Disco 2 cooling mod results

4Runner

Well-known member
May 24, 2007
660
110
Boise Idaho
After building the new 4.6 last year I noticed the motor was running averaging 190’s in winter but would be low 200’s to 218 during the summer., even with a 180 thermostat. Always made me uncomfortable to the point where we drove the other one on really hot days. I figured it was the extra compression and just poor cooling design. Well I changed my new stock water pump to a Flowcoooler. Also did the Chevy HD fan clutch with the trimmed down Chevy fan. Been running it for 2 weeks now in weather from 60’s to mid 90’s and my temp has stayed between 180 and 189 with the air on and letting idle for 20mins in the driveway after l local commute. Couldn’t be happier. Will report back next week when we get triple digits to see how it holds up. Maybe it’s old news but thought I would share my experience.
 
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4Runner

Well-known member
May 24, 2007
660
110
Boise Idaho
So the fam clutch is a Duralast 922626 from Autozone. They only have this model. The Chevy fan is a Dorman 620-602 and you will have to trim about a 1/4” off the end of each blade. Then the FlowKooler water pump is part number 1524.
 

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Toran

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Feb 3, 2017
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Ohio
Congrats!
I had been eyeballing the Flowcooler water pump but it was put on the back burner when learning D2s run a bit hotter that D1s.

Did the water pump come with a gasket or did you need to make your own?
 

4Runner

Well-known member
May 24, 2007
660
110
Boise Idaho
Congrats!
I had been eyeballing the Flowcooler water pump but it was put on the back burner when learning D2s run a bit hotter that D1s.

Did the water pump come with a gasket or did you need to make your own?
Gasket was included.
 
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jymmiejamz

Well-known member
Dec 5, 2004
6,008
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Los Angeles, Ca
If it was running at normal temps until the winter, why do you think it is a badly designed cooling system? You probably just have an old radiator.
 

rover rob

Well-known member
Mar 29, 2016
273
56
upstate NY
Can you report your before and after temperatures?

Thanks
at over 80f in stop and go traffic it would rise to 195f without the ac on, now on a 85f day it runs at 185 ( which is my thermostat temp ) all day long with the ac on. this was driving up into the Adirondack mountains last weekend .
 

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4Runner

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May 24, 2007
660
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Boise Idaho
If it was running at normal temps until the winter, why do you think it is a badly designed cooling system? You probably just have an old radiator.
Sorry. I don’t always give the best back story. I purchased this ( my first ) D2 with the motor having had head gaskets water pump/ radiator in the last 30k. He was sold it to me because he was done spending money on it. When I got it it had slipped liners and was eating itself. Upon disassembly one of the cam bearings had fallen out and all the other bearings were trashed. So fast forward a bit get the new motor built and in towards the end of last summer and got it running. It ran hotter than made me comfortable but then it started to cool off outside so the temps were better. Reading posts it seems like D2 run hotter than D1’s so I wasn’t sure what to do yet if anything. Now the motor is well broken in and temps were rising again so I felt like I had to try something. I guess when I form an opinion on the cooling system, I look at how many parts are there that can fail. I also feel like the D2 cooling system needs to be 100% in order to keep the engine from cooking itself. I feel like 70% is all that’s needed to keep my D1’s cool. If your going to run an engine at the upper limit of heat, you might want to build in some fudge factor in the cooling system and an accurate temp gauge. Seems electronically doable in 2004. Anyhow that’a just my opinion.
 

John Wayne

New member
May 20, 2022
1
1
Clayton, NC
I just had the full treatment done on my 04 D2 (head gaskets, new rad.,new water pump, new T-stat,new coolant hoses + a bunch of "might as well" stuff to boot) with all that I was getting temps between 200F to 218.6F. Installed the 180 in-line thermostat mod and am now running between 183F and 189F. Very satisfied with this fix for under $100. Took less than 45min., a pair of pliers, and a hose cutter. Done.
 
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4Runner

Well-known member
May 24, 2007
660
110
Boise Idaho
So here’s the report back. I’ve been 50 miles of forest roads in the mid to upper 90’s outside. The Mrs. has been driving around in 100+ with the air going, even sitting in traffic 186.9 is the hottest temp so far. Almost seems too good to be true but that’s how it’s going so far.
 
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Aug 20, 2007
2,727
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Nashville TN
that is exceptionally good. I'm at 195-201 sitting in traffic with the same mods and ambient at 100 (112 heat index). it's very humid here though, so that's probably the difference. I'd say you're exactly in the sweet spot now.
 

4Runner

Well-known member
May 24, 2007
660
110
Boise Idaho
that is exceptionally good. I'm at 195-201 sitting in traffic with the same mods and ambient at 100 (112 heat index). it's very humid here though, so that's probably the difference. I'd say you're exactly in the sweet spot now.
Yup. We will see how long it lasts. If it was my D1, I would forget about it but my D2 is such a needy child. Lol
 

donniefitz2

Well-known member
Sep 15, 2020
138
56
Scottsdale, AZ
fitzventure.com
So, I read this thread and went to purchase all of the items only to find that the Flowcooler pumps are sold out. But, I figured that's actually not a bad thing. I would rather try one mod at a time to see the true effect of each.

I went ahead and bought the fan clutch and fan listed above. I trimmed the blades and installed the fan. My Disco already runs fairly cool, but I live in the desert of AZ, so I'll take any drop in temp I can get. I never let it rise above 212 (kill the A/C, put it in neutral and rev to 1,500 rpm, etc).

My results of just adding the fan and clutch (on top of already having a newish radiator and an inline stat mod), I'm seeing a few (maybe 3 or 4) degrees lower temps driving around. The biggest thing I noticed is that I can idle for several minutes without the temp climbing really fast. It still climbs but I was able to idle in my driveway for 15 minutes with the A/C on in 108 degree weather and I only saw 204.8. That's unheard of. Normally it would climb to 208 - 210 and I'd have a panic attack and rev the engine a bit to bring it down.

The other thing I notice is the temps don't fluctuate as much. It's more steady.

Some rough numbers:

108 degrees ambient, 160 degree IAT

City driving 50ish MPH with stop lights:
Before: 197 - 204 After: 194 - 201

Long idle during the day
Before: 201 - 210 After 199 - 204.8 (touched 206 for a second and back to 204.8)

I haven't hit the freeway yet, but I'd guess it won't make much difference there.

I call this a success. It's not huge difference, but every little bit counts. Once the Flowcooler pump is back in stock, I'll add that and see what it's impact is.
 

donniefitz2

Well-known member
Sep 15, 2020
138
56
Scottsdale, AZ
fitzventure.com
Has anyone noticed an impact on fuel economy from the more aggressively valved fan clutches?
That's a really good point and one I forgot to mention. I don't think this clutch is any more aggressive then the stock clutch. It sounds no different than the stock one it replaced and it's not designated as "heavy duty" or "severe duty". I'm guessing there's no impact but if you go with a heavy or severe duty clutch, there probably is.
 

4Runner

Well-known member
May 24, 2007
660
110
Boise Idaho
So far I haven’t noticed anything. I still get a solid 13 on both the D2 and the D1 with a severe duty clutch and a stock fan.
 
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JohnB

Well-known member
Oct 18, 2007
2,292
12
Oregon
With my old D2 I ran a 160 stat with the inline mod. Also ran a real coolant gauge. It seemed to be consistent 180 with the Chevy light duty clutch and a D1 fan blade.

Got 300k on that engine before I stopped giving a shit working on it for all the other D2 related issues.

Long story short the light duty clutch stopped making that air plane noise at start up and I just didn't care and it overheated on a 100 degree day and cracked the radiator.

It's now a toaster at a Walmart near you.