Car runs warm after extend time on the highway

[SuperSonic05]

I am not sure if I should even be worried about this but I have been having cooling issues since my cooling fan resistor when bad in the fall. A few weeks ago, it was again over heating because I had a leaky coolant reservoir cap. Now that I’ve replaced cap I notice that drives of 30mins or more at constant highway speed, the temperate will start creeping to the hot. The max I’ve seen it go is almost 3/4 of the way over. All I have to do to cool it down, is take my foot off the gas for a little bit and it come right back to center. Also the temperature doesn’t rise when I am in stop and go traffic. I was sure that if there was a real issue that would be where I would see it.



I also change the coolant and thermostat after replacing the cooling fan resistor.



Is this normal or something I should be worried about?

 

[Sky Render]

Did you have to redo any wiring when you changed that resistor? I've seen this happen on vehicles where the fan is running in the wrong direction. On the interstate, the fan would be "fighting" the air being pushed through the radiator by your speed, but in stop-and-go traffic there isn't enough speed-induced airflow to matter.

 

[SuperSonic05]

The fan is blowing the right direction, into the engine bay.

 

[JeremyH]

Your thermostat may be sticking.

 

[SuperSonic05]

great, I hated installing that thing. I went through three gaskets to finally get it in right.

 

[Chrome61]

Yours got a gasket? Mine has a o-ring.

 

[Marc s]

If it overheats at highway speeds, it's a coolant flow issue (thermostat or plugged radiator).

If it overheats when stopped but is fine at highway speeds, it's an airflow issue (fan).

 

[SuperSonic05]

If it overheats at highway speeds, it's a coolant flow issue (thermostat or plugged radiator).

how would I know which it is, thermostat or plugged radiator?

 

[Marc s]

Slim chance your radiator is the issue. I would put my money on the thermostat. Also, make sure it's not installed backwards.

 

[SuperSonic05]

I am sure I got it in right, with the spring facing up. Should I just replace it and if I do should I get a 160 thermostat?

 

[mulestang]

Doesn't it go in spring facing down? I haven't changed a T-stat on a 3V 4.6L yet, but that's how it goes in the 3V 5.4L.

 

[SuperSonic05]

http://www.s197forum.com/forum/showpost.php?p=54954&postcount=6

look at Thermostat and Thermostat Housing — Exploded View.pdf

 

[mulestang]

Allrighty then.

 

[JeremyH]

In the picture the spring is down looks like.

 

[gtcs07]

does appear the spring faces down

 

[SuperSonic05]

you guys looking at the 4.6 diagram on page 2?

 

[J.Kidd]

you guys looking at the 4.6 diagram on page 2?

No, they're looking at the 4.0L (six cylinder) diagram. I did the same thing for the first couple seconds. Page to is for the 4.6L 3V V8.

 

[94tbird]

Since you have already checked the direction the fan is blowing, make sure the low AND high speed fan settings work. Some people have blown out one or the other by running the fan with a switch. Also check to see what speeds the fans are set to come on at and they arent too high.

If that checks out try these:

step 1. Make sure you have coolant in there and the system is full and purged of air. Most common problems are air pockets or low coolant

Step 2. if that checks out, remove the thermostat and either test it, or replace it considering they are cheap. Its also cheap insurance by just replacing it. If you have trouble installing it, take the housing out of the car completely, and assemble it beforehand, then place it back into the car and reattach the hoses.

Step 3. You can have a radiator flush done if its possible its a clogging issue. I doubt it but before replacing the radiator for any reason its a good idea.

 

[s8v4o]

Is it possible to install the thermostat backwards?

 

[94tbird]

Is it possible to install the thermostat backwards?

yes but i believe he has already stated he did not