Overheating ONLY ON LONG HILLS!
 

So I took my jeep from oregon to norcal and over the pass it started to over heat to the 210 mark, well I got over the pass and it went down a little bit going downhill and I got to the next town.

Got some subway then left to get to my final destination about 30 miles away which was also over a smaller pass. It overheated again this time it went over the 210 mark and I pulled over and the coolant reservoir cap popped off and all my coolant boiled out...:bs:

I let it cool off, ate my subway, and then filled it back up with water. The next day I went for my camp trip which was also up a HUGE hill, it overheated and boiled out the water TWICE... But as soon as I got over the hill the temp went right down again.

Its NEVER overheated on me driving even hours on flat road or city driving or used even one drop of coolant. The guy I bought it from changed the water pump and tstat just months before I got it so those are less than 6 months old, a bright shiny water pump confirms this.

So whats up? My thought is to replace the clutch fan with a nice electric one, cause it seems to be a air pushing issue. Any other thoughts? Thanks!

I don't know why your water would boil out at 210, mine routinely hits 220 in heavy traffic without boil over.

210 is the normal operating temp for an XJ 4.0 I6. but if you are boiling over at normal temp, you gauge must be faulty and you have other problems. I'd be check head gasket, waterpump, t-stat, and plugged radiator. Don't know much about closed cooling systems, so don't know if that has a pressure release cap, like and open system radiator cap.

on my 89, the radiator was to blame for its overheating issues.... typical thing to change out on a old cherokee...

Its been converted to an open cooling system, should have mentioned that. And theres noway 210 should be the normal op temp of any car. Mine normally stays at the line between nothing and 210, and has NEVER gone more than half way between those.

And how would you not know how water would boil over at 210, water boils at 212... and it does it just over the 210 mark.

And as I bolded in the first post, water pump and tstat are less than 6 months old, I also JUST did a cooling system flush a few weeks ago. I also dont think the HG is bad cause ITS NEVER used a drop of water before and oil and water is clean.

Now just to confirm, I have an expansion tank with a plastic 15lb cap and the coolant openly flows through the plastic tank and through the system, that is the open system right? Compared to a metal release cap directly on the radiator with just an overflow tank?

Well jeeps run at 210, its where they are happy. But your system isnt holding pressure and letting the water boil at 212. I'm not familar with converting renix to open system but it sounds like you need a new rad cap to hold the pressure in

oh another thing I forgot to add lol, by the time I got to my final destination after it boiled the water out 3 times, I checked the cap and it had a crack in the side. I sent someone into town to get a new one but on the way out up the hill it climbed to near 210 again... If thats normal than ok... But that seems like a ridiculously high and its never been more than half way between the line and the 210 before, even in heavy traffic.

Hopefully it will be ok, Ill find out when I go over the pass again in a few days.

yeah.... mine runs a little under 210 since I flushed the cooling system. It never goes over 210 though.

What fans are you running? All electric or manual and electric?

Its normal, stock XJ, YJ, TJ, WJ and ZJ with the 4.0L run around 210, I mean the right t-stat is 195 degs. These motors are suppose to run this hot and if you sue a 170 deg t-stat then your not letting the jeep get into open loop/close loop (i forget which is which) but then the computer doesnt read the O2 sensor and it will burn gas and not run optimal

get a new coolant resivoir cap and a band clamp the same diameter as the cap. when the cap is tight on resivoir, put band clamp around cap and tighten. should proabably do

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Now just to confirm, I have an expansion tank with a plastic 15lb cap and the coolant openly flows through the plastic tank and through the system, that is the open system right? Compared to a metal release cap directly on the radiator with just an overflow tank?
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Actually I think you have it backwards...

Open style - any normal cooling system used today. Opposite of closed style described below.

Closed style - has no radiator cap and utilizes a pressure bottle. This style cooling system was used in 87-90 XJs.

oh ok seems like it should be the opposite but ok, and I thought my bmw had an open system but it like the jeep so I guess its called a closed.

anyway I SAID I GOT A NEW CAP.

As I said in first post, I was thinking about putting an electric fan to replace the clutch fan.

A 195 degree tstat, wow wtf, Ive never seen anything over a 180. Well like Ive said 3 times, mine normally ran at the middle between 210 and the next lower line or even lower more close to that first line. So this near 210 thing to me is new. But if thats where its suppose to get up to... I will see how the new cap does over the pass...

Thanks

MYTH - System won't enter closed loop before coolant temp reaches 195F. That's just false and is one of the many, many myths out there. Closed loop occurs when the up stream O2 sensor reaches approx. 600F-650F and with heated O2s, this occurs in less than a minute after cold engine start-up and well before coolant temp reaches normal. Modern EFI engines run clean and lean within seconds of start-up, not 10-15 minutes after start-up when coolant temp reaches normal.:thumbsup:

well either way the jeep is suppose to run around 200 degs, if it wasnt then they would have been that way from the factory. I dont know if i really believe if goes into closed loop after just one min, I'm pretty sure it waits untill the motor is at operation temp

To the OP, I think you have the wrong cap because you said it would boil over into your overflow bottle. Thats not suppose to happen with an open system and the fact that the coolant is under pressure prevents it from boiling.

I said my cap had a crack in it, I replaced it with a 15lb new cap and we will see how it does now. Also I guess its a closed system not an open, I didn't know the difference. The expansion tank has been replaced so I thought it was converted cause its not the original.

Also it never ran 200 degrees before so I dont know whats up. Im still gonna put an electric fan in place of the clutch fan, they sell kits on ebay for like 60 bucks and Ive been using one in my bmw for over 6 months now and it works good.