Land Rover and Range Rover Forum banner

Disco 2 Cooling System/Hot Temp

12K views 40 replies 9 participants last post by  CT090 
#1 ·
Started getting warm couple weeks ago and see bubbles in overflow (like boiling but it's probably air?). Never overheated. If drive around town temp gets 220 then goes down when accelerate (more air to cool). Top hoses are very hot and pressurized. Bottom hose out of the radiator isn't warm at all. Hoses above thermostat are hot. Radiator is about 75 degrees with thermo scanner but shouldn't it be much hotter if coolant is 200+?. I'll test it again. I removed hoses and attached garden hose to top and water comes out of the radiator bottom ok, an coolant came out of the radiator when I took the bottom hose off. 180 degree thermo installed a year ago and new hoses and water pump. Both fans come on ok. I took out the thermostat and dropped in 200 degree water but it didn't open (still in housing since not supposed to remove), but maybe it needed more water? Local mechanic said it failed block test after 10 minutes but didn't try anything else. My thought is that it could be 2 different issues. Any thoughts on the pressure and being hot at the top but cool at the bottom? Could the radiator still be bad and allow water to go through? Anything I can do to check the thermostat to see if it's working properly? Can I bypass the thermostat (how?). Lot's of questions! Thanks for the help.
 
#3 ·
...one more item to add. It is leaking coolant and has been for a while. External head gasket leak but mechanic said it is still external so not getting in oil. But it is leaking more now and have to add 1/2 gallon of coolant every week vs. one gallon every few months before. Hoses seem ok, but can't tell where the leak is from. Could be from the pressure and getting out somewhere?
 
#12 ·
the HG leak on my truck was at the very back of the passenger side cylinder head. The only way that I could see it was shining a flashlight from the passenger side looking down at the bellhousing where I could then see the telltale sign of a leaky trail that only hit the ground on several occasions throughout course of 1-year. So if it's a slow HG leak at the back you may never see it until it lets go but my guess is that you could get eyes on it if you tried.
 
#5 ·
Cold hose= no stat opening. Use only OEM or MotoRad.

Your radiator could also be plugged. The D2 fan clutch will wear and only partially engage. It's progressive and you don't notice the change in sound.

The truck uses a 18PSI cap. Without cap pressure, you'll reach overheat temp much more quickly. If you keep dicking around and ignoring the HG leak, you're going to find yourself in need of a complete engine.

The discovery never leaks into the crankcase when the head gasket leaks. The passages are too far away. This is a sure fire sign your mechanic doesn't know much about the Rover.
 
#6 ·
Thanks...I'll try a new thermostat first. If this is it then surprised it only lasted a year. Any other way to check to see if the radiator is plugged? The water I put into the top of the radiator came out of the bottom pretty quickly and I didn't have it on very high.
 
#8 ·
Rule out the coolant tank cap too which means put a new one and tighten it well cos there's no other way, if it fails to seal well can cause the described symptom
 
  • Like
Reactions: wrobinson
#9 ·
It depends on the thermostat you bought. If it was some no-name white box stat from a chain store, I'm surprised it lasted a year. My suggestion would be a MotoRad 439-180.

Keep in mind, there's a trend in the parts industry to put the OEM part number or some other reputable manufacturer's number on off-brand parts. Even though the number matches, it may be a POS.
 
#10 ·
Ok, thanks. Good to know. The newer thermostat has grey housing, not sure what brand. The mechanic put it in. Ordered the MotoRad and a new cap so we'll see what happens. I'll then flush the coolant system while I'm at it. After that I guess my next stop is a radiator but hopefully water coming out of the end pretty quickly when I flushed it is a good sign. But there are 125k miles on it and I've had it since 85k, and don't think it's ever been replaced. Let me know if you have any ideas on something to add when I flush it that may clear any blockages. Thanks again for the help. My mechanic suggested I scrap it since a new engine is $5k+, so trying to do what I can to figure out if it's something else first.
 
#11 ·
Once you get the thermostat in it, watch the return line at the top of the expansion tank. If you're not getting a good, brisk return flow, you may have a water pump impeller erosion problem. The plastic impellers wear out.

You can't really flush a radiator in a vehicle with a hose. Pull it and take it to a radiator shop. A garden hose amount of flow will be handled by about 10% of your radiator. it can be 90% blocked and still flow coolant. it just won't cool your truck. It won't cool if a 4GPM flow blasts through ten cores. You are better off if half the flow travels slowly through the entire core. What you can do is flush and drive several times to get the old coolant out and replace with the proper spec- like Zerex G-05
 
#13 ·
You should replace the thermostat/radiator whatever caused the truck to run hot in the first place but the fact remains that you are still losing coolant and HG will have to be replaced sooner than later as it no longer holds water reliably and could cause bigger problems like warpage to the heads as that hot coolant passes more readily, resulting in a loss of pressure and the temp climbs. These engines don't like to be run hot; the coolant temp needs to be 180-190 for reliability sake.
 
#14 ·
I picked up the MotoRad Thermostat today. O'Reilly's had it in stock. Also got a new overflow cap. After installed....max temp idling was 210 then turned the heater back on and it went to 204 and stayed for 20 more minutes. Success!! You all are great. Needless to say I'm going to find another mechanic since this one said for me to scrap my D2. And he only works on Land Rovers so little disappointed but everyone makes mistakes I guess. Thanks again!
 
#15 ·
Not sure why people are recommending Motorad thermostats?? They have failed many LR owners the last 4-5 years...I had one separate internally myself. The only D2 thermostat anyone should refer people to use is the GENUINE OEM GREY 180*. Available from Lucky8 or AB, basically all LR parts houses carry them now. I wouldn't use the Motorad unless I was in a pinch.
 
#16 ·
I bought a couple of 180 stats from Brittish parts of Utah
Was sold as o.e.m.
Box was labelled "britpart" as I recall.
No problems
Runs max 189 deg. Usually around 185
 
#19 ·
Box was labelled "britpart" as I recall.

Runs max 189 deg. Usually around 185
that's cos if they are made by Britpart not just supplied by them probably they are fully opened all the time through the missing bypass flow valve:wink
 
#18 ·
Temperature is irrelevant as long as your cooling system is capable of keeping the radiator contents under boiling point. Being ten degrees under gets you nothing. Being 20 degrees under gets you the exact same amount of nothing. If you cut your fan belt, your temp is going to climb ten degrees in 20 seconds, so being at 180, 170 or lower gets you zero benefit.

If your cooling system can keep up with the vehicle's and the operating environment's demands, then it's working just fine. If it can't, you either need more air flow or more cooling capacity. The Rover grill sucks for airflow, so modifying it is an option. https://landroverforums.com/forum/discovery-i-39/mesh-grill-write-up-33088/page14/#&gid=1&pid=6 The Rover radiator is not exactly over-sized for the application. Fitting a four-core unit would result in a huge increase in cooling capacity.
 
#20 ·
I would say your statement "temperature is irrelevant" is a little bit of a stretch on generalization .
You make it sound like a steady 225 would no o.k. Ass long as it doesn't boil which of course isn't true
The reality is things stand up better if you can keep temps under 200. CT..... I'm sure that's why you did your fan mod, others do the thermostat mod, Safari grille mod. Etc. Etc.
 
#22 ·
I completely omitted pressure from that last one. Add 3 degrees F for every Lb/PSI of pressure. Assuming a good cap that's 18PSI.

Understandably, these are theoretical absolutes. This doesn't account for poor flow and localized flow issues that can result in hot spots, particularly in the cylinder heads. The Rover has a particularly poor coolant flow architecture, so I wouldn't want to be pulling a heavily loaded trailer up a long grade with temp readings at 230. But idling along in traffic, if it will hold that temp steadily and you have a functionally intact cooling system, you're good to go.
 
#24 ·
I think the engine will reach whatever temp it's going to regardless of thermostat set point. If your cooling system is clogged, temps of 230 at idle are common. That's bad, but not horrible. A thermostat opening at 190 will still allow for 230 at idle; it'll just get there a tiny bit faster. A 180 thermo will still reach 230. A clean radiator, good water pump and an otherwise well sorted cooling system is your only way out. Air and water flow are key.
 
#26 ·
...I have no idea how Rover assembled their fuel map. But typically you wouldn't want to pull back on fuel as it would cause a lean condition, increasing EGT's and potentially damaging the exhaust valve. Most likely the profile pulls timing from the motor. Additionally, the increased EGT's would be likely triggering knocking which is picked up by the sensors and the common approach for dealing with that issue is less timing. For the most part, OEM ECU's are watching primary O2, air flow and throttle position. I have never used coolant temp as an operating parameter in constructing a map as the other parameters will usually compensate for any issue in that area....
Then you should believe me cos i have some ideea of how the management works... first of all EGT will rise on overfuelling not on underfuelling but it's not about that...the ECT input is VERY important for the management, i'm not gonna copy paste the whole workshop manual here cos it's long and complicated, if you want to see read the engine management's description and operation , just a flavour :
ENGINE MANAGEMENT SYSTEM - V8; DESCRIPTION AND OPERATION 18-2-15 said:
Engine Coolant Temperature (ECT) sensor (C0196)
The ECT sensor is located at the front of the engine adjacent to the coolant outlet pipe. The ECT sensor forms a vital part of the ECM operating strategy, and therefore the optimum control of the running of the engine. Richer air/ fuel ratio is required at lower coolant temperatures such as cold starting. Coolant temperature information from the ECT sensor is also vital to enable the ECM to weaken the air/ fuel mixture as temperature rises to maintain low emissions and optimum performance.
and from operation
DESCRIPTION AND OPERATION 18-2-43 said:
Function
To be able to calculate the amount of fuel to be injected into each cylinder, the ECM needs to determine the amount of air mass drawn into each cylinder. To perform this calculation, the ECM processes information from the following
sensors:
l Mass air flow (MAF) sensor.
l Crank speed and position (CKP) sensor.
l Engine coolant temperature (ECT) sensor.
l Throttle position (TP) sensor.
So as long as the ECT input is VITAL it matters for the engine to be as close to the NORMAL operating temp as possible so IMO everything matters in the cooling system, even the stat's opening point, believe me that your statements " Running at 180 or 190 or 200 gains you nothing." and "the vehicle wouldn't know any difference at 225 than if it was at 210" are wrong... i'm not trying to argue nor to offend you just to keep things accurate cos it's important
 
#29 ·
first of all EGT will rise on overfuelling not on underfuelling but it's not about that...
You should look a little further into that.



There's very little any engine's EMS can do to compensate for elevated engine coolant temps, aside from enabling a "safe mode" or shutting down altogether. The Rover does neither.

From an internal dynamics perspective, the engine's mechanical operation is completely oblivious to an elevation in temperature of ten or twenty degrees. None of the internal clearances will change due to thermal effects. The oil won't stop lubricating for another hundred degrees. The only conceivable effect is localized heating in the head which can lead to preignition, and with the very thermally-efficient aluminum material of the Rover head, that's abated to a great degree. And even if, this is going to be handled by the ECU's knock sensor system.


Back to the real world, On a warm day, pulling a trailer up a grade at highway speeds, the Rover is going to see coolant temps well above 210. It's what the system was designed for. They're not running a 20PSI cap because they find ruptured hoses and stranded drivers to be amusing.
 
#28 ·
The one in the radiator is named "thermostat monitoring sensor" and it's also part of a complicated agorythm as the ECU compares it's readings with the ECT readings and goes to default if certain mapped values are exceeded, the V8 has an extremely sophisticated management
 
#30 ·
Ok m8.... i'm quoting only a short part of one of your previous statement again: "I have no idea how Rover assembled their fuel map" .... i can say only one thing more, with huge appologies, i have the feeling that you have no ideea how an engine management works,.... no probs, you can stay in the real world while i choose to read and study things from a scientific point of view.....my bad cos i consider that the real world is the same with the one we live within ;)
 
#31 ·
Been doing fuel maps for 20 years. Currently leasing a Superflow. I kinda do.

When I say "I have no idea" what I mean is "No one has any idea". We are all just guessing at exactly what Rover is doing with their ECU programming. I have never heard of anyone breaking one and de-compiling it. No idea why they would want to. But even if they did, and even if they were removing fuel at elevated temps, it could only be a very slight amount.

Want real world? I have a Ford V-10 in the shop right now. 23K/mi. Zero compression/100% leakdown on five of 8. The best of the remaining 3 gives 55PSI. Bores look like chrome. Valves are receded by over 0.100". Electrodes melted. Bad fuel. Ran lean. Cost the driver his job.

By the way, RAVE isn't unassailable. There are more than a few errors to be found in it.
 
#32 ·
....
By the way, RAVE isn't unassailable. There are more than a few errors to be found in it.
I agree... though there are correct parts too... like those quoted by me ;)
 
#34 ·
Back to reality...

I wouldn't be too worried about chasing coolant temp. Unless it's popping the cap, you don't have a problem. If it is, it's not a problem solved by the thermostat.

I'm guessing that Rover wanted the temp up a bit for combustion and catalyst efficiency. You have to remember that the manufacturer is driven by more than just the customer and their satisfaction. In engine management, many things are done to serve the masters of fuel efficiency and emissions standards. One would have to imagine that with the D2, they were at the end of their rope trying to met those requirements of the 21's century using engine technology of the 1950's.
 
#35 ·
I scratch my head thinking about all of the block failures & LR/BMW choice in cooling system components but 6-in-1 hand, a half-dozen in the other, BMW didn't do their due-diligence on the r&d end as it applied to the D2 & p38. They took a principle that worked on a car & applied it to a weak engine in a vehicle that weighed twice as much with probably a couple weeks to meet the NA EPA clearances before the assembly line began to roll.

I have a problem: I was working on PS 2 weeks ago and popped a hole in front of radiator. I missed only damaging the fin by 1mm & instead caught the top of a crosstube. I drained the radiator, dried the area & patched the hole, filled it up & life has been good. Thurs I removed the cap & added couple OZ of water then had a puddle of coolant on the ground @ work Fri afternoon. I cranked the motor, nothing was leaking so I drove it home, held 180-185f as normal. Nothing leaking when I parked but 1-hr later coolant on the ground. I found that it came via overflow tank. I took the cap off, wiped my finger on everything, put it back & drove around...180-185. I haven't looked since then nor paid it much mind but why the hell is the coolant overflowing on cool down?
 
#36 ·
I had odd symptoms with a bad reservoir cap not sealing, causing coolant to collect around the inside the reservoir bottle neck where the small return line puts coolant back into the bottle, then it would spill out the overflow tube onto the ground.

It was odd because the coolant level didnt look like it was "over flowing".

On cooldown - not sure, but maybe if it's not circulating, it's silling out.

Let us know more.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top