There are several factors that may be at play here...

1) Do not trust your O.E. engine temperature gauge. These gauges have proven to be inaccurate and non-linear in the temperature readings. With the engine warmed up as much as is indicated by the O.E. gauge, take a reading with an infra-red temperature gun with the laser pointed to the top of the thermostat housing. Cross reference the reading you get with the gun with another reading taken with an OBDII reader measuring temperature through the engine's computer, (the reading from the OBDII reader ultimately gets its readings from the O.E. temperature sending unit threaded into the firewall side of the thermostat. The readings should be the same or almost the same. If they are not, you either have a faulty O.E. temperature sending unit or an inaccurate infra-red gun. This is a very good test, as it would be exceedingly rare that both test methods have inaccuracies.

2) The O.E. thermostat is a P.O.S. and a waste of time. Better to throw your money down the toilet and save yourself the grief of installing one. The O.E. thermostat is a throwaway part that you have to change out every 50,000 miles or so. At about $150.00 USD plus your time to install it - every time - you can quickly see how soon this gets old. The other problem is the thermostat valve inside the assembly for the North American market Liberty CRDs is set to open up at 176 degrees Fahrenheit... about 20 degrees cooler than the valves in O.E. assemblies in other markets around the world. The reason for the ridiculously low operating temperature is to allow the engine to meet the Environmental Protection Agency's unreasonable NOx pollution standards. So even with a BRAND NEW O.E. thermostat assembly your engine is not getting up to a proper operating temperature. There are other options available than the O.E. thermostat if you know where to look that will get your engine up above 200 degrees Fahrenheit... where it belongs.

3) Are you pulling the radiator hose off just after starting your engine? Pulling the upper rad hose when fully hot is dangerous and should not be attempted. It does appear by your description that you are low on coolant, and that may also be affecting your engine temperature readings. What is the level like in your coolant overflow tank?

Sigh. Proper coolant fill procedure assuming system has been drained AND radiator drain valve is closed - 1) use only HOAT coolant (ca. 50/50 mix with demineralized water); 2) open radiator cap (cap on top of coolant bottle) and bleed valve on passenger side top of radiator (twist to 4 o’clock position and pull up to remove); 3) fill by slowly pouring coolant mix into coolant bottle on firewall until coolant comes out of radiator bleed valve; 4) “burp” upper radiator hose several times to help remove air; 5) top off from coolant tank as needed; 6) close bleed valve (with valve at 4 o’clock position push down gently and twist closed); 7) continue filling until coolant is ca. 1” above the coolant tank mid-line; after several hot to cold drive cycles check coolant tank level which ideally will now be at mid-line, top up if need be.

The OEM tstat is not a POS but it’s not a wonderful design either. Issues - 1) it’s sealed so you cannot replace the tstat without replacing the entire housing; 2) the tstat is a bit on the cool side for ideal diesel operation; 3) its life span can be on the short side (as little as 35K miles); and 4) a good/bad feature is that when it fails it fails open or by opening too soon. Your temp gauge position indicates yours if failing by opening too soon (same as mine did years ago) which causes the engine to run cool at a 10-20% drop if mpg. Solutions - 1) OEM replacment ca. $150 or HDS replacement (ca. $500 IIRC). HDS solution is ideal (better operating temp and replacable tstat) if pricey. In line tstat is NOT a viable option other than short term as it causes coolant circulation issues that may cause head problems. Yes there are DIY mods to the OEM that allow tstat replacement if you have access to machine shop equipment.

The OEM temp gauge is not linear but is accurate if you understand needle position. See the first image at http://www.greendieselengineering.com/j ... st/19.page As noted you are running cold.

I was never actually able to get coolant to come out of the radiator bleed valve, and the upper radiator hose gets tight and hot but does not feel like it's filled with coolant. If I pull it off while it's running a little trickles through like the bypass valve is working but doesn't seem like the thermostat is opening

I'm imagining thermostat issue and I plan on ordering one tomorrow but I'm making sure there's not something I'm missing. I was never actually able to get coolant to come out of the radiator bleed valve, and the upper radiator hose gets tight and hot but does not feel like it's filled with coolant. If I pull it off while it's running a little trickles through like the bypass valve is working but doesn't seem like the thermostat is opening

I don't disagree that the thermostat opens too early for winter situations and that is why I use a winter front but in summer the way I run this vehicle the T-stat functions fine. I typically am on the expressway running 75-80 mph. The gauge is near straight up 12 noon. I have checked it with an IR gun and it tests 195 - 200F.



My concern is why you don't have fluid coming out the bleed valve and when you remove the upper hose why fluid doesn't just pour out. It should be filled 100%. Thermostat issue or not, this hose should be filled if radiator is full.

I am a bit late to this conversation, but FWIW here's my recent experience.

I had been seeing cold temps on the factory gauge, and had assumed that a new thermostat was in my immediate future. Then I noticed the temps climbing up a long hill; nothing awful but higher than they should have been. No signs of coolant loss or contamination, so I assumed it was the fan clutch which was still the original. I replaced the fan clutch. Solved the high temps going up long hills, and surprisingly also solved the running at cold temps too!!!

I can only assume that the old fan clutch was stuck in a middle position, half engaged all the time. It spun too much when the engine was cold and not enough when the engine was hot.

In any case a new fan clutch solved both an over and under heating issue.

Interesting thread. I had a cold motor when I bought my jeep. The heater would never really be warm. I replaced the O.E. thermostat with a Hot Diesel billet version. Really nice piece of kit and the jeep runs in the middle of the gauge no matter the conditions. Also if I want to change the temp range of the thermostat it's a very simple job. I opted for a 193F thermostat.