothwilley]

It is your fans. They just can't keep up with the heat. You need to replace them. Its one of the most common reasons that G35's overheat. Just replace the fans and you should be good to go.

[flyhighusa]

It is your fans. They just can't keep up with the heat. You need to replace them. Its one of the most common reasons that G35's overheat. Just replace the fans and you should be good to go.

fan closest to resrvoir works. checked the fuses. can't check wiring yet. you think it would be the single fan or replace them both?

[flyhighusa]

another quick question do the fans have seperate temp sensors or is it one unit. tried looking online haven't found the diagram yet

[tollboothwilley]

The fans run off the ECU. ECU tells the fans when to kick on/off.

[flyhighusa]

The fans run off the ECU. ECU tells the fans when to kick on/off.

Ok so the ECU controls both fans, since one of them does kick on on-demand i'm assuming my ECU is good. I'm going to try and use the wiring of the working fn and see if the other fan works. just by splicing it. worse come to worse I'll leave it spliced and running until I order a replacement fan unit.

U guys think one bad fan can make the G35 overheat this bad?

[tollboothwilley]

The DS fan is the fan that kicks on for the LOW side. The PS kicks on HIGH side.

DS fan runs much more often.

If you are running AC at all you will overheat quickly.

You need both fans. Period.

[flyhighusa]

I cross-controlled the wires for the fans. and determined that the ds side motor assembly is faulty. trying to see if advance autoparts holds a universal motor for a fan. Hopefully this is the only problem to the overheating and havent blow a gasket yet.

[tollboothwilley]

GL with that. make sure its the same specs. You don't want that to do anything other than what the stock settings are.

[pfarmer]

cloud is from overboiling coolant reservoir. smells great thanks for reading. I appreciate all the help.

I read it. Head gasket leaks can and do show up in both your exhaust and also your reservoir. You stated when you hit traffic but you didn't state if it occurs when you slow way up, as in almost a stop or simply when you slow down. If you have a blown head gasket then you should be able to detect exhaust in your reservoir.

In a dual fan setup if one fan is faulty then you can easily end up short circuiting airflow with the running fan as your car slows way up. The air can short circuit between the front and back of the running fan through the fan that is stopped. Simply blocking it off may help at slow speeds by increasing cool airflow through the running side however can cause a lack of airflow when the car is up to speed.

Perry

[tollboothwilley]

Perry, how can you detect exhaust in your coolant reservoir?

[pfarmer]

Perry, how can you detect exhaust in your coolant reservoir?

If you have a head gasket leak, your combustion pressure is often higher than your coolant pressure so the combustion gasses will flow to the lower pressure circuit and end up in your reservoir. To check you can use a meter or even your nose. The smell is different than that of hot antifreeze.

Another condition that will mimic this without the smell of the combustion process is a seal leak on the water pump. Even with the circuit being overpressure it is possible for the water pump at the eye of the impeller to be sucking air. This may or may not show up as an outward leak with the engine off. My Jeep did this and it wasn't until it got severe enough to leak outward that I figured out what was occurring. I didn't think it was a head gasket since it didn't have the smell to it but it certainly was overflowing the tank.

Perry

[pfarmer]

Perry, how can you detect exhaust in your coolant reservoir?

Another method:

http://www.arrowheadradiator.c...t.htm

Perry

[tollboothwilley]

In AZ I was fighting a spike in coolant temps when it was 110*+. I had to be driving for ~30 min before it ever became an issue. I call it a spike in coolant temps, but really it was the temp needle moving 1-2 clicks above normal. I didn't like that. I'd turn off my AC and it would go back to normal. This happened to me twice while driving on the freeway at about 80 MPH.

I'm still looking for a reason to attribute it to.

[Poyzinous]

heat=evil

[Poyzinous]

I have only seen head gaskets fail in 2 VQ motors my whole life. Its rare. you can also use a carbon monoxide/nox detector in the coolant. those gases leak into the coolant as well.

[tollboothwilley]

those gasses come from the exhaust...right? Or are you saying they come from somewhere else?

I am told that I could have air in the system still, maybe I need to bleed AGAIN??

[pfarmer]

those gasses come from the exhaust...right? Or are you saying they come from somewhere else?

I am told that I could have air in the system still, maybe I need to bleed AGAIN??

I believe he is stating the same as myself which is combustion gasses.

I have had three head gasket leaks. Two of them showed up first (at least where I noticed them first) one in the radiator (55 Plymouth), the other the reservoir (73 Buick). The other looked like a steam engine out the exhaust (87 Hunda). Friends have had them with similar results.

In your case I would tend to think about hooking up an OBD to watch it when it occurs so you can get an accurate reading. I forget your year but it is easy to watch and you can see when things start to occur (such as your thermostat opening).

My 08 runs on the low side at about 179 and I have seen no higher than 195 at an ambient of 104.

Perry

[pfarmer]

I have only seen head gaskets fail in 2 VQ motors my whole life. Its rare. you can also use a carbon monoxide/nox detector in the coolant. those gases leak into the coolant as well.

This could be number 3 especially if it had been in use during hot weather with a faulty cooling component.

Perry

[tollboothwilley]

I'm running aftermarket fans (stock was mechanical fan). Maybe I need to have them start and stop earlier? I had to replace my radiator this summer...started leaking.

I've been told that the water pump doesn't go out very commonly but it is an option.

Many people that have issues with heat creeping up at all can be attributed to air in the coolant lines. I have burped the system a few times.

Coolant levels have dropped maybe a cm every so often, which is my concern. Aside from that no issues.

[pfarmer]

I'm running aftermarket fans (stock was mechanical fan). Maybe I need to have them start and stop earlier? I had to replace my radiator this summer...started leaking.

I've been told that the water pump doesn't go out very commonly but it is an option.

Many people that have issues with heat creeping up at all can be attributed to air in the coolant lines. I have burped the system a few times.

Coolant levels have dropped maybe a cm every so often, which is my concern. Aside from that no issues.

I have never had a water pump impeller fail. However I have had the shaft seal fail and have seen this many times. This can be a source of air into the system. Keep in mind that if you get air into the system that it will blanket various parts of the system keeping water from coming in contact and carrying the heat away. You can actually have your coolant drop in temperature or increase. It may increase since the engine will get hotter and the coolant will then pick up more heat in the areas it does contact. It becomes sort of engine area contact area issue. The air will also displace the coolant. In much the same way as steam will make your coolant lever appear unnaturally high when in reality the system contains less water air will do the same thing and continue to do so until it is vented.

If concerned I would do as I suggested or use some other method of looking at coolant temperature so you may be able to associated it with what you know occurs. For example you know that your thermostat (at least if it is functioning correctly) starts to open at a certain temperature and is fully open at another. You know your fans start at a certain temperature and then shut down at another depending on their bandwidth.

What I have found out for example is that the thermostat on my car (stock) appears to start to open around 178 or so and will be fully open by 190. the reason I think this is true is that it will cycle between these termperatures up to the point the ambient is high enough that the termperature will then rise up to around 195 (ambient around 104). On my temp gauge this isn't all that much needle movement but easily viewable with the OBD gauge.

Perry

[flyhighusa]

Thanks so much for the info!!

So far the update is the following:

- Still waiting on replacement radiator fan assembly, but I took the fan motor apart and cleaned the carbon brushes. The fan runs again (too bad I already bought a new one on Ebay)

It still runs WAY to hot, but doesn't boil

next problem is...now my AC doesn't work anymore for some magical reason. the motor kicks on and the RPM levels around 400. Engine has trouble idling with AC on, the motor kicked of and the RPMs came back up. AC blows hot air now

I'm wondering also if there is any air in the system

- Is there a reset for the AC control or does this also run via the ECU? Trying to do some research online.

[flyhighusa]

my next suspicion is the water pump.

I've let the car idle for a while and it runs warm, but doesn't overheat. as soon as i start to drive it starts boiling. Not sure if there is a great way to test if the water pump has gone bad.

Which one of the pulleys would that be? thanks a bunch.

[tollboothwilley]

Water pump is the bottom on the passenger side I believe.

Have you checked the T-stat? That may be sticking. Its one of the cheaper things to try first. You could have air in your system if you have done anything with the fluid.

[flyhighusa]

Water pump is the bottom on the passenger side I believe.

Have you checked the T-stat? That may be sticking. Its one of the cheaper things to try first. You could have air in your system if you have done anything with the fluid.

Just took the tstat off, not sure how to really check it though. Spring works and valve is closed when i took it off.

It still overheats can keep it from boiling though if i have full heat on in the cabin. AC works at first, but kicks off in about 5 min....

[tollboothwilley]

Put it in a pot of water and put it on the stove. When the water gets close to boiling, it should be open, all the way.

[flyhighusa]

THANKS, i've tested it and doesn't work real well imho. getting a new one for 20 bucks this morning and report back.

[flyhighusa]

- Fans are all fixed- New thermostat- Flushed radiator, added new 50/50 antifreeze and bled the system yet still the engine starts to overheat. I think the only thing thats left is the water pump

ANY SUGGESTIONS? and recommendations on replacing the pump? things i gotta watch out for or other stuff?

thaks a million for the help