Body - STi Clunk Noise In Rear

SOURCE: Subaru Tech Tips

TITLE: Clunk Noise In Rear

APPLIES TO: STi Models only

SERVICE TIP:

If you get a customer concern on a STi of a clunking noise coming from the passenger side rear and it sounds like a bad strut and you've checked the strut, strut mount, and the rear suspension and still can't find anything wrong, check the Intercooler spray reservoir. We received a report from our neighbors to the north (Subaru Canada) where the water level in the reservoir had been filled half way as instructed in the owner's manual for cold weather operation. The water in the reservoir had frozen, and had frozen around the little float level indicator in the tank dislodging the reservoir cover. The chunk of ice was banging around in the reservoir, and the dislodged cover was banging around also. The slightest bump in the road, or sudden acceleration/ deceleration would cause it to knock

An interesting point: with the car sitting in the shop for just under 2 hours, the ice had melted. You can change a strut in that time, and when the car leaves the shop, the noise is gone only to return later when the water refreezes. So, the next time you get a noise in the rear that sounds like a strut or suspension item and the ambient temperature is below freezing you might want to take a look at the reservoir. Especially if the service history shows the strut or strut mount has been replaced previously.