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Stuck open thermostat and emissions.

2K views 7 replies 6 participants last post by  Stefano 
#1 ·
Went to register/change title on my 9000 today, only to find out that they require an emissions test before they will do anything. That's a new one on me. And they give you only two weeks to do it after the sale date, otherwise you pay $25 + $2 per day beyond that. My thermostat doesn't really let the engine get very warm - only a few needle width above the blue zone. It passed the last emissions test 1.5 years ago, but I have no idea if the thermostat was functioning at that point. Does anyone think the colder engine will pretty much guarantee an automatic fail? Or should I chance it and take the test anyway?
 
#2 ·
My thermostat never goes much above 8 o'clock, winter or summer. Not sure about your year, but turbos seem to use low-temp (82 deg) thermostats.

What would I do? Put in a (correct) set of new plugs, go for a 10-minute run and drive straight into the testing station.
 
#4 ·
Well, I went for a little drive tonight including climbing some steep hills. The temperature gauge did get more up towards the middle, and seemed to go up to the cooling fan activation point in a reasonable amount of time, while sitting in my driveway. It's just at cruising that it stays so low. So maybe it's not totally stuck open. I'll just give it a go tomorrow morning. It passed all previous emissions tests with flying colors, and MPG seems fine, so hopefully there will be no trouble.
 
#6 ·
Although the gauges vary, and are adjustable in the later models, there is a normal temperature range.
In all models, all years, the thermostat should open when the gauge reads about one third of its range, the fans should come on at about two thirds, and it's normal for the needle to be just below the red when in traffic on a hot day in the summer. All the new cars (and I've seen hundreds) act like that.
If your car doesn't do that, you should fix it.
 
#7 · (Edited)
Jim Mesthene said:
In all models, all years, the thermostat should open when the gauge reads about one third of its range, the fans should come on at about two thirds, and it's normal for the needle to be just below the red when in traffic on a hot day in the summer. All the new cars (and I've seen hundreds) act like that.
If your car doesn't do that, you should fix it.
Jim,

Yep, by your description, the thermostat isn't working right. The gauge never gets up to 1/3 unless you stop and let the engine idle, or you climb a long steep hill under full boost. The fans come on at the proper point. There's no question that I will have it fixed. I have a thermostat, coolant change, and general checkup scheduled for next week. As it turns it, there was no reason to be concerned regarding the emissions test. The car passed with flying colors:

Cruise: HC = 23/150, CO = 0.07/1.00

Idle: HC = 14/220, CO = 0.01/1.20
 
#8 ·
Aaron Gilbert said:
....and seemed to go up to the cooling fan activation point in a reasonable amount of time, while sitting in my driveway.
I think this is a sign of a good working thermostat, or of a good engine temperature, which will allow a good emission test. Replace the thermostat if you want, it's a maintenance item afterall and only 12$ worth, but I don't think it will give you troubles at emission test.
 
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