Newage STi's seem to suffer from knocking/clunking rear struts when going over bumps or turning. This article shows the reason why the shocks go and two solutions on how to solve the problem without buying new [expensive] shocks.
The grease in the STi inverted struts seems to solidify or dry out so the strut binds then releases leading to a knocking/clunking noise. The noise is like something rolling around in the boot/trunk. There are two solutions, the first a temporary fix, the second a more thorough fix. Both are described in more detail below.
Solution 1 - Temporary Fix - Spray and Go
A few Scooby owners report that the following procedure has been effective. This should be considered a temporary fix which may last up to 12 months or 10K miles.
Equipment for Solution 1
- Can of white lithium grease
- Car jack
Procedure for Solution 1
- Jack up the car till the wheel is off the ground
- Go behind the wheel and pull up the dust boot
- Using a can of white lithium grease, spray for couple seconds over the exposed strut
Solution 2 - Thorough Fix - Re-grease Struts
This is a more thorough fix and will likely last for the lifetime of the strut.
Equipment and Materials for Solution 2
- Spring compressor (essential)
- Air compressor and Impact wrench (not required)
- 14mm socket
- Torque Wrench
- Mobil 1 Sythetic Red Grease (or equivalent)
- Disposable Shop Towels (lots and lots of them, greasing is messy business)
- A good hand cleaner really helps for getting all the grease off your hands
- Small flashlight. When doing the deep greasing, it helps to shine a flashlight down to see if you've missed any spots.
Procedure for Solution 2
- First jack up the rear of the car, make sure it is safely supported with jack stands and remove the tires.
- Remove the back seat starting with the 2 x 12mm bolts on the lower portion of the seat.
- Once the lower seat is removed you will see the 3 x 12mm bolts that hold in the bottom portion of the seat back.
- Remove the 3 bolts then lift the seat back straight up, it has three hooks that hold the metal frame of the seat in place along the top.
- Once the seat is removed you can see the rear strut mounts, they are held in place with 3 x 12mm bolts each. Before removing the top portion of the strut it is easier to break loose the lower bolts that hold the strut to the spindle. Remove one of the bolts but leave one in place to support the strut.
- Make sure you also remove the bolt that holds the brake line to the strut housing.
- With the lower bolts removed go back into the car and remove the upper strut 12mm bolts.
- Once the upper bolts are removed go back to the lower portion and remove the last bolt while supporting the strut assembly.
- The strut is now free to be removed from the car.
DO NOT DISASSEMBLE THE STRUT WITHOUT USING A SPRING COMPRESSOR. Even though they might not look like it the springs are under pressure even with the strut extended. loosening the top strut shaft bolt without having the spring compressed could cause serious injury.
- Once you have the spring compressed safely remove the top strut bolt, remove the upper strut plate and washer then remove the spring and dust boot.
|Disassembled rear strut|
- The strut cartridge is held in place with a nut located on the bottom of the strut housing.
|Nut at bottom of strut housing|
- Put the strut housing in a vice to better hold it during the repacking process.
- Remove the 14mm nut on the lower strut.
|Strut housing in vice with nut removed|
- Once the nut is removed you can easily remove the cartridge. Slide it out of the housing being careful not to damage the lip seal especially when you get to the bump stop.
- Once the cartridge is removed you can look into the housing and see the areas where the grease is trapped between the housing and the cartridge. The factory grease is yellow in color and about the consistency of butter.
- A spatula is a good tool for removing the factory grease inside the housing. Be careful not to scratch the surfaces inside the housing where the cartridge rides or possibly nick the seal. A spatula made of silicone with a plastic handle is best.
- Slide the spatula into the housing using the the thin edge to go along the grease trap edge and scoop out the old grease.
- The factory grease in my struts had started to break down and had become sort of waxy.
- You may notice that there is additional grease further down in the strut housing. Depending on the length of your spatula, you may not be able to reach all the grease. For the adventurous, extend your spatula with a large screwdriver. Make sure you cover up any sharp edges that might scratch the housing.
- Once the housing has been cleaned out with the spatula you may want to use a clean lint free cloth the remove any residual grease. Just wrap a cloth over the end of the spatula rotating the tool as you pull it out of the housing. This should remove any remaining grease.
- Now it's time to re-grease the housing. The author used a synthetic multi-purpose grease (wheel bearing grease). You want a grease that feels slick between your fingers when you rub them together rather than tacky or sticky.
- Using the spatula try to get the grease into the trap area evenly all the way around the housing.
- Be sure to get grease up against the upper and lower edges of the trap area. You don't need to use a whole lot, a total amount of grease about the size of an egg or a racquetball. In the picture below it looks like there is more grease than there really is because the author got a lot around the grease seal area.
- You can now slide the cartridge back into the housing, being careful not to damage the grease seal.
- When the cartridge gets to the bottom, rotate it slightly until it seats into the lower housing section. The cartridge shaft has a "key" or notch that will allow it to be held in place so that it will not rotate. You can see the notch by the point of the screwdriver in the picture.
- With the lower cartridge shaft seated, clean off any excess grease and reinstall the 14mm nut using some Loctite to keep it in place. If you look at the Prodrive bumpstops PDF, they say that the torque spec for the nut at the bottom of the strut is 40 Newton-meters. This is approximately 30 Ft-lbs. When finally torquing that nut back down, a vice with soft jaws will help.
- Now the strut is ready for the dust boot and spring to be re-installed. Be sure that the spring ends are seated against the strut housing and then the upper strut plate. Having the spring twisted and not seated in the proper area can affect ride height. Re-install the washer and strut top then the retaining nut. Put some Locktite on the retaining bolt and pretty much everything else during the reassembly process.
- When putting the reassembled strut assembly back into the car try putting one of the lower bolts in first then guide the upper strut stud through the holes on the area behind the seat. Use a floor jack if needed to help push the studs up far enough to get the nuts started. Be sure to get the upper strut nuts tight, the nut is a pinch nut style and may start to feel snug before it is all the way down the stud and truly tight. The author torqued his to 35 ft-lbs.
- Don't forget the brake line bracket when you are finished with everything else.
Now enjoy your clunk free STi!
Note: The process for the front struts is essentially the same as the rears.
Information Source - SIDC forum thread, Solution To Knocking Newage Rear Struts
Information Source - ScoobyMods forum thread, '04 STi rear strut repacking
Information Source - NASIOC forum thread, Re-greasing STi struts