Drastically different running temps with 2 different thermostats

[COShadow]

I changed my radiator, thermostat, rad cap and hoses out last week to avoid the "milkshake" condition. After this my coolant temp would be between 198 and 203F as read from a scan gauge II. I thought this was odd because before this I had run much cooler. So I changed my thermostat back to the old one and now I'm running between 173 and 177F. Both are about within normal operating conditions (176-203F). I kind of like running a little cooler, this will probably keep the automatic tranny a little cooler too. Both thermostats are Toyota parts, both are stamped with 82C. The "idiot gauge" on the dash was centered using both.

1. If you have some means of reading the exact temp (scan gauge or other), what is your coolant temp running at?

2. What is everyone's opinion on which is better, higher or lower temp?

 

[domstriker]

Let me preface this post by saying I'm by no means an automotive expert.

I don't think that coolant temperature is an accurate measure of the engine operating temperature. I've read that the engine is generally 20 degrees hotter than the coolant temp.

I think that the oem thermostat is 190 degrees meaning that it won't open and start cycling coolant back through the rad until it hits 190. The difference in operating temps is probably due to a different temperature thermostat. The important question is: where is the temperature being read for the coolant temp?

Also, there are a lot of old timers that feel that cooler engine operating temps aren't necessarily better.

Do you have the x gauge code for engine oil temp by any chance?

 

[COShadow]

I don't have the xgauge code for oil temp, good idea, I'll try to find that.

Both thermostats are 82 deg C (180 F) thermostats, both are Toyota OEM. Seems strange that there is such a large difference between the two.

 

[domstriker]

I don't have the xgauge code for oil temp, good idea, I'll try to find that.

Both thermostats are 82 deg C (180 F) thermostats, both are Toyota OEM. Seems strange that there is such a large difference between the two.

Maybe that's not the issue then. When you swapped out the thermostat did you completely drainmand refill your rad?

 

[COShadow]

Yeah, I drained it. About 1/2 of what I drained, I collected in a clean container, so I reused it. The other half I mixed right there. The coolant that I reused had only been in there for a week.

 

[domstriker]

That's strange. I guess the only way to know if both thermostats open at the same temp would be to put them in a pot of water on the stove with a thermometer in the water. I think that's more trouble than it's worth though.

Generally, my coolant temp runs anywhere from 160-180 when driving on level ground at highway speeds. Today, we went rafting in Canon City and my coolant got up to 205 on uphill portions.

 

[COShadow]

Yeah, I'm going to keep the older thermostat that runs cooler in there for a while. The real test is the mountains, if I was running at 198 in the Denver area, I'd hate to see what it would be in the mountains.

 

[COShadow]

Well, I decided to try a second new thermostat. It agrees with the first-- engine runs at about 198F. So I'll run with it. Maybe the old one that ran at about 173-177 was leaking a little coolant when closed.

 

[alp]

My SGII reads anywhere between 195 and 205 at the 90 outside and steady highway driving. In stop and go traffic the temperature can go up to 215 that makes me very nervous. The thermostat has been replaced last summer together with the water pump and timing belt. I have recently changed the old green coolant with the OEM red one hoping this will lower the temperature. No changes at all. What if the temperature sensor is not calibrated correctly.
Can you guys post your SG temperature reading please?

 

[Qyota]

Mine used to show high 180's and low 190's. Now it shows high 190's and low 200's (205 being the highest I've seen...hot day pulling a small pop-up camper). Not sure what changed, but I'm planning a full flush and change out the t-stat soon. Toyota red coolant still looks fine.

 

[domstriker]

My new rad just has water in it. I'm still trying to get pink milkshake bits out of my cooling system.

My coolant temp is running 170-180. Hottest I've seen it is about 205.

This thread still has me wondering where the SG is reading the coolant temp.

 

[alp]

My new rad just has water in it. I'm still trying to get pink milkshake bits out of my cooling system.

My coolant temp is running 170-180. Hottest I've seen it is about 205.

This thread still has me wondering where the SG is reading the coolant temp.

Here you go...

 

[COShadow]

Yeah, my water pump was replaced last year, I have a new radiator, new hoses, new thermostat and twice flushed system with new fluid. Still running at 197-202. What else does coolant run through? I'm okay with these temps, but I'm surprised it's running at least 17 degrees hotter than thermostat opening temp. Maybe I'll look into replacing the temp sensor eventually for s_hits and giggles, depending on price and hassle.

My 2006 Tacoma probably has the same thermostat and runs between 184 and 195, so ??? May be apples and oranges though.

 

[domstriker]

Here you go...

Nice...So the ECT sensor reads the temperature near the upper radiator hose?

 

[Qyota]

I bought a new CTS, planning to install it when I do the coolant/thermostat job. Looks like a fuel line (from the right bank of injectors to the left) needs to be removed...and I didn't buy new gaskets for that yet.

 

[COShadow]

Well, I flipped the thermostat that was in my 4runner so the jiggle valve was at 6 o-clock instead of 12 o-clock (FSM says install it at 6 o-clock). Indeed, my running temps went from 202-206 down to 190-193. Should be smooth sailing now.

Thanks 4runnerers