If we found that the head was out of tolerance, it would’ve required resurfacing. Nissan warns against cutting too much, and I agree that a badly distorted head should be replaced with a quality rebuilt unit. Excessive cutting can get you into trouble on timing chain tension, cam timing and camshaft journals that are no longer in line. The other consideration is if the engine got that hot, it may just make more sense to replace it with a rebuilt or recycled unit.
With no cutting required and no indication of cracking, we’re ready to reassemble. I always use an OEM head gasket to be sure we have the latest part available. We’ve used copper spray with good success, but, in the case of the Nissan, the service information guides us where to apply sealer on installation, as well as the proper sequence and angle required when tightening the bolts. As always, be sure the threads are clean and lubed, as well as the contact area between the bolt and washer.
Reinstalling the valvetrain is fairly straightforward. Use the marks you made to set the cam timing and be sure to hold the camshafts on the hex area when you torque the cam gear bolts.
Reinstall the chain tensioner before removing the locking pin on the intake cam. When the pin is removed, turn the crank clockwise until the camshafts start to rotate, locking the internal lock pin in the retarded position.
Reinstall the other parts that were removed, install a new thermostat and you’re almost ready to fire it up.
But before you do, be sure to bleed the cooling system. Remember, this was the cause of our problem. We use a funnel that attaches to the radiator cap opening allowing the coolant to be higher than any part of the cooling system. With this engine, you’ll notice a copper sealing washer under one of the thermostat bolts; that bolt acts as the bleed valve. Fill the system with this bolt removed, allowing air to escape.
When you get solid coolant, reinstall the bolt, start the engine with the heat set to maximum warm and allow the engine to run until solid heat is felt at the vents. It’s also a good time to ensure that the cooling fans are working as they should.
At this point, turn off the engine and let it cool; when it’s cool, remove your service funnel, top off, if needed, and road test. I always like to do the first road test with heat set to warm in the vent position so I can confirm we have solid heat with no air in the system.
When all is said and done, there’s no reason that Nissan head gasket replacement shouldn’t be a profitable job for your shop. This article is not intended to replace good service information and, like any big job, it truly pays dividends to read up on the job before you start, but there’s no reason to be intimidated by things like variable cam timing and complex-looking timing chain configurations. It’s what the carmakers are using today, so get used to it and prepare for the challenge.
