: thermostat options

08-07-06, 12:48 PM
hey guys, it's been a while since i've posted here. I used to have a 92 4.9 eldo, now I have a 99. My 92 ran hot for about 2 years and every shop I knew of told me it was normal. I eventually found a 160 degree thermostat and it ran cool from then on. But I think I was too late because by then it ran like crap and I sold it before it "popped". I now have a mint 99 with 69,000 miles on it and it runs past the middle mark on the temp needle. when I pop the hood you could fry an egg anywhere under the hood. It doesn't overheat but I suspect the hotter running temp may contribute to the head gasket problem I hear so much about. I ran across a Stant 180 degree for my year N*, anyone here using one and does it help?

08-07-06, 09:44 PM
How far past the 12:00 position is it running?

08-08-06, 04:05 AM
a little past 12 at redlights and right on it at cruising. In midday heat with a/c on it gets about 2 nickel widths past it and stays there for a minute or two. My 92 did the same thing so i just quit using the a/c. Now i'm feeling the same way about this one. I guess my question is will a lower temp. thermo make the n* run cooler or will computer settings keep it running above 200? I don't see why running in the 180 to 200 range instead of 200 to 220 or more, would hurt things. seems like it would last longer if it wasn't always so hot. Any help with this would be greatly appreciated.

08-08-06, 06:42 AM
200-220 is perfectly fine for the N*. Your cooling fans dont even kick on until the engine gets to 224 unless the A/C is on, then they run all the time. Mine runs between 198-206 unless I am stopped for a bit. Then I have seen it reach 220 on a really hot day. But it comes down really quick once I start moving. And I use my A/C all the time.

08-08-06, 06:42 AM
The standard thermostat for a N* is a 180 deg. Remember, the thermostat is on the return side of the cooling system from the radiator, that's why normal operating temperature is 200-225 with a 180 stat.

AC Delco # 131-128 (no gasket)
# 12TH11D ( includes gasket)

Stant # 14228 comes with gasket. Stant manufactures AC Delco's Cadillac thermostats.

08-08-06, 08:47 AM
As a side note, a while back I blew the heater core in my 96DeVille. I've pulled the hoses and joined them together - by-passed the core till I can replace it.

The thing is I am seeing my DeVille run 5-10D cooler now. I run at 196+- at turnpike speeds [75-80] even in this hot humid weather. In traffic I've seen it run up to 222D, but then it drops as soon as I move on. It also takes a bit longer to come up to operating temp on a cold start.

Prior to the core going I would run at 206-212 at speed. The temp seemed to flux all over the place. It still moves around, but I'm seeing temps more in line with what I would expect in a V-8. I just returned from Virginia and was seeing the temp drop to 194!! I'm thinking that could be toooo cold. Never saw that after the engine was up to temp and that was at 75MPH w/ 98D outside temps. Go figure???

So, the heater core seemed to have an effect on running temps. Why it has smoothed out with it removed I can not figure out...........

Clarkz hit the mark. I don't think you're running too hot, and I would be cautious in changing the thermostat. Replace it with the spec unit if you feel it is at fault, but there are other things effecting the engine temp.

I run A/C all the time. I have tried to see if it effects running temp, but see no difference aytall.

08-08-06, 10:50 AM
I have to agree with everyone else. Your temps sound normal. My '97 Deville had a digital temp readout and it ran 206-213. I'd stick with what the factory engineers put in the car rather than trying to re-engineer the cooling system.

08-08-06, 04:18 PM
According to the Great Guru, an enormous effort was put into the design of the North*cooling system and it is unique. Any previous experience with any other engine is of no relavance. The flow rate is way beyond any other engine and the temperature control by the thermostat is apparantly backwards but works very efficiently. Keep it like the designer intended.

08-08-06, 09:21 PM
My aunt boyfriend put a 170-175 therm in a 98 etc try to get a hp bump. Anyway there was no ill effect. If i was u I would leave it stock. My deville stays around 217 no problems

08-09-06, 02:48 AM
Thanks for the help guys.

08-10-06, 10:31 AM
Just to help keep you at ease, I've been driving around Atlanta in the middle of the day when my outside temp gauge is registering 105° on the highway, and at 75mph with heavy traffic I see my car run around 220°, sometimes as high as 230° for a second or two up a hill due to poor airflow, but if the temp is just 10° cooler, or there are less cars on the road the caddy sits at 196-202°. Another thing is that the middle tick mark represents temps from 196-218° or so my digital readout supports this, the first tick mark beyond is around 230°.

08-12-06, 04:40 PM
.... I don't see why running in the 180 to 200 range instead of 200 to 220 or more, would hurt things. seems like it would last longer if it wasn't always so hot. Any help with this would be greatly appreciated.

It is desireable to operate the coolant and the engine and therefore the oil at temperatures that will vaporize the moisture (a by-product of compression), unburned fuel, and other nasty stuff out of the crankcase.

Stick with the OEM specified parts.