Coolant leak only when shutting the car off.
 

Hey guys, I'm currently 700 miles from home and having coolant leak problems when I shut the car off. I took it to the dealership and the technician said the problem was my cap wasn't closed good enough. Of course that didn't solve the problem, but I really didn't know if I wanted that guy to touch my car anymore so I was going to see if anyone else had or has seen this problem before. I have 0 tools to try and locate this leak too. The coolant seems to be coming from the lower half, and it seems to be about a quart of coolant leaking out when I cut the car off after its come up to full pressurized and hot operating temp.

if you are positive that it leak after you shut the car down, and leaking that much coolant. you should be able to locate it by looking on the engine bay after you shut the car down.

I'm no expert, but first thing I would look at is the upper and lower hose

Dealers are idiots. Take a look down in the engine bay with a flashlight to see if you can locate the leak - seems like it should be pretty obvious. Or is there another shop in town you could take it to?

Yeah, you should be able to see where the coolant is coming from. If it's leaking from the bottom half of the motor, it's either coming from the lower radiator hose, radiator itself, or even a cracked block, which is unlikely if you're not really overheating. Have you checked the thermostat, water pump housing, and upper radiator hoses for a leak? You can always rent a cooling system pressure tester and see exactly where the leak is coming from.

Well after finding someone to cut my car off for me so I could try and spot the leak, it is coming from the coolant overflow, which doesn't make much sense to me since the reservoir is only 1/8 or so full of coolant. I was mistaking it coming from the bottom half I guess because the tube goes so far down. The pressure spring in the cap seems fine though so I'm still at a loss. Air in the system would show similar symptoms to these though wouldn't it?

The radiator cap is probably the problem. Most garages can check them or they're cheap enough to replace "just 'cause".

Yeah, that was my first thought too!
A cap can look ok when it's really defective.

my 997 was prone to bad radiator caps,,then the expansion tanks were leaking at a seam at the back that was near impossible to see...new one fixes all..just my .02.

This..... Get one with the proper pressure rating.

BTW, when you get the problem fixed, whatever it turns out to be, be sure to refill/bleed the cooling system.

Yeah I'll have to try to find a hobby shop or something that will let me do my own work with all of it. Is the Nissan blue coolant absolutely needed? I don't know if it has a different boiling point or if the 370 radiator is prone to corrosion with a green 50/50

It's a good idea to stick with whatever is already in there. Some types are not compatible. Not a recommendation, just the first hit: 2012 Nissan 370Z Antifreeze & Additives

Maybe I'm missing some info but this doesn't sound completely right. Is this leaking even if cold? Or only after fully warm? Sounds odd that it is not happening while running and only after being off. There is a bit of a back up after shutting down sometimes as the pump is no longer moving coolant but still sounds odd. Easy enough to have the cap tested. If cap passes and/or it is happening even cold/warm (not hot) I would have the engine block checked.

is there any oil in coolant, possible head gasket?

:iagree:

Our cars have two pressure caps, make sure you replace both. I replace my radiator caps at 3 years or 40k, it's an inexpensive preventive maintenance item.

^^Two radiator caps?? Where's the 2nd one located?

IINM, the reservoir cap is also pressurized on newer Z models. I think 2012+ model years.

I think you're right! Very strange. What benefit would there be to having a separate cap for the overflow tank in addition to the radiator cap? My MY2012 G only has one radiator cap, at the radiator itself. Reservoir uses a traditional screw on cap.

Looking at the 2015 owner's manual, found this pic. Look at part #3 & 12.

http://i.imgur.com/P1V1pLE.png

Google to the rescue!

http://cdn.carwitter.netdna-cdn.com/...-carwitter.jpg

My guess is that it is a pollution control to lessen amount of coolant discharged. I don't see where a two pressure-cap system would do any better at cooling than one and it costs more. But that's just a guess.

Since the OP has a 2012 & mine is the same, I just passed on what mine has. :tup:

Sorry for the confusion...

One cap is actually a non relief cap (the one on the coolant pipe), the other is the traditional relief cap (on the reservoir). Basically it is now like a lot of euro and some American cars where the reservoir is actually a functioning pressurized part of the cooling system and not just an overflow. Do not mix these caps up, they even state which is which in them.