Radiator cap? coolant leak
 

In April we had a pre-purchase inspection done to Z. The one and only thing noted in the inspection was a leaking coolant cap. After we purchased the vehicle, the dealership handed me a new cap under warranty and I replaced it.

Since that inspection we've put on the vehicle only about 600 km. (The Mobil 1 that I put in shortly after purchase isn't even dirty yet.) Because I assumed (yeah, I know) that the coolant leak had been stopped by the new cap, I did not check if the coolant was still leaking. Yesterday, when I checked the oil level, there was the coolant leak staring me in the face. It is shown in the photos below of the area, the sealing side of the cap and the aluminum coolant pipe's cap-opening.

The rubber gasket on the cap, as well as the sealing ring on the aluminum pipe seem fine to me, but, obviously, something is indeed leaking.

This couldn't be an over-pressurization, issue, could it? Coolant temp is normal. Level is still OK in tank.

Is it possible that the machining of the opening on the aluminum pipe is faulty and not allowing the cap's gasket to press down with enough pressure on the aluminum sealing surface? Should I polish (NOT grind) that sealing surface to a mirror finish?

Today I'm taking the vehicle back to Nissan for their assessment. But before I do that, because I doubt if our Z is the one and only Z to have this problem, I thought I'd ask here if other members of the forum have had this same problem and, if so, what the solution was.

Thanks.

Wouldn't be from over pressure as that would just make the cap open and dump into the reservoir. Looking like more possibly a porous aluminum pipe. I would first recommend using a cooling system pressure tester and leave it overnight (after cleaning the area of course). Then see if you find and traces/wetness around the pipe, flags area etc. it may not show as it may only be happening when hot and the aluminum spreads out. If that is the case they have dye you can put into the cooling system and then check with a black light to find the source. Might even just be a bad hose clamp and wicking onto the pipe, fluids can do some weird stuff sometimes.

Thanks for the input. You may be right about the aluminum spreading or a bad hose clamp. Thanks for the recommendations for testing.

The thing I find interesting is that if coolant is leaking / spitting from between the cap's rubber gasket and the aluminum sealing surface that it is pressing against, I would expect to see some remnant of coolant at least somewhere on the gasket-side surface of the cap that is directly adjacent to the gasket.

But, as you can see on the photo of that gasket-side area, there is none, even on the downward-pointing edge of the cap or any of the aluminum just outside of the convex sealing surface, which is weird. I should have noticed whether this was also the case on the original cap, but, once again, I, as well as the tech who did the pre-purchase inspection, may have made a mistake in assuming that it was the cap that was leaking.

Thanks again.

Speaking of hose leaks and clamps, notice the area pointed out by the arrow in the photo below. If the cap is leaking, why would there be coolant residue on that small pipe in that particular area? Is that pipe ever substantially pressurized during normal operation?

Do you think that Nissan's small and large OEM hose clamps shown in this photo clamp down / seal those hoses against the pipes as well as say traditional stainless steel hose clamps that are tightened with a screw?

I ask because I'm wondering if I should save some time, travel and trouble and replace those two OEM clamps with those I just mentioned, because the more I think about it, the more I think that it is not the cap that is leaking.

Thanks.

Usually the Oem clamps I prefer. Very rarely do I have issues with them. They are also nice because they eliminated the possibility to over tighten. People usually have a bad habit of over torque the screw type, the bands have a sharp edge and eventually cut through the hose. The Oem have nice smooth thick edges and can last a lifetime. Again I recommend cleaning and pressure testing. That will tell you right away.

Side question. Is yours a 2012 +? I can't read the cap but it looks to me like it has the pressure relief in it? If so and you have a 2012+ then that is the wrong cap. The one on the pipe should be solid, no relief and the one on the reservoir should have the pressure relief.

As the information under my username indicates, we have a 2014. If you look at the leftmost photo of my first post you can see the two removable caps of the coolant system. The one on the lower right of the photo is on the tank, and you can see that it has a pressure designation printed on it at about the 6 o'clock position. As you can see, the other cap - the one in question -- does not have a pressure designation printed on the label. Does this difference in labeling indicate to you that the questionable cap is indeed the correct one for its location?

By virtue of the locations of the dried coolant drops on the engine relative to the small relief pipe, I'm now thinking that it's possible that that pipe has a pin-hole in it, but this would not explain the residue on top of that pipe, near the hose and hose clamp.

Thanks, Jhill.

I just now noticed the warning printed around / near the top edge of the cap's label: "never fix on the reserver tank". Therefore, I think that this is the correct cap for that location.

Yes that is correct. I couldn't see the images clearly on my phone, gets blurry when zooming.

Looking at the image as clearly as I can. Seeing the white around the metal elbow and the coolant stains below it. I suspect the small hose may be seeping and coolant wicking along that bend and then on top of the coolant pipe. Really need to do a pressure test to know.

Thanks! That should nail down what's really leaking.

Also when the coolant is at operating temp and the system gets pressure on it, move the small hose and see if coolant comes out. I had a truck that had a coolant leak and once I moved the hose coolant started shooting out of a pin hole sized hole. I would also get the cap replaced as well. And as people have previously said, fluids can move in crazy ways.

Last but not least, coolant can sometimes seal an area where it is leaking from once it dries up. So try cleaning up the coolant and put pressure on the system.

It's just the hose clamp. Spring clamps get weak over time. Clean off the area, and replace the spring clamps with worm screw clamps. Then see if it continues to leak. You should be able to get a pack of 4 clamps for $2. I'd do that instead of bringing it back to the dealer. Who knows what they will charge you for.

Remember - only work on your cooling system with the car cold (obviously).

Spring clamps can get weak but usually it's the rubber that gets worn causing less clamping force. But yes you can get it tighter with a worm screw clamp. Just do not over tighten otherwise months later you end up with a cut hose. Good idea to use a spring style 1/4 drive screw driver when tightening a worm style, this will prevent over tightening.

More great news! (Maybe more like an update.)

I did as Dreadnaught suggested and after the engine was at normal operating temperature, I wiggled and pulled a bit on the hose near the OEM clamp. There was no leakage, but I also tried rotating the hose a bit and it did indeed rotate quite easily-- too easily, IMO.

So I spent $3.79 on two stainless steel hose clamps, cleaned the tube and the affected area of any remnants of coolant, removed and saved the OEM clamp and, using a manual nut driver, installed the new clamp just tight enough so that I could not rotate the hose using the same effort that had easily rotated the OEM clamp.

We'll drive the car for some more kms and this time, after each and every ride, I'll be checking for remnants of leakage. I'm betting that there will be none. (And because I have placed a bet, there will definitely be some leakage.)

I'm glad you found that leak on the hose. ;) Also, hoses should not move easily. Your clamp was definitely worn out. And as you said, just monitor the area.

Our vehicle was purchased by its original owner in July of 2014, which means that the clamp has been in "hot" service for probably not much more than 2 years. How the heck it could have worn out in 2 years is beyond me. If it was indeed not holding the hose tightly enough, I bet it's because its spring steel was not quenched correctly by its manufacturer, or it was removed at some point and, as a result of that process, the clamp lost some of its tension.

This is why I think that it's best to stick with a clamp whose "squeeze" can be adjusted at will and re-adjusted over time.

This evening my wife and I went on a joy ride (I say "joy" because it included a stop at DQ to get my wife a banana split) that lasted about 45 minutes. No high performance anything, but when we got home I checked the usual suspect and there was no leakage whatsoever, so I believe I may have fixed with a clamp what an expert technician said required a new cap.

Haha! And as far as the clamp sometimes things just go bad prematurely. :shakes head:

Yes, that's right. What would have happened if that clamp had been just a bit looser and the hose had inconveniently popped right off in Alberta's famous "middle of nowhere" -- for example, half way up some steep mountain hill located half way between Jasper and Lake Louise on the famous Icefields Parkway -- a trip we'd like to take this summer in our fabulous Z?

Considering the reality of what has just happened, I'm now seriously considering whether I should proactively / pre-emptively replace all of the coolant system's OEM spring clamps-- especially the larger ones --- to prevent this possibility. This would not be an expensive or difficult operation and it would completely eliminate both the nagging thought of such a possibility or the any inhibition to "floor it".

Am I being too paranoid?

Yes

Yes you are absolutely being paranoid. Oem spring clamps are usually much better grade than after market screw type. Also all the other bigger hoses will be using a much more robust spring clamp, the one on the little hose is just the wimpy flat spring steal not like the bigger thicker clamps.

As for your professional tech I can tell you what probably happened being I came from the industry. They usually get paid on a system called flat rate so paid per job. Probably got paid for the inspection saw the coolant and then given no time to diag so just threw a cap at it. Not saying it is right but it is what happens which is why I am a huge opponent of flat rate shops. If tech follows the proper steps then they make no money if they cheat they make more.

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

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.

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.

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

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.

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.

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

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.;)

^^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.

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

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.

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).

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.

You are correct and that is what should have been done just usually after a tech says there is a coolant (or other fluid leak) the dealers allways follow up with well what's leaking? I need to know what to sell the customer etc ect and always push for free anweres because they want great customer reviews and not get comments of OMG they charged me $$$ never go here again they are a rip off. So after years and years of fighting for every penny trying to get time to do things the right way, techs just break down and go it's probably just this and shotgun parts at cars. It isn't right, it is a screwed up situation all around.

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.

Good to hear man. :tup:

Figured that would do it. And your correct that previous cap probably never leaked at all. Especially since it isn't even a real rad cap, it's just a seal.