I decided to ditch Dexcool in time for the summer towing season. During last winter, with Dexcool and my existing thermostat, I was running 203 -204.6 on the Ultragauge. Springtime, 204.6 - 206. Since Rave says stock thermo opens @ 179 and full open @ 204 and my bottom radiator hose is 80 deg., I figure a thermostat is in order. Had the system flushed (they said it was clean) and the thermo replaced with a standard replacement, it now runs 212-217 deg still with cold lower radiator hose. I plan to put the old one back in after testing it in boiling water and it opens. Is it likely that thermostats can be that far apart? I think 217 is too hot for spring, let alone summer. No gurgling, hot air from heater core. They used a vacuum system to pull in coolant. Good flow into expansion tank from t-body heater. Any ideas on getting more of the cooler coolant into the block? I've driven it maybe 3 miles and won't drive any distnce till I know this is sorted out.

 

Source of standard replacement - if not OEM (as in from da dealer), there have been posts about them not opening until higher temps.

There is also a thermostat that fits there, is made for a different Rover, and runs about 6 - 10 F degrees cooler. Motorad 439-180 see Land Rover Forums : Land Rover and Range Rover Forum - View Single Post - Installed 180f thermostat in place of 192f thermostat

But let us talk about that cold hose. If the lower hose is cold, that means very little of that 212 water is getting through there, or it is staying in the radiator too long. The radiator tubes run left/right. If the ones on the bottom are blocked by old sludge, the radiator may flush clean; but very little flow if any in bottom tubes. When radiator is warmed up, the temp should be within 10/20 degrees top to bottom on the fins. Feel with Mark 1 palm reader or that swanky infrared thermometer you saw at Home Depot. Blockage at the bottom makes that area colder.

Now lets talk about the thermostat. It is a hose mounted bypass valve stat. The bypass disk opens when main stat is closed (engine cool) and engine revved above idle (heater core can't take the extra pressure). When main stat opens on a bypass valve type, the bypass valve is forced closed, so both are not fighting each other. Standard setup in old Mercedes and some Detroit iron, including Fix Or Repair Daily models. Now to get that stat to open, it has to have some hot water from some where. That would be thru the little holes in the top (the bypass disk). If holes are too small, too few, or clogged with too many mud chiggers, the quantity of hot water getting to the stat will allow the engine to get warmer before the stat opens. Factory tolerances can also be an issue. One forum member poured hot water from a teapot into his suspect stat and it still would not open.

Of course, one good overheat can result in a warped head, blown gasket, even a slipped sleeve.

 

I don't understand how I can have a cold lower hose and not overheat. The hot collant enters the radiator top, driver side. Cooler coolant exits passanger side bottom and then passes to the thermostat. I have never overheated and somehow, someway, I have been getting enough coolant to run in the temp ranges stated as ok in many posts. I am just struggling to understand how sufficiently cool coolant is getting to the block to avoid overheating. Unfortunately, many posts have been started, but quit before an acceptable explanation is conveyed. I can buy that some of a radiator may be blocked and not cool as efficiently as designed, but cold coolant at lower hose got that way somehow and if there is enough flow to not overheat, there has to be flow through the radiator even if diminished in capacity.

 

I believe I may be on my way to a solution. I tested my old thermostat and it opens as described in RAVE @ 179 deg. F. Seems the thermostat NAPA sells is a 192 deg. stat. Sure wish they would disclose that little tid-bit when you order. I have read a lot of posts regarding lower temp stats used in Freelander and others. All the info I see is 82 deg C = 180 deg. F = the stat I have. I want to be in the 190's normal running. Any info on a 160 deg. stat? Using an infrared scanner, my radiator temps run about 150 at top and temp drops top to bottom, left to right to about 90-100 at the outlet. That tells me I have a lot of reserve capacity in the radiator. Any thoughts?