The 309 TD was a 1769cc that did not have an intercooler, and produced 78 BHP, as opposed to the 405 1769cc turbo (pre 93) which produced 92 BHP thanks to an intercooler. From 93 on the 405 went to 19 ...
Check that the radiator is not blocked (run your hand over the matrix when it has been run for a while), this is a known problem where the waterways crust up inside.
My girlfriend ran one of these q ...