Coolant discharge from overflow tank

My wife was driving our 97 XJ today (154K miles) . When she got home she told me it was leaking coolant . When I checked it out it appears that the coolant discharged from the overflow port on the recovery bottle.

Here is the strange part. The coolant level is still at the full mark, where it always is. The temp gauge stayed at the normal 200-210 range. In December I replaced the radiator, water pump, thermostat, radiator cap, and all hoses.

Is it possible that I had air in the system , that caused a temporary temp spike and blew out the coolant ?

Yea, those closed systems work in odd ways. Mine will purge water here and there until it's comfortable, but my water level never goes down either. It could be the summer heat has made it run just a tad hotter, which would make it purge a little more, I wouldn't sweat it unless the problem persists or the temp gauge starts creeping up to the redline.

EDIT: My bad, didn't look at your year lol, you don't have a closed system. I still wouldn't worry about it much, but may check for small cracks in the reservoir, they can be tricky. Fill it up with water and let it idle til the t-stat opens, see what happens. I traced down a leak this way and simply slapped some JB weld on the darn thing lol. Those cracks tend to be tiny.

He has a 97...that's an open system....

Ya, you might just have a crack in the plastic bottle....check the hose ends too, i actually got some hose clamps for the ends of the overflow hose, cause i was leaking just a tad on both sides - replacement hose just didn't fit tight enough...

can you tell how much coolant leaked out? Was it just a little bit or did it leave a huge puddle?

Yea, good point, i forgot i did the same thing. Replace the hose clamps and if you have the "plier squeeze" kind, ditch em and get the screwdriver kind. My Jeep was very picky on hose clamps lol. I finally got the right tension and whatnot on all of em, and now i can floor it everywhere and it won't leak a drop.

I replaced the over flow hose when I did the other hoses. I also used a small spring clamp wher the hose attaches to the bottle.

I am pretty sure that the coolant came out the over flow spout. It was wet and there was coolant on the metal bracket directly below the spout where the bottle attaches to the bracket.

The amount of coolant leakage was probably a few onces. Not just a few drops.

Another thing to try is to put a bit of turning strength on that cap when you put it on. My old cap would actually spin off and begin to re-thread, and upon closer inspection it was actually cracked in a few places, but it was hard to see. I got another one at a meet and greet from a buddy of mine for free, but even if you had to replace it completely i can't imagine it'd be more than 10 bucks.

Remember this is an open system. The cap is not a screw on . It just snaps in place.

Still wondering if I have air in the system.

Jeeeeeez, I already forgot LOL. Sorry, brain is not working today.

Skwerly, No problem. I appreciate the suggestions.

Bump.

If the system is working properly and the fluid is correct, the only thing that I can think of that would cause the coolant to overflow the reservoir tank is if the coolant boiled over, that usually does it.

BUT, a bad pressure cap could let a big surge pass the cap and into the bottle spraying fluid out of it. As well, a bad pressure cap that doesn't hold 16PSI in the system can cause the system to boil over at a much lower temp.

Bad fluid can allow a boil over, the old conventional green anti-freeze is supposed to be changed every 2 years. If its older, it may allow the coolant to boil at lower temps.

Any leak in the system (on the pressure cap side, since its an open system) would cause lower pressure which let it boil sooner.

The open system, you need to check the fluid level in two places. Every time you drive the car (warms and cools) the fluid expands and contracts, the excess is forced past the pressure cap and into the reservoir. When the system cools, the fluid contracts and the vacuum pulls fluid past a little valve in the center of the pressure cap back into the system from the reservoir. If anything goes wrong with that coolant recovery system, the slightest leak, that tiny flimsy valve in the pressure cap fails, it will NOT draw back fluid into the radiator.

So, from time to time, you should pull the radiator pressure cap and check the fluid level in the radiator is right up to the bottom of the pressure cap, NO air in it. Sometimes the fluid is NOT up to the bottom of the pressure cap, its has some air in there, meaning you need to check out that recovery system and find whats wrong.

A couple onces of fluid can make a fairly big mess and not really show in the fluid level that is nearly 3 gallons total capacity. OR If you have a coolant recovery problem, air got into the system and thus the reservoir level is correct, but the fluid is low because all the missing fluid was replaced by air in the system now, pull the pressure cap and check.

One more to consider, clutch fans go bad after a couple of years and its tough to tell they're bad. The worst part about them is they fail only part time or intermittently, usually work great at low temps but at high temps they stop working and cause an overheat. So maybe a bad clutch fan caused a slight overheat and boil over, and once it cooled back down the clutch fan "seems" normal again.

If any maintenance is due for your cooling system, I would do it now. New Anti-Freeze mixed 50/50 with distilled water, a new thermostat and pressure cap. Check over for leaks, holding pressure and hoses all in good condition. Flush the system, if there are signs of gunk or scaling in the system, use the harsh chemical flushes, if the system looks good, then just drain fully and fill with distilled water and run till its warm and drain and re-fill with new coolant.

Remember, completely draining the system means pulling the plug for the water jacket on the engine block and draining it, as well, pull a heater hose and blow/suck all the coolant out of the heater core.

Remember that now almost all the manufacturers have replace their old conventional green anti-freeze with an "Extended Life Universal" anti-freeze, that is really a derivative of Dex-Cool dyed green. You'll have to search for old conventional green anti-freeze that has silicates and phosphates in the ingredients. If you use the new "Extended Life Universal" anti-freeze make sure you follow the fine print on the bottle and fully drain and flush the system of all of the original/old anti-freeze. The new stuff is getting controversial, since if its NOT compatible with old anti-freeze is it really "Universal" as well, several companies and experts believe the best fluid is what your cooling system was really designed to use.

Rick,

Thank you for your reply to my post.

I did a complete flush back in the fall when I replaced all of the hoses,radiator,water pump and thermostat. I replaced the coolant with traditional green Prestone and distilled water 50/50 mix.

I drove the Jeep today in mid 80s temps and stop and go traffic. The temp gauge never got past 210. After shut down the coolant level was at the top edge of full. After cool down it was at the lower mark of full.

No indication of coolant loss. I will just continue to keep an eye on things after each drive.

Thank you again .
Jeff

The problem could be that your temperature sending switch is pooched. Do your fans kick on?

Fans work fine. The electric one cycles on and off with the AC .

Does it cycle on when the A/C is off and your jeep runs hot?