Coolant Temp Sensor

[contraption22]

Question for you all. Is it possible that a coolant temp sensor can read lower than actual temperature?

I recently swapped out a thermostat on this particular car, a '93 TBI, because it seemed to have been running way too cold. Well it is running warmer, but the coolant temp on the scanner rarely reads above 170 degrees unless it sits and idles for a long time. I'm worried about this because it may mean that the fan won't come on until dangerously hot temperatures.

What effect would the coolant rarely surpassing 180 degrees have on fuel economy?

Thanks!

[turbovanman²]

Yes, they can read lower. Are you sure you put a 195 thermostat in?

Do have one of those heat guns to check actual temp?

180 in winter can affect fuel economy, it depends on how cold it gets in your neck of the woods.

[88_pacifica]

Question for you all. Is it possible that a coolant temp sensor can read lower than actual temperature?

I recently swapped out a thermostat on this particular car, a '93 TBI, because it seemed to have been running way too cold. Well it is running warmer, but the coolant temp on the scanner rarely reads above 170 degrees unless it sits and idles for a long time. I'm worried about this because it may mean that the fan won't come on until dangerously hot temperatures.

What is the brand of the coolant sensor? Does it appear new? Is there a corrosion of any sort on the metal internally that could reduce it's sensitivity? Is it within spec as tested with a voltmeter? If these are unknown, I would spend the $20 or so to get a new OEM one as this is what controls damn near everything on these cars obviously(timing, fuel curve, etc). The winter can play a slight amount of variance though...

What effect would the coolant rarely surpassing 180 degrees have on fuel economy?

Thanks!

It would run richer and not burn off the increase in gas entirely as it is trying to "warm up" still and reach normal operating temps.....

[sdac guy]

IIRC, the ecu will not go into closed loop until 180 degrees is reached. I'm not entirely sure on the actual effect. But I seem to recall hearing this at an SDAC tech session some time ago. It came up because folks were running 170-180 degree t-stats.

Barry

[contraption22]

As far as I know the CTS is original and has never been changed, although I am not positive. I know at some point in it's life, this car received a new cylinder head under warranty when a valve seat dropped out.

I am positive I put in a 195 degree stat. The one I took out was a 180 stat. Not sure why that was in there.

[turbovanman²]

I am positive I put in a 195 degree stat. The one I took out was a 180 stat. Not sure why that was in there.

Slight increase in power during the summer months, car runs cooler so easier on the head gasket.

[contraption22]

Slight increase in power during the summer months, car runs cooler so easier on the head gasket.

Hehe. I'm aware of the benefits of such a 180 stat. I just don't know why it would be in Grandma's Acclaim.

Anyway, did some road-testing with my patented C22 Datalogger system on the way home from work this afternoon. It warmed up fairly quickly, to the mid 170's. And it kind of leveled off there. I did have the heat on because it was PDC out. Once I got on the road, it hovered around those temps, getting up to about 180-185 at stop lights. At one spot where I was crawling/stopped I turned the blower fan off and moved the blend all the way to cold, and it did climb up to the ~195 neighborhood. When I was back cruising at 45-55mph the temp slowly came back down to 177-179.

I half---- tested the CTS readings by using my handy-dandy Craftsman multi-meter which has a thermocouple input. I let the car idle in the driveway. I let it get up to temperature till the fan cycled. I placed the probe in the radiator fins right near the upper hose and it read consistenly within 1-2 degrees of the CTS reading on the 4000E. So I am guessing the CTS is reading correctly.

So what do you think? Thermostat opening earlier than the advertised 195 degrees? It's a Stant stat from the local parts store.

[cordes]

If the CTS and a temp probe right there are both reading about the same, then I would think a new themostat would be worth a look.

[contraption22]

If the CTS and a temp probe right there are both reading about the same, then I would think a new themostat would be worth a look.

Haha that's the beotch of it. I just put a fresh one in last weekend. Oh well, at least the TU Stat housing(The only shiney thing in the engine compartment) will make doing the job the 2nd time a bit easier.

[turbovanman²]

I'm thinking you got a bad one or they gave you the 180 version. The temps correspond with a 180 unit.

[contraption22]

Well i pulled it off the shelf myself and "195" was stamped on the actual stat....

I guess I will try another one.

Anybody know of any brand of stat is better than another?

[turbovanman²]

I've used Stant with no issues before, OE is a good one of course. Gates, there all good.

[BadAssPerformance]

I like Stant... test it by hand (press the valve and open it with your fingers) to make sure it is not stuck before you even leave the parts store. Years ago I had a Stant rep tell me that they had 1/5 that were sticky if left on the shelf too long

[cordes]

I like Stant... test it by hand (press the valve and open it with your fingers) to make sure it is not stuck before you even leave the parts store. Years ago I had a Stant rep tell me that they had 1/5 that were sticky if left on the shelf too long

Thanks for posting that up JT. That is a truly shocking statistic, especially coming from a rep. I will certainly check all of mine from now on.

[BadAssPerformance]

Cool... Since I heard that I have found more than one that was stuck out of the box.

[contraption22]

I put another 195 stat in it... we'll see what happens.

On a side note... Is anybody like me in that they enjoy working on their fun cars, but hate tinkering with annoying crap like this?

[cordes]

I put another 195 stat in it... we'll see what happens.

On a side note... Is anybody like me in that they enjoy working on their fun cars, but hate tinkering with annoying crap like this?

At times, I have an overwhelming drive to understand how everything works. I don't like working on cars that I hate though. My GF's Saturn drives me nuts because it won't stop for anything, and can't pass a car without a country mile to do it, but I keep fixing it.

[contraption22]

So last night, in my boredom, I actually tested a couple "195" thermostats. They cracked ~190 degrees... but didn't close until about 175.... So what good is it?
I get frustrated. Car still runs cool. Oh well...

[csxtra]

So Mike, after all this work, where's your coolant at?

[Pat]

On a side note... Is anybody like me in that they enjoy working on their fun cars, but hate tinkering with annoying crap like this?

Yes!

Improving/upgrading things is fun. Fixing stuff sucks.