No sooner had I fixed the noise from the belt tensioner than another issue arose. Once the squealing noise from the tensioner assembly was sorted out, a Banshee screeching started to make itself known in the engine bay. Our local Nissan dealer thought that the problem could be a leaking exhaust manifold, so I did more checking and I discovered a leak where the exhaust manifold and EGT pipe connected. I cleaned things up and made sure that things went back together properly, but that still didn’t fix things. I also checked as best that I could around the exhaust manifold and no where could I spot the tell-tale marks of a leak. It also didn’t seem logical that the noise was coming from the exhaust manifold, as it varied so much, coming on and off at different times. However, then I found that the turbo dump pipe had a large crack at the turbo flange. So a new dump pipe was installed (great service from DEA Performance), yet even that didn’t make any difference to the sound, nor was there any noise to give away that the dump pipe had cracked.
So once again my head was buried deep in the engine bay of the Patrol, this time using a mirror to poke around every nook and cranny of the exhaust side of the engine and that’s when I spotted the telltale signs of a leaking exhaust gasket. And leaking it must be, as the soot around the spot was pretty significant. It was in such an awkward spot that only with a mirror held just right could you see the evidence. So I had no choice but to start removing things to replace the exhaust gasket. One more thing that is easier said than done. The turbo and associated bits and pieces came off easily, except for one item. There’s a small heat shield on the exhaust manifold (not the main one around the turbo) that’s held on by three (not two) bolts and one of those bolts sits right under a set of water pipes. There’s no access to the bolt from the top, as that’s covered by the water pipes, and there’s only the smallest amount of room between the bolt head and water pipe.
I managed to get a ratchet wrench onto the bolt head and start loosening the bolt; however, as the bolt came out, the head of the ratchet began to bind against the water pipe and the bolt wasn’t coming out. The last thing I wanted to do was remove the water pipes just for one bolt. Worse still, the ratchet was a one way ratchet (you had to flip it over for it to go the other way) so I couldn’t even reverse the process. Anyway, after a lot of cursing and levering of the partly loosened water pies, the bolt came free. I was then able to remove the exhaust manifold which, after inspection, was warped at both ends. So rather than find some place to machine the manifold I decided to get a new one and, given where I live, probably ended up not paying a great deal more overall than if I’d tried to get the manifold machined.
On removing the heat shield, I discovered that the top-front exhaust stud had broken off, with the stud remainder inside the cylinder head. I was aware of the potential for broken studs, but had been hoping for that not to happen. The remainder of the exhaust removal was easy, especially as two more studs broke off like cheese sticks, so I now had three stud corpses embedded in the cylinder head. I’d sprayed everything with WD40 over a couple of days, after discovering the first broken stud, in the hope that the remaining studs would come out without breaking. Prior to this I had already ordered gaskets and new studs for the manifold, as well as ones for the other bits that had been removed. But after failing to make any headway on removing the easiest of the broken studs and almost making a mess of things, I was beginning to wonder whether I would have to take the Patrol to a proper workshop where the head would have to be removed.
But rather than give up, I decided to order some tools and parts that I didn’t have and persevere with the repair, rather than face an immediate bill of probably $3000 just before Christmas. Clearly I needed a tool that I could use to guide the drilling process so that holes could be made in the centre of the broken studs, rather than having the drill go off-centre as happened with the first broken stud. I also needed some Helicoils, as it was very likely that the first stud hole thread would need fixing. Also, because of the very awkward location of the broken studs, I needed tools that would enable me to reach and work in that awkward location. Thankfully, what I needed were things that wouldn’t go to waste and weren’t that expensive. As for the drill guidance tool, I went to see one of our local engineering places (a big thanks to Hulls Engineering) where they were able to use the old manifold gasket to make up a plate with form-fitting holes that would allow me to more precisely drill those essential holes into the centre of the broken studs. I also bought some milling bits to flatten the broken studs before drilling, but they may not have been essential. I would also suggest getting a 10mm cobalt drill to drill out the broken studs, as this makes the job a lot easier.
Can I suggest for anyone that encounters this problem and plans to do the work themselves, which is not an impossible task, that they make this template from the outset. All you need is a 10mm thick by 90mm wide piece of flat bar the same length as the exhaust gasket. Use the exhaust gasket as a template with which to drill 10mm holes in the exact centre of where the manifold bolt holes go. This only cost $56, and it was a God send. I then tack welded some 10mm hexagonal nuts that are used to join threaded bar to the holes that aligned with the broken studs. These were used as a guide to drill out the broken studs. This involved a lot of patience and removal and replacement of the template numerous times to check progress. Also, once you’ve drilled out the broken studs, you don’t need to use the supplied Helicoil drill, as the 10mm drill used to drill out the studs is only a fraction smaller and the tap will remove enough from the hole in any case. So once the studs were drilled out, I then removed the guide nuts from the template and tapped the Helicoil thread into each of the holes of the template. The threaded holes gave me the perfect start for tapping into the cylinder head and getting the holes straight.
Once the holes were tapped out, I inserted the Helicoils and was ready for the re-installation of all the parts. However, the top-front helicoil didn’t go in quite far enough and started to pull out when I inserted one of the new studs. Clearly I hadn’t tapped deep enough and the thread was exposed. The helicoil wasn’t going to unscrew, so I had to very carefully use a pair of needle nose pliers to unwind the helicoil and remove it from the threaded hole. There was some sweating and swearing at this point, as the Helicoil was in the worst possible location where just seeing the hole was a problem. Anyway, I managed to remove the helicoil and run the tap through again (after grinding a small amount off the tap end) and this time the hole was deep enough. I didn’t want to go through this again and made doubly certain the remaining holes were tapped sufficiently.
There was one stud that wouldn’t come out no matter what I did and I didn’t want to put too much force on the stud in case it broke and in doing so cause more damage. So decided to leave that stud in place and install the seven other studs. Now these had to be torqued to around 40Nm and required a special tool called an e-torx socket. This was an essential tool, as it was the only way that you could safely engage the stud head and torque the stud. A complete set only cost $20 delivered, so you’d be mad not to get a set. I also needed a set of ratchet adapters, as my torque wrench was 1/2″ and the e-torx socket I needed to use was 1/8″. So another set of tools was needed, but at $9, was again well worth getting. I’ll go through all of these additional tools at the end with links to where I bought them on eBay.
Now for some advice on what to do and get if you ever face having to do this yourself. First off, obviously get new gaskets, stud and nuts for the entire setup. Buy genuine rather than aftermarket, even though you can find aftermarket somewhat cheaper. If you live where you can get the exhaust manifold machined fairly cheaply (my new one cost $295 delivered from Ringwood Nissan), do so, but compare prices first and I’d personally spend an extra $100 for a new one rather than have it machined by a shop that I didn’t know (add the machining and travel costs). Also, get a tub of anti-seize and put anti-seize on every nut, bolt and stud that you replace or reinstall. Then I suggest that you get the following tools if you don’t already have them. The Lisle tap sockets were the most expensive single buy, but they made the impossible, possible. There was no way any other tool would have allowed me to get the tap to the worst of the holes (using a 3/8″ extension bar and ratchet handle). The right-angle drill attachment also made work far easier than anything else would have done. The other tools I mentioned earlier and I’ve enclosed photos and eBay links to all of these.
My Patrol was off the road for three weeks, but that was mainly waiting for tools and parts to arrive, waiting out the wet weather, as well as the stuffing around before getting the template made. Once I had the template made, things went fairly quickly and I had the Patrol back together in a couple of days. So far it’s been good, as everything looks to be normal once again and I do hope that I’ve done a decent job that will last.