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1999-2009 [Subscribe to Daily Digest] |
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Just did a little testing to see if I could isolate the issue with my 99 lpt warming up very slowly on the highway (see post below). Ambient temp here today is 25F.
With my Scangauge hooked up I let the car warm up in the driveway for about 5 minutes. Water temp rose from 70F (I had the car out three hours ago, engine still residually warm, verified by feeling engine) to 125F (needle on the dash gauge at the top of the blue hash mark at 120F) over that time, rising evenly. Began the first portion of my testing loop, a hilly drive of about 5 miles with only one stop sign. I had no traffic and drove at 40-45mph over its length. Water temp continued to rise to 170F, only dropping a few degrees on a long downhill stretch.
I then got on the highway at the bottom of a long, steep hill. By the time I reached the top, temp was at 184F (operating temp on the dash gauge). Running at 65mph, the temp began to drop slightly as soon as the road leveled, falling to 173F over only a couple miles. Temps rose back to 180F over the mile or so of smaller roads I took to get back home.
I popped the hood immediately and felt both radiator hoses: the top one was warm but certainly nowhere near 180F, and could be easily held for an extended period of time with no discomfort. The lower hose was cool to the touch. Idling for another 2-3 minutes in the driveway, temps rose to 186F before I shut the car down. The upper radiator hose became noticeably warmer over those few minutes.
While it is possible the thermostat may be slightly open under all conditions, it does not appear to be wide open or anywhere close to it, as evidenced by the fairly rapid heating at idle and slower driving, and the lower temperature of the upper hose after driving on the highway at operating temperature (if the t'stat had failed open, that hose would have been flowing 180F coolant through it, and thus been much hotter). Further, temperatures appear to be regulated properly in most conditions, indicating the t'stat is functioning to some degree.
Running steadily at less than highway speeds (40-45mph in my test) resulted in normal warm-up. Only the higher airflow of highway running at 65mph, combined with low engine load, resulted in temps dropping.
I need to check the upper radiator hose temp during warm-up from a cold start condition. If it starts to warm up before the engine reaches operating temperature, that would indicate a faulty t'stat; if it does not, it would suggest that the combination of cold temps and the efficient G-05 coolant are combining to reduce engine temps under highway running. (FWIW, I've seen noticeable reductions in coolant temperature in other vehicles when switching from the old green coolant to G-05 and similar high efficiency coolants.)
posted by 68.198.1...
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