Speed_racer said:
With these 4.0's. I have only had good experiences with factory temp thermos, 195*, and runnin no thermo at all in this so called "winter" season we have here in Florida.
Little tip for the factory thermo, straight up top in the middle of the outer ring, drill a 1/16" hole, park your jeep uphill, and leave the cap off (open system), let it run for 10-15 minutes, when it cycles you will see bubbles escaping to the surface of the coolant, this is called BURPING.
Once its sucessfully burped,you have no chance of air pockets causing you to overheat intermittently.
Half marks - drill
two holes on opposite sides of the circle (should be 180* apart.) You can get a "traffic jam" with a single hole - with two, the upper hole passes air OUT, and the lower one passes coolant IN. Reference my numerous posts on this topic...
There is no trouble with running a 180* thermostat - I've got three in service. I wouldn't run a 160*, but running a 180* is a part of why I've got rigs that don't run up around 210-215* anymore. (I know, that's design temperature. I don't like it. I run down around 195* or so, and I've gotten a bit of extra fuel economy and lowered tailpipe emissions as a result. So, I would be highly inclined to say that reducing operating temperature
slightly is actually a good thing - at least, on RENIX. No experience with OBD yet...)
However, it is correct that the thermostat's job is to allow the engine to warm up. The specification refers to when the poppet opens and allows coolant flow - before that, it's closed and allowing the coolant in the engine block to heat up. Allowing coolant to flow a
little earlier can help, allowing it to flow a
lot earlier can be a problem - especially with OBD vehicles (1991-up XJ/MJ, for instance.) RENIX (1984-1990 XJ/MJ w/AMC engine) tends to be a bit more adaptable, I've noted.
I've only seen three vehicles that didn't like having thermostats in 30 years - a 1980 Honda Accord, a 1985 Cavalier with the 2.8, and a 1988 XJ w/4.0 (I've owned all three, and still have the XJ.) I don't know why, but installing
any thermostat caused an overheat. The XJ runs just ducky without the thermostat, still heats up normally (a bit slower, but not much...) and runs about the same temperature as the other RENIX XJ's I've got - around 195*F. I can't figure it out - the radiator has been replaced, the block flushed, and all the plumbing is wide open - nothing wrong with it - but it's just quirky that way, I suppose.
5-90