There are three generations of the Rover V8:
- “Lucas” engines: 3.5L, 3.9L, and 4.2L
- “GEMS” engines: MY1995 through early 1999 4.0L and 4.6L
- “Bosch” engines: MY1999.5+ 4.0L and 4.6L
The “GEMS” engines are considered the most reliable. “Bosch” engines are smoother and have more torque thanks to a redesigned intake and new engine management system, but the production machinery was very old and worn out by the time they were made, so tolerances slipped. “Lucas” engines are simple, but had head gasket issues (albeit not to the level of Bosch engines) thanks to a poor design of the head bolt pattern.
Land Rovers – which were by far the most popular use of these engines in the United States – historically had undersized cooling systems, which poses a problem as overheating will kill the aluminum engine block (as described below). As such, it is imperative that the cooling system be kept in top shape, with regular coolant flushes occurring every two years at the latest. Immediately following any purchase of a used car with a Rover V8, the new owner should flush the cooling system using a cooling system cleaner, followed by several rounds of distilled water, to get all the old corrosion and crud out. Owners should also ensure that the clutch on the viscous fan is working as it should, and that the thermostat, radiator, and radiator hoses don’t have any leaks.
Land Rover temperature gauges are also historically awful. A vehicle can overheat and suffer catastrophic damage without even causing the needle on the gauge to move beyond normal. It is highly advisable to monitor coolant temperatures using OBD2 where possible (such as through a Bluetooth scanner connected to a smartphone) or an aftermarket digital gauge.
If you’re mechanically inclined, you may be tempted to purchase a Land Rover that has failed head gaskets and repair it yourself. This can be a great way to get a good vehicle for cheap. However, be very careful, as cracked engine blocks and slipped cylinder liners can often manifest very similar symptoms to failed head gaskets. Head gaskets are repairable, but cylinder liners require a resleeve (for which you should use top-hat liners if you go that route) and cracked blocks are not repairable at all.
- Issues caused by overheating:
- Head gaskets
- Lucas engines – Typically fail every 80-100k miles, caused by a bad cylinder head design that puts a lot of stress on the head gaskets around the head bolts
- GEMS and Bosch engines – These have a different cylinder head design than Lucas engines which only has 10 head bolts instead of 14, which dramatically reduces stress on the head gasket. Failure is typically due to mild overheating, especially on Bosch engines.
- Slipped cylinder liners – easiest preventative solution is to pin the cylinder liners, though “top hat” liners are the best solution and should be done during any engine rebuild. If the cylinder liners slip, then the only possible repair is a full rebuild of the block with new sleeves.
- Cracked engine block – if this happens, the engine block is scrap
- Head gaskets
- Ticking, caused by worn lifters/camshaft – this doesn’t necessarily pose a problem, and it’s not too difficult to replace these due to the engine’s OHV pushrod design. Camshafts usually wear because owners used oil without ZDDP, due to the engine’s “flat-tappet” design. Using oil made for flat-tappet engines or that has ZDDP additives significantly helps prolong the life of the engine.
- Oil leaks in general, but specifically on:
- Valve cover gaskets
- Intake valley gasket
- Oil pan gasket
- Oil drain plug
- Rear main seal – this can only be fixed by removing the transmission, but generally the leak is slow enough to not pose a problem on its own
- Oil cooler lines – mostly a problem on older cars. The lines can cause oil to leak on the hot engine, resulting in engine fires. Lucky 8 and PT Schram sell upgraded lines which don’t have these issues – preventative replacement is HIGHLY recommended.
- Oxygen sensors – these last for about ~90k miles before dying. GEMS and Bosch engines don’t like sensors made by any brand other than Bosch or NGK/NTK, and have 4 total sensors. Lucas engines are far less picky and only have 2 sensors.
- Carbureted engines (all vehicles produced prior to 1987) are legendarily unreliable; those with fuel injection are much better
- The factory black coolant reservoir is notorious for cracking and/or bursting. Land Rover released an updated part which solves this, and there are many aftermarket parts available. Preventative replacement is highly recommend.
- Susceptible to head gasket failure through simply through age
With a redesigned intake to produce significantly more torque, and a new engine management system that provided smoother power delivery, the so-called “Bosch” generation of the Rover V8 should have been the grand finale of the engine. Instead, production issues turned them into curse words.
The root of the problem is simple – Rover had been producing the V8 for decades, and the production machinery was very worn out. Blocks had cylinder walls that were too thin, and the cylinder liners didn’t fit quite as well as they had in the older engines. Although the Rover V8 had its longstanding head gasket issues fixed in the “GEMS” generation of engines, the Bosch engines saw them start blowing again upon even mild overheating.
This time, though, head gasket failures were almost always accompanied by slipped liners or cracked engine blocks (which themselves often led to slipped liners for a holy trifecta of catastrophic engine damage). Although 1999 engines weren’t too bad, problems became worse with each succeeding year, peaking with the MY03-04 Discovery 2. Compounding the issues were the Discovery 2’s higher operating temperatures for emissions reasons.
Some also claim that the P38 Range Rover had stricter standards for the engine blocks, and that its rejected 4.6L engines ended up in the MY03-04 Discovery 2. This may explain why the P38 engines do not seem to have these issues while the D2 is infamous for it.
Some people in the Land Rover community claim that the 4.6L Rover V8 is most prone to slipped liners. This is not true, nor does it make sense, as the 4.6L block is identical to the 4.0L block – the 4.6L simply has a different crank, rods, and pistons. What is true is that the infamous MY03-04 engines just so happened to be 4.6L engines.