|Pic:||Leak prone area:||Description / Fix:|
|Turbo Inlet Duct||The rubber turbo inlet duct is prone to cracking, especially on the turbo
side. Check the clamps (there are several) for tightness and leaking.
|Wastegate Vacuum Hose||This hose is not prone to failing unless it has been removed, but the metal
fitting on the turbo compressor housing can get loose and pop off.
There are several clamps that hold the hose sections in place; check these
connections for leaks.
|Splitter Pipe||Zenki units are cast aluminum, while Kouki units are plastic. Although
failure of the Zenki cast units is rare, the Kouki plastic ones can crack.
There are a number of clamps and hoses that are connected to this pipe, so
check all of clamps. The hoses are originally reinforced rubber, so
they do not fail that easily.
The stock BOV / CBV attaches to this splitter pipe with another hose. See below for more info.
Of specific note, the BAC valve hose attaches to this pipe and is not clamped from the factory. This hose regularly fails, especially with elevated boost. We highly recommend to clamp this hose on both ends!
|Intercooler Hoses||Inlet and outlet hoses are reinforced rubber, so they rarely fail. The
clamps do go bad from constant removal.
|Intercooler||We serious doubt the intercooler is leaking unless under extreme circumstances.
The intercoler does have a couple fitting in the rear, passenger corner to
a couple of bypass solenoids.
|Throttle Body||The throttle body inlet does have a triangle-shaped o-ring on it. You
can typically reuse this o-ring. The outlet of the throttle body mated
to a black plastic spacer and uses no gasket. If the nuts are tightened
to spec, there is very little leakage here. If you do use some kinda
gasket or sealer, be careful not to plug several vacuum holes in the black
|Upper Intake Manifold||Major areas are the flange to lower intake manifold and several vacuum fittings.
Originally, Mazda used a paper gasket that seals the the upper intake manifold to
the lower intake manifold. Removal of the upper intake manifold is usually
met with some resistance, as the Mazda paper gasket basically glues both flanges
together. With some gentle tapping with a hammer, the upper intake manifold
should come loose. The Mazda gasket typically stays in one piece on one of
the flanges, so if it does, just use some silicone RTV for a better seal. If
the gasket comes apart, all of it has to be removed.
Due to heat and age, the many vacuum hoses can go hard and loosen. It's recommended to replace these hoses. Silicone vacuum hoses are popular.
|BAC Valve||This has been mentioned in the Splitter Pipe area above.
This hose to the splitter pipe is not clamped from the factory, and we
highly recommend you do so now. If the hose is warped or
cracked, replace the hose.
|Blow-Off Valve /
||The stock BOV connects to the splitter pipe and the TID. Stock clamps are
inferior single-wire type that can easily leak.
|Lower Intake Manifold||Like the upper intake manifold, the lower intake manifold is similar. The
lower intake manifold seals the manifold to the engine itself. Fuel and
coolant leaks on top of the engine degrades this gasket, and eventually it will
leak. As with the upper intake manifold, there are several vacuum hoses
on this manifold as well.
|Fuel Injectors||What does the fuel injectors have to do with intake vacuum leaks?
Well, it is one of the most ignored areas when looking for leaks.
The lower rubber grommets on all injectors are used to seal the fuel
injectors to the lower intake manifold (secondaries) or to the engine
itself (primaries). These lower rubber grommets harden and shrink
quickly, so even new ones are prone to leaking within a few months.
We've found out that 10mm I.D. silicone hose makes an excellent substitute. A one-foot length of 10mm I.D. silicone hose can make like 20 of these grommets. Using a sharp razor blade, cut a 3mm to 4mm section of hose that fits under each fuel injector. The silicone hose will stay flexible longer in the engine heat.
|EGR Valve||The EGR valve diaphram can tear and induce an intake vacuum leak.