Greetings guys and gals. I am in need of some advice about the cooling system on my 87 YJ, 4.2, BBD, Man-trans, A/C. I overhauled the cooling system over the past two weekends and replaced the leaking radiator, thermostat, all the hoses, waterpump, fan clutch, and even the failing heater core. The system was flushed with the usual prestone goodies, refilled and burped. Prior to the overhaul the temp gauge never hit 180 around town and never dropped below 210 on the highway (65-70mph). Since the overhaul, the temp begins a slow climb to 210 and stays there +/- 10. I always read things that say the cooler the better, but as near as I can figure this nice steady temp is a healthy sign. The factory recommended a 195 thermostat so that is what I installed to make sure things were getting warm enough for the computer to go closed loop. Does this sound like an OK situation or should I pursue another method of lowering nominal operating temperature? BTW the rig is run at 5280ft altitude, 8 deg BTDC @ 1600rpm.
Guest
G
210 +/- 10 is just fine for a 258. The more consistent it holds temp, the better.
Engines are designed to run at certain temperatures. The thought that "cooler is always better" is completely bogus. The tolerances for the engine were engineered to run at a certain temp. For the 258, I guess that was 210* (thus the 195* thermostat). As long as you don't have any overheating problems you are good. There was a thread about this sort of thing not long ago and the overwhelming educated advice (as I remember it) was to run it consistently as close to design temp as possible.
Engines are designed to run at certain temperatures. The thought that "cooler is always better" is completely bogus. The tolerances for the engine were engineered to run at a certain temp. For the 258, I guess that was 210* (thus the 195* thermostat). As long as you don't have any overheating problems you are good. There was a thread about this sort of thing not long ago and the overwhelming educated advice (as I remember it) was to run it consistently as close to design temp as possible.
If you think you're running hot:
The 258s in both the CJs and YJs had the option of both a standard and a reverse rotation water pump. The rotation depends on which belt setup you have - serpentine or v-belt. Serpentine setups used a reverse rotation pump while v-belts used a standard rotation.
The increase in temperature could be either due to replacing the old thermostat with a "hotter" one, or it could be because the pump is not working the way it should. I'd double check the water pump part #s and make sure.
The 258s in both the CJs and YJs had the option of both a standard and a reverse rotation water pump. The rotation depends on which belt setup you have - serpentine or v-belt. Serpentine setups used a reverse rotation pump while v-belts used a standard rotation.
The increase in temperature could be either due to replacing the old thermostat with a "hotter" one, or it could be because the pump is not working the way it should. I'd double check the water pump part #s and make sure.
From what I always hear, you don't want to run your engine real cool. Less than 200 is too cool in my opinion. The metal needs to heat up and expand to tighten up all the tolorences. I can't explain it real well, maybe you understand? My YJ's 4.0 sits right around 210 all day long.
Wasn't this covered about 1-2 months ago in MASSIVE detail (35-40 posts)? Try here:http://tellico.off-road.com/ubbthreads/search.php?Cat=
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