I just replaced my fan clutch, water pump, thermostat and radiator cap. Previously, the fan clutch wasn't working at all, and I had a slow leak somewhere around the mounting surface of the old water pump. Finished the job two days ago and haven't seen any leaks since.

I let it warm up in the garage and idle for a little while. Once it warmed up (with the heater on full blast), the temp locked in just above 210 - probably around 212 or so. Never climbed any higher than that.

Drove it yesterday (highway) and it stayed cool the whole time - just below 210. However, I parked it while I was out, shut it off, let it sit for a minute or two, then when I started it back up the idling temperature jumped right back up to that 212ish range. It dropped back below 210 once I got back out on the highway.

Is this normal, or am I still overheating a little bit? I guess I'm just not certain what the standard operating temp should be. Thanks for any help.

 

Yep 210-212 is the normal operating range for these. This is why having a good coolant mixture is important. 212 is boiling point right?

 

What do you mean by "good," exactly? Just an even 50/50 split, or something else of which I'm unaware?

 

Yes... just like you say, 50/50. Some let it get too lean on coolant and this causes problems. Just that little bit of difference that coolant makes in raising the boiling temperature a few degrees is huge in these things.

 

And if the split is heavier on coolant than water?

 

Water cools better than coolant. Coolant raises the boiling point, lowers the freezing point, controls corrosion, and a few other things that pure water doesn't do. Pure coolant would likely cause it to over heat where pure water would run the coolest. 50/50 is the 'standard' mix ratio but many people run higher or lower ratios.

The boiling point of water is 212, but ignore that because it doesn't really matter as far as that number vs. what you see on the gauge. That's the boiling point without coolant and without pressure. The other reason I say to ignore that is because what you see on the gauge is the temperature of the coolant leaving the engine and where you'll likely have boiling issues are at isolated hot spots within the engine. Your gauge could read well below boiling and have boiling happening, it can also read well above with no boiling happening. With everything as it should be the boiling point in your system will be around 260-270 but you'll get boiling at the hot spots well below that temperature reading.

All said, your temps are fine. You'll likely find that after a drive and being stopped for a bit when you turn the key back on your temp will read much higher, then drop fairly quickly after starting the engine, also completely normal. When you stop the engine the heat in the engine keeps heating the coolant that's no longer moving. All engines do it to some extent, some more than others. On hot days I've seen my temp nearly in the red after a heat soak, once I fire it up it settles back to the 210ish area.

 

90Cherokee has it right on. Most coolant manufacturers say you can go as high as 70% coolant safely, but as said before as long as your right around 50/50 you shouldn't have any problems. Higher than 70% and you'll start to run into issues with the lower heat capacity of ethylene glycol compared to water, and much lower than 50% you'll have lower protection for corrosion, freezing, and could run into potential boiling issues.

 

Not only does he have it right on... That is probably one of the most well worded succinct yet comprehensive explanations about how it works I think I have ever read. It is a bonafide short article on the subject!

And you just picked up and added even more important points and knowledge to the base on this... Very well done guys... Thank you...

 

Yep, Cant run pure water in these things. My trouble is the opposite. It never gets warmed up fully....

 

probably a thermostat issue

 

What are the symptoms? It could also just be a bad temperature sender causing an incorrect gauge reading.

 

Pure water can be run in any system, but bad things start to happen. Cars that do racetrack time often run pure water, in some cases the track mandates it, then go back to coolant mix for street driving.

Pure water won't keep an engine from being able to warm up if everything's working right, sounds like you have a bad thermostat or the coolant is getting around it. Troubles with the housing or gasket can let the coolant by-pass the thermostat.

 

That's completely normal. A hot engine that is shut down has no way to remove the heat so it starts to cook. Fire it up and that hot water starts to circulate until the radiator starts doing its job again.

An important last step of finishing a cooling system is to purge out the air. I drill a 3/16" hole in the t-stat base plate to aid with removing the air. The purge and pack of water is quick and easy. Get her hot enough to open the stat and hold the throttle open to around 2500 while adding water mix until she wont take any more. Without dropping the throttle secure the radiator cap. Then fill the overflow tank to the top. After she sits over night, the system will continue to purge and suck water if needed.

 

Good to know. Thanks!

And thanks to everyone else for contributing, too. I've driven it every day since my OP, and so far I haven't encountered any issues. Normal temps, and no leaks that I can see (at least not from the cooling system - still have the rear main seal to deal with).

 

Just an FYI Double check that the rear main is the culprit. I had two shops wanting to pull the engine to replace that seal. After a good pressure washing I discovered the leak was from the valve cover. Replaced the gasket and used "Right Stuff" to seal it up. No leaks after three years of DD