We don't know the exact number, but there must be literally hundreds of thousands of 6.2L and 6.5L engines roaming the world. Loved by some and despised by others, these engines have the distinction of being the only diesels offered in 11/42-, 31/44-, and 1-ton trucks.
So why the bad rap? For starters, the 6.2L and 6.5L engines were ahead of their time. In the '80s, General Motors was the most prolific user of diesel engines in American vehicles. The versatile engine featured indirect injection for emissions purposes, but that design also meant the engine would need an enormous amount of cooling capacity to keep it from literally cooking itself.
It's unlikely the 6.2L or 6.5L engines will ever be as powerful as the current crop of common-rail diesels on the market, but that doesn't mean owners should feel they have to trade in their trucks just to be part of the diesel revolution. We went searching for solutions for the most common 6.2L and 6.5L problems and came across Heath Diesel Power in Ellensburg, Washington.
After years of working on 6.2L and 6.5L GM diesel engines, Heath Diesel has developed performance parts and packages for owners of 6.2L and 6.5L turbodiesels who are looking for maximum reliability from their engines. If you own a 6.2L or 6.5L, you need them on speed dial.
We told Heath Diesel Power we had a '95 Chevy K2500 6.5L turbodiesel with 144,000 miles that we wanted to build into an all-purpose work truck that we could take out and play with on the weekends. Of course, we asked for more power first, but Heath Diesel recommended the first thing we do was address the engine's cooling system for improved reliability. In future installments, we'll pour on some power and add some utility to the rest of the truck with bolt-on parts.
The key to a reliable 6.5L turbodiesel engine is proper cooling. Heath Diesel Power recommended updating the cooling system on our '95 6.5L with its Extra Heavy Duty Cooling System Upgrade (PN HDP1600: $409) that works on '92-'96 6.5L engines. The kit includes a high-flow water pump, a huge nine-blade cooling fan, a clutch, and a pressure-balanced, bypass-blocking thermostat with a gasket. Heath Diesel also recommended updating our lift pump with its latest heavy-duty version (PN HDP1300: $109), heavy-duty oil pressure switch (PN HDP1484: $38), PMD Isolator System (PN HDP1296: $549), and electronic filter harness (PN HDP1559: $58). We also had Heath Diesel throw in a new crankcase depression regulator (CDR) valve for $58. | 
We enlisted GM Truck Center in Burbank, California, to do the installation. John Hughbanks tore into our 6.5L so we could be in and out of the shop in one day. Hughbanks pulled the upper half of the fan shroud off the radiator while he drained the coolant into a bucket. | 
The Heath Diesel Extra Heavy Duty Cooling System Upgrade includes a new water pump that replaced our original unit for improved airflow. The new pump also had provisions for the new nine-blade cooling fan that attached to the pump pulley with a massive screw-on hub. |