P0597 - Thermostat or entire housing?

[gnonne]

Wife's 2012 LT 1.8L sedan had CEL come on again today. About 75k miles...

Its the code for the open circuit on thermostat. Last time it did this, I unplugged the connector, then re-plugged it and the light went off. Lasted maybe 15k miles. I've also thought I smelled a small coolant leak a month or so ago, but found no residue or leakage around the thermostat area, which is where it would leak.

Question: Do I need to replace just the thermostat and the "front" housing (aluminum part with the sensor) or the entire "octopus"? I'd rather not replace the whole thing because it is cheaper to do the front part only and you don't need to mess with all the rear hoses and the oil cooler this way. I have three Sonics and this one is the "beater" of the bunch. Runs well, but the less $ I put into it the better.

All that being said, I can certainly see why replacing the whole thing might be advisable, since the plastic parts are known to leak eventually. Anyone have a link for a bargain on an all-aluminum replacement unit?

Thanks in advance.

 

[Sailurman]

Wife's 2012 LT 1.8L sedan had CEL come on again today. About 75k miles...

Its the code for the open circuit on thermostat. Last time it did this, I unplugged the connector, then re-plugged it and the light went off. Lasted maybe 15k miles. I've also thought I smelled a small coolant leak a month or so ago, but found no residue or leakage around the thermostat area, which is where it would leak.

Question: Do I need to replace just the thermostat and the "front" housing (aluminum part with the sensor) or the entire "octopus"? I'd rather not replace the whole thing because it is cheaper to do the front part only and you don't need to mess with all the rear hoses and the oil cooler this way. I have three Sonics and this one is the "beater" of the bunch. Runs well, but the less $ I put into it the better.

All that being said, I can certainly see why replacing the whole thing might be advisable, since the plastic parts are known to leak eventually. Anyone have a link for a bargain on an all-aluminum replacement unit?

Thanks in advance.

Get it pressure checked to find what needs to be replaced once and for all.

 

[Ponchoguy]

Wife's 2012 LT 1.8L sedan had CEL come on again today. About 75k miles...

Its the code for the open circuit on thermostat. Last time it did this, I unplugged the connector, then re-plugged it and the light went off. Lasted maybe 15k miles. I've also thought I smelled a small coolant leak a month or so ago, but found no residue or leakage around the thermostat area, which is where it would leak.

Question: Do I need to replace just the thermostat and the "front" housing (aluminum part with the sensor) or the entire "octopus"? I'd rather not replace the whole thing because it is cheaper to do the front part only and you don't need to mess with all the rear hoses and the oil cooler this way. I have three Sonics and this one is the "beater" of the bunch. Runs well, but the less $ I put into it the better.

All that being said, I can certainly see why replacing the whole thing might be advisable, since the plastic parts are known to leak eventually. Anyone have a link for a bargain on an all-aluminum replacement unit?

Thanks in advance.

Is the code you're getting indicative of a thermostat code?

 

[gnonne]

P0597

Yes, Coolant thermostat heater circuit open.

 

[gnonne]

Leaks?

I could have it pressure checked, but nothing is leaking, just the T-stat code and CEL is on.

 

[Sailurman]

I could have it pressure checked, but nothing is leaking, just the T-stat code and CEL is on.

Oh, thought you said you had smelled coolant.

 

[gnonne]

Connector?

The CEL went off today. It did not illuminate on my wife's second short trip with the car. Must have went through enough start cycles or cold/hot cycles to reset by itself.

Looked at it very closely with a bright light this afternoon... I could not find any leaks and we are not losing coolant. Drove it around tonight, CEL did not come back on and it drives very well. It pulled 41 mpg on the 10-mile 55 mph test route I use with the outside temp being 28 F.

I'm beginning to think it is just some salt or something in the connector on the t-stat housing. The first time it did this, I unplugged the wire, cleaned and re-plugged it, light stayed off for 15k. This time it went off by itself, but the temps increased from near 0 F to 35 F in about a day. Maybe I'll take the connector off and put some dielectric grease in and see if that helps.

If it does need a replacement t-stat (sensor) why is the "updated housing" better? I looked at one a the dealer parts counter today and it is plastic, just like the original. Can;t see the money and hassle in doing that when the aluminum part is just four bolts and one hose clamp, and only $20 online.

 

[Dafson2]

I had intermittent issues with my thermostat in my 2012. Bought just thermostat at first, but cracked the housing when I put it on. Soon found out whole housing wasn’t that much harder to change.

 

[gnonne]

Part Ordered

OK, now we have very limited heat and CEL is back on. Pretty sure t-stat is stuck open... Ordered the whole thing last night.

How does one release the connection for the throttle body line? I've heard this is easy to break. Also, the new part does not come with the special seal for the oil cooler line (not even from GM.) Can that be re-used?

Are the three hose clamps basically one-time use items, or can they be re-used? I did some coolant work on a 500cc Italian scooter I had a few years ago and replaced all the tension rings with stainless steel hose clamps. It had a plastic water pump housing, so you can't make these too tight. I used blue sealant under the hoses. Next guy probably will not have an easy time removing the hoses, but no leaks.

Help/advice appreciated, GN

 

[Dafson2]

OK, now we have very limited heat and CEL is back on. Pretty sure t-stat is stuck open... Ordered the whole thing last night.

How does one release the connection for the throttle body line? I've heard this is easy to break. Also, the new part does not come with the special seal for the oil cooler line (not even from GM.) Can that be re-used?

Are the three hose clamps basically one-time use items, or can they be re-used? I did some coolant work on a 500cc Italian scooter I had a few years ago and replaced all the tension rings with stainless steel hose clamps. It had a plastic water pump housing, so you can't make these too tight. I used blue sealant under the hoses. Next guy probably will not have an easy time removing the hoses, but no leaks.

Help/advice appreciated, GN

I reused everything from my old unit. The throttle body line is fragile, I recently broke it on the throttle body side. I left that on while I took mounting bolts out of the unit so I had more room and sorta wedged it off with my fingers.

 

[gnonne]

Done

I replaced the t-stat assembly this morning. Not easy, but not too bad either, at least it is done from the top of the engine. The head snapped off one of the E-10 bolts, but I had plenty of length left, a can of PB blaster, and a good vise grips, so it came out. Replaced the bolt with an Allen socket head from Lowe's. I had an Italian motor bike and the whole thing was metric Allen socket head bolts, so I have set of "drivers" for them. I also removed the overflow tank to get a bit more room to work.

Refilled with 50/50 Dex-cool and test drove about 10 miles - no issues.

 

[gnonne]

One other thing

I was surprised to see that the original thermostat housing was plastic. The new part I bought had an aluminum t-stat housing and all the other parts are plastic.

Oddly, the plastic parts were NOT cracked or leaking, just a bad thermostat.

 

[JTee2017]

I was surprised to see that the original thermostat housing was plastic. The new part I bought had an aluminum t-stat housing and all the other parts are plastic.

Oddly, the plastic parts were NOT cracked or leaking, just a bad thermostat.

Daughter just got her's replaced on her 2014 Sonic HB. . . 73,000 miles and was done under warranty.
The replacement also was a metal thermostat cap bolted onto the plastic housing.

The T-Stat was ok. . just leaking coolant from near the electrical connection on top.

 

[gnonne]

2012 Sedan LT 1.8

I asked about it at the dealer, but at 6+ yrs old and 76k, they said it was not covered. If it had been a newer model year, or if it was a physical problem, like a leak, they may have covered it, but 6+yrs is pretty far out of warranty.

While I'm still satisfied with the car overall, GM can't deny that this was a poorly designed part that would never have made it through the Honda or Toyota quality control department.

 

[JTee2017]

I asked about it at the dealer, but at 6+ yrs old and 76k, they said it was not covered. If it had been a newer model year, or if it was a physical problem, like a leak, they may have covered it, but 6+yrs is pretty far out of warranty.

While I'm still satisfied with the car overall, GM can't deny that this was a poorly designed part that would never have made it through the Honda or Toyota quality control department.

I wouldn't be too sure about that. Both Honda and Toyota are plagued with their own particular issues. I would not touch a Honda Fit or HR-V.

https://www.google.com/search?q=Honda+Fit+issues+site:www.fitfreak.net&client=firefox-b-1&sa=X&ved=0ahUKEwi6nqTUiujYAhVO8WMKHZ_lDqcQrQIIUigEMAQ&biw=1152&bih=628


And Toyota has their own as well. . .remember the unintended acceleration and engine sludging issues? There is more recent also - -

Excessive oil consumption? - Toyota Yaris Forums - Ultimate Yaris Enthusiast Site

Toyota Yaris Recall Information - Recalls and Problems

And, as you say, many vehicles in the past have needed the T-stat to be replaced after 6 or 7 years. Not just the mileage, bu the number of hot/cold cycles it goes through.

Plus, you can get a Sonic T-stat and housing on Amazon and elsewhere for $40 to $60. Not a lot of money for the whole thing.

I actually selected the SOnic with the 1.8L rather than the 1.4L turbo since the 1.8L known maintenance and repair items are pretty low cost and minor.

 

[Tonyc712000]

I asked about it at the dealer, but at 6+ yrs old and 76k, they said it was not covered. If it had been a newer model year, or if it was a physical problem, like a leak, they may have covered it, but 6+yrs is pretty far out of warranty.

While I'm still satisfied with the car overall, GM can't deny that this was a poorly designed part that would never have made it through the Honda or Toyota quality control department.

Guess I'm a day late and a dolla short.....I just had mine replaced. Had both parts replaced at moron.....I mean, monro. Got ripped for price, and it took too long. I missed a day of work. Long story short, it is now all metal and I don't have to worry about cheap plastic parts on a hot engine.

And, Rock Auto has the metal replacement parts - cheap - as well. I just don't have the time, tools, or place to do this. Wish I did.

:sadbanana: