Borneo Batman

Hey guys verified the temp guage is accurate with an IR temp gun. I thought about air in the system again so I thought I'd give it one last go before I took it somewhere to have it flushed. I jacked the jeep up so that the rad cap would be higher in the coolant system than any other component, took the cap off, turned the heat on and let it run for almost 1/2 hour. I kept topping the coolant off and opened and closed the cap several times. Once things stabilized I put the cap back on, topped off the overflow tank and let it sit for about 4 hours. With ambient temp in the high 20s I took her for a test drive. I noticed it took a lot longer for it to heat up so I knew I had to be on the right track. Once the tstat opened I got a temp drop of about 25 degrees verses the usual 60! I quick pulled over and verified this temp with the gun. I only had a little needle wondering after that and it only wondered about 20 degrees (from 205 down to about 185). I think I might still have a small bit of air in the system and I'm hoping after a few heating cycles I'll have it 100%. Thanks again for all the help, I guess sometimes the simple answer is the right answer.

I thought about why I couldn't get the trapped air out this time, but had before no prob when I replaced the water pump only. I think the slightly lower position of the vent hole in this mopar stat verses the old one came in to play. The old tstat had the vent in the body of the tstat, this new one has the vent inside the actual moving valve. So it's about 1/4" lower in the new tstat. That's why I hoped elevating the jeep would help. So I'm in much better shape, a few more drives and I hope to be 100%, if not I think a professional flush should do the trick.

Thanks again to everyone, Jason

Firestorm500

Thanks for the follow-up.

CrawlerXJ

Figured that's what it was I put a 1/8" hole in the t-stat to help burb it.

But, glad it's fixed!

Borneo Batman

Hey guys needle was still wondering a bit so I decided to take it in and have it professionally flushed. After my flush I still have some needle wondering (maybe only 20 degrees, from 205-185, but it's very slow and only in town, rock solid on the highway) and I still get the plunge from 205-160ish, but it is slower and only happenes 2x in the warm-up process instead of 4. So anyone else have any ideas or should I just let it go, I'm still a little worried about shock cooling, am I being parinoid? Someone mentioned a restrictor, been thinking that over. Other than that I don't think I can do anything else. I've installed new: water pump (autozone), t-stat (mopar), new hoses and rad cap (autozone), and new fan clutch (autozone), and now a professional flush by a really good shop. Other than adding a restrcitor and trying that route can't think of anything else. Never had this problem before replacing the t-stat.

I think I just need to let it go. May cram a piece of cardboard in the rad (blocking about 1/2 of the engine driven fan size), I know that will help stabalize temps a bit too, is cheap, and easy to undo without opening up the system again.

Thanks, Jason

djb383

Somebody explain "shock cooling" to me. Shock cooling would make sense IF the bypass loop suddenly stopped flowing hot coolant, the t-stat suddenly snapped wide open and a surge of cold coolant from the radiator loop suddenly entered the motor. That ain't the way it happens (the coolant flow throughout the cooling system).

I thought the 205 to 160 had been corrected.......apparently not.

cruiser54

Shock cooling is a crock.
Got a factory thermostat in it?

Borneo Batman

No I thought it was looking like I had it figured out, but no, still does the temp plunge once or twice on the initial warm-up on these cold days.

And yes I have a new OEM Mopar t-stat in it.

Thanks, Jason

cruiser54

Have you verified the temp is indeed dropping? Do you feel a difference in heater output or anything? Could it be the gauge/sending unit is messed up instead?

Borneo Batman

No I have verified temp is dropping. Heat gets a little weaker and checked temp with IR temp gun.

Jason

djb383

This is a stumper (if that's a word). Seems odd that a IR gun pointed at the t-stat cover would indicate a big 60* coolant temp swing. The t-stat cover is where hot coolant constantly exits a running motor, not where cold coolant enters the motor.

Firestorm500

Not meaning to sound disheartening or anything, but if it's not hurting anything maybe we should just accept it does what it does for now?

djb383

Yep, agree that's probably not hurting anything......just puzzeling.

Borneo Batman

Yep you guys are right, I'll let it go. Sorry, I'm one of those **** people that drives themselves nuts when they can't figure out the answer to something! Thanks for putting up with me (a phrase I have to say to my wife all to often).

Thanks, Jason

djb383

Something (the cause) is there, we're just not seeing/picking up on it. We have a ScanGauge on our XJ and the 1st time the stat starts to open after a cold start, temp drops 5* at the most, then quickly gains those 5* back.

cruiser54

I understand. Try not to drive US nuts, and realize it's a very short drive for djb383!! LOL.