Why the Discovery 2 "Inline Thermostat" mod is a BAD idea
Mudding
Joined: Nov 2016
Posts: 235
Likes: 60
From: Kitsap County WA
I've not had head gasket issues with my D2. I bought it with a blown engine and put a Turner in it, and I have 80K+ miles on the Turner.
Camel Trophy
Joined: Sep 2017
Posts: 3,820
Likes: 1,337
From: Mission BC Canada
@Mntnceguy There is no back pressure issue this is a 16 psi system, that ran with a typical V8 on top of the Rover V8 engine thermostat until BMW needed a hotter engine for Emissions and SAI. All the inline does is go back to the bog standard V8 system used on all V8's for decades including the Rover V8
I appreciate the effort you are making but you are getting a few things wrong, other than a larger displacement their really no significant difference in the 04 block to the 1999 block.
I appreciate the effort you are making but you are getting a few things wrong, other than a larger displacement their really no significant difference in the 04 block to the 1999 block.
I'll have to apologize for right now, as I'm still working on this issue and don't have an answer I'm comfortable giving 100% assurances about quite yet. While I don't think it's the best option, my thoughts at this point are that if your OE system is healthy and operating normally, I'd leave it alone. The added back pressure and altered internal engine hot spots caused by the inline thermostat will likely not do you any favors, since you are already struggling with head gasket issues. I've got multiple friends and other D2 mechanics in my area that are still using the OE system, and as long as it's healthy, they've had no major issues. They do tend to think the FlowKooler pump is a nice addition to compliment the OE stuff tho, if that helps ya....
It's taking me a bit of time to source parts, test fit and stress test what I've done, assess and then make any needed adjustments, so I appreciate everyone's patience. Parts did start showing up today tho, and I expect the remainder sometime late next week. As Always, I will post my findings and parts lists on the forum here, when I'm sure I'm not leading folks astray with bad info. For those that know my work, you'll know I don't post mods before I'm sure it's the kind of thing I'd feel good about doing to a customers car, rather than those requiring constant Ultra Gauge usage and a seasonal parts change list to even make it work properly
It's taking me a bit of time to source parts, test fit and stress test what I've done, assess and then make any needed adjustments, so I appreciate everyone's patience. Parts did start showing up today tho, and I expect the remainder sometime late next week. As Always, I will post my findings and parts lists on the forum here, when I'm sure I'm not leading folks astray with bad info. For those that know my work, you'll know I don't post mods before I'm sure it's the kind of thing I'd feel good about doing to a customers car, rather than those requiring constant Ultra Gauge usage and a seasonal parts change list to even make it work properly
People have done inline mods on plenty of vehicles for many many many years. Extinct's kit was the first put together kit offered for sale for specifically for the D2.
You are doing far more damage to your D2 running the OEM 190/195F thermostat vs the LR OEM Grey (diesel) 180F thermostat or the inline 180 (or the thermostat temp of your choice... I live in TX and see crazy temps in the summer. HD fan clutch, 620-112 fan blade, flowkooler wp, 180F thermostat, and aluminum T/Y, and bypassed throttle body heater. Works great and 250k on my Kalahari with zero issues.
Last edited by Best4x4; Jan 29, 2025 at 08:06 PM.
Recovery Vehicle
Joined: Jan 2011
Posts: 1,170
Likes: 300
From: StL, MO
in the midwest July heat (upper 90's Fahrenheit) i have towed a pontoon back and forth from the lake for 4 hours each way at highway speeds (70 mph) with no issues and steady temps. the inline thermostat is the only cooling system mod i have.
i used the inline in my other '04, which traveled between St. Louis, MO and Tulsa, OK numerous times over four years of my daughter's university days. no issues there either. well, until the front driveshaft grenaded and took out the transmission. but, and, take this with a grain of salt, i'm no mechanic or former mechanic, i don't think the inline thermostat caused that particular issue.
Edit: full disclosure, i have bypassed the throttle body heater. so, that may count as a secondary mod to the cooling system.
Last edited by jastutte; Jan 29, 2025 at 09:59 PM.
Recovery Vehicle
Joined: Jul 2012
Posts: 976
Likes: 154
From: Mideast US
Hotblockoutlet---->radiator---->pumpsuction---->blockinlet
The thermostat does not regulate coolant operating temperature. The stock thermostat closes bypass path and opens radiator path at its rated rising temperature, period.
Nothing else than re-routes coolant path. Does not regulate coolant temperature. The thermostat is there to avoid the engine to run cold for too long. A car manufacturer does not know if will be sold for Siberia or Panamá and is fitted to all cars made.
The operating coolant temperature is set by air ambient temperature + air speed flow + coolant mass flow in radiator + lead foot + climbing + rpm + towing + lean mixture + brakes drag... masked on purpose by an inoperant-by-design dash thermometer.
Last edited by Externet; Jan 30, 2025 at 09:18 AM.
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LOL at the golf ball idea - ingenious! However that will not solve the issue of the thermostat not opening the path from radiator to water pump - I have had probably half a dozen that had that issue. You can usually tell because they will not make it a city block without overheating. One of the frequent failure modes of the OEM design stat. Unfortunately with the OEM stat you cannot quickly remove the thermostat element to open the path and you cannot do it without losing most of the coolant. One of the biggest advantages of the inline thermostat is you can quickly and easily remove the thermostat element form the housing while loosing less than a cup of coolant and continue on your way. Maybe not ideal for heater temperature in cold weather but survivable whereas a thermostat that fails closed basically renders the vehicle undrivable very quickly.
TReK
Joined: Sep 2020
Posts: 2,956
Likes: 754
From: British Columbia Canada
[QUOTE=Mntnceguy;922055]I'll have to apologize for right now, as I'm still working on this issue and don't have an answer I'm comfortable giving 100% assurances about quite yet.
Mntnceguy, it doesn’t matter whether you are right or wrong on the thermostat issue, you owe Extinct a big apology for calling his reputation into question. You can read an awful lot of posts here from people he has helped, people he has sold things to, and you will find that his reputation is stellar. This is not an “apologize for now” issue.
Mntnceguy, it doesn’t matter whether you are right or wrong on the thermostat issue, you owe Extinct a big apology for calling his reputation into question. You can read an awful lot of posts here from people he has helped, people he has sold things to, and you will find that his reputation is stellar. This is not an “apologize for now” issue.
Thread Starter
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Banned
Joined: Aug 2021
Posts: 260
Likes: 181
[QUOTE=Harvlr;922151]
I wasn't apologizing to anyone but that poster I was replying to, to be clear
But, you are right, Harvir, I obviously have some healing to do pertaining to how I react when I feel taken advantage of and made a fool of, for that, I will apologize. It seems it has resulted in me making it worse by making a fool of myself in the process of trying to bring the reasons why I felt that way to the attention of others in order to save them the embarrassment. Like I said in my post, I'm an old mechanic, and the requirement for accountability as a professional in my industry for ones repairs or information knows no niceties. That's just how we talk to each other, how we demand accountability, how we hold feet to the fire, as they say. In fact, the stuff I say here would be considered tame in the bays...lol. But regardless, I apologize, I hope you can see past my shortcomings, and hear the message I was trying to point out.
I'd also have to say I probably qualify to have someone whip out that meme that said something like, "You AIN'T wrong, but you ARE an aszhole". I'll take my lumps, and be accountable for who I am, and I'll always admit my shortcomings.
As always, Happy modding.... from the Aszhole
I'll have to apologize for right now, as I'm still working on this issue and don't have an answer I'm comfortable giving 100% assurances about quite yet.
Mntnceguy, it doesn’t matter whether you are right or wrong on the thermostat issue, you owe Extinct a big apology for calling his reputation into question. You can read an awful lot of posts here from people he has helped, people he has sold things to, and you will find that his reputation is stellar. This is not an “apologize for now” issue.
Mntnceguy, it doesn’t matter whether you are right or wrong on the thermostat issue, you owe Extinct a big apology for calling his reputation into question. You can read an awful lot of posts here from people he has helped, people he has sold things to, and you will find that his reputation is stellar. This is not an “apologize for now” issue.
But, you are right, Harvir, I obviously have some healing to do pertaining to how I react when I feel taken advantage of and made a fool of, for that, I will apologize. It seems it has resulted in me making it worse by making a fool of myself in the process of trying to bring the reasons why I felt that way to the attention of others in order to save them the embarrassment. Like I said in my post, I'm an old mechanic, and the requirement for accountability as a professional in my industry for ones repairs or information knows no niceties. That's just how we talk to each other, how we demand accountability, how we hold feet to the fire, as they say. In fact, the stuff I say here would be considered tame in the bays...lol. But regardless, I apologize, I hope you can see past my shortcomings, and hear the message I was trying to point out.
I'd also have to say I probably qualify to have someone whip out that meme that said something like, "You AIN'T wrong, but you ARE an aszhole". I'll take my lumps, and be accountable for who I am, and I'll always admit my shortcomings.
As always, Happy modding.... from the Aszhole
Last edited by RA122125; Feb 1, 2025 at 12:23 AM.
