Thread: American know how.

Originally Posted by ozscott

Nice Job mate. I take the points about easy and cheap replacement of the Stat.

As for the temp it is interesting. Mine with the low temp stat (stock set up otherwise) runs around town at 85 degrees and if idling in this weather for a while 87 degrees. I had it offroad clibming up to 3000 feet recently at GVM all low range stuff and it was always around 85-87 degrees.

I am very keen to see your temps when summer hits, but also with towing etc. If you are sitting on say 85-88 or so even when towing and in summer then I will probably do the mod (in summer mine didnt go higher than 94 from memory in heavy traffic and idling on a very hot Brissy day but if it could stay under 90 all the time that woud be great!!).

Cheers

Thanks Ozscott, Yes, summer will be the big test. However, if I need to run cooler in summer I just need to spend $14 and get a 170 or a 160 thermostat.

My temps before the mod were 90 - 92 around town and if idling in traffic on a hot day sometimes it would go up to as high as 105. And that's what prompted me to do the mod.

Cheers

Originally Posted by gavinwibrow

So, without reading the whole thread, is this mod peculiar to V8s or should it also work on a diesel eg TD5 that gets too hot towing a large/heavy van?

It's for the V8 but I can't see why you couldn't do it to a TD5.

Hi Battler,

Yes 105 is too hot.

Mate this is a post I did from the thermostat thread

"...My 82 degree thermostat copped a work out today. 38 degrees outside and 67 degree intake temp. I gave it a hard time then idled it for a while and allowed temp to top out at 94. Later on heavy traffic at 39 degrees outside the coolant reached 95. AC going flat out at all times.

I reckon these temps are still sound. With the 4.0 running a stock stat it was 104-105 in the same conditions.

Cheers"

The stock stat does have them running too hot. I am happy at the moment with the engine because it has such a small temp fluctuation with the cooler stat and in very hot weather the max temp is acceptable to me at 94/95.

Cheers

So glad I did not happen across this earlier in the discussion. WOW some people have little respect for others experience and knowledge.

FWIW:
There are two OEM bypass thermostats for the D2.
V8 & Diesel.
Different temps, same bypass spring tension.

The Freelander thermostat has both a lower temp and softer spring.

From first hand experience and hours of bench testing, with the Freelander 82 degree soft spring thermostat my 4.6 will sit on 87.7 degrees in city running, maybe get to 92 in summer stopped in traffic and highway running 85 degrees.

I've dealt with many from the states who have done the in line mod, well before our ranter has, with varying degrees of success. Several have gone back using the freelander thermostat and not looked back.

In essence, everyone will end up with a preference. But attitude is everything when trying to convince others of the worthiness and quality of a concept. Proven or not.

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...

Hi Mark - how did you go with the further testing for the thermostat?

Cheers

OK I am sick of the cooling system of the D2. It is overengineered and probably never a good thing. My hoses are rock hard when running and at normal operating temp. Inline stat in and...normal pressure has been restored to the hoses. My mechanic and I will experiment with best positioning etc.

Cheers

+1 for the Freelander OEM thermostat here, TD5 auto.

everyday temp 87 degrees, regardless of traffic, highway cruising or pottering around town. towing i see 92, not a degree more, and thats comming back from sydney on a warm spring day with a dualcab courier on a rental trailer.

obvoiusly right foot plays a fair part in regulating ur temps also, i dont particularly want to break my td5, so I treat it with respect.

G 'day fellas.
What year/engine FL thermostat is that?