I've had a 1999 SL1 for 5 years. During that time the temperature guage hovered under the 1/4 mark, even when sitting and idling for 5-15 minutes. This is what was normal for all those years.


It started getting hotter and was above the 1/4 mark (sitting closer to the half-way point),all the time. When I sit for a minute or so at a light or anything, the guagestarts moving higher and when it gets to the half-way point, my fan kicks in and cools it down a bit. However, there have been times, I've had to turn on the heater to get some air flow going which cools it down. It doesn't seem to get very much past the halfway point, so the fan is doing its job.


When I took it in for its 3,000 mile maintenance, I was told the water pump was leaking. So it was replaced and they put in a new thermometer (as well as the usual stuff like oil change, DAX replacement, etc.)


After that, it is still running hotter than normal. My repair guy says this is normal for the car. That's fine and I believe what he's saying, but my problem here is that there is definitely a change in the car and it can't be good. I've heard as a car gets older, the engine wear can cause it to run hotter.


If this is due to the car just getting older, there isn't much I can do about it. But I'm writing this post to find out if there might be something else.


Thanks for your consideration.

 

most of the time it's the coolant temp sensor or cooling fan. possible radiator

 

1/2 way between the 1/4 and half tick on the temp gauge is normal for these cars. I have over 400K on two S cars....it is the norm. Gauge actually goes up to 3/4 mark before fan kicks on to cool it.


Temp gauge sitting at 1/4 or below with car warmed up sounds like bad thermostat (stuck open) or possibly bad coolant temp sensor. Probably didn't run all that well.....


They likely replaced your thermostat (I think that is what you meant) when they did the water pump. Which would explain the new "resting place" of the temp gauge, which sounds entirely normal.


The fan comes on automatically if you turn on the A/C -- so if you are freaking out about the car overheating (which it won't if the cooling system is ok/no leaks), you can cycle your A/C in traffic to rest your mind.


Derf


400K+ mi, 2 SC2's, never overheated

 

I have had the EXACT same thing happen with my 1999 SL2.


For the first two+ years I had it (bought it used), the temp gauge NEVER got over 1/4.


Couple months back, it shot up to 1/2 while I was in a (fairly) rare traffic jam. I had the system checked out, they said it was fine, the temperature was normal.


I drove from Chicago to Arizona in September, through Oklahoma, Texas and New Mexico, and I was never in danger of overheating. I had the oil changed and fluids checked right before I left, no problem.


Now I'm in Phoenix (I know, desert- but it was 60 degrees here this morning and we're past the really hottest part of the year) and I'm regularly getting to the halfway point (and, last night in slow traffic on a surface road, just a nudge above that).


When I get up to speed on the highway (which, at rush hour, doesn't happen all that frequently depending on where you are here), it drops back down to just over 1/4 or slightly more than that, usually. Last night it stayed kinda high for a while.


As I understand it, it's about air moving over the surface? The coolant reservoir was very nearly full when I checked it this morning, so that's not the problem.


But I find myself obsessing about this thing every time I drive now (I have 86k miles on it). This is no way to live. Is what I'm experiencing normal or what?


Thank you!Edited by: flg8or