XJ running very warm. Please help!!

I've done a ton of searching but nothing seems to apply to my situation.

I replaced the motor and have since put 600 miles on the new one.
It's been running at 240* on the freeway and around 225* on city roads.

With the motor i installed new water pump, hoses, T-stat, and sensors. I got it running and it runs warm.
Yesterday i pulled the radiator, flushed it and checked flow(good). Filled it and found out i cracked my T-stat housing. Drained it again, replaced with new T-stat, and housing from the dealer.

Today I pulled the overflow and flushed that along with blowing the line clean.
I called the dealer again asking about a new gauge sensor and if the one i got from NAPA was inaccurate. They need to order it and there's now garantee that's the issue.

I have been on the verge of ordering a new radiator but i really want to know that's the problem before spending the money.

Help me out i know there are a few of you with expertise in the cooling area. Thanks.

what year? open or closed sytem?

What T-stat?

Sorry, it's a 94 40L with the open cooling system.

I'm running the 195* T-stat from the dealer now. It has the check ball in the top.

Rule of thumb, running hot on the freeway, radiator is shot, hot in traffic, fan clutch is bad, you may have good flow but that says nothing about the degradation of the core and the ability of the fins to transfer heat. Cores do go rotten. The lower hose, does it have the internal spring ? high flow rates can collapse a hose and starve the engine for coolant.
Did you burp it ? With the open system it's pretty easy, refill the cooling system with the nose pointed uphill, keep the filler neck full while it's warming up and watch the coolant, it will look like fizzy green pop, not like it's got a head on it but just bubbles mixed in, thats air, it will escape as you are looking, the air does not like being mixed in with the coolant so it will go 'flat' just like pop, keep that neck full so you can see it, each time you add coolant the tstat will slam shut and you have to wait, this takes about 20-30 minutes by the way. On the last top off once you can't see any air in the coolant blip the throttle and it will suck in more coolant, quickly top it off and put the cap on, three hands is handy for this Before you do this make sure the overflow bottle is between the cold and hot marks. Over the next few hours of running it will settle out. Replace the cap too, it should be a 16#'er.

Yes, 16 PSI radiator cap! The stores like to sell you 13 psi for some reason.

I've heard of an issue with the gauge sender at the back of the block - you have to buy one from the dealer. Something about the calibration of the gauge with the sensor.....

So once you get that....if you stil notice the temps being hot, you know it's telling you the truth.

I did just as you said burbing the system and i'm getting no bubbles and system seems to be full. My question is when will it pull from the overflow?

I do have the spring on the bottom. I know the radiator is circulating but it doesn't seem like it's moving fast. Should it be noticable. I poured water in and it mixed but it wasn't "fizzilly"

I've got radiatobarn.com pulled up and i'm ready to order. I hope that solves my issue.

$125 for the 2-row
$170 for the 3-row
I know there is mixed reaction on these. Any opinions will be welcome.

The gauge sending switch will be in on tuesday, i'll pick up a new cap also. Seeing as how i bought a 13psi cap from NAPA.

I'll update when everything comes in and let you guys know if it worked. Thanks

make sure you have a shroud around the fan-it does help alot!

Check www.radiatorwarehouse.com for better prices and make sure you get an all metal, brass/copper radiator, I hear some have plastic tanks on the radiator (JUNK!).

When I flush my system I take a hose and put the hose into the end of the radiator hose that goes into the T-stat housing. I use vise grip to hold the radiator hose around the water hose and turn the water on. This back flushes the system and has actually unclogged my lines. I was having problems with getting hot too. After I did this it ran 20-30* cooler. I have an entirely new system as of last year so I new it was all good. Down the highway I run between 160-170 and sitting is about 190 -200. Not sure this will help you but it has helped me. Now that the water is nice and clean I am going to add new coolant and some water wetter. Good luck and let us know what works for you.

lbsnowryder said:

I did just as you said burbing the system and i'm getting no bubbles and system seems to be full. My question is when will it pull from the overflow?

Click to expand...

It will "push" coolant into the overflow when the coolant gets hots enough and expands to cause the cap to release the extra pressure. Once the engine cools, the contracting fluid will create a partial "vacuum" and will draw the coolant back from the overflow bottle.

I've got radiatobarn.com pulled up and i'm ready to order. I hope that solves my issue.

$125 for the 2-row
$170 for the 3-row
I know there is mixed reaction on these. Any opinions will be welcome.

Click to expand...

My 2 cents. I got a 2 core all metal from Radiatorbarn for my '88 last month. Great guys, great service! Had it the next day. Fit like a glove! 'nuff said!

Air in the system, radiator, worn water pump, or the coolant temp sensor on your thermostat housing could be bad as well.......

You've got the thermostat replaced so that's off the list.

Well, good thing it's not my only vehicle. I've got it parked in the garage and taken apart for the week.
The new radiator, both temp sensors, and new cap will be here before i get done working for the week. It's all going in on Thursday.

I really didn't want to throw parts at it but, it's a new motor and i figured starting with all new parts is a good thing as long as it cures the problem.

Once i get this done and out of the way i've got protection, lifting and a spare tire to deal with.

I've had the jeep 3 months and i put a new motor in and installed a rear hitch, JCR stage 4 front, herculined rockers and bumpers, new u-joints, and fluid changes on everything. As well as removed seats and gave it a good shampooing.

How did it turn out? Was it the rad? Mine just started the same thing. Climbing temps at highway speeds.

Ya, what was it?

Everything in my cooling system is new + fully burped and them temp hovers around 225 the entire time I drive. Even gets to below redzone sometimes.

It will stay below 210 for awhile but then it will gradually rise and stay at 225 until you turn it off!

Somebody suggested a worn timing chain could be causing retarded timing which would increase engine temps and such.

I replaced my rotor+cap about 2 months ago and I don't recall any excess play that wasn't there a year ago with the distributor when I had the cap off last summer!

Bah.

Well, it seems as though the problem has disappered with the $$ i droped into it. It still gets a little warm in traffic though. Plugging in my fan might help that though, i discovered it was unplugged while i wired up some foglights today.

I don't know about the timing chain theory but i installed new water pump, T-stat and housing, sensors, hoses, and radiator. I am not upset though because as mentioned before this is a new motor and replacing 13 year old parts doesn't bother me to much.

FYI, the timing is ran by vaccum and self adjusts. You would notice if it skipped a tooth.

Hm. Ok, skipped a tooth - but what about if the chain was a bit loose. Hard to describe.

Rad, rad hoses, water pump, thermostat (jeepoem), thermostat housing (jeep oem), fan clutch, heater valve, rad cap, and gauge sender (jeep oem) are all new. Flushed the system a few times (even used a chemical flush last year). Everything was fine and it ran cool last summer!

I also replaced the coolant temp sensor on the thermostat housing. Although it was a used one I had. That's the only thing that wasn't brand new.

I even replaced the fan clutch and thermostat again to verify one of them wasn't to blame.

It doesn't matter where I drive - highway or city. And it's not like I have an airflow restriction infront of my radiator. 4 lights and a pushbumper. Last summer, had the same stuff - it ran cool.

It'll stay below 210 for awhile but then rises. Like it will stay below 210 for a long while. But after that, it rises. That's why this problem doesn't make any sense. City, or highway.

I just installed a CSF three core brass radiator and Flowkooler pump in mine, flushed the system really well, and the overheating problem is gone. I started with replacing the fan clutch and bypassing the sensor on the electric fan so I can turn it on with a dash switch, then upgraded the rad and pump.

Mine was fine last summer with the radiator I used. Flushed it really well a few times too!

Blaine B. said:

Mine was fine last summer with the radiator I used. Flushed it really well a few times too!

Click to expand...

How old was that radiator? They get to a certain age where you can't flush them clean enough to maintain the same cooling capacity. You can take them to a rad shop and have the tanks removed, the core replaced or rodded out, and tanks re-brazed on, but by that time and expense you may as well just buy a new or aftermarket one.