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Rebuilding a Nissan Silvia S12
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These tips and tweaks supplied by SilviaGod
Tools for turbo removal Turbo Removal/Replacement
In the picture are the modified tools needed to remove the turbo complete with the exhaust manifold. They are half a 14mm ring spanner, part of a 14mm open-ended spanner and a chisel with a 'v' cut in it. Other tools needed are a 10mm, 14mm 17mm socket and ratchet, mole grips, hammer, 10mm and 12 spanners, a jack, axle stands, screwdrivers and a bucket to collect drained coolant. If a strut brace is fitted a 17mm socket will be required to remove it but the bolts must be returned before jacking the car. The car is jacked up for three reasons, one is to access the clip holding the oil return pipe and the 3 bolts attaching the exhaust to the down-pipe, the other is to make the job less painful on the back of the legs and lower back and the final reason is to make life easier to retrieve the spanners that inevitably drop in the process.
So, as stated jack and support the vehicle and drain the coolant into a bucket using the drain cock to the base turbo side of the radiator, remove the exhaust from the down-pipe held on with three 17mm bolts. It's easier to use a 'wobble drive' extension with a socket as one of the bolts can be obstructed by the exhaust when trying to get vertically on it. Put a rag in the exhaust because if you accidently drop a spanner down it, it will take ages to retrieve it. Undo the oil feed pipe, and the water pipes along with their brackets. Undo the clip holding the oil return hose where it attaches to the sump and twist the pipe a little to break any adhesion. Remove the charge pipe coming out of the turbo. Remove the induction pipe completely by disconnecting the oil breather undoing the clips at the air-flow meter and turbo. Remove the manifold bolts and withdraw the turbo along with its pipes, manifold and down-pipe. The oil return pipe should pull off in the process.
There are two variations to the oil feed arrangements for the uk engine, and these are as follows: Before 1987 models have the oil feed pipe coming from near the oil filter, this pipe is routed up to just below the cylinder head and then to the rear of the engine, round the back, then along the opposite side and into the turbo. The later models have a short pipe running from a drilling in the block below the distributor going only a short distance into the top of the turbo. Nissan recommend that the engine is removed to change a turbo probably due to the restricted access available, but it can be done with the engine in place using tools similar to those shown. The only difference between the two is that the oil feed pipe is attached to a bracket holding the lower water pipe and there is a compression joint in the oil feed pipe behind the engine above the bell-housing. This is where the part open-ended 14mm spanner and chisel are needed. This must be done before the pipe brackets are loosened as it keeps the compression joint secure. Balance the part-spanner on the nut and locate the groove of the chisel on the part-spanner, hit the chisel with a hammer and this should loosen the nut. The nut should then spin off by hand and when it is ready to be reassembled a pair of mole-grips clamped to the part-spanner should provide sufficient leverage for re-tightening it. From memory there are two 10mm bolts holding a pipe bracket behind the engine on the turbo side and one on the inlet side along with a 12mm nut holding a bracket on the inlet side for the top water pipe. The water pipes are joined near the rear of the engine on the inlet side and it is easier if these are removed along with the turbo rather than attempt to remove the connections at the turbo.
The manifold has 4 bolts at the top and two underneath, three are straight forward whilst the fourth requires the half ring spanner for access to the bolt. You will find the awkward one under the manifold and closest to the bulkhead. When you have fitted a replacement turbo it is recommended that an oil change is done at the same time and that the engine is turned over for 15 seconds with the coil lead removed. This guarantees that oil is present in the turbo before the engine fires.
Problems you might encounter are as follows: Manifold bolts won't tighten due to stripped threads in the head. This can only be rectified correctly by drilling and fitting helicoils. Care must be taken regarding the depth of the drilling. Do not drill any deeper than the existing hole as the oil galleries are right behind. Uneven surfaces caused by exhaust gasses blowing past joints. In such circumstances the mating faces need to be machined flat before reassembly. Manifold to turbo joints are the most common although I have heard of manifold to engine faces becoming distorted. Studs snapping/stripping on the down-pipe where the exhaust attaches. These will need to be removed/drilled out and new studs fitted. I have seen the holes drilled out and nuts and bolts fitted but this makes future dismantling more difficult. Water pipes to turbo difficult to bolt back due to excessive bending on removal. This is inevitable so try to bend any pipes as little as possible when removing a turbo. It is essential that the lower water pipe is attached by it's bracket near where it connects to the rubber hose otherwise the pressure may blow it off. Nissan recommend that new nuts and split washers are used when refitting a manifold and new locking tabs are used when bolting a turbo to a manifold or a down-pipe to a turbo.
It is also recommend that the water and oil pipes are inspected thoroughly, any surface rust removed and the pipes painted with a heat-resistant paint such as Hammerite. If any pipes have deep pitting of rust they must be replaced otherwise you may have to remove the turbo again to replace a leaking pipe.

The T25 turbo will fit the Silvia but you will need to modify the oil return pipe, the exhaust at the down-pipe and grind a lug off the bell housing. You will also need to modify the oil feed pipe if the Silvia was made before 1987. It is worth doing because the T25 runs much cooler and will handle 14 psi all day. The outlet pipe is also different as it exits above the turbo but if you are fitting an intercooler then it doesn’t make much difference.
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