I'm very close to you. 188 highway 201 tops but I usually don't hit 200

 

Ok, here are my temps, out side temp makes no matter once fully warmed up.
195-199 while moving, upto 202 while sitting in traffic or the drive thru.
I run a 195*F t-stat and normal duty fan clutch, a/c on or off make's no difference.
Engine temp spikes in the 212-215 range when driving first thing after sitting all night/day.

 

Okay so i had a friend change my thermostat to a motorad 439-180 tonight, drained and flushed as much fluid he could. With my guidance of course. Put in the new thermo and refiled system with prestone and distilled water.

With air on max 65mph temp 197.6°

With air on max 35mph temp 199.4° to 201.4

With air on max 0mph temp reached 204.8 sitting for 30 minutes most of time we were @ 202.1°

With out heat or air 65mph 194.0° to 195.8°

With out heat 35mph 199.4°

With out heat 0mph temp never went above 203°

With heat on there were no changes to any of the above temps recorded

I thought temps would have been a little lower with the motorad 439-180° but i never seen 188° except for when it started climbing after initial start.

 

Keep in mind difference between a D1 (stat inside block, inch or two from coolant sensor) and D2 with remote stat (some distance from coolant sensor, which stayed home at the top of the manifold). So there will be some "thermal lag" to get the remote stat warmed up to operate, based on distance the coolant passes, air blast cooling the connecting hoses, and size of the "metering" holes in the top of the remote stat. Those holes must pass the water to warm up the stat (mixing with lower temp coolant from bottom of the radiator). Any blockage just makes stat even slower to respond.

The cold start "spike" before normal temps is just thermal overshoot of the mechanical thermostat being warmed up vs the digital ECU sampling of the coolant sensor. Just like putting a thermometer in a room and waiting for it to slowly change, vs an IR thermometer and "instant reading". In other words, don't worry about the initial spike, as long as it drops back off.

IMHO there is a virtue to having a stable range of temps (+/- 5 degrees) as compared to really wide swings that give the gaskets and aluminum more reason to dislike each other and those intake bolts to magically loosen up, etc.

 

All temps with a/c on. outside temps mid 90's & humid

Extended drive thru (starbucks) - 197f
10 min drive at speeds ranging between 35-50mph - 188-194f
15 min drive on highway, speed between 65-70mph - 211-219f

 

Thanks guys. This all re-enforces my thought that something still isn't right.

One thing that I want to also mention despite the fact that it hasn't come up is that I replaced the fan clutch at 96k with an Imperial severe duty fan clutch. It was fine before the fan blew itself up, and by all indications is fully functional now...it can't be freely spun by hand, and looks to be moving a lot of air. The fan clutch was one of the first things I checked out as I had one fail on my D1 earlier this summer. At this point, both my D2 and my D1 are running exactly the same fan clutch and both the 2 yr old one on the D2 and the new one on the D1 behave exactly the same, so that is pretty effectively ruled out.

Anyway, yesterday afternoon I blew out the radiator and AC condenser. (Most of the silt was in the condenser...which makes sense...) This definitely seems to have helped matters in that the engine isn't heating up as quickly. (As several guys have pointed out, this was a pretty obvious step and the improvement was expected.) Sadly, this doesn't appear to have resolved the problem...

I ran my daughter to school this morning and then sat in the truck and let it idle up to temp to see how high it would go. With the AC on, and the AC fan running I let it idle in my driveway after the short trip, it took roughly 20 minutes get from 188.6* (when I pulled in) to 221*. At 221* I kicked on the heater. The temps then dropped from 221* to 199* pretty quickly (i.e.- it took less than 7 minutes) once the heater was on.



I'm going to run to the auto parts store and pick up a radiator comb at lunch time today and see if that helps.

I'll probably revisit bleeding the cooling system again too. I'm not getting any of the classic 'waterfall' sounds, and I've bled it following the directions on this site (which have worked for me in the past), so I'll be doing this more because I'm not sure what else to do at this point than anything else...

If combing the fins and bleeding the system again don't work, I'm thinking I will have to look at throwing a different radiator in to see if it helps. (I have a nearly identical D2 tucked away for my next Rover, so I can grab its radiator. The catch is that it needs a head gasket and the previous owner might have used K-Seal on it, so I'm concerned that the radiator there may be no better.)

I need this truck up and running ASAP so I can work out any other bugs I encounter before I drive it to VA for Conclave...

 

unless you have a really large area on the radator that the fins are crushed on, a fin comb isnt really going to make a difference. I think you might be right is swapping out radiators.

 

drowssap is right.

Check condenser electric fan to be sure it comes on.

In a D2 turning on the heater does not add a new quantity of coolant to the system. The heater core already has hot coolant in it, no on/off valve. You just added airflow past it. If you noticed a dip, the ratio of the size of heater core to size of radiator is not much. The heater core has a low speed fan, perhaps with some cold air from AC still there. IMHO your main rad is on the edge, due to internal clogged up. When heated up, and truck switched off, you can test fin areas with IR thermometer, should be with in 10F or so top to bottom. If bottoms rows blocked up they will be much cooler than top rows.

 

Well, I'll have to poke around at it more tomorrow. It's a brand new radiator, so it certainly shouldn't be clogged...

 

just get a 180 thermostat, did u switch to universal coolant?