I just recently started having a problem on my 99 xj, with my radiator cap leaking coolant when it gets to operating temp. It doesn't overheat but that's only because I keep adding distilled water almost every day. It doesn't spray out or anything like that, just drips out quickly when it gets warm.

A little background... I just bought the jeep a few months ago and about a month ago I took the radiator cap off to check the coolant. I found out the guy I bought it from had used tap water and there was a ton of build up on the cap and the coolant was not even recognizable as coolant. I drained the radiator then refilled it with 50/50 coolant/water. I also replaced the cap.

I already replaced the new cap thinking it was the problem. I know the xj's are kinda notorious for cooling system issues. Can anyone help me out?

 

Well, even though you drained it, there could still easily be a potential that there could be gunk buildup inside the radiator, and depending on how long the tap water was in
there, it could have started rusting the radiator.

When you drained the radiator did you use the little bolt on the passenger side of it to drain? If so, did you twist it all the way back in?

I would personally have the radiator checked, not just the coolant itself. You could also check to see that all of your hoses are on all the way, and they have no cracks and aren't collapsed.

 

Oh, I forgot to mention... it leaks from the radiator cap/fill neck. I didn't really make that clear.

 

Possible that the threads on the resevoir tank are damaged? Pressure test for a tight seal. Also did you burp the system when you refilled it?

 

Took it in today to get pressure tested. They said the water pump is leaking. Would this cause the problem?

 

Could certainly be. My WJ sprung a leak in the water pump gasket and caused the symptoms you describe. Change it out and report back.

 

Alright. I just came out to start the water pump replacement and noticed the lower radiator hose is completely collapsed. When I took the radiator cap off it came back open. What the hell is going on?

 

Kinda sounds like there is a blockage somewhere.

Did the hose pop right back out when you pulled the cap or did it slowly pop back out?

Have you flushed your radiator recently?

It may be the radiator clogging and not the water pump. Coolant flows to the pump from the radiator.

Is kinda like sucking on a straw, suck on one end with your finer over the other and it collapses, remove your finger and it opens.

 

It popped right back and sucked a bunch of air with it.

I haven't had it flushed yet. I'm gonna go ahead and replace the pump, thermostat, and lower hose and see how it is. Will most likely get the whole system flushed next week.

 

Replaced the pump, thermostat, and lower hose. Now it's spraying water out of the cap. This is a new cap!

 

......but is it the right/correct cap? Is the neck of the rad (the sealing surface) smooth/not cracked/split? That ain't the right color of coolant, don't continue to neglect the cooling system as the PO did.

 

Are there different caps for this radiator?

Neck is not cracked and clean.

It's not coolant at all. I used distilled water. Not trying to waste coolant til I get it solved.

 

This can't be good

 

first, That is some NASTY brown crude coming out of that cap!
Second the new cap is rated to 16psi, if it blows like that it is because there pressure problem.
Rip that sucka apart and DIY new cooling system.
It's NOT HARD, I'm dumb and I did it in one day. ALL OF IT, nothing left out.

If you have plans on keeping it for a long time and need it reliable then do it right or do it twice.

 

Boot move on my part. The cap wasn't tight. I hate plastic radiators.

I'm gonna replace the overflow hose and flush the whole system. See where that gets me.