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Discussion Starter #1
Long time reader, first time poster...be gentle.

I have spent a number of hours researching overheating on this forum. My symptom is that on hot days (over 85 Fahrenheit) the car will overheat to the point of shutting off the AC while on the highway at 75+ mph. The way I am able to immediately get it to drop in temp back to normal each time is to down shift to 3rd which brings the RPM up to around 3000. Within seconds, the temp goes down and within a minute or so the temp is at normal. This seems different than what most of the other posts say...for me driving it harder seems to reduce the overheating. I normally drive for 2 to 4 hours per trip on the highway, the overheating has never occurred during around town driving and about 1 in 10 times during highway driving.

165k miles, new coolant 5k ago, new cap, new thermostat, 3/8" line to top of coolant tank flowing coolant at idle (per forum recommendations). No exhaust gasses in coolant test done yet.
 

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1997 SLS
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550 Posts
It sounds like you have done most of the recommended maintenance for the cooling system. I will assume there are no leaks from hoses either. Any codes? Also, what is the condition of the water pump belt? (Under a housing on the drivers side). If it's not tensioned properly, maybe your pump isn't circulating as it should during normal speeds. Also, are the radiator fans kicking in as they should?
 

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White Diamond '03 DHS (with DTS floor shift)
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Your symptoms do ring of a belt tensioner. Check that out and if OK, then do the coolant test. Also be sure that the condenser fins are not clogged with dead bugs.
 

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94 ETC,97 STS
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I concur with the other opinions. The tensioner can bind and not exert enough pressure so check that also. Make sure the belt and pulleys are not polished. If the pulleys look polished roughen them with sandpaper and change the belt.

The exhaust gas check needs to be done sooner rather than later. It's just to keep you in the right direction and not waste time and money on unneeded things.
 

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Discussion Starter #5 (Edited)
All, thanks for responses.

Codes, all are HISTORY and go away on reset:

IPM B1334 - Read door/ rear deck error?
PCM P0741 TCC (always off error?)
PCM P1599 Stall Detected (TRUE, happens after long trips slowing down on offramps)
PCM P1611 Loss of serial data
DDM U1225 Serial Data Malfunction
RSS C1743 Speed Sensor Fault (replaced all hub bearings, still get once in a while)
IPC B1983 Device Power Circuit Low (related to dead battery a few weeks ago?)

Taking off shield for water pump belt now to check tensioner...

The belt appears glazed, not severely. It is at least 50K old, probably more, taking off the cover brought back memories of changing it the first time. The tensioner appears to be giving proper tension, the roller squeaks a little when it is spun by hand...possibly some resistance when at speed?

The system fans do turn on, I don't know how to tell if they are spinning at the appropriate speed. Would I check by voltage going to fans with car at temp? Condenser fins have some bugs and some damage due to rock strikes, etc. Is picking the bugs out by toothpick the way to do this?
 

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94 ETC,97 STS
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Picking bugs out...Whatever tool works. A long skinny screwdriver or a spring hook, like a crochet hook.

If there aren't many in the radiator I wouldn't worry. Check between the AC condenser and the radiator. That has filled up on some cars. It would have to have quite a bit to be a problem.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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:eek: Tensioner pulley squeaks ???? Spend the bucks for a new tensioner before you are stranded somewhere........the lube has dried out. Fans should be on low speed with A/C on or at ~220 degrees (you can't hear them then). High speed at 234(?) and you CAN hear them. (Fan temps are in a thread somewhere in here....) Yep, pick out the bugs, and, Ranger cringes in pain, but I have had good luck with fitting a piece of 1/8" mesh hardware cloth, painted flat black, in front of the condenser/radiator. A little tinsnip and wiretie work, and you're good to go, even for rocks......and the temp pointer never went past 12:00 o'clock, even in GA-SC last week.....
 

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White Diamond '03 DHS (with DTS floor shift)
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Ranger cringes in pain, but I have had good luck with fitting a piece of 1/8" mesh hardware cloth, painted flat black, in front of the condenser/radiator.
Yes, that does make me cringe. That stuff deflects more air than it passes. Stopped using it many years ago when it caused an overheat situation. Just keep a close watch on the temp gauge when using that stuff. Personally, I learned the hard way and would rather pick bugs, straighten fins and flush it with a garden hose occasionally.
 
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