I apologize up front if what I'm entering is repetitive; but I thought I'd like to share my most recent incident with my 2000 Intrigue with the 3.5 L V6. This should be applicable to an Aurora with a 3.5 L V6 or a 4.0 L V8 as well.
The darned thing started to overheat-not exactly overheat, but having an extremely high water temperature hysteresis during operation. Temperatures would rise erratically to as high as 225 F and then drop back to the 180 F range. Fan operation was just too often taking into account the cold (40 F) relative current ambients. I suspected a thermostat issue; so I ordered an ACDelco OEM from RockAuto. This was as a result of information I had learned from other people who had used "will-fits" that fit, but didn't work. Well, the ACDelco thermostat arrived in the box and when I changed it, I noticed that although it was reportedly OEM, it "didn't look like" the one I took out. It was clearly missing a molded-on seal on the sealing portion and "looked different" in other less critical aspects. It was also identified as "made in Israel."

Cutting to the chase, I "boiled" the part before installing it. It opened as designed at approximately 180 F (using a meat thermometer to measure water temperature.) The removed thermostat could best be described as "lazy." It opened eventually, but well above the 180 F point and had to be in water at a rolling boil for a considerable period of time before finally extending. I installed the replacement thermostat following the shop manual instructions and it just did not fix my issue. Others have reported problems bleeding the trapped air in the cooling system-I merely followed the shop manual instructions with one small deviation-as written, I couldn't get the coolant to statically bleed out the bleed vent in the radiator. Covering the surge tank opening and applying a slight pressure to the overflow line with the surge tank filled to the cold-hot level readily addressed this issue and I could quickly get a reasonable flow out the bleed vent.

I then ordered an ACDelco 15-10570 thermostat/housing assembly. When it arrived, I was initially skeptical; because it came in a non-descript box and was marked "made in Brazil." However, the thermostat had the requisite molded-on seal and "looked considerably more like" the thermostat I removed. When I subsequently changed it out, I likewise found that all the casting marks on the thermostat housing matched up with the ones on the housing that was on my car. So I guess I was a little gun-shy, but once burned, twice cautious. This change-out was a success and simple. I'm now quite adept at changing a thermostat. I replaced the assembly in it's entirety, bled the system as per the shop manual using a slight pressure assist, and the car is now cooling like a champ. It warms up quickly and once warm, the water temperature hysteresis during a 40 F day is only about 5 F.

...So that was my experience and what I learned. I hope others will find this helpful.
Thanks.

 

I have been tearing my hair out over here, going through pretty much the same steps you described, and reaching the same basic conclusions. I wasn't sure of any of the mess until I read this- simple, to the point, solidifies and summerizes my own woes- and I'm absolutely elated that you even listen the part numbers!...BUT ...I did a search for the therm/housing you ended up using (the ACDelco 15-10570 thermostat/housing) and it is most certainly the one I need as well, however, every website I checked said "not cureently available" or showed they longer carried or it! I mean, I can't find a replacement for this thing ANYWHERE on the fraking Internet! and I have been searching /researching myself into a migraine! Am I missing something? is there a site you might be able to recommend? I feel so totally overwhelmed by this whole thermostat hunt, like NO ONE sells the right one! They all say they fit, but, they dont! Or thier missing the gasket, or thier the world shape, size, ect....it just maddening.. Sorry if this was a little melodramatic, but I never run into dead ends like this with my Olds (and I have run into PLENTY of problems and replaced tons of parts with only minor bumps and headaches), and I need my car back in shape as soon as possible, and at this point i am sick to death of the whole "changing the damn thermostat" process, especially when it ends in frustration and more research....so any info you could give me, or any direction you could steer my quest would be amazing!

 

I am working on 2000 Intrigue with 29000 miles.
The only OEM insert I found so far is from this thermostat housing 12570247 or 15-10571. If anyone has any better experience, please share. I already ordered two from Gates and this one. Part number 12T106D is a simple Motorad in AC delco box. I will test them and post here the results.

 

So here is the update. First I installed Gates 33593, comes complete with the housing, THE PICTURES online for this part number are not actual, do not be confused.
Whatever you order 95723ZD, W0133-1821988 or 33953 from my experience you will receive a box with 33593 inside. Again if you go online all the pictures will show a different item. Check these numbers 95723ZD, W0133-1821988 to have an idea how the actual 33593 item looks. Save money and time ordering Gates 33593.
I replaced the Gates 33593 with the OEM one.
Back to the tests. The Aurora OEM Tstat housings are available, so you can take the actual tstat and use your old housing. They are the same. In my case the OEM tstat was working almost good, it warms the car faster, but after the car reaches around 200F from idling and I start driving it the temp drops to 174-170-168 which is an issue for me, and after a while it may cause an engine block/cyl heads crack. It can be "lazy" closing tstat or just a defective one, not going to order a new oem one. After few tests I decided to put back the one from GATES. I can say that I am 100% satisfied with the results. Keeps the temperature between 186 and 190F once the car is in motion. For this particullar vehicle makes the bleeding fairly easy. Opens easily and after few cycles the car has no air in the cooling system. Some other guys have very good instuctions how to make the bleeding, but I am not very confortable with tap water into the cooling system. Still, you need to know what are you doing or seriuos injuries from the HOT coolant may occur.
My advice to all owners with LX5 engines, switch to Gates.

Pros: Steady temperature, updated design, a lot easier air bleeding process from the system even if you don't do it right from the first time, which means you may leave some air if you already did your best, or in other words you don't need the pressure from your household hose

Cons: A bit lower operating temp compared to the oem Tstat, but can't be 100% sure, because the OEM one been tested did not perform as expected, so no other oem one was available to confirm the results.

If you have any questions, just PM or replay here.

 

AxelZ, thanks for the post. I am looking at replacing my thermostat, since my Intrigue is running hot when idling. After reading a few posts online, I saw that I should stay away from cheap Autozone or Advanced, that is the complete housing/thermostat combo. I read posts stating the housing is a little different than the OEM ones & causes the engine to run hot. Like you, all the OEM parts are 'not available'.
I was then thinking of just replacing the thermostat itself, and keep the existing housing.
So did you end up using the Gates thermostat with the original housing, or the combo Gates housing & thermostat ?

Ted



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