So I have been saying lately how great the 78 c bearmach thermostat has been for the past 2 months welllll
went for a 3 hour drive this morning came home all was fine temps 188-198

went to take the dog to the park after 5 min ultraguage starts beeping I look down it’s 215 degrees climbing steady until 235

holy crap I turn the heat on full blast lots of heat so water pump is working get out feet the bottom of the stat it’s cold

let it cool off for 30 min drive home with heat full blast.
I got a new rad and I’m almost positive it’s the stat
I still have my reliable warm weather tstat from AB. Gotta swap it out

this pisses me offf

 

Inline thermostat and you could replace it (assuming it ever went bad) without losing more than a cup of coolant. I never run OEM design thermostats from anyone, not worth the HG trouble.

 

you know im really considering this now. This is crazy.

 

Was there not someone here that had a kit ? I thought it was in the sticky section

 

In all my years of working on vehicles (since I was 12) I have yet to see a water pump that stopped pumping water. I've seen some rusty impellers in my day, but I've never seen a single one where there was nothing left to circulate the coolant. Water pumps fail 90% of the time when the bearing goes out. It creates play, then the water pump will start to seep out the weep hole indicating the internal seal has failed. Besides that if the engine is spinning the pump = it is circulating coolant/water.

Did you open up the T after it cooled to see if it had coolant right there? Or was it air? When the system has zero air if you remove the cap from the T coolant should be right at the threads.

Best mod I've ever done = pyrex tube. I can pop the hood and tell instantly if I have air in the coolant, low coolant, or contaminated coolant. No guessing what is going on. I've never ran the inline mod, but I've owned right at 14 D2's all of which either had the OEM thermostat temp range 190/195F (when they were new), or the 180F thermostat. No issues in SETX with the AC on full blast cruising at 75-80MPH. I'd have tried the inline setup by now if I had issues. I've also compared my temps with several people that have the inline mod and we're so darn close it's not worth the swap for me. #1 place I see the temps rise is at idle or heavy stop n go traffic. Besides that I'm 184-202F normally all the time.

Check the coolant level when it cools, and open the T and see if you have coolant or air.

 

the coolant was fine I opened the hood at 235 and coolant was rising in the tank It’s not the water pump as I had tons of heat coming from the vents. That’s how I made it home

 

Yeah but don't open it while it's hot... Like Best said, let it cool overnight and open the bleeder screw in the T. That is your easiest first clue in troubleshooting your issue.

 

I know it's not the water pump, once it cooled down how was the coolant level? Air at the T? Was it gurgling? Normally in the 230F range it'll be gurgling pretty good. Saturnine had an issue like this way back with crazy temp readings and a flawless cooling system. Ended up being a cheap no name temp sensor was causing his Ultra Gauge to go nuts even when the D2 technically wasn't overheating. I think he ended up getting an OEM temp sensor and his issues never came back.

aux Efan on?

 

Coolant is at normal level when it cooled also no air. Got the warm weather AB back in there steady 192-204 idle

pretty damm scary how when these fail the temperature just goes up fast.
The ultraguage just paid for itself 100x over

 

Now that it's out slap the 78C into a pot of boiling water and watch it. If it has failed it will not open at all.

I've only seen one do that and it was the nearly 20 year old OEM unit with what I would describe as mud/clay packed into the bottom of it (I really think it was dexcool/green coolant debris/goo). It refused to open, but that is the only one I've ever seen in all my years of working on LR's. D2 came to me after the customer had just spent nearly 2k on a HG job. The shop replaced the HG's, but failed to replace the clogged thermostat/radiator which was the cause of the HG's going out in the first place! They drove it home, and the next day it overheated on them and it was towed to me. I found the cooling system in poor shape, then I found the nasty OEM thermostat staring me in the face and I had a feeling that had something to do with it, and once I removed the lower coolant hose on the radiator it was obvious what the problem was. Slapped in a Britpart 78C 180F thermostat, and a 65.00 Ebay radiator after I flushed that system like a mad man and it was in the 193F to 206F range vs 215-225F (not at idle or in traffic). I also recommended the Dorman 620-112 fan blade, and Hayden 2991 fan clutch which they later had me install. They never had anymore issues with the cooling system after that. I'm just glad the shop actually did the HG decently.

Whenever I see an OEM creme colored thermostat I cringe, and when I see one that's more orange than creme I know without a doubt that LR has been running way way way to hot, and to expect HG, slipped sleeves, or a crack in the block. I've also seen the OEM T's turn a light tan/orange = also another sign she's running way to hot. The 03-04's without oil coolers are just so asking for trouble because if you think the coolant temp is hot just imagine how hot that oil is.