Thermostat Going Bad?
Thread Starter
Member
Joined: May 2011
Posts: 235
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From: Southern California
97 Lexus LS400, 04 Mustang, 08 Corvette Z51, 92 Honda Civic Si, 02 CL500, 03 E500
Thermostat Going Bad?
Hi there, I've recently noticed my temperature gauge on my CL500 has gradually moved up to the 3/4 mark during rush hours. When car is driven on freeway with no traffic, the needle is right in the middle of gauge, however if there's traffic ahead & then some stop & go, within a few minutes, the needle will move up to the 3/4 mark. Initially, I thought some air may have been trapped in the system so I did a few purges by opening the reservoir cap after car was driven & warmed up but still no change. Is this normal or the thermostat is on its way out as it's not fully open as it should be? Please advise. Thanks.
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Joined: May 2015
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From: Miami, FL
2003 CL 600
3/4? You mean 100 *C?
That's normal on these cars. It's not like any other car i've seen, but the t-stat opens at 80C, so on the highway it will cool down to about the 80 mark and stay there. The fan doesn't turn on until 95C if the A/C is off, so it's normal for it to go back up to that point once you're stationary or even normal slow driving. The car requires a LOT of airflow to keep it cool, that's why the fan is so massive.
That's normal on these cars. It's not like any other car i've seen, but the t-stat opens at 80C, so on the highway it will cool down to about the 80 mark and stay there. The fan doesn't turn on until 95C if the A/C is off, so it's normal for it to go back up to that point once you're stationary or even normal slow driving. The car requires a LOT of airflow to keep it cool, that's why the fan is so massive.
Thread Starter
Member
Joined: May 2011
Posts: 235
Likes: 23
From: Southern California
97 Lexus LS400, 04 Mustang, 08 Corvette Z51, 92 Honda Civic Si, 02 CL500, 03 E500
Joe- The car was at home so I don't remember the exact temperatures when I posted the question. Anyway, yes the middle & 3/4 marks are at 80 & 100 deg C, respectively. The reason I asked is because the temperature gauges on my Lexus, Mustang & Corvette are smack in the middle once cars are warmed up & the gauges don't move up or down at all. I'm glad you're telling me it's normal for the CL otherwise I was going to replace the thermostat this weekend. Thanks.
MBWorld Fanatic!
Joined: May 2015
Posts: 4,037
Likes: 1,012
From: Miami, FL
2003 CL 600
^^ Exactly, most cars it's just sitting at "normal" until it needs to change to show you it's overheating. The CL has an actual, literal temperature gauge, which is kinda neat but makes it move around all the time.
This is the same reason new cars have eliminated temp gauges completely, you just get a light for overheating warnings. Most newer cars have electronically controlled thermostats anyway so they can be running 30-40 degrees hotter than normal for efficiency reasons if not needed, or open the t-stat sooner if conditions are appropriate.
This is the same reason new cars have eliminated temp gauges completely, you just get a light for overheating warnings. Most newer cars have electronically controlled thermostats anyway so they can be running 30-40 degrees hotter than normal for efficiency reasons if not needed, or open the t-stat sooner if conditions are appropriate.
