Nissan bleeder caps

By Steve Schaeber, MACS Technical Editor

Coolant leaks take on many different forms. Some we’re used to seeing, as they’re common failures that make up some of the bread and butter of cooling system service. But there are others that, while they may not be too difficult to diagnose and fix, make us take note and think about other ways we can apply the same repair methods to other vehicle systems.

One such issue shows up on certain 2014-15 Nissan NVs with either the V6 or V8 engine. The NV (Nissan Van) is the first of Nissan’s new full-size van models for the US and Canada built on the same F-Alpha platform as their Titan pickup counterparts. These rear wheel drive vehicles are set up in two main configurations, depending on whether it’s the cargo van or passenger van model. The cargo van has an in-dash front heater, while the passenger version has both front and rear heater cores. With either setup, a coolant leak may appear at the bleeder cap on the heater hose junction near the firewall. Two potential leak concerns are described in service bulletin NTB15-097: the bleeder cap may not be fully seated down and/or cracking of the bleeder cap itself.

If it turns out that the bleeder cap is simply not seated, the technician could attempt a repair by fully seating the cap to stop the leak. That should be relatively easy to figure out as an unseated cap would be immediately noticeable. But if the cap is found to be properly seated, it’s possible the leak could be coming from tiny cracks in the rubber bleeder cap itself, although you may not notice them at first glance. Try pressing down on the cap or squeezing it from the sides to expose the problem.

Cracking of hoses or other rubber components is often not immediately noticeable with a simple visual inspection. In fact, it’s usually necessary to deform the material in some way in order to expose potential problem areas. Take a vacuum hose for example; at first glance it may not appear that anything is wrong, but pinching the side of the hose may expose several cracks which can allow vacuum to leak, affecting system operation or performance. Same thing goes for some types of drive belts, particularly if they’re Chloroprene (Neoprene). Depending on their construction, you may be able to expose belt cracking by flipping them inside out and bending them backwards. Keep in mind however, that this doesn’t work with newer EPDM (ethylene propylene diene monomer) belts.

In either case, Nissan’s recommendation is to replace the bleeder cap, following all directions in their electronic service manual. This includes partially draining the cooling system to allow for cap replacement without making a mess. They caution however to not replace the heater hose assembly should this incident occur as it’s likely not causing the leak. Replacement bleeder caps are relatively inexpensive, and can be ordered from Nissan using part number 92570-51E00. Be sure to also replace any coolant removed from the system with fresh, preferably 999MP-L25500P Blue Nissan Long Life Antifreeze/Coolant.

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