I don’t know if anyone else has had this issue, but it was horrible. I just wanted to share my experience with this and hope it does not happen to anyone else. (sorry about my grammar if it is bad.)

My 2008 g35 currently has 187k miles. Around 186k I put new tires on and the car was driving fine. Later that day I was driving, and I heard a noise like I was running over road strips and felt like it as well. Like when you run over the bumps on the side of the hwy and it was only in the rear of the car. It would go on for about 2 seconds. I was like woah what was going on. So, I got home and swapped the wheels to the front to back. The next day I was driving to work, and I heard the same thing coming from the rear again. So after work I drove back home and it was happening more often. Then my car also started to slip when trying to shift. Then I was like oh crap lol. Then I popped open the hood and looked around and I found that there was transmission fluid inside of coolant reservoir…… So long story short. I took it to the mechanic and the radiator had failed internally causing coolant to leak into my transmission causing my perfectly running car to fail me for once… I ended up having to get a new radiator and transmission. A radiator from infinity was $612 and value radiator was $499. I should have waited to find a manual lol.. Pics coming soon.

 

Why did it require a new transmission?

 

Coolant got mixed with the transmission fluid

 

coolant got mixed with the transmission fluid inside the transmission.

 

Dude sort of same thing happened to me, radiator blew and spewed coolant everywhere, but also transmission fluid??! Then when I gassed it to get it on the bed of tow truck it revved up but the car didn't move. Yes it was in gear. It was acting like a manual tranny as you release the clutch. Wtf is going on I'm so nervous the tranny is screwed somehow.

 

I'm very curious to know how this happens. Anyone have an idea?

 

Well I thought the G35 with 5AT used a separate transmission cooler but apparently not. Most manufacturers went away from the radiators that had internal transmission cooling for exactly this reason. The radiator fails and you can end up with coolant in the transmission fluid section of the radiator.

 

Is there a way to bypass this? Like install an external cooler to avoid this issue?

 

Yes an external cooler will eliminate any potential coolant contamination and if your G35 doesn't have one I STRONGLY recommend getting one because all OEM radiators are weak POS.

I just realized this thread was for an HR equipped sedan so I think your car is fine, pretty sure the early G's had a separate tranny cooler.

EDIT: NVM, forgot you just bought a HR sedan >.<

SECOND EDIT: You should still look under the car and follow the transmission cooler lines from the tranny up to the radiator to make sure they actually DO go into the radiator, I could have sworn my neighbors coupe has a separate cooler but sedans might be different.

 

Reaaaally, the radiator is also an oil cooler? So radiator fail can possibly = transmission fail. Screw that. Guess I'll be looking into changing that

 

Yep seems like it....ugh. I don't like that. Here: http://www.nicoclub.com/FSM/G35/Seda...m.pdf#G1240677
Page 220 goes into cleaning the cooler

 

It would be easy to find out if the tranny fluid was part of the liquid mess by checking the level of fluid with the dipstick. A lot of car manufacturers use the radiator as a transmission fluid cooler but that part doesn't fail nearly as often as just the coolant part of the radiator. My 06 GTO is one example of the dual cooling design, glad I have the M6.

 

The GM ones are different then the style than those used on a lot of light passenger vehicles, my 1500 Sierra (2500 has a separate cooler) has an internal but it's actually a completely separate part of the radiator, you can see the welds at the seam where the radiator and transmission cooler were welded together, I suspect your GTO is that style as well. Light duty cars the transmission cooling in the side caps are actually surrounded by coolant where the tubes make a u-turn back into the center section.

 

Hmm.. Now you're getting me worried. Does anybody know the failure rate of the radiators which result in this type of damage?

 

Probably not as rare as you think but I would imagine 150k would be a good time to replace the radiator or bypass the internal coller completely by adding an external cooler before it fails.