Temp issues again

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So I replaced the thermostat in the saturn sl2. It's a 188 thermostat.
Today about 70 degrees the car was running down the highway 70-75 mph and the scanner is reading between 172-183. Then pulling into the store the car was at 172

As soon as I parked i grabbed both hoses. The lower hose (hose with the thermostat) was warm but the top hose was so hot you couldn't hold it. A pretty noticeable temp difference between the two hoses.
The car sitting quickly went up to 190 and the lower hose started to get Warmer. It seems like running down the road it isn't warming up enough to open the stat.
What gives? I don't understand an over cooling position. I mean how can it be cooler than the t stats opening temp range. Any ideas?
 
The upper rad hose will be hotter than the lower rad hose. The heat transfers from the engine to the coolant thru the upper hose to the radiator. Once in the radiator the coolant transfers heat to the fins and exits out the lower hose.
 
177-183, I don't think you have a problem. Thermostats do not regulate temperature that precisely. If its within 10 degress, i'd be okay with it. Running down the road, its a small engine , aluminum block and cools easily.
 
I've had new stats that didn't work well.
Is 188 the recommended stat?

Also keep in mind the coolant needs enough time in the radiator to cool. I've seen folks remove the stat and it worked out well, while some had the coolant pass through the radiator to fast and caused problems. Water pump impeller condition, rad core etc.
It needs flow but also need time in the rad to cool too.
Many will buy & use OEM stats to try and avoid problems.
I also like to replace the rad cap (and clean the fill neck) when I do a stat job.
 
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Originally Posted By: spasm3
177-183, I don't think you have a problem. Thermostats do not regulate temperature that precisely. If its within 10 degress, i'd be okay with it. Running down the road, its a small engine , aluminum block and cools easily.


I'd say this is probably the right point. IIRC the OBD reading on our "cooler" cars is 182-ish in the heat of the summertime. So 177 is probably within the realm of correct.

Ive heard many times that folks should test a t-stat in a pot of water first to ensure it opens at the right temp and correctly. Apparently there are many duds. Its only because good due dilligence is being done here that we are even talking about it.
 
Where is your temp gauge after thermostat replacement? Should be 1/8 inch or so to right of the quarter mark. Two OEM and one Stant in my Saturn put temp gauge in that general area when engine was warm.
 
It's always right above the 1/4 mark by maybe one needle thickness. Sometimes it's almost on the 1/4 mark.

Call me crazy but how can 172 be ok? That's Almost 20 degrees off. Another thing I noticed is the long term fuel trim are around -4 they used to be -16 - -18

My gas mileage is averaging. 29 and it used to avg 33 or so.
 
Originally Posted By: ram_man
So I replaced the thermostat in the saturn sl2. It's a 188 thermostat.
Today about 70 degrees the car was running down the highway 70-75 mph and the scanner is reading between 172-183. Then pulling into the store the car was at 172

As soon as I parked i grabbed both hoses. The lower hose (hose with the thermostat) was warm but the top hose was so hot you couldn't hold it. A pretty noticeable temp difference between the two hoses.
The car sitting quickly went up to 190 and the lower hose started to get Warmer. It seems like running down the road it isn't warming up enough to open the stat.
What gives? I don't understand an over cooling position. I mean how can it be cooler than the t stats opening temp range. Any ideas?


Head gasket?

I'm serious.. any signs other than temp difference? (Can say a lot)
 
Nope the car is rock solid. Honesty I'm wondering kind of a stretch but maybe the radiator and water pump both are newer are improved over the originals and offer better flowing characteristics. My honda does not fluctuate more than 4 degrees the Saturn is 10-12 degree swings. It's weird.
 
ever tested a stat? they are supposed to be fully open at the rated temp. they start to crack open before.

being that the cold hose was still cold, it sounds like it was just cracked open, letting small flow through.

i think this is ok. if you had a bigger load on the engine, the temps would creep up some more.

also, as stated above, I would totally understand being off by a few degrees, too. these systems are not "precision."
 
Originally Posted By: ram_man
Used a napa the local gm dealer couldn't get the gm stat for it.


Sure he can.

It's still available, I just looked it up. My best freind had the same problem you're having twice on his parents cars. Went through more aftermarket stats than you can shake a stick at. Ended up at the dealer, and that stat worked correctly until the cars were sold.
 
The gm dealer here said he could not get it. Is that true I don't know. It's just what he said.

Wouldn't going down the highway at 3,000rpm be plenty of load?
 
Originally Posted By: The_Eric
Did you use an OE stat?




BINGO!! Learned that lesson many,many Moon`s ago. And especially those friggin Stant thermostat`s.....Junk.
 
Quote:
Another thing I noticed is the long term fuel trim are around -4 they used to be -16 - -18
This is why manufacturers don't put real gauges in the car anymore! The long term fuel trim should be closer to zero than to 15.

As far as your coolant temperature is concerned, you may have got a one which does not open at exactly 188 degrees but that is OK. As long as it opens around that temperature.

Seriously, if you did not have the scanner, would you have noticed any of this?
 
Yes. I started following it with a scanner because I noticed the guage would sometimes be on 1/4 it should be closer to 3/8
 
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