How will your bench test replicate vehicle running conditions? Knowing it opens and closes at a certain temperature isn't enough. The flow rate through the stat will be very significant in its efficiency. Will you be able to replicate that?

For $80 you should be fitting one of these. http://www.roversnorth.com/ProductDe...L500110&type=0

 

i test a modorad using my britter coffee maker, set the temp at 180 nope, set it at 200 nope, even turning it up to 210 final opened . granted a britter coffee maker is not a scientific instrument but the temps did check with a reg tempometer.

 

So I just went out with an IR temp gauge. No weirdly high temps. The upper hoses were 160-170. Rad was only 100 at the bottom. The thermostat was 150. Shot the heads and the block. The heads were around 200-220 near the spark plugs (also close to the exhaust manifolds), block was 180-190. UG read 178.

So weird for there to be no flow through the radiator and still have temps this cool. This was after about 20 minutes of idling/running up and down the street.

Charlie

 

Remember that those are external temps and not internal temps. There will be some variation between internal and external, though I don't know how much.

 

Right. I imagine the head temps to be a little high because of the location close to the exhaust headers and the coolant hose temps to be about 5-10* colder than actual. It's just mind boggling how the radiator can be so cold and the truck not be overheating at all. Even with the heat off I only say about 200 on the UG under load. I called Atlantic British to see if they had any insight and pretty much said they couldn't do anything had no info for me. A little rude if I'm being honest.

 

Yes, the sensor is behind the AC, next to the throttle body nipple. The radiator on my LR V8s stay cold at the bottom, especially so in winter. The external tstats blend coolant from the radiator with that of the engine to maintain temp. Doing so minimizes thermal shock to the block. As a result, radiator flow can be minimal if outside temps and engine loads are low.

 

I stand corrected, I thought the probe was right beside the bottom outlet (inlet?) on the radiator.

 

I believe that one is for the ECU to help control fuel mixes based on the difference in temp.

I put the new rad and thermostat in tonight. Bled it out the best I could, but got the waterfall symptom on the test drive. Got it to my house and parked it on a big hill to get ready and bleed again in the morning.

 

Alex_M - My 01 does not have the radiator sensor, but the 03 does. As CScott notes, I think the ecu uses it for a reality check on outside temps. I have had the manifold sensor go bad. and as a result the 03 cranks up to 2.5G on start up. Apparently it thinks it is 50 below out. After a few seconds, it settles down to 1.2G as usual, which is what I think the radiator sensor checks.

 

I was going to say, I don't think that radiator sensor was used until 2003 or so. I thought it had something to do with the SAI, but can find no references to it in the SAI section of RAVE. In fact, just finding anything on it took some time. I saw it called a radiator temperature sensor in one location, and somewhere else mentioned a thermostat monitoring sensor, but I couldn't find anything about what its real purpose is in RAVE.

Edit: Found info in RAVE.
"The thermostat monitoring sensor is located in the radiator, adjacent the bottom hose. The ECM compares the
temperature measured by the thermostat monitoring sensor to the temperature measured by the ECT sensor. If the
difference between the two readings is too great, the ECM determines the thermostat is stuck. In this case, the ECM
registers a fault code in its memory.
The thermostat monitoring sensor works as a Negative Temperature Coefficient (NTC) sensor. As temperature rises,
the resistance in the sensor decreases, as temperature decreases, the resistance in the sensor increases. With this
information, the ECM is able to monitor the performance of the thermostat. The normal operating parameters of the
thermostat monitoring sensor are as follows..."