oldls400 Posted May 3, 2007 Share Posted May 3, 2007 Hi: I have a 90 model LS 400 with appx 215k on it. Over the last year or so the temp gage has slowly appeared to show the car running cooler and cooler. Now, after about 10 min. the gage will move from rest to just barely above the first hash mark, and stay there - no matter how hot outside, AC or not etc. Thinking the temp sender was bad, I just changed it and it had no effect whatsoever. While changing it I tested the gage by grounding the wire and the gage immediately pegs to the high side - which would seem to indicate the gage is working properly. The car runs fine otherwise, but I really don't like the idea of driving around not knowing true eng. temp. It can't possibly be running that cool. Anybody have any ideas? Quote Link to comment Share on other sites More sharing options...
LS400_Fan Posted May 4, 2007 Share Posted May 4, 2007 Coolant temp sensor could be bad or you might need a new thermostat (stuck open). Quote Link to comment Share on other sites More sharing options...
bdjh Posted May 5, 2007 Share Posted May 5, 2007 Coolant temp sensor could be bad or you might need a new thermostat (stuck open). bdjh My 92 did same thing. Barley moved past first hash mark. Replaced thermostast solved my problem. Usually they are designed to stick open when they go bad to prevent engine from overheating. Quote Link to comment Share on other sites More sharing options...
miamistyle Posted May 5, 2007 Share Posted May 5, 2007 Seeing the temp sensor has already been replaced, I'm with everybody else on the thermostat, don't forget the t-stat gasket and go OEM for sure. Quote Link to comment Share on other sites More sharing options...
chilkoot Posted May 6, 2007 Share Posted May 6, 2007 mine was doing the same thing. I'm in the middle of working on it so I can't say if it fixed it or not, but the thermostat I removed was definitely hosed. the above posters seem to be correct. Quote Link to comment Share on other sites More sharing options...
oldls400 Posted May 9, 2007 Author Share Posted May 9, 2007 You guys may be right , but I can't believe the car could run that cool even with the t-stat stuck wide open. If I ever get around to changing it I'll post the results. By the way I just did the power steering pump rebuild using the info here on the site and it went great! Its been leaking for years and the car was really a mess underneath but its done now and good to go. never did kill the alternator so I guess I just got lucky. Thanks! Quote Link to comment Share on other sites More sharing options...
LS400_Fan Posted May 9, 2007 Share Posted May 9, 2007 My girlfriend's saturn had the thermo stuck open, wouldn't get above the first white line. Quote Link to comment Share on other sites More sharing options...
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