Does anybody know how to tell if a Land Rover Disc II radiator is working adequately? After running it a while I notice the radiator is only hot on the top half. Middle & lower is cool.

 

We will be watching this thread as I used the infrared thermometer on our 2003 Discovery and have varying temps with the center the coldest (maybe the fan's influence). The bottom radiator hose has very little if any heat and this just does not seem to right.

We purchase our 2003 in July 2011 and have since replace the fan/ clutch, thermostat, upper hose, water pump and Throttle Body gasket. Yet the condenser fan still comes on after a highway drive. Most days the Hawkeye shows temps on the highway 93 C and town driving 96/98 C with the occasional 100 C in town after a long highway drive. All temp are during the winter in NY. Appears the consensus is the temp should be around 93 C.

We need to replace the power steering lines so in the spring we will do the radiator (no service history for the radiator) at the same time along with the remain coolant hoses and the European Thermostat rated a 88 C rather than 92 C for the North American Thermostat.

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2003 Discovery 125K with high miles service complete.

 

The lower should be colder than the top.. that's the flow of the radiator. Top is input from thermostat/engine..... lower output to water pump back into engine. Should be a noticable difference... like 20 degrees or something. Just google radiator heat transfer. You'll find the answer

 

now this is what im talkin bout.. how long does it take the condenser fan to cool things down?? seems like mines always running 15 minutes after I start the thing.. and staying on.. even when I shut down for a few minutes and start back up

 

Typical scenario with outdoor temp about 3 C.

I will drive to work and the typical traffic pattern is 30 mph for five mins, 70 mph for about 25 minutes (93 C), 55 mph about 15 mins (97/98 C) and then 25/ 30 mph for 15 mins (96 C) - all with no condenser fan.

On the way home the traffic pattern is 30 mph for 15 min (95 C), 65/70 for 50 mins. (93/94 C) and 30 mph for five min. (99/ 100 C) - this is has the condenser fan come on. The fan stays on for the five minutes home. (If I shut down and go back out again in 20 min or so there is no fan for the town driving).

Around town temp is about 96 C.

The top of the radiator is hot but the out let is cold and if the outlet is cold there should not be any need for the condenser fan in 3 C weather. The thermostat is new and we found the sensor holes to be clear during the water pump replacement in January so my next guess is the flow through the radiator is not sufficient for coolant. If the pump was pulling water through the radiator, I would expect warm water in the outlet.

No water fall sounds and temp gauge in the truck always tick below 3 PM.

2003 Discovery 125 K with high miles service complete.

 

The radiator takes in hot coolant on the driver side (North American). That coolant is flowing at about 2.6 gallons a minute at 1000 rpm of water pump speed. The coolant enters the entire side of the tank, and flows across the rows of tubes. If tubes are blocked at the bottom, then the bottom will be much cooler than the rest. My indy rad shop guy, who does all size rads from Disco to big earthmoving gear, says 10 degrees spread across the face of the radiator is a good sign. So 10 - 20 sounds OK.

Why do tubes block at the bottom?

(A.) Someone installed "stopz leekz" to deal with a cooling or leak problem. The material may actually work, but the real leak only needs a match head piece of material, the rest of the jug of "fairy dust" settles into the lower tubes of the radiator and congeals.

(B.) The original coolant was Dexcool, soemone decided this never needed to be changed, or mixed other coolant of incompatible type with it, resulting in Dexcool sludge, which also clogs up the bottom rows of tubes.

When bottom to middle of rad is clogged up, the fan clutch on the water pump fan is not triggered to go back to "high coupling" and increase cooling. The face of the fan clutch needs to get well above 170F to force the internal fluids and valve to increase the coupling and power to the main fan. So engine gets hot, but nothing is done about it. Air flow needs to be hot on the fan clutch for it to work as expected. Rad fins can also be blocked with mud and act the same way. Ditto for the condenser, oil cooler, and transmission cooler mounted in the air stream ahead of the engine radiator.

If condenser fan is coming on, that is the Disco way of telling you that coolant is 212F or hotter. It is supposed to drop off at 202 F. A scanner or Ultra Gauge can show you a good picture of what is going on inside. The stock stat is supposed to start opening at 180F, and is fully open at 204F. If you are above that temp now, what will you do in summer? Pix of a clogged radiator, and you can see that tubes are in "parallel", so temp should be more even in a clear radiator.

Some radiators can be hot flushed by a shop, and rodded out. A D2 rad is around $235, a D1 is about $600.

 

My guess is the previous owner's mechanic or friend (she did not do her own maintenance) put stop leak in the coolant system.

When we purchased the truck in July last year and knew then there was coolant issues, there was leak detector dye in the coolant, the thermostat inlet from the block was leaking and the throttle body heater was leaking.

So while I need to replace the power steering lines (pitted with rust) we are going to replace the radiator along with the lower hoses and heater core hoses.

We do no want any issues when we start towing the boat in the summer.

2003 Discovery with high miles service complete.

 

Might want to look at the water pump also.

 

The pump was done in January and of course the pump did not wait for the warmer weather of spring.

Started to smell coolant again and saw coolant leaking out of the weep hole. Wished I had knew as another member stated the fan clutch and water pump usually go off together hand in hand. The pump failed about month after the fan clutch was replaced.

Did not skimp and bought the ATX pump with two year warranty.

2003 Discovery with high miles service complete

 

I notice it's still overheating and when I pull over to take a look (Hood Up) I notice the radiator is cool.. That may be an indication that the radiator is not functioning right or maybe as someone commented.. The water pump I replaced might be faulty. What a drag (After all that work I did).