jabeaudett

So I have recently re-geared from 3.21 to 4.88s. Ever since my re-gear, my engine seems to be running warmer. When sitting still at idle, my motor will run around 225 degrees. Once I get moving it drops to around 212, but its cold here in Maryland so that makes sense. Before the re-gear I would pretty much run around between 205 during idling or moving.

I am just curious if anyone else has experienced this and if I need to look into replacing my thermostat or doing a coolant flush or any other advice. I understand with the new gears I run higher RPMs, but my temp starts to creep while at idle. Just want to figure out if there is an issue before summer comes around and I have a tough time cooling my motor.

Thanks for any help and advice!!

jedg

That's odd on a couple points. First, regear shouldn't have much (if any) effect on engine temperature. Also, dropping from 225 degF to 112 degF isn't even close to normal (even if it's really cold in Maine).... that's below normal operating temperature. If it's really reporting that much change, I'd start looking at the temp sensor not working correctly.

jabeaudett

Yea I didnt think the regear should had any changes on the operating temp. I will look into testing my temp sensor see if that is the issue. Thanks for the help

resharp001

LOL, surely the 112* is a typo, and he meant it drops to 212* That would make some sense to me. I monitored my fan this summer very closely and noticed on my '13, the fan kicked on around 224*, and turned off around 210*, so the range makes sense. I regeared years ago from 4.10 to 5.13, and I think my 3.6L definitely runs hotter than it used to based on the RPMs now.....although my climate is much hotter here in Texas. I never monitored my temp well prior to re-gearing, but I'd say my avg is now in that 220-225 range and swear it was much lower before.....more ike 210, but I don't have hard proof of it.

jabeaudett

Ha yes you are right. I definitely meant 212. I will make that change. But yea sounds like you are experienced the same thing. Ill change my resistance on my sensor just to make sure my sensor is still good. But sounds like your system did well in summer and no issues. That is my fear is my jeep is fine with its 30-40 degrees outside, but when it is 80-90 degrees I have overheating issues. I need to monitor when my fan comes on and off as well.

resharp001

There is one more piece to my puzzle i guess.....i replaced my radiator this year with an OSC radiator rather than another factory unit. I started monitoring things closely because I DID have a few issues over the summer. This summer, when temps crept up well over 100*, I did catch the jeep running all the way up to 240* a couple times Granted, I run ~3k RPM at interstate speeds. I also head up in to Colorado, and went to Moab this summer. I noticed a couple times on long mountain climbs the temp would start creeping higher and I'd back off the skinny pedal a bit. I really can't say how much of this issue might be the different radiator, and how much of it might just have been abnormal circumstances. I'd say the heat this summer was definitely more than we usually have here in DFW. I personally think my jeep runs a bit warmer than it should, but still within a "normal" range for the 3.6L which seems to run on the hotter side. I think you're ok, but would continue monitoring it. If I recall, my fan also kicked in to high when temps got up above 232* +/-

Rednroll

jabeaudett, when you did the re-gear did you also program your JK with the new gear size via Flashcal, Procal, dealer flash etc? That typically goes hand in hand with a re-gear. Maybe that could be the reason for the change either doing the programming or not doing the programming?

When I look at the temps you posted, they don't seem to be out of the norm to me. However, I have the 3.8L where I find it normally runs around 212deg F and it will raise when I'm sitting still regardless of the season of the year due to heat builds up under the hood when sitting still. Water boils at 212deg F, where I find most any vehicle seems to be designed when fully warmed up to run right around that 212ish temp area. My theory on the reason most vehicles are designed that way is because although coolant raises the boiling point above 212F when mixed with water, in the event your coolant is low, straight water can be used in a pinch to fill the system and not leave you stranded.

Are you certain about the 205 temps prior to the re-gear or could it be something you just started paying attention to after the re-gear? From what I've read from others, the 3.6L is known to run hotter than the 3.8L, where I'm certain my 3.8L runs pretty consistently at the 212deg F temp.

jabeaudett

Rednroll, thanks for the response. I have reprogrammed with the new gear ratio using my Trial Dash 2.

I have heard that the 3.6L runs warmer than other motors. I will have to start writing numbers down as i see them so i can recall more accurate numbers. I have always paid pretty close attention to my temps ever since I blew a motor by not paying attention to them 7 years ago. Running around 212 sounds about right and I didn't think about sitting still and all that heat just collecting under the hood. I have always noticed that heat will roll out of the hood after a day of use and the engine stays warm for a very long time.

I might look into installing some hood louvers or something.

Again, thanks for the response!

jabeaudett

So just to document what I have done to fix my slight overheating issue.

I replaced the thermostat and the water pump. I also did a coolant flush. This all helped a little bit but not enough to be back to normal. I then realized how filthy the inside of my radiator was. I took everything apart so I can easily access the rear of the radiator and then sprayed simple green all over it, let it sit and then took about an hour to slowly get all of the mud out from the radiator. Once all that was done, my temperature dropped 10-15 degrees. So I am sure I am not the only one that over looked such an obvious issue. I have attached my before and after pictures as well.


This was before I cleaned the radiator. All the mud was killing my heat transfer.

This is after I cleaned it. Looks so much better and breathes so much better!!

karls10jk

The dirty radiator is one that is frequently overlooked because it is still reducing the temperature of the coolant, just not as efficiently as previously. Every time I see it, I think that I should go clean mine up but then ADHD gets in the way and I end up doing everything other than that. Thanks for posting to remind folks not to overlook the simple solution.