Reviving the Bosch 4.6 Land Rover V8 Engine...
There’s a problem in the Land Rover world. Engines in Discovery II and P38 Range Rovers are dying at a quite steady pace.
When Land Rover started making V8 engines – fifty-plus years ago – the tooling was all fresh and everything was spot on. While most engines don’t last long on the production line, Land Rover V8 held on for a long time. Other manufacturers introduced more sophisticated engines, but Rover stood firm with the old 1960s V8.
The longer it stayed in production the more worn the tooling became. Machines that originally bored holes with an accuracy of a few ten-thousands of an inch lost their precision. In some cases, the tolerances slipped by a factor of ten. The result? …Those were the engines that began failing.
Failures happened when the engine got hot enough, even if the initial overheating could be caused by anything – water pump leakage, fan belt failure, or a blown hose. Many of these engines failed after the cars were overheated and for some engines that translated to more serious problems hidden inside. It turned out that the overheating was also causing cracks in the aluminum block castings.
Sometimes the cracks allowed oil and coolant to mix, leading to another engine failure. Other times, cracks allowed combustion gases to get into the coolant, which led to another thermal incident.
But yet, the tooling is not the culprit here, the second issue comes in – the coolant. In 1999, Rover began using Dex-Cool in place of the green coolant they’d used for the previous thirty-some years. There have been some recent lawsuits alleging corrosion when Dex-Cool is used in late model engines, and the revelations of those cases may shed some light on the Land Rover situation.
It appears that Dex-Cool can react with the materials in the engine if there is an excess of air in the cooling system, as happens when the level is low. Dex-Cool can also react with other coolants, something that happens if old-style green coolant is added to the system.
So, before we decide to work on these engines, we always perform a block pressure test where we apply compressed air into the coolant channels to simulate what happens when pressures build up as the motor runs. If there are no leaks, then we can revive the V8 to run as new.