Hello all it has been a long time since I have had to diagnose a cooling issue and this situation is odd.

1st off this Discovery is new to me

My cooling issue is pretty simple under load IE going up a steep hill my temp runs up to 210 - 212 F, not too terrible, but when coasting down the other side the temps will drop to 196 -197.

Once I give her more gas to keep my speed up 60 KPH it goes to what is normal driving road temps 206 to 210, at least for this Discovery.

Thermostat is the yellow/green type but unknown - gray 180 is on it's way.

Rad is warm all the way down hotter at the top

Primary fan and clutch appear to working correctly - clutch maybe iffy further testing required. Looks pretty old. I need to check the the fan movement cold and hot but it does spin.

Electric fan replaced now working

No coolant loss over 600Km

Belt is correct

Coolant bled as per RAVE, will be done again after thermostat install.

No unusual noises- there is an exhaust leak which I am tracking down.

Any suggestions ? I am leaning towards the primary fan not working correctly but it is a guess at this point.

 

Partially clogged radiators can cause them to warm up under load as well

 

Thanks for the feedback

That was my initial thought too,it is a Nissen Rad and "looks" like it has been replaced.

I used the ever so sensitive hand test to check temps on a warm engine, hot on top, noticeably cooler but warm on the bottom.

I can get a replacement of 100.00 CDN shipped to my door so it would not be the end of the world to replace it is a pretty easy job.

 

Don't jump into replacing Radiator b4 checking other things first,
You said uphill 212* & then downhill 196- 197*, that makes me believe either your T-star is 190* or it doesn't function correctly, even with 190 T-stat going downhill your temp should drop below 190,
I would flush Radiator backwards very good, and thenflush engine, also will flush heater core backwards & see if water flows trough it freely, (most ppl overlook heater core) then instal the 180* T-stat you ordered & go from there,
At cruising speed of 60KPH (40mph), engine should run its coolest, with everything in good order it shouldn't even reach 188* at that speed,
If all this didn't help & you know for a fact it's the Radiator that's bad, instead of stock radiator I would purchase an all aluminum rad with bigger capacity & retrofit in place of stock unit (that's what I would do next time if I need a new rad) stock unit is not able to properly cool the engine in high heat or under load, even when it's new,

 

Thanks for the feedback - I was going to replace old thermostat before going the rad route. Seeing as I will be 1/2 way to a flush at that point it is worth a try, I have nothing to lose except a bit of coolant.

 

I have a 4 month old Turner 4.6 long block in my truck. With the new engine, I did all new hoses, 180 genuine thermostat, new Nissens radiator, new water pump, and new reservoir with cap. I have a HD fan clutch with new fan and a perfect aux electric fan. I run 188-201 depending on speed and outside temps. Uphill, I'll sometimes see 206-208. At Red light idles I will sometimes see 208-210(even 212 rarely), which drops to 195-201 within a quarter mile of driving. Some trucks run hotter than others. 2003-2004 lack an oil cooler and tend to run warmer usually. If you are under 210 except at idle after driving or steep uphill, don't be alarmed. You should be in the 190-201 range the majority of the time. Best of luck with the flush and recheck your coolant bleeding for a week or so of driving.

 

Thanks for your input, as with everyone's it is very helpful I tend be very proactive on maint, my theory is a well looked after vehicle will always get me home.

My concern with heat is it seems heat up quickly but cools off slowly, under load, which to my mind is poor coolant flow. Having a dead condenser fan did not help, works very well now and in the right direction.

I have decided to upgrade my copy Torque ODB monitoring to allow for reporting so I can get a better picture of what is going on.

The coolant was new when I got the Discovery, but I have a feeling the PO went cheap here and there, the thermostat I suspect being on of those places.

 

I think a genuine 180 thermostat with a flush and proper bleed will have you sorted out. Cheers!

 

Also a new fan clutch/fan blade isn’t a bad idea. 620-112 Dorman fan blade & new HD Fan Clutch should do the trick.

 

What HD fan clutches are people using ? I can add these to my list.