Getting warm offroad

I have a 2000 4.0 automatic, that I just replaced the head on, 80,000 miles, all stock.


While driving on the road/highway the Jeep runs anywhere between 195-212. Which I assume is normal. (I am using a OBD bluetooth adapter with the android Torque app for gauges, because all I have are idiot lights, for now).

But when driving on slow dirt roads, nothing extreme just mostly fire roads with decent uphill grades, the temperature goes up. With A/C on, the temp went to 226 and with A/C off, it was at 217. These temperatures were measure when going uphill @ about 10-15mph. The weather was high 90's. These seems high to me, is that correct?

I replaced the thermostat with a 195 and new coolant when I drained it to do the head. I checked and the electric fan is coming on.

I am going to do a full coolant flush today and see if that helps at all and get a new radiator cap. Any other suggestions would be appreciated.

Thanks!

Sounds like the thermostatic clutch for the mechanical fan may not be functioning properly.
As the heat increases going thru the radiator the thermostatic fan will engage to spin at 60% engine speed.

Thanks for the help, I just went and checked the mechanical fan. There seems to be a good amount of resistance. I tried spinning it (motor is cold) and it wont free spin at all. There is no side to side play either. Any other way I should check it?

I did notice my fan shroud has been damaged and is missing the lower section, (broke off??). I just ordered a new one, would that make much of a difference?

Thanks!

normal temps for slow speeds.

Start the engine and run it for about five minutes--this allows the silicone fluid that leaks out of the reservoir overnight to be spun back into the reservoir.

Now, see how much resistance you feel in the fan.

Ok, now run the engine--drive the vehicle--for at least 20 minutes to fully warm up the engine and transmission. Drive around town so that the airflow is lower and that will cause the thermal spring to open the reservoir and engage the clutch. Shut off the engine and feel the resistance to the fan's turning--it should be a noticeable difference than it was when the engine had only run for five minutes.

All that said, Digger87xj is right. Hot, pulling grades, a/c on--those temps sound normal to me.

However, for peace of mind you should test your coolant--50/50 or even up to 70 distilled water to 30 coolant in the summer. Don't forget a high-quality radiator cap of the correct or higher pressure. I think OEM is 13 psi; a 16 psi should be fine--I pressure test cooling systems at 20 psi routinely.

Thanks again for all the replies.

If those temperatures are normal for the driving situation how long can you comfortably drive with it that high? At what temp should you give your Jeep a rest?

I noticed a little after I turned the Jeep off after that drive I heard bubbling and saw my coolant reservoir filling up to almost overflowing. After a little while the coolant level returned back down to the marked "high" level. Is that normal?

Excuse all my paranoia over the Jeep, after just buying it and having to replace a cracked head I don't want any big fixes anytime soon.

Thanks!

Replacing the broken shroud should have a impact on the coolant temperatures.

4jeep4 said:

Thanks again for all the replies.

If those temperatures are normal for the driving situation how long can you comfortably drive with it that high? At what temp should you give your Jeep a rest?

I noticed a little after I turned the Jeep off after that drive I heard bubbling and saw my coolant reservoir filling up to almost overflowing. After a little while the coolant level returned back down to the marked "high" level. Is that normal?

Excuse all my paranoia over the Jeep, after just buying it and having to replace a cracked head I don't want any big fixes anytime soon.

Thanks!

Click to expand...

225 is not high. 240+ is high.

a 16 lbs cap will fix the bubble over. use a 95 dodge 1500 5.9 for an application.