[Orb]

This is a good post in this section but needs some clarifications. If you replacing the check valve house assembly it will be a good idea to replace the seal. The method from “PhaseP” works well if you are creative in rigging up an installation tool for the seal.

There is nothing wrong with the seal design but a better design could have been used. The sealing takes place in the radial grove of the grommet and brake booster when the check valve is inserted in the seal. The compression of seal is about 30% so comments about the size problem excreta are not valid. The real sealing problem in this area is caused by containments on the sealing surface or poor surface finish on the brake booster with latter not being that common.

The most important step in replacing the seal is to clean the brake booster sealing surfaces with Isotropic alcohol and make sure you do a good job. The reason you need to do this is all seal material will leave a film on the sealing surface due to material loss which can causes leaks ( happens with any vacuum system). If you miss this step and you are likely to have problems.

There are two solutions to this problem. I would recommend using silicon grease (or vacuum grease). Apply a thin film (.05 – 0.1 mm thick) on grease inside the grommet sealing grove (3 surfaces), the lead-in chamfer of the seal to aid insertion, and the inside diameter of the seal where the hose barb is inserted. This is well know and typically done when working with any vacuum sealing system. The alternative is to use a silicon RTV sealant. Use only a thin film (0.05 mm thick) of RTV on the radial part of the seal grommet grove. Once the seal is inserted the silicon will spread on all sealing surfaces. If you use to much you risk getting pieces of the RTV getting sucked into vacuum pump. I would not recommend the RTV method unless there is no choice.

If you have replaced the check valve hose assembly and experience random hard brake pedal then you likely have a slow leak somewhere else in the system. The check valve in the brake booster is designed to holder higher vacuum than the rest of the system when the car is turned off. In other word, if you turn off the car then you should be holding about 28 hg in the brake booster and 16 hg past the check valve. If there is a leak past the check valve and the system leaks down to atmosphere pressure, then the check valve in brake booster will leak down significantly and you will have various degrees of a hard brake pedal. If you do have a slow leak in your system you will typically hear the waste gate rattle at start up that last more than 2 seconds since the vacuum has leaked done to atmosphere pressure and it take a while for the system build up a vacuum which can take 5-20 seconds. There should be no rattle of the waste gates at start up if the system is healthy.

To check for leaks you need a hand vacuum pump and gauge then you will be able to identify which component is the problem. Check all tubing individually for leaks. The list below is typical issues with this car:

• Two vacuum canisters. They should hold 30 hg more than hour when tested discretely.

• The two vacuum lines behind the oil filter housing will leak after time (replace every 3-4 years). Mine had a very slow leak.

• The waste gate pressure converters tend to leak randomly on pre 09 cars. Mine needed to replace although I had no issues with the car.

In my case, I had to replace 50% vacuum lines, check valve hose assembly + seal and the pressure coveters to fix the hard brake pedal problem.