WebStream (Clear cache)

Anybody knows, how clean cache from WebStream?
Using code:

AssetBundleCreateRequest acr;
acr = AssetBundle.CreateFromMemory (memoryAssetBundle);
while (!acr.isDone) {
	yield return acr;
}
assetBundle = acr.assetBundle;
obj = assetBundle.LoadAllAssets (typeof(GameObject));
assetBundle.Unload (false);

Count of loading bundles over 100.
Everytime after AssetBundle.CreateFromMemory is executed, size of WebStream increases by 8 Mb

Call Resources.UnloadUnusedAssets after bundle.Unload will help