Strange Cooling System Issue
05-22-2019, 09:36 PM
#1
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Strange Cooling System Issue Recently, put a 376/480 crate motor in 2015 Jeep Wrangler. It will run a little warm on a hot day but doesn't really overheat, except I believe it would have if I allowed it to while hauling a trailer once. the symptoms seem curious to my experience.
Setup:
LS3 376/480 new GM Crate motor
New 3 row aluminum radiator I believe to be adequate.
Plenty of electric fan flow well shrouded. Fan on medium at 175 deg on high 205 deg.
I believe a 195 thermostat.
Symptoms:
75 degrees or less ambient runs steady 195 no matter what
Hot day say 85+ temp can creep up to 210 never really see more that 213 even on a 95 deg day (except when hauling a trailer.) WOT will bring up temp quick.
Slow down cools right down never idles hot infact it can be running between 205-210 at cruise, stop at a light and be cooled down 197 before the light turns green
Today was 95 degrees outside and when I got home from work with engine heat soaked I sat in the driveway at idle 197deg. ran rpms up to 2500 (in park no load) and temp went to 206 went back to idle and temp came back down to 197.
Any thoughts
Setup:
LS3 376/480 new GM Crate motor
New 3 row aluminum radiator I believe to be adequate.
Plenty of electric fan flow well shrouded. Fan on medium at 175 deg on high 205 deg.
I believe a 195 thermostat.
Symptoms:
75 degrees or less ambient runs steady 195 no matter what
Hot day say 85+ temp can creep up to 210 never really see more that 213 even on a 95 deg day (except when hauling a trailer.) WOT will bring up temp quick.
Slow down cools right down never idles hot infact it can be running between 205-210 at cruise, stop at a light and be cooled down 197 before the light turns green
Today was 95 degrees outside and when I got home from work with engine heat soaked I sat in the driveway at idle 197deg. ran rpms up to 2500 (in park no load) and temp went to 206 went back to idle and temp came back down to 197.
Any thoughts
05-22-2019, 11:33 PM
#2
TECH Senior Member
I'm wondering if you still have some air pocket(s) in the engine. What might help is put the front end on some ramps and pull the top hose off, pointing it upward. Maybe the incline will help the air out. Worth a shot!
06-04-2019, 11:02 AM
#3
I don't think the motor is too hot. People believe these motors operate at the thermostat temp. Running at 210 at 70 on the highway is normal. The system is obviously working because it cools off after reving up the motor. Did you install a surge tank?
A good test would be to drive the jeep at high sustained speeds for say 1/2 an hour. If the temps level off at 210-15 you are ok. If it continues to rise, then there is a problem. Such as slowly creeping upto 220, then 225, then 230 etc. Keep in mind 50-50 antifreeze doesn't boil until about 250, plus the cap will take it upto about 265. Also, the oil temperature should be about 30* higher than the water temp. So, a motor operating at 210, the oil will be about 240.
Also, and because this is a motor swap, I would suspect air flow through the radiator and out flow against the firewall and motor is different. This would be the first place I would look, if the motor is truely overheating.
A good test would be to drive the jeep at high sustained speeds for say 1/2 an hour. If the temps level off at 210-15 you are ok. If it continues to rise, then there is a problem. Such as slowly creeping upto 220, then 225, then 230 etc. Keep in mind 50-50 antifreeze doesn't boil until about 250, plus the cap will take it upto about 265. Also, the oil temperature should be about 30* higher than the water temp. So, a motor operating at 210, the oil will be about 240.
Also, and because this is a motor swap, I would suspect air flow through the radiator and out flow against the firewall and motor is different. This would be the first place I would look, if the motor is truely overheating.
06-05-2019, 08:08 AM
#5
Majority of aftermarket electric fans are weak. Convenient, but weak. Need to up fan power, via different/more electric choice or switch to belt driven unit. Try to modify and use an OEM fan if possible, even if it ends up a little ugly. They are typically more powerful, much larger blade surface, better water resistance, etc...., as compared to aftermarket. Agree todays engines run a pinch above t-stat temp, this is due to minimized cooling volume in the engine for fast warm up vs yesteryear's engines.
Also t-stat could be flunky behavior, especially when new. I have swapped more than one brand new stat, to straighten out errant temp gauge readings. They seem to have infant mortality, they may have the creepers the entire time from new, or once you get a good one, will last a surprisingly long time. The original one in my 1999 Jeep Cherokee went 243,000 miles and still worked perfect, never changed it, even after rebuilding the 4.0L I6 engine.
Also t-stat could be flunky behavior, especially when new. I have swapped more than one brand new stat, to straighten out errant temp gauge readings. They seem to have infant mortality, they may have the creepers the entire time from new, or once you get a good one, will last a surprisingly long time. The original one in my 1999 Jeep Cherokee went 243,000 miles and still worked perfect, never changed it, even after rebuilding the 4.0L I6 engine.