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T Stat Modification

12K views 48 replies 10 participants last post by  Doug Myers 
#1 ·
I'm preparing to drive my 03 Discovery down the Baja to Cabo San Lucas, Mx.
I've been looking at the cooling system modifications to help deal with the Temps I May/will run into in the region.
As you know. My options are the inline thermostat modification or the PEL500110 thermostat.
I like the "Keep it simple stupid " modification of the PEL500110 on this one as I am new to Land Rovers.
This however flies in the face of my "highly customize everything" nature.
Any opinions would be greatly appreciated on this.

Thx

Tony
 
#5 ·
Does the BMW thermostat produce the same type of spikes and fluctuations that the LR Tstat does? Obviously it has to fluctuate some, but can you give an example? The LR180 gives me 194 on the highway but when I get off it will go up 201-203 really quickly. That's a good 10 degree spike in a few seconds
 
#9 ·
Chubbs I don't know... when I have checked it while driving with real time scan function, the temp stays steady 170; Haven't noticed any spikes or abrupt fluctuations but I have not looked for them so it could be occurring between glances.
When I get back to Louisiana, I'll run the scan tool real time to see if this is occurring.

Doug
 
#6 ·
#8 ·
I read about this before changing mine. Sounded like the 180 was the best solution.
 
#15 ·
I have read where more than a few guys claim the Bosch system will go to closed-loop after 140 deg so I think you may be getting ahead of yourself. That subject with open/closed loop and low-temp Tstats has been beaten to death with no hard evidence to support any drawbacks of running engine at temps well under 190. Furthermore, a 160 deg Tstat doesn't actually maintain 160 deg operating temps, more like 170-180 range such as Doug has noted. Why in the hell would these manufacturers put an oil cooler on a D2 if the engine oil was supposedly detrimental to said engine under a certain temp? Dont believe everything you read, much less on the world-wide-web where anyone can post any damn thing with no factual basis. Do everything you can to get your coolant and motor oil temps down, this 60-year old Buick is begging for it. I'm putting an inline 180 Tstat and oil cooler on my truck this weekend. Maybe the headgaskets will last a few more months. I can't believe the number of you guys that continue to stand behind these LR Tstats, 180 or not. The damn things pull 10-15 degree temp swings all day long. So what if I'm running 194 deg, 95 percent of the time when it spikes to 203 in 5 seconds and takes 5 min to cool back down to 194 again? I can do without that, but the family I bought this truck from couldn't have cared any less about improving and upgrading vital components so the HGs were already on its last leg, unfortunately. Won't happen again though! Not on my watch, at least
 
#18 ·
I have read where more than a few guys claim the Bosch system will go to closed-loop after 140 deg so I think you may be getting ahead of yourself.
I have done extensive research on the Land Rover EFI systems. I did this because I wanted to drop the thermostat rating to get the engine to run cooler. Every bit of official documentation I could find indicated that the fuel enrichment stops once the operating temp reaches 80C. That is why I chose a thermostat temp of 180F. Which is the recommended thermostat by Land Rover for a DII.

If the cooling system on your car is adequate for your vehicle, your engine should operate at a temp just above the opening temp of your thermostat. That is, mine operates at around 182F.

If your car is running 10 to 15 degrees above your thermostat temp, I suggest you have a close look at your cooling system.

If your car operates at around 190F with a 160F, your change in thermostat is having no benefit to the operating temp of your vehicle. It is not getting to run any cooler. It is actually a proven fact that trying to get the motor to run cooler by having no thermostat, or a low temp one, actually causes the cooling system to struggle to keep the engine cool and at the right temp. All you are doing is making it take longer to get to this operating temp by opening the thermostat early. So there is no benefit, yet it is increasing the wear on your motor and you are chewing through extra fuel when it is cold.
 
#22 ·
Our winter temps rarely make it down to single digits in winter, and we hit mid to upper 90s fahrenheit in summer. I did use the Royal Purple Ice additive. Staying below 200 so far. I will continue to monitor it. I can't remember who had temps going over 200 or what forum I was on. Hope mine stays lower.
 
#23 ·
The actual thermostats for this motor in the beginning (early 60's) were varying degrees. GM designed the 3.5 L (215) offering thermostats from 160, 180, 195 depending on the region the car was sold within the US & optional equipment installed such as A/C.
Since the thermostat sets a baseline not a ceiling on temperature, the 160 simply opens quicker than thermostats of other higher temperatures but does not keep the running engine @ that temp. As I have stated the temperature operates in the 170 range on the highway,(summer is not here yet in the south) this occurs because the thermostat is completely open which generally makes it useless for temperature control with that falling to the efficiency of the radiator (new) and ambient airflow through the radiator and other flow obstructions located in front of it. Less restricted airflow to the radiator was one consideration for the offering of the Saudi grill as it's known for use in very warm climates such as middle eastern regions.
There is much information on the potential damaging effects of running low temperature thermostat setups, mostly by auto engine tuners, but I submit that this is another belief and not gospel and that is ok. When auto motors are used within the marine industry that is up until EPA got involved in 2012 here the thermostats for various v8's was predominately 140 simply because water temperatures rarely climbed above 85 degrees and that is too cold to operate efficiently not because of cold water engine damage. Now with O2 sensors required & convertors the stats have again risen into the 200 range simply for emission control since EPA invaded the marine industry. I have built and played with boats as far back as 1968 models that have never had the heads off much less bearing replacement do to low operating temp damage many with circulation pumps and no thermostat for the majority of their life.
If there is any significant damage potential to engines from temperature, it reasons that it's in the upper end, not the lower end of the temperature range and is directly adjoined to proper airflow over the cooling area of the radiator & total cooling system integrity more so when sitting still without ambient airflow over the cooling coils. I fully understand expansion to eliminate excessive clearances with bearings and such in combustion engines and their designs and agree that there is always wear on rotating mass where bearings are involved @ start-up when cold rather than warm without any load, but I do believe the potential for catastrophic damage is minimal over the life of the engine due to cooler operating temperatures as opposed to higher temperatures and in particular with aluminum engines, antiquated cooling systems and in particular the by-pass cooling set-up. IMO

Doug
 
#24 ·
If you think that running cold does not cause extra wear, I suggest you talk to a taxi driver and see how many miles they get from a motor and compare that to your grandmother who only does short trips to Church on Sundays.

Expansion is one of the wear items. Even though the Rover V8 has a aluminium block, the sleeves of the bore are steel. Therefore correct expansion is important to keep those sleeves in place.

The next item to consider is lubrication of the bores. Each time the piston goes up and down a small amount of oil is left on the bores for lubrication. When you run a rich mixture, like when the motor is cold, the extra fuel washes off the oil and increases wear.

Another point is the radiator itself. It cools a lot better when there is a reduced coolant flow through it. With the thermostat just open, there is actually a large pool of cool water sitting in your radiator waiting to be used when you need it. Running a cold thermostat means that there is a lot more flow through the radiator and temp of all the coolant is about the same. So when you have to load up the motor up a hill, etc, there is no reserves to keep it cool. Therefore the motor will get hotter. It also then takes a lot longer for everything to cool down again.

So use a thermostat to get the motor to run at the temp that best suits it, that is 180. There is absolutely no point in getting it to run any cooler
 
#26 ·
It's minimal wear when compared to excessive heat. No thermostat is controlling flow when open regardless of opening degree. The radiator, ambient air flow, system integrity & engine operational parameters are now in control of the temperature which will always be above the thermostat opening degree; this is subject to change with extended heat cycles being one reason why they fail in the closed position, deterioration of spring tension due to heat.
I'm not disagreeing with the wear statements you are making, including the minor quantity of additional cold start fuel which is normally not enough to wash out and dilute oil from the walls of the barrel; cylinder washout occurred more frequently with carbureted cars due to bad needle valves and improper adjustment coupled to a larger than necessary carb for a particular engine size & those early injected cars using a thermo-time switch to control warm-up fuel flow like Datsun Z cars. Generally speaking there is no washout occurring in a properly maintained fuel injected motor @ or after start-up.
Additionally since the coolant temp sensor is supplied voltage by the ECM as a cold reference, as the sensor warms the resistance changes returning a voltage signal to the ECM that is a single part of pulse width adjustment of the injector. If you match the coolant temp sensor maximum degree to the operation of the thermostat you should be able to eliminate any potential excess fuel based on injector pulse width difference at a given temperature. Make sense?
Wear occurs any time the engine is operational and these motors fail frequently from excessive heat; no thermostat degree opening will make a difference if the thermostat fails in the closed position, I submit without a very sophisticated measuring capability, you can not determine the amount of wear connected to a cooler operating motor over the life of that motor, where you can definitely tell the damage from an engine operating @ temperatures that are detrimental to the design of the engine. I know you understand aluminum is not as forgiving as cast iron with heat.
When GM designed this engine it was considered ahead of its time. Why? Who knows. Aluminum was used prior to their design, perhaps it was not on the scale that GM did or it was power to weight ratio whatever it was the engine could be ordered in 3 makes of midsize cars, 3 different power outputs with 3 different thermostats for different regions of the country. In effect, the design which had not been substantially changed in the 1st 10 years of production after it was licensed to the British manufacturers in the mid 60's was capable of operation without issue with a 160 degree thermostat which did not maintain the engine temp at 160, it simply allowed less restricted flow through the cooling system quicker than the 180 or the 195's allowing for an engine to operate efficiently at a temperature a few degrees less, which overtime might actually increase the longevity of these engines with this antiquated cooling system and poor ambient air flow characteristics. Proof of your expansion statement can be measured by the failure of the 4.6 which had substantially less wall thickness than the 3.9 allowing excessive cylinder liner movement.
So I'm not arguing with your statements rather I'm saying the cost vs return of a lower temperature is better than the alternative when dealing with aluminum.

Doug
 
#25 ·
My radiator contractor owns several DIIs.

He modifies the stock thermostats by enlarging the holes in the plate visible through the bottom of the thermostat.

He claims it improves warm-up and cold engine coolant flow.
 
#29 ·
The DII radiator is pitifully undersized.

With a low temp stat, you may find the ECM cycling between open and closed loop, especially on cold days and coming off idle, like at a stoplight. You may suffer a minor drop in MPG if you do much city driving but you should pick up quite a bit in MPHG.
 
#30 ·
I'm searching the Bosch catalog for a coolant temperature sensor with lower opening and closing thresholds to match the thermostat opening temp of 160. So far the nice thing is there are so many for so many different cars and countries that finding one that works with the factory connector is easy.
Leading the way are Bosch sensors for early BMW's I do believe this will work just fine with the lower temp thermostat solving any potential situation with closed/open loop settings.

Doug
 
#31 ·
...?
What are you searching for? Sensor? The correct sensor is the correct sensor
What do you figure a different sensor will do?
Fix The shitty gauge?
I expect a long, drawn out explanation to follow suit with this thread :wink:laugh
 
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#33 ·
I'm no expert on that particular system, but my guess is that its a voltage based sensor. That's what the majority of modern ECM systems work on. It may even be CAN driven. If this system is anything like the one's I'm familiar with, you would have to dig into the firmware to get it to change operating parameters.

The old resistance sensors drove analog gauges. The bi-metal switch sensors were for idiot lights.

I wouldn't sweat it going into open loop occasionally. I drove a Chevy Tahoe over 100K stuck permanently in open loom that had an open campaign on it I didn't know about. It was a $16 harness adapter with a different ground. Found out about it by accident. The "fix" had no noticeable effect.
 
#34 ·
These are all thermister type sensors and yes the resistance changes with temperature.
Unfortunately changing the sensor with one from a different eh ice application will only give an inaccurate reading.
The value is interpreted by the e.c.m. as a value benchmark for closed loop.
I have read about your bmw 160 stat setup and question that it may be a little low but should not disallow closed loop.
Are you running in closed loop?
I don't think there is much you can do shy of having the program rewritten and I don't see that being worthwhile and although I agree that heat kills I also agree with rangie that too cool is also "not cool". Cylinder wash, carbon buildup, plug fouling etc.
 
#35 ·
It is not just a simple matter of open or closed loop. The vehicle will basically be running in closed loop all the time. The ECU monitors a number of things to determine what fuel mixture, timing advance, etc to run on the motor. Coolant temp is one of those. So if you want to try and trick the ECU into thinking that it is running at a different temp to what it really is, you run the risk of stuffing up the tuning of the car.

It is really not worth discussing any further. It is clear that overall running temp is not being reduced by the colder thermostat, so it is having no overall benefit. It just means that the motor will sit at 160 until the coolant in the radiator heats up enough and then the temp will rise further. Not one benefit has been listed for keeping the motor at 160 for as long as possible, yet there are these discussions now about tricking the ECU to think it has a warmer thermostat in it. The next discussion will be about how you get the radiator fans to cut in at a lower temp, and then so on.

Can we just move on
 
#38 ·
My engine was a complete rebuild with flanged liners. New good quality water pump. Less than 2 months and less than 2000 kilometres.
Completely stock with the exception of a 180 stat ( original style) and bypassed throttle plate heater.
Runs max 189. Usually 185 driving and 182 at speed.
So if anyone is assuming that it cannot be done it can
chubbs, I would say If you are running the recommended 180 stat and still running at 194 to 204 you have another problem.
 
#40 ·
I have a reason for testing various ideas and it's a good platform on which to experiment, as a result I have learned in the process what I was attempting to prove. Ultimately in the "unsophisticated" management system of the older models, changing some control parameters without complication is possible by matching sensors & switches even if designed for other applications, the joys of Bosch electronics. While some recommendations should be adhered to, some recommendations are no more than serving suggestions, such is the cooling system operating temperature & F.I. operation. The temperature can be changed to work in harmony with the ECM. That is what I wanted to know.

The next test group with this control system entails learning which crank angle & cam angle sensor (inputs/outputs) for later model GM multi-port systems are compatible with this ECM, injector impedance and compatibility of other required sensors. Before I swap in the small block, I intend to have the control system sorted. That is the underlying reason for all of this. In the mean time, I'll pass on what I learn in case there are other hot rod mechanics interested. I'm going for a boat ride, it's a beautiful day to sail.

Doug
 
#41 ·
I don't have another problem. I use the 180 factory Tstat and there are hundreds of other Disco2 owners with the same factory setup, all new parts, operating temps in the 190s and spikes to 205. We have a dozen threads on this subject at LRFs. We have beaten this subject to death over there. We have a thread where we all posted our temps in relation to every driving scenario, various ambient temperatures, all variables possible under the one constant that the system is factory, every part is OEM new replacement and the 180 Tstat installed. The factory stat and the bypass loop causes spikes and that's that. The only way around it is the inline mod, eliminate the bypass loop and external housing. Once again, we have dozens of threads over there on Tstat mod with plenty of research and hard numbers to back-up the theory on how beneficial the swap is and the overall benefits to engine and extending the life of the Rover V8/disco2. There is just way too much data for both sides of the fence to even debate it. A LOT of people are making the switch.
 
#42 ·
I found the crank and cam sensor (GM) to use on the 5.7 that are compatible with the Bosch ECM. The connectors are different but not a problem changing those out. The other necessary components currently in the Bosch system are compatible with the GM early multi-port intake manifold (summit Racing) Bosch 14.4 ohm, 24lb/hr. @ 43.5 psi injectors, GM throttle plate assembly, TPS and the L/R MAF all work with the Bosch ECM; the firing orders are identical, ignition is electronic on both motors requiring connector changes. Typical resolutions to throttle cable and c/c cable location should not be a issue as the stock cables are the same style and simply point straight ahead almost in an even arc swing to the right of where they attach now; will need A/C lines made up and some work on the P/S lines as well, the really nice result is a normal cooling system & Chevrolet reliability. I took advantage of a sale @ the rover salvage in Tampa by getting another stock exhaust rear section & pipe for $30 + shipping. Then found a fiber heat shield from a Jaguar which completely isolates the exhaust pipe from the fuel inlet hose allowing dual exhaust on the fuel inlet side without heat danger while looking completely stock and increasing exhaust flow through true dual exhaust. I do believe that completes 99% of the problems associated with the swap and the software.

Interestingly while researching parts and ideas I came across new information based on the popularity of the LS aluminum swaps into everything hotrod, there are now available aluminum motor mount adapter plates for the LS which return the motor mount location back to the original small block frame mount location using stock GM motor mounts. Know what this means? The LS swap into the DII meant removing the stock L/R frame engine mounts and welding them forward to mount the LS V8, not any more, now the LS is bolt in and no suspension work is necessary based on reduced weight of the LS motor. HOT DAMN! There are certainly other considerations and upgrades necessary to swap the LS into the DII mainly the transmission & driveline capability to handle the torque output, but this trans handled the V12 750il and other euro hot rods in excess of 350lb ft. of torque, being freshened up with some HP24 internals it will not be a problem in the LS application driven sanely I think.

At any rate this is what I found out, all that is left is the swap so as soon as the MGB and the boat are completed the DII gets it's new heart. Take Care.

Doug
 
#43 · (Edited)
In response (again) to your statement that I have other issues with the cooling system and LR180 Tstat because it operates between 194-204 (like everyone else,) after modifying to the inline Tstat im now operating between 183-187 with a Stant Superflow 180 model. I didn't replace anything except the Tstat...

Edit: it seems to stick on 189 quite a bit with AC but that's only 6 degrees from the 183-185 operating temp. I can't complain. It should be alright for a while.
 
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#45 ·
No, I wasn't addressing you Doug
Red truck the expert said that I have other issues with my cooling system because of the spikes. I have a stack of receipts and a dozen threads on LRFs that says otherwise. I know his temps spike too. All Discos do. If his actually does not, which is possible because of the rebuild or otherwise, it is the first D2 with a completely stable operating temp. Obviously it wasn't always as such or it wouldn't have cooked itself in the first place. What a crock of ****.
 
#47 ·
I did many other mods to get to that 172 temp, the BMW stat was a single part of the equation. I replaced the hoses with BMW parts, forcing the "Y" pipe into the smaller diameter hose. The better way to go is the inline stat talked about by chubbs and others. All of the mods I did on my truck were to prep the motor for fitment into the 72 MGB which has a smaller cross section for radiator flow. The BMW stat simply has a lower opening threshold, once open, it does not effect any temperature drop, it might hurt depending upon the cooling system overall condition. I installed a HI flow GM circulation pump, under drive pulley, new radiator, head gaskets, head studs and other things that affect cooling, new timing chain, gears, & camshaft, oil pump, engine seals and gaskets, all of this contributed to the lower operating temperature. This motor is coming out, the by pass system is being trashed in both the truck & the car for single in/out flow systems.

I'm not privy to your mechanical skill set, I've been building stuff for 45 years, if you're just starting out or relatively new to these vehicles, it's better to copy what several other members do & say here than what I post which is sometimes just to see if I can do it & it works as researched. There are successes and failures. I will answer your questions if I can, but this site is ripe with guys that know what works, how to do it correctly and where to get the parts. Read all of the posts concerning the cooling system, the system is archaic and problematic, install a temp gauge that reads in increments as opposed to the factory, cold, ok, you're too late. Good Luck with your truck
Doug
 
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