LOST JEEPS :: View topic - Intermittent Overheating

Just towed a 1200lb trailer for 1.5 hours at 75 MPH @ 95 deg F ambient (AC on) with 2005 CRD. Temp gauge normally runs firmly just a hair below the midpoint. Today, after 7 min of operation, temp gauge went close to the letter "H" in the fourth quadrant. After 5 min, it slowly returned to normal over about 5 min. Two more times during the 90 min, it briefly crept into the fourth quadrant again (though not as high) and came back to normal in 2-3 min.

None of the above events were related to either gradiant, throttle or speed changes. Had it been limited to one episode shortly after startup, I would have strongly suspected a sticking thermostat. However, given the repeat episodes, I suspect a weak fan clutch and/or intermittent operation of the electric fan. (No obvious coolant loss)

I did the fan clutch test suggested by a LOST member and it only went half a turn before stopping.

Anyone have any thoughts? (I need to point the dealership CRD tech in the right direction.)

Thanks,

DOC

Author:	DOC4444 [ Sat Jul 19, 2008 4:21 pm ]
Post subject:	Intermittent Overheating
Just towed a 1200lb trailer for 1.5 hours at 75 MPH @ 95 deg F ambient (AC on) with 2005 CRD. Temp gauge normally runs firmly just a hair below the midpoint. Today, after 7 min of operation, temp gauge went close to the letter "H" in the fourth quadrant. After 5 min, it slowly returned to normal over about 5 min. Two more times during the 90 min, it briefly crept into the fourth quadrant again (though not as high) and came back to normal in 2-3 min. None of the above events were related to either gradiant, throttle or speed changes. Had it been limited to one episode shortly after startup, I would have strongly suspected a sticking thermostat. However, given the repeat episodes, I suspect a weak mechanical fan clutch and/or intermittent/low speed operation of the electric fan. (No obvious coolant loss) I did the fan clutch test suggested by a LOST member and it only went half a turn before stopping. So, by his method, it isn't completely shot, but maybe there are degrees of degradation. BTW, most vehicles with electric fans generally run the fan(s) for a few minutes after shut-off in hot weather. This Jeep has never done that. Could that mean that an electric fan is either not running or not running at the high speed it should be with the AC on? Does your CRD electric fan keep running after shut-off in hot weather? Anyone have any thoughts? (I need to point the dealership CRD tech in the right direction.) Thanks, DOC

Author:	msilbernagel [ Sat Jul 19, 2008 5:27 pm ]
Post subject:	Re: Intermittent Overheating
There's a bulletin regarding high readings, and a software fix for the ECM... but I don't recall if it applies to 2005, 2006, or both. It's been mentioned elsewhere in the Liberty section of LOST - sorry I don't have the reference handy. Beyond that, take a look at Evans Waterless Coolant (http://www.evanscooling.com/catalog/C_npg1.htm). I used it with a 2004.5 model year cummins diesel - and since it boils at 375F, you can pretty much let the engine heat up until the oil is in danger of overtemp.. and if you're using synthetic, that's not much of a problem either. What it does with that higher boiling temp is let your system run a close to zero PSI and gives you a big margin for those temp excursions you see when climbing a hill. So rather than the sudden boilover, you can clear the top, cool off, and motor on as usual (and no ill effects). Worth a thought if you tow much. Regards, Mark -- DOC4444 wrote: Just towed a 1200lb trailer for 1.5 hours at 75 MPH @ 95 deg F ambient (AC on) with 2005 CRD. Temp gauge normally runs firmly just a hair below the midpoint. Today, after 7 min of operation, temp gauge went close to the letter "H" in the fourth quadrant. After 5 min, it slowly returned to normal over about 5 min. Two more times during the 90 min, it briefly crept into the fourth quadrant again (though not as high) and came back to normal in 2-3 min. None of the above events were related to either gradiant, throttle or speed changes. Had it been limited to one episode shortly after startup, I would have strongly suspected a sticking thermostat. However, given the repeat episodes, I suspect a weak fan clutch and/or intermittent operation of the electric fan. (No obvious coolant loss) I did the fan clutch test suggested by a LOST member and it only went half a turn before stopping. Anyone have any thoughts? (I need to point the dealership CRD tech in the right direction.) Thanks, DOC

Author:	naturist [ Sat Jul 19, 2008 8:58 pm ]
Post subject:
There is indeed a TSB on this issue, and it applies to 2005s. Had my dealer apply it, not sure it did any good, but it does call for a software flash. Others on here claim it makes a difference.

Author:	DOC4444 [ Sat Jul 19, 2008 9:26 pm ]
Post subject:	Intermittent Overheating
It's starting to look like the 2-speed cooling fan is not running at the higher speed as well as the fan clutch possibly slipping. A reflash would mean sending my ECU back to InMotion, so that would be a last resort. DOC

Author:	fastRob [ Sat Jul 19, 2008 11:08 pm ]
Post subject:	Clutch Fan #1
The clutch fan provides much more air flow than the electric. I would start there. Are the fins clean? Bugs bodies interfere with heat transfer. Be gentle cleaning, a strong blast of water can damage the radiator fins. Please let us know what you find.

LOST JEEPS http://www.lostjeeps.com/forum/phpBB3/

Intermittent Overheating http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=34255	Page 1 of 1

Page 1 of 1	All times are UTC - 5 hours [ DST ]
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/