The secondary camshaft timing/drive belt can intermittently exhibit a "whine" or "warble" type noise under certain load, temperature and/or speed conditions. This is normal. The plastic belt covers and aluminum front engine cover are equipped with sealed joints in order to contain this noise. If a noise of this type occurs, verify that all covers and seals are installed and are intact. Also make sure that no gaps exist at any joint. Use RTV sealant in order to close any gaps in these cover joints. Sealing the gaps will effectively reduce the noise.