Hi,

I've been reading and searching on this forum for the past few days. Still have a few questions about what happened and what to do next.

What happened: I am the 3rd owner of a 98 Sport, 137K miles, I have owned it about 3 months, no problems in that time other than simple brake pad replacement and A/C only works for 30 minutes.

I was driving up a mountain (I live in Utah) last weekend, everything was going good, but temp was climbing up past 210 into the 220 range. I turned onto an even steeper road, had to go slower and higher, and about a mile in, the idiot light came on and I noticed I was in the red. I pulled over and shut it down. Soon I heard the coolant boiling in the overflow reservoir. I popped the hood and visually confirmed this. I also noticed a small amount of steam coming from the right side (if facing) of the motor. I also heard a wheeze coming from the radiator cap.

After about 15 minutes I tried to continue up the mountain, but about 10 minutes later it redlined again. This time I pulled off the road and idled 30 seconds till the temp was back down out of the red and then turned around and went down. I stopped about halfway down the mountain (the temp read fine, I just wanted to stop and hike a while) and it puked a lot of coolant out of the reservoir. I hiked a while, cam back and topped it off with some water and went home.

It has driven fine since, though a few times this week I have noticed that after shutting off the XJ, the coolant is boiling in the reservoir. No more over heating though, the temp gauge is acting "normal" (hanging around 210 while normal/freeway driving, even in 100+ weather.) I have topped off the coolant a few times this week, mainly I think because of all it puked out over the weekend. I have noticed small leaks, from what I think is the radiator near the back of the engine (if facing.)

The coolant is a nice brown color...but I can't confirm if it's oil in there. It doesn't sheen nor smell of oil. The oil itself is very clean and doesn't seem to be leaking. Transmission oil is clean too.

All I have done is replace the radiator cap (did that just a few hours ago). I have not noticed any boiling coolant after a drive and getting up to 210 temp for 20+ minutes. I was thinking that the old cap may not be keeping the coolant under pressure and thus allowing it to boil at lower temps.

Could it really be this simple? It was one of the most common suggestions I found on this forum about dealing with boiling coolant.

If the problem persists, what should my next step be? I was thinking of doing a coolant flush this weekend, since I don't know when the PO did it last. Also, possibly just install the cooling system new, since I want to be able to make it up mountains with this Jeep.

No problems idling, or stopped in traffic. The only times I see the temp go above 210 is when going up long hills/mountains.

On a side note, I have gone up other mountains without trouble, but this was just the highest and steepest grade I have been on. The check gauges light came on during the two steepest parts as well.

I don't know much about working on vehicles, but I'm willing to learn. I really want to make this Jeep last as long as possible and have fun with it.

Thanks

 

Sure. Caps are a regular maintenance item, they do wear out. I'd do the flush too, particularly since you don't know when it was last done.

 

Its a closed cooling sytem so any leaks will cause it to over heat. If you think the raditor is leaking try to confim that. Check the hoses maybe. Also does the fan ever kick in?

 

Yup, the fan does kick on, around 210-220, and will stabilize the temp during normal driving, though doesn't seem to help much going up long hills.

 

yeah pinpoint the leaks and fix whats bad...

 

My bet is on a hairline crack right side bracket of the radiator. Normal day to say driving you're probably not going to see any problems but at higher temps, the increased temps causing it to boil over. Sometimes hard to see these cracks when they're not actively shooting out steam. Get a good LED flashlight in there when it's pretty hot like after a steep hill. The flashlight will show the steam better.

 

Brown coolant is pretty much a dead give away to PO and continued cooling system neglect. Could be 14 years worth of neglect, who knows? +/-$250 buys a complete new cooling system including a new radiator and 99% of the time, complete replacement will eliminate overheat guessing. If u replace it all at once, u only have to do one coolant drain/re-fill.

 

Thanks for the suggestions everyone. I will get to work on replacing the entire coolant system and figure out how much I can do, and how much I need the pros for.

 

Could any of these coolant problems be affecting the A/C as well? I noticed that the A/C hose is laying against the coolant reservoir. It's normally about the time the engine is at 210 that the A/C starts getting warmer.

 

Good chance there's not enough air being pulled through the AC cooler in front of the rad. Could be clogged fins or bad/weak clutch fan. I just refurbed my XJ(new fan clutch among other things) and powerwashed and compressed aired the rad and AC cooler. It made a diff in the AC. My normal op temp went from 210 to 195.

 

An earlier poster said yours was a closed cooling system. It's not, it's an open one.

Brown coolant is either neglect or oil in it from blown head gasket.

 

The reservoir should never be empty though, correct? Otherwise air can get sucked in the system?

 

Yes, never empty and never over filled. 1/3 to 1/2 level, motor COLD, this will allow for expansion into the bottle while driving. On an open cooling system, the rad cap is a 2 way valve and must function correctly to allow some coolant/any air to escape from the rad and allow only coolant to return to the rad.

 

How has your xj been running? Still overheating? Also a good idea to replace your thermostat.

 

Brown coolant = Not good.

As mentioned, either an abused cooling system or possibly worse.

You have some work to do.