[v8volvo]

1986: This was the final year for the availability of factory built diesel engine Volvo models sold in the US market. Diesel model options were much more limited for this year, available only in the 740 GLE model, sedan or wagon, and only with the ZF automatic trans. The D24T engine continued with no changes from 1985, but three important changes in the 740 platform occurred for this final year that make them desirable: 1) the 1986 diesel 740 cars introduced a composite battery tray that is not prone to corrosion like the earlier steel trays were; 2) all 700 series cars, gas and diesel, gained a molded plastic fuel tank rather than the earlier type steel tank that is likewise immune to rust; and 3) all 700 series cars, gas and diesel, saw the introduction for 1986 of a redesigned and reinforced front engine crossmember that is not prone to cracking and failure like the 1985 and older crossmembers are. This later type crossmember is interchangeable with the early type, so early cars experiencing crossmember failures can have the crossmember retrofitted with the later type as a permanent bolt-in repair. Note however that the diesel crossmember is a unique part, not shared with gas engine models of the same years. It is, however, shared with the 1989-1991 740 and 940 GLE 16-valve cars so they can also provide upgrade replacements.

Although 1986 was the final year for Volvo diesels in the US and only with a limited model range, in the rest of the world, wider availability of the D24 and D24T engines in the 700 series models with both manual and automatic transmissions continued. In addition to availability of naturally aspirated 240 diesel models. Note that no turbodiesel 200 series cars were ever built for regular production by the factory, for any market European or US. Any 200 series car with a turbodiesel engine is a custom creation.

1987: I am hoping some UK and European members may help with these later years, since the knowledge I and other US based members have gets fuzzy from 1987 onward since these are vehicles we have never seen here.

However, one important design change was introduced for both the D24 and D24T engines in 1987 as far as I know: the cylinder head switched from a mechanical to a hydraulic valvetrain. Different head casting, different lifters, maybe a different cam.

This may have also been the first year of availability for the intercooled D24TIC engine. The D24TIC features a different turbocharger calibrated for higher boost pressure (around 12.5 psi vs the 10 psi of the D24T), using a traditional external rod-operated wastegate rather than the D24T's internal poppet type wastegate, as well as a different (oil-to-air rather than oil-to-water) oil cooler, different intake manifold, probably different calibration for the injection pump, and of course the intercooler and related plumbing. Some D24TIC engines incorporated EGR systems for emission control while others did not, depending on the year and the regulations of the market where they were originally sold.

1988-1994 or so?: No significant changes I am aware of, though that does not mean there weren't any. Availability outside the US of D24, D24T, and D24TIC engines continued in 700 series and in the 900 series that was introduced in 1991, as well as D24 engines in the 240 until the end of its production in 1993 I believe.

1995?: Somewhere around this year, the front timing belt system received a major redesign. The system changed from the original design that uses a single idler roller and a water pump with slots that is moved to adjust belt tension in a somewhat finicky and delicate process, to a new design where the water pump is installed in one permanently fixed position and an additional tensioner roller is added, located just below the cam pulley. Similar changes were made to other engines in the general family, for example the 2.5L gasoline 5-cylinder engines in VW Transporter vans. These later systems are more user-friendly and require less attention to set belt tension correctly. However, those with later model cars and engines need to use care when ordering service parts related to the front timing belt system since they are all different -- different belt, water pump, idler(s?), etc.

Production of the D24 family continued as far as I know until 1996 or 1997 in Volvos, and well past 2000 for Pinzgauer military applications, before finally being replaced by variants of the TDI engine family.