https://landroverforums.com/forum/di...bad-fan-29867/

I found this post, wish the guy put up what solved it. I have very similar symptoms to him. I am thinking of ordering a new OEM t-stat from AB just to cross it off the list.

 

No matter which fan you have, do blades have cupped side toward engine block?

 

Yeah I double checked it. Fan looks like yours. I am leaning towards t stat. Heater works just fine. I didn't get a chance to try the bag trick tonight, but will try that at some point. Does anyone have firsthand experience with a bad t stat? I bought the cheaper aftermarket I wish I would have gotten the OEM now

 

I bought a cheap one too.... from atlantic british. I haven't had any problems. Even an OEM part could be bad every now and then.

 

Some one posted a pix a while back of a D2 stat, looking up the tube, and the four "vent bypass" holes that surround the mounting flange were clogged, this was causing overheat problems. IMHO that might be due to allowing an air bubble not to bypass the stat, and a stat in air (even a steam room) won't open at same point as immersed in water. Might want to pull stat housing and examine with flashlight.


Notes from the RAVE for consideration:


The thermostat is used to maintain the coolant at the optimum temperature for efficient combustion and to aid engine warm-up. The thermostat is closed at temperatures below approximately 82

In cold ambient temperatures, the engine temperature is raised by approximately 10°C (50°F) to compensate for the heat loss of 10% exposure to the cold coolant returning from the bottom hose.

Wonder how that trick is accomplished? IAT sensor? What if the parts that do that process "malfunction" and raise engine temp 50 degrees during normal temps? If the ECU is involved, consider that it computes and generates the signal to make the pointer move on the heat guage, and if the ECU thinks it is cold, then engine needs to be extra hot, but this is normal, so make guage stay in the middle. And what makes the ECU think the engine is cold? If you disconnect your coolant temp sensor, your scanner will show coolant temp of -40 F. So could a loose wire make engine bump up 50 degrees? Scary.

The by-pass flow valve is held closed by a light spring. It operates to further aid heater warm-up. When the main valve is closed and the engine speed is at idle, the coolant pump does not produce sufficient flow and pressure to open the valve. In this condition the valve prevents coolant circulating through the by-pass circuit and forces the coolant through the heater matrix only. This provides a higher flow of coolant through the heater matrix to improve passenger comfort in cold conditions.

When the engine speed increases above idle the coolant pump produces a greater flow and pressure than the heater circuit can take. The pressure acts on the flow valve and overcomes the valve spring pressure, opening the valve and limiting the pressure in the heater circuit. The valve modulates to provide maximum coolant flow through the heater matrix and yet allowing excess coolant to flow into the by-pass circuit to provide the engine's cooling needs at higher engine rev/min.

So some coolant should flow at all times, the thermostat just controls the volume of it, from trickle to torrent. And at idle, the main stat (there are two sections inside the plastic) won't open unless hot water reaches it. Cooling water for the engine is what little is going thru heater circuit and bypass holes. In a D1 and older engines, the main stat was in the block, so it was in water jacket of the engine. Here it is remote, and if the heater core is blocked, or those bypass holes are blocked, it takes a lot longer for water to heat up through the piping to reach the main stat and allow it to open. In hot summer weather, no one pays much attention to the heater. But if the heater or bypass holes are clogged, your cooling system is "toast". Even if they are blocked a little it would impact the main stat performance.

So to test for heater core problems, should you bypass it with rubber hose to see if overheat goes away? If heater core was restricted it will impact cooling at idle.

 

If heater core was clogged, would the heater get hot? It gets nice and hot. I may get a small U shaped rubber hose to loop both heater hoses together and see what it does. That's a good suggestion and would help me rule out one more thing before I drop $35 on a another thermostat.

 

no the heat would not get hot and a blocked heater core will not make your truck run hot.

 

IMHO a restricted heater core or trash filled thermostat reduces the water flow through those little holes. If the coolant is close to standing still in the big pipe, hot coolant may take a while to circulate to the thermostat and cause it to open. Meanwhile, truck is getting hotter because main thermostat is not getting a constant supply of "current temperature water" from the engine. This would show up at idle first. The system depends on the water circulating at all times to provide hot water to operate the main stat at the proper time. Otherwise, one hole in the stat body would be enough to allow gas bubbles to pass. When main stat closes, water at that point is like 170- 180. That water, if not moving, has to heat up from the block not by circulation, but by touching the water next to it (conduction). That would take longer. Meanwhile the block is getting double japeleno warm.

IMHO dexcool sludge, stopz leekz from previous owner, scale from not using distilled water, and pond water used on that off road trip that you never flushed out all contribute to this. Inspection of the stat holes should be easy to do, wil have coolant loss (use a big tub).

Pix submitted of trash in stat holes: https://landroverforums.com/forum/at...mostat-005-jpg

 

Wow those are tiny holes. I ordered a new OEM t stat from AB this morning. Should be here middle of next week. When I get it in I will pull the old one and take pics. its a nasty mess to take the stat out and coolant goes everywhere so i don't plan to do it more than necessary. I willl check those holes in the old one and hopefully they are clogged. Either way I will have a different t stat to try and see what happens with a diff t stat.

 

Finally got around to putting in a new tstat. Runs like it should now. Temp never climbs over 200 even while idling for awhile. Temp gauge acts much different, that was definitely the problem. Annoys me because I replaced radiator and fan clutch/fan trying to figure it out. Never thought a t stat could be bad out of the box. THe tiny holes weren't clogged at all. Not a speck of dirt or grit anywhere in the old t stat I think it just had a bad bypass valve or whatever directs coolant at idle. so nice to not have to stare at the temp gauge every time i come to a stoplight