Elexwiz

This past weekend I FINALLY got my XJ on the trial for the first time. My dad gave me my 87 XJ at Thanksgiving. He told me the engine ran great and it was his daily driver for the last several years. I spent the last 5 months working on/upgrading everything except the engine. I was excited to get it on the trail. I've been driving it around since the 2nd week of May making sure everything works properly.

Last Friday we drove to Uwharrie (I trailered the jeep) and got there early enough to get some wheeling in before night-fall. 15 minutes after we hit the trail my upper radiator hose blew! WTF?! A nice 6 inch gash right before it goes through the t-stat. I got towed back to camp and called a friend who was on the way there and he stopped and picked up a new hose, high-heat RTV, and coolant.

The next morning we removed the t-stat, installed the new hose, filled and burped, and hit the trial. 15 minutes later I'm overheating AGAIN! Nothing blew up this time. I checked the e-fan (which I didn't do the first time) and it had 12 volts to the fan, but no workie-workie. Another tow back to camp, jumped in my truck, and high-tailed it to the Advance Auto about 30 minutes away. Soon after I had a new e-fan. Just to be sure it worked we wired it to the battery so it ran all the time. We burped again (just for s&g's) and had good coolant flow as seen in the overflow bottle and stiff coolant hoses all the way around. I don't have gauges, only idiot lights. Since the high-temp light never came on I assumed the sensor was bad so I wheeled for the next 4 hours with the heat on and the hood popped (not open all the way, just popped)! The heat made for a slightly miserable ride but I was just happy to be wheeling!!

After dinner we decided to hit Daniel Trail for some night wheeling. I made it to the top of the difficult side and just as I pulled in and stopped, POW!! The coolant bottle split on the rear seam. We were at the top and only had to go down the easier side so I gathered all the water I could, filled the bottle, and hauled a$$!! We stopped a few times to refill and cool the engine some. Once we hit the road I was towed back to the camp.

I didn't wheel on Sunday. My question is this. My e-fan was on continuous all the time, I had good coolant flow and good heat. WHY did my bottle blow? The only thing I didn't have was the thermostat. I'm skeptical about my water pump, but I did have good heat and a little "geyser" in the bottle when viewed from the driver side with the cap off. What could it be???

Fast forward to last night. I found the temp sensor on the rear of the engine and pulled the connector to check it. I quickly found out WHY I never got the temp light, the wire is broken and was just hanging behind the engine. I can't find the other side. Where does this wire go? Inside one of the bundles or down the back of the engine?

Thanks!

Gee oh Dee

Do you have just the efan?

An 87 should have a mechanical fan and fan clutch. Fan clutch could be bad.

Could also be a bad water pump, even though you said it has good coolant flow.

Or even a bad head gasket.

Elexwiz

I do have the mech fan, which I forgot to mention. I spun the fan and it stopped immediately after my finger came off the fan blade. I believe the clutch to be good.

I don't have any oil in the coolant or coolant in the oil. I didn't mention it but I did check for it. Could it still be a head gasket?

Like I said, I'm skeptical about the water pump. If I'm going to pull it to check I might as well replace it. I'm also considering getting rid of the mech fan and installing dual e-fans.

Gee oh Dee

Idk about for you cuz I get a special discount, but a water pump is like $28.

If your concerned, replace it.

Elexwiz

Another question I have is about the t-stat. I always believed, and witnessed, that removing the t-stat will keep an engine cooler than normal and not allow it to reach its optimum operating temp. I had a t-stat go bad in my explorer (it stayed open) and the engine never got hot, so I barely had any heat.

I learned this weekend (after taking out my t-stat) that running without one can be just as bad. It was explained to me like this; even when fully open the t-stat limits coolant flow keeping the coolant in the radiator long enough to be cooled off before it flows back into the engine. I never heard that before (and neither did some of my other friends). removing the t-stat caused the coolant to remain hotter than it normally would have. Do you think this could be why my bottle burst?

djb383

What u were told about "the t-stat......keeping the coolant in the radiator long enough to be cooled off" is a myth, misunderstanding of how a cooling system works and totally false. A properly functioning t-stat does 1 thing only and that is control MINIMUM coolant temp. The motor needs a t-stat. All of the other cooling system components along with ambient temp and operating conditions control/determine MAXIMUM coolant temp. Might want to ask dad what kind of cooling system maintenance was done, if any. Cooling system maintenance is the 1st thing that should be addressed in an old vehicle.....the cooling system is a regular maintenance item, not a if it ain't broke don't fix it item.

Gee oh Dee

Truth!

Elexwiz

Thanks. I did some more digging last night. Its doubtful that the lack of a thermostat caused my engine to overheat. I say "overheat" because the bottle burst on the last run. I don't know what my actual engine temp was. For all I know the bottle was just old and it was time to go to bottle heaven. Either way, I'm replacing the bottle (duh), water pump, and t-stat. I'm also swapping in a cluster with gauges. Once I get everything back together I will do a proper flush.

I talked to my Dad last night. He had no idea the temp sensor was broken and the e-fan didn't work. The radiator was replaced in March 2011 (and system flushed) because the old one was leaking. That was the extent of the cooling system maintenance performed since he owned it....

Can anyone tell me where the temp sensor wire goes? I opened up the various wiring bundles that are around that area but couldn't find the other end. Its a red wire.

Thanks!

djb383

Don't forget a new fan clutch. Without going back and re-reading, r fans shrouds intact/in place?

Elexwiz

Yup, fan shrouds are in place and intact. I'm still researching the pros/cons of a dual e-fan conversion. Plenty of pros, so I'm on the hunt for cons.

djb383

Be very careful about changing the stock cooling fan set-up.....the weak link in the XJ cooling system is the small/dinky radiator, not the fans. A properly functioning clutch fan, when engaged, will pull way more CFM, at just above idle, than the OE electric fan pulls. Max air flow, at low vehicle speed, and a entire cooling system in top notch condition r key to avoiding overheating.

U might consider converting your closed cooling system to a open system before modding the OE fans.

Elexwiz

Did not consider the CFM difference. Thanks. More research awaits...

itsalwayssunny

Same thing is happening to my XJ, e-fan only kicks on when the heater/AC is engaged. Stays in the 220 - 240 range. Looking to replace the radiator with a HD one. Already replaced the t-stat, t-stat housing, temp sensor, water pump and indicator sensor. temp sensor should be attached to the t-stat housing.

djb383

Replace the rad and fan clutch. '96 down, the temp gauge sending unit is located in the back of the head drivers side. '97 up, the temp gauge and ECU utilize the coolant temp sensor in the t-stat housing.

Elexwiz

Been doing lots of reading today (i love my job) and I am converting to an open system and leaving the mech fan in place (with a new clutch and serp belt for good measure). The only thing I'm stuck on is the radiator. 2 or 3 core? CFS? Champion? I read convincing pros and cons for each one. I'm leaning towards the Champion 2 core. Any suggestions?