Reply With QuoteMate Murray has a growing table of 3 way stock thermostats and a bench top with brass connectors to take the place of the 3 way. He is changing a lot over now. Cheers
Fossicker
SupporterOur modified in line thermostat, which has a small but absolutely crucial bleed hole drilled in it, changes the system from a true dead head (where the discharge side of the pump is completely dead due to being blocked by a thermostat closed due to low temperature) to a not completely dead head system as there is a permissible flow of water. As discussed, this stops the hot/cold water column problems which can occur when the thermostat finally opens as the water column from the block reaches opening temperature (82c 87c 93c or whatever) and results in the circuit fully opening, relatively quickly. This allows cold ambient temperature water from the bottom of the radiator returning in through the bottom of the engine to be pushed up through the engine, resulting in a potential chill to an otherwise hot block. There is as always, a price to be paid, and that is that the engine takes longer to reach operating temperature due to the permitted bleed. In Brisbane (27S), during day driving, in summer, daylight temperatures are usually above 15c and are usually up above 30c. In these conditions, the small delay in reaching operating temperature is not critical. I accept that in colder climates one may need to run a hotter temperature thermostat to keep the engine up at operating temperature. From my reading of many posts now about this, I discern that a lot of the rationale for that bypass system was actually for occupants' comfort in relatively cold weather, by enabling the heater to "work quickly". It also makes the engine more efficient. Because it was colder, the engine could reach and stay at operating temperature quickly, heat the cabin and use the radiator when needed. Thus the bypass is feeding the heater matrix in preference to the radiator. Given that the heating system is a small radiator, it makes sense that again, in very cold weather, the heater would be cooling the engine water temperature, as well as the ambient temperature being very low. So for instance in a 2c environment, a heater operating at 18c or 20c, would be cooling the engine significantly. In hotter parts, this is simply not indicated and poses a real and sadly too often seen as a catastrophic failure.
Scott, I agree with respect. I would be very interested to research the catastrophic failure rates in subtropical and tropical climates. I am in touch with Foleys out in Zambia so will ask them.
ForumSage
SubscriberMate Murray has a growing table of 3 way stock thermostats and a bench top with brass connectors to take the place of the 3 way. He is changing a lot over now. Cheers
Fossicker
SupporterAn explanation from the manual: with my comments/conjecture
General
The cooling system used on the V8 engine is a pressure relief by-pass type system which allows coolant to circulate around the cylinder block and the heater circuit when the thermostat is closed. With coolant not passing through the radiator, this promotes faster heater warm-up which in turn improves passenger comfort. [This is not needed in hot climes] A coolant pump is located in a housing at the front of the engine and is driven by a drive belt. The pump is connected into the coolant passages cast in the cylinder block and pumps coolant from the radiator through the cylinder block. [when the thermostat is open ] A viscous fan is attached by means of a nut to the coolant pump pulley drive spindle. The fan draws air through the radiator to assist in cooling when the vehicle is stationary. The fan rotational speed is controlled relative to the running temperature of the engine by a thermostatic valve regulated by a bi-metallic coil. The cooling system uses a 50/50 mix of anti-freeze and water.
Thermostat housing
A plastic thermostat housing is located behind the radiator. The housing has three connections which locate the radiator bottom hose, top hose [return from the engine, pushed out by the water pump] and coolant pump feed hose [Used by the pump to suck water up to the pump]. The housing contains a wax element and a spring loaded by-pass flow valve. The offset side top pipe goes to the pump through which water is pulled. The top straight up one is one inlet to the stat and is hot water exiting from from the engine, coming to the stat as an alternative to going to the radiator thanks to the T junction and a closed stat. This upper chamber forms the non radiator circuit when stat is closed. The four sensing holes in a brass "bypass valve" see below allow hot engine water to be drawn into this upper chamber at idle. At higher revs the upper light spring opens and allows a greater flow round this bypass system. NB at this stage the radiator is not used until the main temperature based thermostat valve opens, allowing cool radiator water to be sucked into the lower entry pipe.
Thermostat - Main valve
The thermostat is used to maintain the coolant at the optimum temperature for efficient combustion and to aid engine
warm-upin the UK conditions as interpreted by BMW...the 3500s did 500,000 miles if serviced with a simple in line stat. Sure, heater might take longer to fire up but the engines would not blow! Now that I reflect upon it, I see lots of old Rovers and Land Rovers but no old BMWs...!. The thermostat is closed at temperatures below approximately 82 C (179 F). When the coolant temperature reaches approximately 82 C the thermostat starts to open [mine did not start to open until 93C. The radiator circuit relies on the pump sucking water through the side top tube through a now open stat at a greater flow than it just circulating through the bypass circuit. Now if, and this is conjecture, the radiator water coming into the bottom or lower lower chamber of the stat housing is too cold it May be causing the thermostat to not fully open. As soon as revs drop off ie idling in traffic, the "light spring" top by-pass flow valve closes, see below, there is less hot water entering the upper chamber, and cold radiator water entering the lower, and I submit this closes the stat, and most water then just circuits in the heater matrix circuit. and is fully open at approximately 96 C (204 F). In this condition the full flow of coolant is directed through the radiator. [I am not understanding how it is "directed" around the radiator circuit if the is an equal diameter though arguably restricted bypass circuit. The thermostat is exposed to 90% hot coolant from the engine on one side and 10% cold coolant returning from the radiator bottom hose on the other side. Hot coolant from the engine passes from the by-pass pipe through four sensing holes* in the flow valve into a tube surrounding 90% of the thermostat sensitive area. Cold coolant returning from the engine[no-if it's from the engine its hot. Only from the radiator is it cold. , cooled by the radiator, conducts through 10% of the sensitive area. In cold ambient temperatures, the engine temperature is raised by approximately 10 C (50 F) to compensate for the heat loss of 10% exposure to the cold coolant returning from the bottom hose. [I do not understand this? How?
*The sensing holes in mine may have been partially blocked by the stop leak put into the system?? And scale. This would especially at idle allow the by-pass flow valve to block hot water from the engine trying to enter the 93c thermostat in the upper chamber. This would keep the stat fully or partially closed and overheat the engine by sending it all through the heater matrix especially at idle
By-pass flow valve
The by-pass flow valve is held closed by a light spring.[Freelander is lighter still. It operates to further aid heater warm-up. When the main valve is closed and the engine speed is at idle, the coolant pump does not produce sufficient flow and pressure to open the valve. In this condition the valve prevents coolant circulating through the by-pass circuit and forces the coolant through the heater matrix only. This provides a higher flow of coolant through the heater matrix to improve passenger comfort in cold conditions. [I cannot remember when I last used the heater in Brisbane! My engine was always hot hot hot. The previous owner had a catastrophic failure. I nearly did when a heater hose cracked and I heard the hissing ...just dumb luck and GOD. When the engine speed increases above idle the coolant pump produces a greater flow and pressure than the heater circuit can take. The pressure acts on the flow valve and overcomes the valve spring pressure, opening the valve and limiting the pressure in the heater circuit. The valve modulates to provide maximum coolant flow through the heater matrix and yet allowing excess coolant to flow into the by-pass circuit to provide the engine's cooling needs at higher engine rev/minute.[Herein is the problem I suspect. This system ie the upper bypass circuit in my vehicle has clearly been working in preference to the radiator circuit (in to the stat housing from cold bottom of radiator up through the lower single pipe through an open stat and out the side upper pipe to the pump then back out of the engine HOT and to the top hose, ignoring the by-pass circuit by turning 90 degrees at the top T junction and into the top of the radiator to work down, get cooled and leave by the bottom radiator hose. No. The upper chamber on a new stat was stained from coolant but not the lower. For some reason the system was favouring the upper by-pass circuit My vehicle's overheating got much worse after a new radiator was installed. I pose the question: Could the new rad actually be cooling the water to such an extent that the cold water in the base of the stat caused it to not or only partially open?
http://http://workshop-manuals.com/landrover/discovery-ii/cooling_system_v8/description_and_operation/description/page_503/
Fossicker
SupporterI know Scott! Thanks for your great help! He is also working on a really cheap efficient temp gauge that's easy to read and works from the sender or another sender.Originally Posted by ozscott
I have engine watchdog which is 3 to 4, degrees cooler but has a screamer for the wife to hear.
I also have OBDC wireless and OBDC fusion which is great.
Here is a screen shot of the return from Boonah ambient circa 16 C
Unheard of temp is on right
Master
Boy are there some theories in this thread, some backed up with data.
I was told by a DII owner mechanic and workshop owner to go easy with the OAT concentrate coolant, "It will find it's way out anywhere". To that point a set of hoses bought from a reliable supplier on this site bled coolant through the cordage within the hoses after a very short time. My 'new' current TD5 has the same problem, there is evidence of coolant leaks at most hoses and upon closer inspection it has bled through the cord within the hose.
I have always believed in the 'Oils ain't oils' brand of coolant, the Army used it and I figure if it's good enough for them to use, it's good enough for me, but with my Landys I have stuck with OAT. No more, when I change my hoses over I will change my coolant, with all the necessary precautions of not mixing the two.
On the temperature side, I have run the vehicle with my Nanocom hooked up and the temperature has fluctuated depending on what is going on outside, down hill drop back to 85ish pulling up a hill way past 110 and that is at a constant speed.
An argument put in this thread is that the original thermostat set up will keep a more even temperature in the system. From my observation this is not so.
I am going to set up my 2003 TD5 Disco with the simplest of systems and a thermostat in the top hose seems the way to go.
I also want to try find silicone hoses that will do the job with the least number of joints. Another thing about clamps, I always try put them on so I can get them off on the roadside if I have to, the mechanic who put them on this car did it before the radiator went in so all the clamps were in impossible spots to get to without a great deal of trouble (that seems to be my middle name, but it still hurts).
I think the thermostat needs to be after the heater take off and I wonder why there can not be a bleed off (where the air bleed is) that constantly bleeds into the radiator bleed off, I thought that was what that is there for, what other purpose can it have?
If it is possible to not have a high point where air can get trapped could I do away with the air bleed screw?
Just have to make sure that the fuel cooler gets fed somehow.
Argh, already my head hurts.
Cheers
Mike
Fossicker
How about this bad boy, that allows you to choose the operating temperature you require?
It's just a prototype for now, but will be undergoing fully instrumented testing on the engine...
https://www.facebook.com/tornadosyst...type=3&theater
Master
Nice.
ForumSage
SubscriberIf it still blends at least 10% hot water from the block it is still a compromise. I don't see from the photo text how it works. Great looking though. Mark can you elaborate? Thanks for continuing great product development for D2.
Just an interesting thing to remember. If you think your fan hub is suspect it may not be activating, but may be fine. It relies on radiant heat from the radiator to activate - and will lag if the radiator is not heating up properly due to being blocked. I noticed when I put my new radiator in (old heavily blocked) that suddenly I am hearing my clutch fan a lot more.
Cheers
Fossicker
SupporterIt's just the same as OEM but allows a hotter or cooler stat to be swapped out
Fossicker
Absolutely right! We have just found it impossible to get an 82 Degree thermostat still in production that works correctly. A suitable stock one would definitely be the cheaper way to go. Sadly the "Hot Climates" 82 Degree version offered by Land Rover has long since been obsolete.
There is one very well known brand available, but it has a fatal flaw in the design that leads to operating temperatures way above the 82 degrees that the thermostat opens at. Obviously I can't say who makes it here, but the design flaw is that the bypass is fully closed with significant spring pressure even when the thermostat is closed.
As we have tested quite a few different thermostats, this is the one that gave the most scary behavior. When it was installed for the first time, the engine got up to 118 Degrees C before the thermostat finally opened! I was just about to terminate the test, but it did eventually open. This is despite the thermostat inside starting to open at a genuine 82 Degrees, as we chopped it up to get the thermostat out for testing.
We tested another identical one from the same manufacturer to make sure it was not a one-off, as it is always dangerous to base your conclusions on a sample of one!
In operation, it ran at 95-97 degrees, and when idling in traffic on a hot day (only 35 Degrees, but hot by UK standards!) with the AC on the temperature went up to 115 Degrees easily. All in all, a great way to kill your motor.
Note that absolutely all the stock Rover V8 cooling systems allow some bypass of the main radiator via the heater circuit. The amount of resistance to the thermostat bypass relative to the heater circuit is a critical factor in determining how well the thermostat reacts to the rise in temperature, and the rate at which it opens.
It is quite possible that with this type of PRT thermostat that the heater circuit could be eliminated on competition vehicles, or any other vehicles that will never need the heater. More testing is required first though.
Before this thermostat reaches the point of sale, it will be run through some very demanding scenarios on an engine dyno. This allows it to be fully instrumented for temperature and pressure. I used to have a lot of data for these tests, but sadlyit got lost in a house move a long time ago. Anything we do is based on science with documented results, and this will be no exception.
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