My 2000 s-type had coolant expansion tank develop a crack @ 24,000 miles...OEM poorly made and problematic for Jags. Tank is located next to firewall inside engine compartment. Minor leak, but consistent and difficult to detect since coolant only escapes when pressure in cooling system builds up. After drive, I discovered small trail of coolant in wheel well, just under expansion tank area. If coolant smell ever present when driving, likely a cracked tank; if not that, a leaky coolant hose, or leaky hose connection. It could be a head gasket leak, but the smell of coolant would likely be less or non-existent since evaporating in hot exhaust, and perhaps a little rough engine running due to combustion contamination. Check out the tank and hoses before having head gasket checked.
