Hi. Some background. I'm the original owner of an 08 G35X with about 145K miles. With the exception of oil changes which I've done myself, all other service has been done at the dealer.

Had my upper and lower radiator hoses replaced 4 months ago. This past week while in stopped in traffic, I heard the engine fan kick on. Knew it was not normal so paid close attention to the temperature gauge. Sure enough, when I was moving, the temp was at the normal temp but when I was stopped, I saw the needle move up a bit.

So I got home and poured in 6 x 6 ounces of 50/50 Nissan coolant and left the car overnight. The next day I went to check on the car and saw quite a bit of coolant on the floor. Given I didn't drive the car and still had the coolant leak, would it be safe to say that my best case scenario is that one of the hose connections came loose? Saw some posts about some kind of valve (2) on the back on each side of the engine, up against the firewall, that could crack, water pump failure (I hope not), radiator failure (I hope not),.. Anything else?

I haven't had the chance to get under the car as I'm in NJ and it was cold this week. I am thinking of getting under the car, removing the entire belly pan and see what's leaking. Really hoping it's just a loose hose clamp.

This is on top of me seeing an oil leak right after I changed the oil on the car a couple weeks ago. Thought it was the filter but I tightened it a bit more and I'm still seeing a small leak.....

 

You can pick up a telescoping inspection mirror and get a good flashlight to look around from the top to find the leak. Shouldn't be too hard to find if it's leaking as much as you say.

Personally I prefer the rectangular inspection mirrors over the circle ones, more surface area to look through. Protip you aim the flashlight at the MIRROR and it will reflect the light onto what you're trying to inspect.

Start at the radiator hoses, but I really doubt it's going 4 months working fine then suddenly starts hemorrhaging coolant, that does sound more like the air purge valve on the heater core hoses which are made of plastic that only lasts about 15 years...

 

I picked up an inspection mirror yesterday. Going to poke around. I really hope it's something simple.

Just to be clear, after adding the extra coolant I didn't drive the car so it sat there overnight and still leaked the coolant. So the system wasn't pressurized.

Assuming it's the air purge valves, how are is it to change the air purge valves on the heater core hoses?

 

There is only one purge valve. It is located on the driver side in my '07 G35x. On the passenger side it is just a straight hose connector, which is plastic and disintegrated in my G35x and had to be replaced. I kept smelling coolant for a week or so prior to that, but could not find out where the leak was until the connector broke in half. It was a PITA to replace. Not much room to squeeze the hose clamps. I replaced them with the worm gear type. They were much easier to replace.

 

I don't think I smelled any coolant before I noticed the leak....

 

I replaced coolant/radiator hoses/heaters hoses and installed Z1 bleeders back in late 2020.

I know stock there is only one stock bleeder back there but I handed two to mine

https://g35driver.com/forums/v36-eng...ml#post7197433

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https://www.z1motorsports.com/z1-pro...e-p-11190.html

 

Update.

Dealer found the water pump leaking, recommended the heater core hoses be replaced. Found housing that holds the oil filter leaking. So a gasket has to be replaced. Also said the valve cover gasket needs to be replaced

So when all is said and done, the following is being done:

Valve cover gasket and plugs.
Water pump, timing chain, etc.
Oil filter housing gasket
Heater core.hose

Ouch, ouch..

Oh, and also was told there were chunks of metal coming out of the rear diff when i asked them to replace the fromt and rear diff gear oil...

So that is not going to be fun...

Triple ouch..

 

Metal in the diff is probably just because the fluid isn't getting changed every 30k miles like it's supposed to. I would wait on that one since 100k mile diff oil is going to have a significant amount of glitter in it, in another 30k if it still has an unreasonable amount of glitter then just run it until it dies then junk yard a new differential since they're so easy to swap and only costs about $500 for a used one.

Water pump though unfortunately requires the entire timing chain cover to be replaced since Nissan in their infinite wisdom decided to remove the water pump access cover on the HR engine, probably because too many techs were screwing up and making the chain jump a tooth on the DE due to not rotating the crank back ever so slightly.

Oil cooler gasket is simple, remove the oil filter, remove the stud in the middle, pull out the o-ring gasket, put in a new one, torque the stud, put the oil filter back on. That's like a 15 minute job.

Heater core hoses themselves are probably fine however if they're tearing the system apart you SHOULD replace those plastic fittings with metal ones like what Z1 Motorsports sells. Might as well buy the Z1 hose kit and replace those heater core hoses with nice silicone ones while it's off though, they last longer than the factory rubber.

Valve cover gasket is somewhat common, however it involves replacing the valve covers themselves due to the non-serviceable spark plug well tube boots, I would definitely not recommend having them take apart the valve cover and reuse it with a new main gasket but existing well tube gaskets, it will probably start leaking oil in the well tubes immediately. Personally I would just do this in the future later once you do start getting oil in the well tubes, unless it's dripping oil on the ground. If it's not then just wait on this repair you won't save any labor $ doing it now compared to later.

So I would recommend water pump, timing chain, heater core bleed valve to metal one (same with the driver side which is just a coupling), oil cooler sandwich adapter o-ring which they better not be charging you a full hour of labor for...

Ignore the valve cover and differential stuff.

If you have 50k or more on the plugs see if they'll give you a discount on bundling them in with the other repairs, otherwise just do it yourself. If less than 50k miles then you probably do NOT need new plugs, the service interval is like 70k.

 

Just to reiterate, if you go 100k miles on a differential without changing the gear oil you WILL have a significant amount of metal built up in it, this is 100% normal.

I've popped the cork on diffs that had 200k and you should see the metal in that... I usually have to take off the cover and use brake cleaner and a rag to wipe up the glitter sludge caked to the bottom. Those differentials still work just fine after servicing.