Radiator cap? coolant leak

Jsolo

What's the benefit of pressurizing the reservoir tank too?

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Dreadnaught

If you put pressure on the cooling system with a pressure tester, coolant will leak out of a gasket, o-ring, or hose that is worn out or faulty.

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Jhill

On a 2012+ the reservoir is actually part of the pressurized cooling system so you need to pressure test it there to test the complete system.

Jsolo

Wrong context. I mean't why have it pressurized at all. It's odd to see a car with two radiator caps.

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Jhill

It's not uncommon to see a cooling system where the reservoir is actually part of the pressurized system. 99% if not 100% of all euro cars operate this way and American is about a 50/50. As to design function vs an "overflow" reservoir the only thing I can think is they get that little bit of extra volume of coolant to use. As for why the z has two caps, pre 2012 the solid cap would have been the pressure relief cap allowing coolant to go to the overflow, post 2012 the reservoir cap is the pressure relief one and the one on pipe is solid so in a sense it is now just a pipe, save cost on manufacturing a whole new pipe.

Oh and some systems where the radiator is actually not the highest point in the cooling system they can mount the remote reservoir to a high position (typically by the firewall) so now it is easier to purge air from the system.

Darwins Child

Therefore, because the hose and tank are pressurized, and one of the two small OEM clamps has already leaked, I used the second SS worm clamp in the 2-pack to replace the other small OEM clamp on the same hose where it attaches to the tank. (The second small clamp was considerably tighter than the first, but I replaced it anyway.)

Just out of curiosity, I checked our '10 Mit. Outlander which has 106,000 km (versus 9,500 km on the Z) and it has the same type of larger hose clamps and they've never failed, so I'll accept the same risk on the Z's larger clamps holding. Knock on wood.

For the $180+ cost of Nissan's pre-purhcase inspection, the tech should have diagnosed that leakage correctly (if it does indeed turn out to be the hose clamp that was leaking, which at this point I'm 90% certain of). The tech stating with certainty that it was the cap that was leaking (almost certainly without doing a pressure test) was not only just plain wrong, it sent me down diagnostic paths that I would not normally have taken-- for example, starting this thread because I assumed that the tech was correct and that the new replacement cap must still somehow be the problem; and just exactly WHAT could the problem be with the new cap or the part it seals against, etc, as I detailed in my first and ensuing comments.

If I had discovered those signs of leakage myself, without the input from an "expert", I would have replaced the clamp first thing, monitored the result, and not bothered this forum, let alone a stealership, with something so trivial.

This experience once again reinforces my long-held policy to take what "experts" in various professions -- from health to finance to politics to automotive -- only as advice, and with a very big, very skeptical grain of salt. In this case, even though I have never had to replace a radiator cap on any vehicle I've ever owned, because the Z has what to me is an unusual cooling system arrangement, I assumed that the tech actually knew what he was talking about when it comes to the Z.

Thanks for all the help, guys. I appreciate it.

BTW, I did not forget to re-install the cap on the tank before I closed the hood (for the second time), but I must admit that posting this latest photo was indeed a helpful reminder.

Attached Images

coolant leak 8.jpg (100.3 KB, 22 views)

Jhill

Ok so let me break this down for you as to what the auto tech experiences. That 180.00 you pay is about 1 hr drive rate time which the tech gets about 20.00-24.00 of. Generally diag is 1hr. What you are asking now is for the tech to do his whole inspection and now do diag for no additional cost. This is why techs are leaving in waves because flate rate pay and expecting us to do everything for free, it isn't our fault that the drive rates are so high but yet the dealers don't want to lower or ask for the extra hour. No they just expect the techs to take it and eat it. That coolant pressure test system, a professional one that will last pressure test and not fall apart after three uses will cost about 360.00, guess who has to buy it, the tech.

And now your asking him to work for 10-15. An hour if you factor his hourly rate spread over the free diag time.

This is why you don't find qualified techs were all leaving the sinking ship.

Darwins Child

And, therefore, what the Nissan tech should have written was that "there is a coolant leak that requires further diagnosis" in the area that I've shown in the initial photos. Period. I would then have taken note of it and probably proceeded as I stated in my last comment rather then being led astray, etc.

Jsolo

Interesting.

Regarding ease of purging air, vacuum filling is best for this. That's the method I used during the last drain/fill. Refilling took all of 5 minutes and no need to purge any air from the system.

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Jhill

You are correct vacuum filling is absolutely the best way to go.

Jsolo

^^Lots of assumptions. Techs are not gods. Was this a dealer tech or independent shop? I'd likely be more trusting of the latter.

Btw, probably a good idea to replace a radiator cap anytime a drain/fill is done. Cheap insurance.

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RadioFlyer

The second clamp being considerably tighter is a result of the amount of heat the spring clamps are exposed to.

Jhill

Oh jsolo one other side benefit of a the reservoir being part of the pressurized system vs an overflow is the coolant is always circulating through the clear reservoir, this is great for a visual condition check of the coolant for if any signs of oil contamination from a oil to water cooler (Common on vw, GM), also if you have no constant/consistent circulation then you know the impeller of the water pump has broken (extremely common vw/Audi 1.8t).

Darwins Child

The "diagnosis" of the leakage is complete. In short, the Nissan tech's statement on the pre-purchase inspection that the rad cap was leaking was incorrect. The small OEM clamp closest to the cap was what was leaking.

How do I know? Because I drove the Z for 3 hours on Sunday during 27C weather. Also got in a little bit of 120-mph "track time" on a remote "raceway". Checked for coolant leakage before, during and after this driving experience and there was absolutely none.

Likely the original cap was also not leaking, but because I had to return the cap to Nissan in order to get the replacement cap under warranty, I can't re-install it to determine absolutely that it was also not leaking.

Dreadnaught

Good to hear man.

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