John Robison did a good write up of the failing Rover engines. Make s a lot more since than the wrong thermostat.
"There’s a new problem in the Land Rover world. Engines in Discovery II and P38 Range Rovers are dying, and I’m about to tell you why . . .
The story begins at the foundry in Solihull, England, where Land Rover engine blocks are cast from aluminum alloy. The block is the innermost component of the engine; it’s the foundation everything else is built upon. After the engines are cast the rough holes for the cylinders are bored out and finished. After that, eight sections of steel tube are pressed into place, one for each bore. After being cut off and machined flush, those tubes become the cylinder liners. It’s those blocks and liners that are going bad.
At the plant, the raw aluminum blocks are expanded by heating, while the liners are shrunk by chilling. The block swells to maximum size, while the liners contract as much as possible. At that point, the two are pressed together. Even then, the liners are a tight fit into the block, but that’s what powerful hydraulic rams are for. Once in place, the liners expand for an even tighter fit. They are there to stay, or at least, that was the idea.
Unfortunately, things did not quite work out that way. The liners started moving, and engines began failing. How could that happen? The liners are subject to constant up-and-down forces as the pistons move within them in the running engine. In some engines, the press fit between steel liner and aluminum block just wasn’t tight enough to last.
When Land Rover started making V8 engines – thirty-plus years ago – the tooling was all fresh and everything was spot on. The engineers had calculated exactly how big the block bores should be, and what diameter was needed for the liner tubes. When those liners were pressed in place, they never moved.
Whatever else went wrong with Land Rover engines, the blocks stayed strong. And that was good, because it seemed like everything else gave trouble. Some would say, the vehicles required a lot of tinkering. Such is the British way.
That’s how it was for the first couple decades of engine production. Most engines don’t last that long on the production line, but the Land Rover V8 held on. Other manufacturers introduced more sophisticated overhead cam engines, but Rover stood firm with the old 1960s vintage pushrod V8.
I wish I could say that was a testament to its wonderful design, but the truth is, Rover really didn’t have the money or engineering resources to develop a replacement. 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? Some engines left the factory with tight liners, while others were a tiny bit loose. Those were the engines that began failing.
The designers knew that steel and aluminum expand at different rates when heated. And car engines make the transition from cold to hot every time they are run. So it was absolutely vital that the steel liners be fitted tightly enough that they would never move, no matter hot how the engine got. When the tooling was new, that was what happened. When the tooling wore out, the liners weren’t always so tight anymore.
The block problems were compounded by ongoing engine development. The first Rover engines displaced 3.5 liters and made a little over 120 horsepower. In thirty years the displacement grew by 35% and power almost doubled. The displacement increase meant there was less metal in the block to soak up heat and energy, and the power increase meant there was a lot more to handle.
At the same time, today’s need for fuel efficiency and low emissions has resulted in significantly higher operating temperatures, especially inside the combustion chamber. That puts even more stress on an old design.
Problems began appearing about ten years ago. Mechanics began talking about “dropped liners,” a phrase I’d never encountered before. The constant heat cycling as the engine ran combined with the running motion and caused the liners to break loose. When they did, coolant leaked around them into the combustion chambers, and the engines failed. The solution: a new engine block, and a repair bill near $10,000. Current overhaul costs (winter 2014-15) with the new flanged liners run $11-14,000 parts and labor, removed and installed.
As you can imagine, owners were outraged. To most people, the engine block is like the back seat. You just take it for granted, and it lasts the life of the vehicle. It does not wear out or fail. It’s not a wear item like a fan belt, tire, or spark plug. Yet the blocks were failing, and in large numbers.
I wrote an article about the situation a few years ago, and we developed a way to repair the blocks. We used sleeves with flanges on top, referred to as “top hat” liners. The flange kept them from moving up and down, and the problem seemed solved. Unfortunately, it wasn’t permanent.
Failures happened when the engine got hot enough that thermal expansion made the liner loose in the block casting. For most people, that meant liner failure followed what we euphemistically called a thermal incident. In other words, the engines failed after the cars were overheated. The initial overheating could be caused by anything – water pump leakage, fan belt failure, or a blown hose.
The out-of-place liner was a visible evidence of failure, but some engines had 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.
When the blocks developed cracks we were stuck. Repair of the cracks required removal of every liner from the block, and costs were prohibitive. Replacement blocks were the only answer, or so it seemed.
The problem got so bad that Lad Rover began supplying warranty exchange blocks to dealers for about $1,000. By doing that, they in effect subsidized the repair of thousands of engines over a period of several years. The problem was, the new engines weren’t any better. They were all susceptible to failures.
However, they were all we had to work with, so we made the best of the situation. The main thing we learned was: Never drive a Rover with an overheated engine! By following that advice and preventing overheats we kept the problem at a manageable level.
Until this year.
That was when we saw our first Rover that had combustion gases leaking into the coolant with no prior history of overheating. And when the motor was torn down for inspection, all the liners were in place and there was no sign of thermal damage. Yet the block failed a pressure test where we applied compressed air to the cylinder to simulate what happens when pressures build up as the motor runs. The air leaked right into the coolant passages. How could that be?
We removed the leaky liner, and made an alarming discovery. The aluminum casting that should have supported the liner had rotted away. The inside of the block looked like a piece of decomposing cheese. It was an ugly situation, one of the only failures for which we could see no repair option. It was like looking at rusted floor boards . . . at a certain point, there is no solid metal left to fix.
Since that time, we have seen a few more engines failed in the same way. Other blocks that didn't rot, cracked instead. The symptoms can be subtle at first. There may be slow loss of coolant, and the truck may develop a misfire as spark plugs become fouled by white deposits from coolant that leaks in and burns.
We’ve been wondering what would cause this new, severe, failure and I think we’ve got some answers.
The first problem is the tooling. As the tooling aged, production tolerances became sloppier and sloppier. We’ve seen new engine castings with actual holes where the aluminum failed to fill in. Overall production quality on the last pushrod V8 engines was a far cry from what we saw at the beginning.
That means the last crop of engine blocks – those made from the late 1990s through the end of production in 2005 – are weaker than the blocks that came before. That makes them more vulnerable to corrosion because there’s less consistency in the metal. Something must have changed, since these blocks have been in production a long time and we’ve never before seen these gross corrosion failures.
That’s where 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.
I believe those are the issues that underlie the current block failures, but I can’t rule out the possibility that something more is going on. What does it mean for you? I’ll close with some specific tips for any of you who own or service 1999-2004 Land Rover Discovery or P38 Range Rovers.
First, I urge you to follow Rover’s recommendation and change your coolant every 30,000 miles. It’s very important that you use the correct Dex-Cool product. If your system has been contaminated by mixing several types of coolant, flush it thoroughly before filling.
Before you drive, always make sure the expansion tank is full to the proper level. Don’t drive the vehicle if the level is low, and don’t drive it at all if it’s overheated.
Finally, if you work on these cars pay close attention to the cooling system pressure. One early giveaway of block failure is high pressure in the system before the engine is really warm. I’ve seen Rovers that pressurize the radiator hoses rock hard while the engine is still cold. That’s a sure sign of a serious internal problem.
Another thing to look for is white deposits on spark plugs. If you see six or seven clean-looking plugs and one or two fouled with white a deposit, that’s a sign of coolant intrusion into the cylinders.
I wish I could close with a quick and easy answer, but I’m afraid there’s no such thing. It’s a serious problem that can be managed but if you experience a failure, the only cure that has lasted is overhaul with new pistons and flanged liners. We at Robison Service are proud to have pioneered that process in North America."
