Thanks - Yes, I’m just still confused what’s going on here. From what I’ve been told, there’s no chance this is one of those engines and the issue was the front cover (or me). I’ll have a better idea when the new one arrives - hopefully soon. If it slides on easily as I expected it to, the problem was the SKP cover. If it doesn’t… we’ll see, but I’m fairly certain I was doing this properly and had everything cleaned enough. SKP and Rockauto screwed me there, so I’m out $300 from that… Definitely don’t recommend either.

From what I understand after speaking with AB, the Hobourn covers aren’t supplied anymore and what’s arriving will be something from Britpart or AllMakes or something like that. I believe Hobourn was the original manufacturer, which their product image shows, but I guess those days are over. Hopefully the replacement works out - this hasn’t been a very fun part of all of this, right when I was on a roll.

I’ll update again ASAP.

 

Also, thanks for all the input on using the inline thermostat with the upgraded water pump. I’m going to take the advice to start with the new regular water pump and see how things go, but I’m in a warm climate and it could help upgrading later on. I feel it won’t be a big job to replace just the water pump if needed.

A cooling system pressure sensor is a great idea. I guess you’d just monitor or set an alarm if it starts going above 20 psi? Or just notice that it’s starting to climb?

I’m still wondering if I can reliably use a coolant temp sensor in the port on the inline thermostat - I read that people see a lower temp than the system sensor - maybe 8 degrees F lower if measured at the thermostat. I also don’t know if the sensor will interfere with the fan/shroud or if I’ll need to cut into the upper radiator hose instead. I’ll have to look into that later though. For now, I have the thermostat port sealed up with black RTV on the threads of the plug in it.

 

If AB doesn’t sell the OE cover anymore as long as they stand behind the fitment I would go with them. The only other option for OE would be getting a good used cover from Goldwing or Will Tillery or any other reputable breaker.
Pay no attention to the 03 vin range issue. None of those defective blocks exist anymore. Long since replaced under warranty.

 

Because I ordered the inline mod in the orientation that is not really feasible with a temp sensor, I purchased the glowshift temp sensor adaptor fitting tube and spliced the top hose post inline tstat housing. Fits right in the middle of the shroud. I will send a pic.

So the pressure gauge is an interesting thing. Some background, if you check out the inline mod post, you’ll read that extinct and some other folks run their expansion tank X turns loose. Presumably to reduce the relief pressure of cap. I dont know what expansion tank they run with, but I have the Carrs4x4 aluminum expansion tank with the upgraded version 2 sight glass. The cap that came with it years ago is rated to 16 psi and have reported to need replacement after some use. I ditched the Carrs Cap and replaced it with a denso radiator cap with a pressure rating of 14psi?

So the coolant system operating pressures are interesting. With a sealed up no leaks system at temp, 180ish, the system operates at 9psi to 10psi. Get on the highway and get up to highway speeds and temps, 65-75mph, with A\C stress, the pressure increases as the coolant temp rises. The interesting thing is that with that replacement denso 7720 radiator cap I have observed pressures more than 14psi. Which concerned me at first but I didn't observe any coolant loss or sudden drops of pressure as a result of venting. So I am still pondering this one.

For me, the pressure sensor has been worth it for me because it has made me realize what my operating pressures are supposed to be, and any fluctuation from that means something is going on. For example, when I completed the exact job you are doing, pump, oil gear, inline mod, etc etc, I didn’t know I was experiencing a heater core hose leak, my pressures were only building to 4-10 psi, and I had visible coolant loss that leaks so bad it destroyed the post cat passenger brand new O2 sensor. Replaced some hoses and clamps, big coolant leak fixed, and my pressures bumped up to 7-10 psi. I was so happy to see quantitative improvement post leak repair that I posted about the pressures on my coolant pressure gauge post as the operating pressures. Cut to a few weeks later to an unknown source of small coolant loss identified itself as a steady drip and stream pressurizing out of the Carrs aluminum coolant sight glass. Until the leak was identified as coming from the sight glass, I watched the pressure drop over the course of a week or so from 7-10 to 4-6 psi. Turns out, the entire sight glass was broken, and the nice people at Carrs provided me the upgraded version of the sight glass as a replacement. The upgraded sight glass is thicker and laser cut, which the previously thinner version was machine cut and as a result created micro fractures that eventually grow into fractures with heat cycles and time. Bolted on the new sight glass and the operating pressure was finally indicative of a pressure tight system and operating from a range of 9-14 psi immediately.

On a trip recently, the D2 drove many hours through harsh ambient temperature. The only cooling issue that came to pass was that after many hours of use the sight glass bolts loosened a bit and caused a pressure drop in the system to about 3-7psi. It wasn’t an issue on flat driving and temps were fine. However, as I was climbing in 2nd and 3rd to a campsite outside of Zion, the resulting pressure drop I believe reduced the overall efficiency of the cooling system and didn’t operate at full capacity. Took it slow, didn’t breach 220, got to the campsite, let it cool over night, tightened the sight glass bolts, and never had an issue again.

So to comment on the temp reading difference. The 04’ temp sensor is threaded into the lower intake manifold pointing straight down. This is the reading of the coolant as it exits the engine via the coolant eIbow. This is the one the Ultragauge measures. Originally I thought there would be a noticeable difference between the UG measurement, and the inline Temp sensor, however that is not the case. When the inline tstat is open the UG temp and the post tstat inline temp sensor are equal in temp. The only observable difference is when the tstat is closed. I thought about removing one but having both has served as helpful information. The ultragauge is pre tstat temp, and the inline temp is post tstat temp.

 

Thanks man, I’ve really enjoyed reading all the responses here. I can see it being useful to have both the UG and another temp sensor to compare the data. I’ll probably install it the way you did rather than trying to remove the silicone I put on the sensor plug and dealing with that. Did you need to simply cut the upper radiator hose or remove an inch of it to fit the sensor coupling? I’d put about 16 psi into the system and found the old thermostat was leaking - great design that thing has since I’d already replaced it once. Sounds like your trip went well. That’s the dream, getting to the point your Rover is actually somewhat reliable, but still not to be driven anywhere without plenty of tools haha I think by the end of this, I’ll have a pretty good understanding of this vehicle.

I’m expecting the cover to arrive soon, so I’ll see what news that brings - bit excited, but also a bit apprehensive on case it also won’t fit properly…

 

By the way, I decided to get AB’s water pump bolt set, which includes washers. I can’t remember if the original had washers. Sort of wondering if people use washers on the oil pump bolts as well. I think I’ll use Loctite 243 on these bolts.