"Normal" Coolant Temperature

I replaced my radiator hoses this weekend, and pulled the t-stat with the intent of changing it. However, it must have been changed in the not to distant past as it looked pretty pristine, and I was having no observable heating issues. So, I put it back, connected the new hoses, filled up the radiator and attempted to burp any air out. (I am fairly sure Autozone gave me the wrong t-stat to change so I kept my old one in)

Now I have been paying attention to the temps (was not so much before), and noticing that, intermittently, my dial starts climbing to just under the red zone, then drops back to mid range. Happens on occasion as I am driving. I had not noticed my temp gauge moving much at all from center point in the past week I have owed the truck. Hooked up my ScanGauge II, and watched the water temp. It seems to run at about 196 or so in the "mid range" of the dial, and when it is at the high point just below the red zone the gauge is indicating about 212 or so (it flashed to 222 once then dropped, but my dial on the truck never hit the red zone). Then as the needle drops I see the gauge drop back to 196/197 or possibly a tad lower.

I will pull apart my upper hose again tonight to make sure I did not cock up something at the t-stat, but what is "normal" and "hot" anyway? Is 196 or so normal under typical driving conditions (no load on the truck, 5th gear highway driving)? 2.7L 4x4 but I have yet to put it in 4 wheel to try that out.

Earlier that day I was climbing a grade and was in 2nd gear a bit longer than I have been in the past, and my gear shifter got pretty warm - even the knob. Since I had the hoses out, coolant drained and t-stat removed I am paying a lot more attention to the temps than I was, so not sure if this is new behavior or just "normal"; but I would swear I never saw that dial move past mid point in the past, and now it is climbing then dropping.

Just a side note: I also changed all the belts with new ones, and had pulled the radiator as I was flirting with getting a new one anyway. Since all that was out I had pulled the fan off to make changing the belts easier, and when putting back in the radiator managed to push in some of the cooling fins a bit on that back side. No leaks, but a small amount of fins in an arc are pushed flat on that back side (I did a DUH moment when I tried to put the fan back in with the radiator in first, so made contact as I was moving the fan in and back out). I realize this will change the cooling ability a tad, but can't imagine it would cause any noticeable difference; very small area affected.

 

Over the years I've changed out a few thermostats. Its kinda tough to tell if one is failing. I even remember getting a new one and it was actually faulty. It might look ok, but looks are deceiving when it comes to thermostats. Test it out first in boiling water to see if it opens. Then you'll be sure that its working properly.
As for the temp, I think 196 degrees should be ok & it will go up or down as it opens & closes as needed.

 

If a few fins make the difference between normal and overheating, you have bigger problems. A thermostat is usually either good or bad, not much of in between. I guess if it's somehow sticking it may be slower to move but that's about it.

196'ish sounds about normal but it should say somewhere in the manual what temp thermostat to use. It's main job is to allow cooling at 1 temp, where it should stay pretty steady once it reaches. Fluctuations sounds like air in the system.

 

I second that the system isn't completely purged of air.

 

^^^ what he said.

 

what is the temp of outside air and where you in stop and go traffic when it hit 222,I like my scan guage also and in the summer it fluctuates from 186 to maybe 222 but thats a little high if its atthat high a temp Im in stop and go traffic in like 105 outside ambient temp but on the highway itll go all the way down to 186 sometimes. also to purge air out I usually fill the rad leave cap on but not clicked air tight and run it for around 15 minutes with heater on at operating temp say its a 185 degree T-stat run it at T-stat open for 15 then top off fluid and good to go,also usually T-stats fail either open which would run cool or closed you would overheat. I think its working correctly but I would spray compressed air through your radiator to clean out the dirt and it takes time but you can bend those fins back to say 75% fixed and fin combs suck dont wast your time just use a pick and dont puncture anything..hope I help maybe just a tad..

 

That has been my running assumption, that there is air in there and I am hitting air pockets, the temp rises until the air is past and then returns to normal. I'll go through the bleed process again, as I did run the heater on full with the radiator cap off, for awhile anyway, but never saw any air bubbles come to the surface. I let it run long enough to allow the t-stat to open, I thought, but maybe not. I'll try it again.

 

Ambient temps were in the upper 80's or so, and at night when I noticed the ScanGauge hit 222 it was in the low 70's, no traffic, just cruising in 5th gear. I probably did not run the engine long enough to get all the air out is my guess, so that is my next run at this.

 

OP, is the jiggle valve in the 12 o'clock position? Also try this, drive the truck up onto blocks or ramps if you have them and start the engine and let it get up to temp.

The theory behind this is that trapped air will rise to the highest point thus circulating through the block and finding its way out to the radiator. I have done this with success, but I normally do it when I'm filling the radiator with coolant after a T-stat change, not after the fact. I haven't experienced any troubles since doing it this way. Hope this helps and gives you a simple solution.

 

I had an air problem a while back, even on an incline i couldnt get it out. Walmart sells a prestone flush kit for about a buck, installs a t in the upper heater hose so it is always the highest part. Took 5 minutes to install and 1 minute to purge the air.

 

mine are usually in between 194-212 depending on the temp outside

 

I'll check the jiggle vale, I very well could have not positioned it properly. And I'll try the blocks idea. Thanks!

 

My truck runs at 185 degrees in town. When its 90 degrees and I'm driving 70 up into the mountains (high stress) it will peak at 200.

 

The jiggle valve is supposed to be at the 6 o'clock position. I was seeing a 10 degree increase due to the juggle valve being in the 12 o'clock position. At the 6 o'clock position my temps are pretty much 190 then increases a small amount when in stop and go traffic. At the 12 o'clock position normal temps were 200-205 and then closer to 215 in stop and go.

My luck for getting air pockets out has been to rev the engine between 1500-2500 RPM while in park or neutral, after filling the cooling system, until the air through the vents comes out hot. I have yet to see this fail.

 

Mine is always 186-190, NEVER goes above 190 even on the hottest days....

 

XR, if I read OP's post correctly, he has a 2.7 4cyl engine, and the jiggle valve should be at the 12 o'clock position. The 3.0/3.4 6 cyl engine has the jiggle valve at the 6 o'clock position as yours does. No?

Just trying to get him the correct information so he can solve his problem.

 

I did miss that part of his posting so I apologize.

At least the part about increasing the engine RPM and getting hot air to blow to help purge the system can possibly help.

 

I agree. Get that water flowing to purge it is a great idea.

 

Well, my jiggle valve was at 12 - wish I had x-ray vision to avoid the inevitable coolant mess there! I noted that the radiator was low on coolant, so it must have purged some air out when I was driving it, leaving a nice air head on top of the radiator. As I went back to the parts store to grab extra coolant it struck me - I probably filled that thing with concentrate Prestone, not the 50/50. They are right next to each other, same yellow bottle, just different color label. Went home and yep - the concentrate empty laying there all "WAHT UPPP!!!!" like. DOH. So I ran that thing 100+ miles with full on concentrate, not a mix. And the air pocket. I had not removed all that air and topped it all the way the other night.

I emptied the radiator, again (nice flush by now, considering I have run 6+ gallons of coolant through the thing now!), filled it all the way this time, and let that sucker run with the heater full blast for some time. Could never get it to go over 188 with the heater on, when I turned it off I could squeak up to 193. Turned the heater back on and dropped back to 186ish after a bit. So not sure if my t-stat ever opened up, unless the heater going opened it up.

Going to drive it to work tomorrow to see if I notice the needle fluctuations.

 

yeah its interesting, coolant doesnt cool that well,but it has a excellent freeze protection water cools much better but will freeze, so depending on where you live will tell you the amount of protection you need, straight water cools much better but has no lubricants or anti corrosive agents that coolant has, therefor a mix is allways ideal.