Hi everyone! I got my Disco back from the shop with the new Turner 4.6 engine! Hurray! That being said we have one little (but familiar) problem: coolant temps.

First here is all the data I have collected so far:

Scangauge temps:
Parked idle hood open, ac off: 220f
Parked idle hood open, ac on: 220f
Parked idle hood open heater on: 215f
Parked idle hood closed: 224f (yikes)

The following are temperatures taken with an IR thermometer (at the very hotest measurements):
T at bleed nipple (where x is bleed nipple):
183 x 185
177

Hose on bottom of thermostat: 113f
Bent hose coming out of the top of the thermostat: 190f

Is it normal for there to be such a big difference between the hoses on the top and bottom of the t-stat?

I have a 180 degree thermostat on order.

Thoughts:
Does this sound like a faulty temp gauge?

Thanks for everything everyone! I am trying to remain calm here.

 

Follow up question: where can I IR temp to make sure the temperature being read by the scanguage is correct? Thanks!

 

#1: Bleed coolant system
#2: check that your 210F fan is coming on (secondary fan)
#3: Verify that your radiator has no debris on its fins

If those 3 don't suggest an easy answer then
#4: replace thermostat (inline is good)

If that doesn't help then

#5: replace main fan/clutch

 

 

What's the temp right at the sender? It's located at the front of the lower manifold. Check there, your scan gauge is getting it's information from there...so, if there is a large discrepancy...scan gauge reading 240, but IR is saying 180...l'd assume the sender is bad.

​​​​​​​ Brian.

 

Yes, turning on the heat drops the temps at idle by about 5-6 degrees F

 

 

Thanks again for all the quick replies.

I believe the system is bled correctly:

• When the truck stone cold, I cracked the bleed valve with the coolant tank raised and full with the cap off. Coolant came rushing out immediately.
• There is no sign of air in the system (no gushing or gurgling, heater works really well).

In regards to temp sensor / sender:

• Took some readings around the sensor / sender and they are about 15F cooler than scan gauge.
  • ScanGuage at idle with heater on: 207f
  • Heater Core Inlet tube ( to the left of the Coolant Temperature Sensor) : 190f
  • Coolant outlet pipe (runs from right below sender to bleed T): 185f

In regards to thermostat:

• 180 degree stat is on order
• Hose from radiator to bottom of thermostat is cold (~105f) at all times (red flag?)
• Hose that goes from top of thermostat to water pump is quite hot (~190). Shouldn't this be the mix of cold water from the radiator and hot water from the engine? This (to me) suggests that the thermostat is not working.

Other data:

• Brand new radiator and hoses
• Front (smaller) fan kicked on when ScanGuage read 207f
• Heater reduces temp by 5-6f
• Giving revs at idle reduces temps by 10f

The good news is that the temps never went about 210 at idle on this cool morning so at least I am not in short term danger zone. Right guys....?

 

 

The problem you have is your truck is cooling inconsistently, assuming you have a standard 190 thermostat in there then your temps will be in the normal range. But jump and drops of 10 deg are not normal.

With a 180 thermostat my truck runs between 186 -194 all day long, getting up to 197 on long uphills at hiway speed. I hit 205 on very hot days sitting at very long lights.

The stock thermostat opens at 194, so temps between 200 and 220 are to be expected, running your heater fan will help as you found out.

But how are your temps moving, if I hit say 202 at a long light within a minute I am back down to 197, then 194 in short order, and then 188 if I keep moving.

I should not even though I am in the Pacific Northwest at 34 deg C this summer these numbers did not vary much