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Three Rebuild Kits — Pick the Right One

This is the thing to get right before anything else on the page. There are three master kits for the 5VZ and they are not interchangeable:

Note that the later kit comes with MLS head gaskets rather than composite. That is not a marketing upgrade — it reflects what the later engine uses, and it is a real difference in how the head has to be prepared.

MLS Head Gaskets — and Why There Are Two of Them

The 5VZ is a V6, so it has two cylinder heads and the gaskets are handed. Coming from a four-cylinder this is the easiest mistake to make.

MLS demands a properly finished deck and head surface. It handles cylinder pressure far better than a composite gasket but it will not hide an imperfect surface the way a composite one forgives. If you are fitting MLS, have the surfaces finished correctly.

Bolts or studs

The OE head bolt set is correct for a stock rebuild. For boost, high compression or MLS gaskets, use the Pro head stud set — studs clamp more evenly and let you torque properly without dragging the threads through the block.

Seals

Every one of these is behind something expensive to remove. Do them all while the engine is apart.

  • Rear main seal — behind the flywheel. Leaving it is how a fresh engine ends up leaking onto a new clutch.
  • Front crankshaft seal — behind the timing belt. Oil from this seal destroys a rubber timing belt, so it is not optional on this engine.
  • Seal Savers — front and rear. If the crank has worn a groove, a new seal riding in that groove leaks immediately; the sleeve gives it a fresh surface.

Also here: the bottom end gasket set and brass freeze plugs — eleven of them on this engine, and a sensible upgrade over steel while the block is bare.

Valve cover gaskets — the leak most 3.4s have

The OEM valve cover gasket set covers 1995.5-2004 Tacoma and 4Runner. It is edge-moulded silicone over a rigid carrier, which is what stops a gasket being pulled in on overrun or pushed out by crankcase pressure.

Two heads, so two covers — the set does both.

Worth knowing where else this leak shows up: oil escaping the cam area finds its way into the spark plug wells, sits around the plug boots, and produces a misfire that comes and goes. If you have been chasing one of those, look at the spark plug tube seals at the same time. The two jobs share most of their access.

Three Things to Do While It Is Apart

  1. Timing belt, tensioner and hydraulic adjuster. Non-negotiable on a belt engine — see Timing Belt Components.
  2. Water pump. Belt driven, so the labour is already paid for. Check whether yours takes the cooler tube version. See Cooling.
  3. Front crank seal. The one that ruins a new belt if you skip it.

Tell us the year, vehicle and mileage and we will confirm which rebuild kit you need before you order.

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