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Picked up a new Prestone Performance Thermostat...


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A 160 degree thermostat is not a good idea.

Agree -- if you could find a 190*F thermostat, it might not be such a bad idea. What's wrong with OE though? It's cheaper than the Prestone, flows completely adequate to cool the engine, and you know it has a good reputation. Under extreme conditions, the thermostat is not the deciding factor on engine temperatures anyway -- it's wide open by the time you get to about 205*F (with the OE 'stat). It's the amount of airflow across the radiator that determines how high your temperatures creep. That's why, once the fan kicks in at 229*F, the temperatures fall right back down -- because you're getting plenty of airflow across the radiator. You'll notice no difference there with a different brand thermostat.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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I appreciate the input, and understand the thermodynamics as well, but I have a situation where the temp runs 205-225 at speed, up to 234-235 stop and go. All within a workable range. On a cool day (mid to high 70's) she will run at 185-195 which is fin. I pulled what I had in there, looked like a high end Stant 160 degree, so with the entire cooling system new, I was hoping to keep the temps a little lower than they have been running. Theorizing that the existing thermostat may not be flowing fully, aor a little more restrictive. I discovered that this Hi-po Prestone is made by Robert Shaw, in doing a search on the net, it appears that many people are in search of a Robert Shaw brand thermostat, especially Mopar performance guys. The stat is a cylindrical cartridge type, looks like a big button that fits into the block. It opens itself by turning as opposed to a plunger. I'll run a it a few days to see if temps differ any...question though. My mechanic neighbor thought that this series Caddies OEM thermostat, had an extended plunger type device that extended into the block, that sealed off another passage that prevented overheating? Can you guys that are familiar with the original or replacement GM brand confirm that? Or does it look like a regular Stant type, (disk with plunger) or similar? Thanks guys!!! :D

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Most of the reason why they want the engine to run a little 'hot' is so that it burns off carbon deposits. If you could keep the engine at 160 all the time of course it would perform a little better but lots of buildup would occur and it's not emmissions approved, etc etc. There are tons of reasons why things are done and depending on how you drive you can change things around. Would be nice to have a totally programmable car but i'd suppose the EPA would throw a huge fit (unless it was a ethanol or propane or natural gas car heheh)

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The OE thermostat is a very long, yes. Probably 4" long if I recall correctly. Not sure of the purpose.

I've had a Robertshaw thermostat before...actually a Mr. Gasket brand. I had a 180*F thermostat in my Olds 403 in my Buick Regal. It ran good all the time, but temps climbed pretty quick after getting off the interstate. Fell back down (with the mechanical fan clutch engaged) after a few minutes. I put one in my '84 Cutlass with a 307 and it ran rock solid all the time. Good products. I'd get the proper temp 'stat for your Cadillac, though, even if you do go with the Prestone brand.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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I did some experimentation with the thermostat 2 winters ago. I removed the thermostat completely and the car would still get to 200f idiling and 190 driving on the highway with the ambient temps below 30f. I figure that the thermostat is basically open 100% of the time after the engine warm up period.

For gits and shiggles I installed a 180 thermostat, I notice no difference in the running temp vs. the stock 190.

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I'll go by and pick up an OEM, especially if it is 4" long, perhaps my neighbor friend was right, there may be an additional passage further down into the manifold that the thermostat controls...this Prestone one seems to make no difference, in fact was running hotter, I believe I had some air in the system last night, it went to 252..then 261 got the usually shut down messages.checked this morning was about 1/2 gallon low on coolant...I'll run it today, and try and get an OEM tomorrow. Is the Caddy dealer the only place to get one? And what should I expect to pay? Thanks guys!

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This discussion brings up a really good point. I literally sweat as my car gets into the 225 to 230 range and more in traffic and usually turn off my AC (call me a wuss, I know). I was eyeing this one from stant, a SUPERSTAT.. it looks really well made. I have almost always used aftermarket stats.

http://www.stant.com/brochure.cfm?brochure...location_id=168

I have never used an OEM stat usually off the shelf stuff from the local auto parts shops. Listening to this discussion, I think I am going to go OEM when I get back from vacation. I found it interesting in my research that stats are only warranteed for 2 years. If the calibration goes off or it binds the slightest bit that could be the reason I experience high temps... Thanks, Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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The thermostat is P/N 12559807, list at $18.90 from GM when I bought mine. Try gmpartsdirect for a better price ($7.68 plus shipping).

Mike, don't turn the A/C off when in traffic. Your temperatures will stay higher, since you're locking out the fans...until the temps rise to 229*F and you get nervous! :)

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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I went through all this up to the point of installing a 4 core radiator. The factory temp stat is the way to go. Too much flow and the fluid does not stay out in front long enough to get cool, it just zips right through hot and returns hot. The factory model leaves it out there long enough to get cool. If it is not getting cool enough, be looking for a blockage in the radiator, air flow, maybe fan problems. Put the special stat on the shelf wi the K & N filters. MC

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All righty now...Installed a Genuine AC Delco Thermostat, (195 F) yesterday, and made some observations...First it looks like a run of the mill Stant brand, nothing special, it is not 4" long, looks rather cheaply made. So far I have used a Stant Superstat (160 looks well built, stainless steel), Prestone Performance Plus (160), and now the AC Delco (195). AC Delco warms up faster, (Duh) :rolleyes: all seem to run at the same temp on the highway...I guess the real test will be stop and go traffic today with 100 degree heat...someone had a posted theory that the stat is pretty much open all the time, (hot weather), and I am starting to subscribe to that theory :P , soo...we shall see how it works out.

And yes, I do have too much time on my hands... ;):blink:

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someone had a posted theory that the stat is pretty much open all the time, (hot weather), and I am starting to subscribe to that theory

The OE thermostat starts to open at about 190*F and is FULLY open at about 205*F. This means that if you're seeing coolant temperatures hovering around 190*F, the thermostat is probably not full open...it's partially open, and a lot of coolant is recirculating through the block, which it does anyway. By the time the coolant heats up much past 200*F, the 'stat is all the way open, whether you have an AC-Delco thermostat, Stant, Prestone, Mr. Gasket, Robertshaw, etc. At that time, since these cars don't have mechanical fans, your cooling capacity is controlled largely by the airflow across the radiator...either by you driving or by the cooling fans pulling air through.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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Hi Guru, sounds good, mine is a 4.9 '92 Seville, and the OEM Thermostat looks like a regular off the shelf type. Seems to be doing ok with OEM, no better, no worse. Since it is a 195, seeing 210-225 doesn't bug me that much. Gotta get the PCM or IPC fixed now...then she will be good to go. Passed state inspection today, flying colors on the emissions, not bad for 148k miles. The 4.9L motor appears to be a rock solid design! I have heard several mechanics say it is Cadillac's most durable of the recent series engines. I just sold my N* and at 107k, it was running fine as well. Will prob get a newer Caddy, prob an '01 or '02 Deville towards the end of the year...Thanks

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In the middle 60's I bought a 55 Ford that always hesitated and never had good power. For some reason, probably a broken hose, I had occation to change the thermostat which I found to be a 160 degree model. With the proper one in place the car behaved much better and had better power.

I talking this over with my grandfather he laughed and pointed out that 160 degree was used when they used alcohol for antifreeze.

Funny thing about that. All these years later the 160 stats are still around and people still buy them.

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I have no problem at all seeing 230+ degrees coolant temp. Used to race up lonely roads in the shenandoah mts (near lynchburg) to get to Skyline drive and then back down the other side, and watched the temp as I went up, hairpin corner, then wot to the next hairpin, over and over. I think I saw 232 in those situations, even in late autumn. Scotty ... relax!!

Later, after driving to the west coast, I had a situation in San Francisco, because when diagonising an hvac failure, I misplaced a fuse and (did not know that I) had NO cooling fans. So, in the summer at rush hour. My wife and 3 sons in the car, 40 miles from home and its pushing 250 degrees. I think it reported 252 before the limp home mode kicked in.

I have posted about this before, IT WORKED. Three years ago, my northstar protected itself, and took me and my family home. Once I got onto the highway, with 4 cyls and low power, the air flow cooled things down, and the whole enchalada lite up and I was back to 100%. Magnificent! Its at 140k now and still runs beautifully.

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rmac-etc THANKS! And as usual bbobynski is relaxing my fears! Thanks.. I am sure he sees higher temps in testing..

I just got back from vacation in Scottsdale, Arizona talking about temps it was 104 to 110 all week (but a dry heat :lol: )

Rented a 2004 Deville, loved it, the cooled seat feature was nice in that temp. On the 2 hour drive up to Sedona, there was a five mile climb and they warned you to TURN OFF THE AC! Never saw a warning like that before. Well I said, hell I'm leaving it on, I'll watch the temp and do a field test for bbobynski!! The temp never went above 220 all the way up to 4,000 feet at 75 - 80 MPH at an incredible incline. She breezed up to 4,000 feet with ease, while lots of cars labored and some were on the shoulder cooling off. Quite amazing given that it was over 100 degrees there. The speed limit on Route 17 North is 75 MPH. I have not seen speed limit that high in years, and cars were FLYING! The Deville at 90 MPH was outstanding and very stable even with a strong crosswind. Felt very safe.

Has anyone ever seen a warning to TURN OFF THE AC before? Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Has anyone ever seen a warning to TURN OFF THE AC before? Mike

There are two or three places around Death Valley in California where they have those warning signs. They are generally located at the base of grades that go from near sea level to fairly high altitude in the desert where temperatures reach well over 100 degrees in the summertime.

How much did it cost to rent the Deville? My wife and I are planning a driving trip to Utah and, possibly, western Montana this fall and I'd like to do it in a rented Deville.

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Happiness is owning a Cadillac with no codes.

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Has anyone ever seen a warning to TURN OFF THE AC before? Mike

There are two or three places around Death Valley in California where they have those warning signs. They are generally located at the base of grades that go from near sea level to fairly high altitude in the desert where temperatures reach well over 100 degrees in the summertime.

How much did it cost to rent the Deville? My wife and I are planning a driving trip to Utah and, possibly, western Montana this fall and I'd like to do it in a rented Deville.

The DEVILLE was $400 for 5 days from AVIS. The IMPALA was $229 so it was QUITE an $UPGRADE$, but as we know well worth it! :) Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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The DEVILLE was $400 for 5 days from AVIS. The IMPALA was $229 so it was QUITE an $UPGRADE$, but as we know well worth it! :) Mike

Ouch $400 from Avis? I know that the rates vary from place to place and time to time, but that's on the high end.

In the southwest USA, I can usually get a Deville for $322 per week, or an Impala for $180 or so. I drove a Mustang convertible all last week out in LA for $260.

Forgive me if you already knew this, but if you sign up for the Avis "Preferred" service, the rates are a bit lower. They also take you right to your car without having to stop at the desk. It's a pretty sweet deal. They also offer special promotional fares to preferred members from time to time if you keep your eyes pealed. It's worth signing up even if you don't rent that often. www.avis.com

Some even cheaper rates are available from some of the off-name companies. www.orbitz.com is a good place to look. Most of these companies don't have caddys though and sometimes the cars aren't that great. I usually stick with Avis.

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The DEVILLE was $400 for 5 days from AVIS.  The IMPALA was $229 so it was QUITE an $UPGRADE$, but as we know well worth it!    :)  Mike

Ouch $400 from Avis? I know that the rates vary from place to place and time to time, but that's on the high end.

In the southwest USA, I can usually get a Deville for $322 per week, or an Impala for $180 or so. I drove a Mustang convertible all last week out in LA for $260.

Forgive me if you already knew this, but if you sign up for the Avis "Preferred" service, the rates are a bit lower. They also take you right to your car without having to stop at the desk. It's a pretty sweet deal. They also offer special promotional fares to preferred members from time to time if you keep your eyes pealed. It's worth signing up even if you don't rent that often. www.avis.com

Some even cheaper rates are available from some of the off-name companies. www.orbitz.com is a good place to look. Most of these companies don't have caddys though and sometimes the cars aren't that great. I usually stick with Avis.

I did not know that their preferred service was cheaper but I will join it ASAP, Thanks. Yes it was expensive I admit, very expensive, but it was worth it when I was on Route 17 where the speed limit was 75 and everyone was doing 90... :lol:

I will look into the preferred service, usually I rent from Hertz... Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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