First off - my motor runs fine currently. I am just curious to learn from the community!

I posted about this on a Rover V8 Facebook Group and did not get any answers pertaining to my original question. Just folks recommending running a cooler T-Stat etc.

This is more a high level question out of curiosity. Rover V8 block issues seem to be more severe in the later Thor Engines. The North American DII 4.6 seems to have the worst reputation for various block related issues all stemming from poor machining tolerances near the end of the Rover V8's production run. We all know the inherent design and age of the Rover V8 makes it oddly charming, fairly rugged and simple, but somewhat fragile.

My question is:

Did all late production 4.6 motors suffer from the machining issues that seem to be the main cause of cracked blocks, leading to slipped liners and blown headgaskets?

Or, do only some suffer depending on when the motor was built and if the tooling had been reset and had tolerances checked recently to not?

Comment with your knowledge...

My $0.02:

To me it seems unlikely that all engines suffered from poor machining quality since the tooling was undoubtedly looked over from time to time, and some of the tolerance issues were noticeable by the naked eye (RPI engineering has a video about it).
I know that the block can be damaged by excessive overheating which is common due to the factory cooling system, higher temp thermostat, and no warning from the gauge. Is this documented somewhere and I just have not found it yet?

 

I believe the prevailing thought of the Land Rover community is that Land Rover knew there were casting issues with the 4.6 the last years of production. The blocks were graded and the highest grades when to the Range Rover P38. My thoughts are when the P38 was discontinued after 2002 Land Rover was left with a lot of 4.6 blocks and they all were put into production. Maybe this is why the 2003 year for the D2 has such a bad reputation.

I do think the block issue may not be as bad as it's reputation. I believe a lot of D2 engines went bad due to the higher temperature thermostats, the water temp gauges with settings too high for the needle to show the engine is running hot and incorrect oil being put into the engines.

 

The local Rover mechanic in my area has shared the same thought process with me. Best blocks went to the P38's and the remainder were used for the later DII's.

He also believes the issues are overblown, but has no real evidence to support that. Is the P38 thermostat different, and did they come with a lower temp (lower than 190 F) thermostat?

 

@arains44 the short answer is no there is no real central repository of knowledge. But to address your points :

1. All aluminum engines suffer from the same heat related issues as the Rover V8 to some extent, BMW series sedans suffer from micro cracks in the heads, and head gasket issues are not really that unusual in aluminum engines.
2. Liner slipping - although it can a happen it generally requires massive overheat while the engine is turning, not just a small overheat. This of course is made more possible as our engines ran hot from the factory leaving less overhead
3. Block cracks - these are tougher my gut feeling is that it is a casting flaw similar to the BMW head issue, so in some engines the casting resulted in a thin spot that cracks as a result of thermal action over time (heating and cooling cycles). There is no way to know if this is really all that common.
4. Head gasket failures 3 causes aluminum engines they just seem to need head gaskets more often (large generalization here), overheat resulting in head warpage, bad torque due the use of TTY bolts and not enough care taken by secondary repair shops /owners

Beyond that there is really bad about the Rover V8, the biggest issue was boring the engine out to 4.6 and not adding top hated liners.

Your point about NA seeming worse is more about the fact we are the largest user of the 4.6 V8 because we could not get the diesel, the rest of the world is flipped mostly diesels with far fewer V8's

 

@Richard Gallant very logical and apt assessment.

My Porsche 944 Turbo needed a HG and it's an iron block motor. I think the coolant was so old it was acidic and ate away at the gasket material.

From what I have read the initial bore change was from the 3.5L to the 3.9/4.0. The 4.6 shares the same bore, but I assume is more prone to overheats and subsequent issues because it produces more power and torque which = more heat?

So it seems as though there's no knowledge of a % of blocks that left the line with below average machining tolerances. Great conversation.

 

^Correct, the 4.6 has different rods and crank than a 4.0 but the bore is the same

 

I have a 2002 P38 and a 2003 D2.

The P38 has the standard thermostat
The D2 has the low temperature thermostat

I use an iPhone with a Bluetooth receiver to monitor both of their engine temperatures. They are both very similar. High 180's to mid 190's is the norm.

Before I swapped the D2 with a lower temperature thermostat the temperatures were a good 10 degrees more.

 

@keninnc That's a great data point. So D2's seem to run hotter from the factory than P38's, which is likely a huge contributor to the failure rate I would think.

I'm running the low temp thermostat on my 04' D2 with 185-195 temps 95% of the time. Highest it will get it 199 at hot idle, then back to 190-194.

That means most D2's left the lot idling at 205 degrees+. Seems hot for an old school aluminum motor. All of this has been discussed before, but still enjoying this conversation.

I am racer and driver coach by profession. Was working with a team with a modern BMW 240ir (factory racecar built on the street car platform), and found that that motor can withstand sustained 230+ degree temps without causing measurable damage. It's an all aluminum straight six. The team said it takes 260 degree + to hurt the motor. With an electric water pump they have very precise control of the temp. The car routinely runs between 210-225 at normal operating temperature. That's all so crazy to me, but I guess hotter is better for tuning the motor for emissions.

 

@arains44 Race cars can run hotter they generally get way less miles and way more work done to them, even our V8 is "good" to 220 but in my mind that is just pushing stuff way to hard.

According to the Rave as shipped the thermostat is not fully open until 204 degrees.
The temperature gauge range is -40 to 284 and I know it will not move from center between 171 and 212

 

I think 220 is as hot as you really want any thing Sportbike motors also run really hot 215-225.

My D2 went to 217 once after idling for 20 minutes with worn out fan clutch and no aux fan. New fan clutch, new aux fan, and can idle for an hour under 200.

Hard to believe they signed off on that thermostat. I know it was for emissions compliance, but still... They already had the 180 t stat in the diesels!