03 LS 3.9 replaced thermostat, but still not heating up

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blazincopper

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Last week I noticed my LS not heating up to temp, so I replaced the thermostat. It is still not heating up. It will heat up at idle, but once you start moving the temp starts dropping. I think I put the thermostat in right, it has one of those 3 piece thermostats. Anyone have any suggestions or even a diagram of how the thermostat goes in. I'm pretty sure it is in right, but I don't understand how it works.
Oh yeah, the fans are not running. Any help would be great, Thanks
 
It's possible you had two defective thermostats in a row or you did install it wrong. That definitely sounds like a thermostat problem to me. The LS cooling system is a little weird so maybe someone with more understanding of the v8 will help better.
 
"Oh yeah, the fans are not running. "
I see this statement (or similar) every so often here, and it bugs me. The [stock] LS has only one cooling fan. If you have more than one, then someone has modified your car and that may be the source of your problem.

If you didn't find the thermostat difficult to push together, then you did it wrong.
Here's a diagram and some instructions.
http://deneau.info/ls/s6x~us~en~file=s6x33007.htm~gen~ref.htm
 
Simple question, what is the standard operating temp anyways?

On my dashhawk I see between 180-185 and it takes a while to get there.
 
a way to check the thermostat before or after you take it out to make sure its good is to boil a pot of water for about 10 minutes, then drop in the closed tstat, if it expands within 5-7 minutes, then the tstat isnt the problem, take it out, cool it off until it retracts, then move on to the next thing it could be
LJ
 
smdandb2 said:
Simple question, what is the standard operating temp anyways?

On my dashhawk I see between 180-185 and it takes a while to get there.
Click to expand...

The service manual says that the thermostat should start opening at 192 F. I believe that up to 219 F is not considered overheating.
 
joegr said:
The service manual says that the thermostat should start opening at 192 F. I believe that up to 219 F is not considered overheating.
Click to expand...

LOL, in the summer I see upwards of 230+ at times.

So yeah, if my car never even hits 190 in the winter my tstat has probably seen better days.
 
We have had some pretty cold weather lately in Florida and mine too doesnt reach full operating temp. On a few occasions it threw a P0128 code, which means its not hitting operating temp. The temp gauge usually sits right at 9 o'clock, but lately with the temps being in the 30's-40's it hovers between 7-8 o'clock. The heat works good and heats up pretty quick but i noticed if i turn the heat off the gauge will rise slightly. I've got 121k miles and i figure the t-stat is going bad but i'm not too worried about it short term.
 
I took the Tstat back out and I think that I had the middle spring on backwards - I turned it around and it seemed to help alittle. I can let it warm up in the driveway for about 10 minutes (gauge will get up to about 8:00) and get in it and drive on the highway and it drops to about 7:00. It was about 10 degrees outside this morning, so I don't know it that is normal for a Lincoln or not. I know most cars will come up to temp in about 10 minutes. Are other people seeing this or do I still have a problem.
 
Like LJ said putting the Tstat in boiling water is a good way to make sure its working properly. I live in MN and mine goes to the same position it did while driving in El Paso Texas in the Summer, so I don't think the chilly weather in the South is going to cause your car to run cooler. If the Tstat is good, then you likely have a bad temp sensor sending unit.
 
185F in boiling water

As Lincoln Jealous stated, put the thermostat in boiling water. I tried this suggestion from this post and had the meat gauge in the water to check temp...when the gauge reached 185F the thermostat began to open.
 
Re-install the thermostat according to the diagram Joegr posted.

Then if the needle doesn't come up to roughly 9:00, but you feel plenty of heat out of the vents, and you're getting normal power and performance, you may have a bad temp sensor on the engine, or a bad gauge. Most likely the sensor.
 
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