Thread: American know how.

Originally Posted by Battler

Wow! Shots fired!

One at me for supporting my comment on the intentional design of the bypass system by providing information from the manufacturer and one at the Texans.

I have the upmost respect for Mark Adams. I was extremely happy with the conversations I had with him and the work he did for me on my ECM for my modified 4.6L. However, in your link there is a clue as to what Mark is a specialist in, and most likely is the best in the world. And, by his own admission by saying he has an open mind, he is not a specialist in engine cooling systems.

From what I have read on other forums (in particular landroverforums.com), many D2 owners in USA have done this modification which reduced and stabilised their operating temperature range without any issues in a variety of climates. This has to be a good thing?

I must state I too am not a specialist in cooling systems (or anything else related to Land Rover) and I also have an open mind.

Deleted this comment after some thought.

Originally Posted by Mark Adams

Sorry but I totally disagree. I've been doing a lot of research and testing on these to find the best solution, and I'm a total convert to the Pressure Relief Thermostat (PRT) system.

What I have learned though extensive reading and testing, is that I had totally misunderstood (for years!) how the system works and the benefits it gives.

I have run engines covered in thermocouples to find out what goes on inside it, and it's quite a different story to what you see at the coolant outlet on the manifold.

The PRT bypass port is closed by the thermostat as it opens. What it does do is to stabilise the block temperature, as the water inlet to the pump is blended. Without it, the block temperature goes up and down by several degrees as the thermostat opens and closes. It is far more stable with a PRT, which reduces thermal stress between the block and liners.

In the case of the old thermostat in the top hose (which has served very well for over fifty years), there is also only one place for the water to go when the thermostat is closed. Of course that is the heater, which has to take the full flow. With the PRT there is the bypass circuit as well, which is fully available when the thermostat is closed.

When the thermostat opens, water is blended (hot with cold from the radiator) before being fed back to the engine. Because the bypass is open the flow is much faster through the engine block and head, so the temperature of the water coming down the bypass much more accurately reflects the block temperature.

Originally this system was developed to stabilise the temperature in smaller engines, with Cast Iron Wet Liners seated in Aluminium alloy cylinder blocks. The reason a stable temperature was required was that the rapid increases and drops in the temperature around the cylinder liners would cause them to un-seat from the block, and lead to leaks around the base of the liner seat and early head gasket failure.

I have measured this in some cases with a four cylinder engine, and found that in typical conditions the thermostat outlet temperature drops by 2-3 degrees after the thermostat opens, but it has taken some time for the cold water from the radiator to go through the water pump and all around the block to reach the thermostat. Where the water enters the block, the temperature will vary by 8-12 degrees (Centigrade of course). With a PRT, the temperature is stable throughout within 1-2 Degrees.

Although I cannot find any proof of this, I believe the principle was developed by Honda (I may be very wrong with that), as they were amongst the first to use this type of system. Since then, nearly every modern production car uses this system; partly for emissions, partly for longevity.

PRTs crossed from Honda to Rover (with the introduction of the K-Series engine), and then on to Land Rover. All Land Rover V8s since the arrival of the Disco 2 have used this system, as do Jaguar, BMW, etc.

We all know that car manufacturers are a tight bunch, and won't put anything there unless it's absolutely required. PRTs cost more, so there must be a reason.

As far as I can see, the only challenge with the PRT is the massive lack of choice of opening temperatures. All European Disco 2 and Range Rover P38 V8 motors came with a 92 'stat, which means they run at 95-96 degrees normally.

Whilst there was an 82 Degree hot climate 'stat available for the D2, it has long since been obsolete. This would have given an operating temperature of 85 Degrees, which is pretty much ideal for a road-going V8. I have recently bought loads of different 'stats (many advertised as 82 Degree) to test, but most of them have turned out to be 87 Degree. Nonetheless, that gives an operating temperature of 90 Degrees, which is still better than 95 Degrees. Tomorrow I am testing yet another 82 Degree version, and I have high hopes for this one. Of course I'll let you know what I find.

Out of interest, 95 Degrees is the point at which the Rover V8 starts to lose power. The difference between 95-102 Degrees is around 15 BHP lost. Heat is also a factor in facilitating the dreaded slipped liner.

I'm in the process of converting all my top-thermostat V8s to PRTs, and the results look very good so far.

However, I always have an open mind...

In the spirit of open-mindedness, I did entertain the notion of keeping my system stock and replacing the LR 180 I had with this BMW housing and one of their 180 deg stats. Mark, you should try one of these to lower the temps further. eBay has Tstats in a variety of temp ratings starting at 160 which was the factory model.

Funnily enough the lowering of operating temps for V8 D2's has been a high priority for D2's pretty much all round the world,,,

just that in OZ ( and we obviously followed England, who'd a thunk?? ) we used factory parts,, who knows why we didnt look at Nth America?? all our parts manuals tell us you're there--


your way of lowering temps is new to us..

Sorry, but I don't think that the current system is some special design - However only the project engineers could truly confirm any of our theories.

Car manufacturers no longer listen to engineers - nor do most executives of major companies in Australia or elsewhere. They are only sales driven and bonus driven. Their only motivation is the great human motivator " what's in it for me", and so sales and marketing trump function and longevity.In this case, the fundamental emphasis was to provide faster heater matrix warm up, which they probaly garnered from a customer survey.

The engineers then had to come up with a compromise solution. This is the cooling system we have in the Discovery and P38.

I can just imagine the engineers complaining, but being sarcastically howled down by the executives. The engineers parting words would have been " this decision will come back to haunt you in poor reliability".

The poor engineer would have been told to go elsewhere if he didn't like the decision from the "design team".

I'm with the Texas camp on this one. It's simple and it works.

Could I ask chubs878 to post some pictures please and some part numbers for hoses, thermostat housing etc so I can follow suit. I'll be changing over ASAP.

Originally Posted by peter51

Sorry, but I don't think that the current system is some special design - However only the project engineers could truly confirm any of our theories.

Car manufacturers no longer listen to engineers - nor do most executives of major companies in Australia or elsewhere. They are only sales driven and bonus driven. Their only motivation is the great human motivator " what's in it for me", and so sales and marketing trump function and longevity.In this case, the fundamental emphasis was to provide faster heater matrix warm up, which they probaly garnered from a customer survey.

The engineers then had to come up with a compromise solution. This is the cooling system we have in the Discovery and P38.

I can just imagine the engineers complaining, but being sarcastically howled down by the executives. The engineers parting words would have been " this decision will come back to haunt you in poor reliability".

The poor engineer would have been told to go elsewhere if he didn't like the decision from the "design team".

I'm with the Texas camp on this one. It's simple and it works.

Could I ask chubs878 to post some pictures please and some part numbers for hoses, thermostat housing etc so I can follow suit. I'll be changing over ASAP.

I intended to do so yesterday but was discouraged as the compatibility of the mobile website and the iPhone doesn't allow me to post more than 1 photo with a post. I will have something for you guys by tomorrow. Furthermore, I have already improved upon the modification as seen in the US instructions but have yet to do it myself, so you guys will be the first to utilize the new and improved.

Originally Posted by Pedro_The_Swift

Funnily enough the lowering of operating temps for V8 D2's has been a high priority for D2's pretty much all round the world,,,

just that in OZ ( and we obviously followed England, who'd a thunk?? ) we used factory parts,, who knows why we didnt look at Nth America?? all our parts manuals tell us you're there--


your way of lowering temps is new to us..

There have been a couple of threads that I found on the inline setup dating back to 2012, but when LR came out with the 180-deg "soft spring" Tstat, everyone ditched the inline-tstat mod in favor of this which required no modification. When engines were still failing enthusiasts discovered with the help of their aftermarket temperature gauges that the thermostats weren't running a whole lot cooler than the factory stat, and the 20-degree spikes were still present. Even their 180 stat runs at 190 and spikes almost to 210 with the AC running so back to the inline-mod they went. And furiously for the past 6-12 months as we now have substantial data dating back several YEARS to our forefather's efforts and conquests of which to confirm the validity and benefits of running the inline stat. I will tell you guys what I told another member just this morning who said he was comfortable with his Disco (also in TX) operating at 210 and spiking to 218F with the AC on, in traffic, because he has over 200K miles and no issues to date. And that is my truck which I bought a year ago, started ticking/tapping a couple weeks later so I asked the PO what was going on. His statement to me was that "all Discos have a tick and that's what they are famous for." I knew the tick was something which was being caused by something. I started searching forums and the first thing I found was the factory temp gauge doesn't work. That made sense as I had the water pump go out on me the 2nd week of ownership and I saw steam before the needle on the gauge cluster ever moved! Next I put my OBD with live data readout to it and immediately saw 218F at idle. That's when I replaced everything including the thermostat (with LR180) and flushed the DexCool in favor of generic green ethylene antifreeze. I was then experiencing operating temps of 194-200F. The "tick/tap" noise was gone and has yet to return. I became obsessed with lower operating temps on this truck right then and there, especially having read numerous stories of slipping cylinder liners and the block cracking behind the liners, inbetween the bores and around the head bolt threads. We also found that other members who had the same tapping sound resolved that issue by lowering the operating temps and so it has become an epidemic. I still don't know what was making the noise at higher temps. Could it have been the cylinder/cylinderS liners moving? Possibly. That's seems to be the general consensus. But the point is that if the temps are low enough, the cylinder liners never get the change to move or loosen inside the overheated and expanded cylinder bore, thereby preventing serious issues and catastrophic failure.

Mate, thanks for taking the time to post up the info.

2 questions with the lower temps

1. Has anyone noticed any loss of engine efficiency (fuel economy/slightly rough running etc) and 2. Why didnt you like Dexcool given that the gaskets in the D2 are not affected by it like early GM V6 motors were and where Dexcool has a very high boiling point (ie just in case a component fails or there is sudden coolant loss etc it gives a margin of safety)?

Cheers

Originally Posted by Chubbs878

I'm sorry about my comment. We are on opposing sides, so I really just don't have any interest in the bypass and external thermostat blending at the radiator outlet. If that worked on these trucks, they wouldn't be a dime-a-dozen parts trucks and recyclables with blown engines; you wouldn't be able to buy them for $3500 US on any given day. The Disco has no resale value because of its reputation for vomiting head gasket and cylinder liners. All of these problems are related to the OAT coolant and operating temps. Think about it. Get away from the bypass loop and save what's left of your Rover V8. Nothing but success stories and happy enthusiasts as result of the thermostat mod. We should be talking about that and not entertaining ideas of a bypass system on the old Disco. LR engineering dropped the ball on this one. 180 degree Thermostat on the outlet manifold would have probably prevented catastrophic failures on all of these aluminum blocks. The liners can't slip of the temp stays under 200F. Obviously a fully and reliably functioning temperature gauge would help the overheating incidents as well. Don't know how they work on overseas models, but over here we deal with a 3-position temp switch that reads stone-cold, 150-230 center of gauge, and HOT but the warning is already too little, too late. It seems to me that LR WANTED to blow every last engine.

Quite a few of us just use a Scanguage or Ultraguage to keep an eye on temps. Ultra has benefit of being able to set an audio and visual alarm at whatever temp.

Cheers