Overheated, not sure why; coming out of rad. cap and resivoir!

[Blaine B.]

Hey, was just cruising down the road when I noticed a few droplets on the windsheild. Hey, it's raining I thought, since it was lightning in the distance......then I peered down into my instrument cluster to see the temp gauge reading 260. Oh crap, I say, and pull over, immediately turning the vehicle off.

After opening the hood, I inspect coolant gurgling and coming out of the radiator cap, as well as out of the coolant resivoir.

So I let it sit a little, fill the radiator up with water I had in the trunk, and let it run. The temp gauge cools down to below 210, and the radiator is sucking the coolant back out of the resivoir.

Any ideas why? I didn't know coolant is supposed to leak out of the radiator cap. It is a new cap and radiator as of July, and the cap is one of those with the red lever on top.

By the time I drove the two miles or so and came home, the resivoir was nearly empty, meaning the radiator sucked all of that coolant back in. I filled the resivoir with water.

What should I do, flush the entire system AGAIN and refill with 50/50?

By the way, the pressure cap didn't stick up (the red lever) Isn't it supposed to? Like I said the cap is new as of July. When I opened the hood I lifted the red lever on the top of the radiator cap and it seemed like the pressure relieved itself more quickly.

Any other thoughts? Thanks!

[jeepdude10000]

im guessing that is a closed rad system, that info, along with year would help.

[johnlv6]

Sounds like what happened to me last week...you replaced the thermostat yet?

[PETEY]

If you have a closed loop system (a plastic bottle near the firewall) , a new cap "should" solve your problem. They a cheap and prone to failure. At leat start with that and see if it fixes your problem. They cost about 5 bucks from here:

http://www.quadratec.com/products/product_search.php?kw=overflow+bottle&submit=Go%21

oh ya closed systems in fact do not have radiator caps.

[MY92XJ]

Not to scare you but the same thing happened to us this summer. Unfortuneatly we had to have the head resurfaced cause it blew the head gasket when it cooled down.

We replaced the head gasket,Replaced the thermostat,Replaced the waterpump, Replaced the Radiator and she is still running around 230 on the freeway

BTW......
(hint) :doh: Closed systems dont have radiator caps.

Diana

[xjbubba]

My memory may be fuzzy here, but with a closed radiator system--one with a reservoir that accumulates the excess coolant when the engine gets hot, then feeds it back to the radiator as the engine cools--has a radiator cap specifically designed for that purpose; it should not "vent", accept into the coolant bottle. I'd suspect a bad, or incorrect rad cap.

[Rev Den]

Well...you have a 95...it should have the open system if memory serves me.

I would do the following -

Chage thermostat
Change cap.

and see where that leaves you.

Rev

[Rocketman]

Hell Rev, with all that, might as well spend $60 more and throw on a new water pump too. You have it apart. Probably needs one anyway. Get a Robert Shaw thermo, MANY different names and brands, Part number almost everwhere is 330-195

[xjbubba]

Since the late-model cooling system on my '88--referred to on NAXJ often as "open cooling" I'm not sure if it was really an "open system". A "closed system" vents directly into a non-pressurized reservoir to accommodate coolant expansion as the engine heats up, and then sucks the coolant back into the radiator as it contracts during engine cool-down. The radiator cap does not vent to atmospher, as it does in a true "open cooling" system. I suppose if an engine really overheated, the excess coolant from the radiator would over whelm the capacity of the coolant bottle, even in a "closed system". And I suppose if the wrong, or a bad radiator cap was installed on a closed system radiator, coolant would leak arround the cap, resulting in an overheated engine, and an over whelmed reservoir. I beleive radiator caps are designed differently for "open" vs "closed" systems. The reservoir bottle on my '88's so-called closed system had a pressure relief cap that vented to atmosphere. The cooling system I installed on '88 along with my Cheby engine is a true "closed system", and doesn't vent to atmospher, unless "things" get completely out of hand.

[jeepdude10000]

Since the late-model cooling system on my '88--referred to on NAXJ often as "open cooling" I'm not sure if it was really an "open system". A "closed system" vents directly into a non-pressurized reservoir to accommodate coolant expansion as the engine heats up, and then sucks the coolant back into the radiator as it contracts during engine cool-down. The radiator cap does not vent to atmospher, as it does in a true "open cooling" system. I suppose if an engine really overheated, the excess coolant from the radiator would over whelm the capacity of the coolant bottle, even in a "closed system". And I suppose if the wrong, or a bad radiator cap was installed on a closed system radiator, coolant would leak arround the cap, resulting in an overheated engine, and an over whelmed reservoir. I beleive radiator caps are designed differently for "open" vs "closed" systems. The reservoir bottle on my '88's so-called closed system had a pressure relief cap that vented to atmosphere. The cooling system I installed on '88 along with my Cheby engine is a true "closed system", and doesn't vent to atmospher, unless "things" get completely out of hand.


Ok to clear things up, first of all, the wrong rad cap would mean, the wrong pressure.
Second, an open systerm would be a rad with a cap on the rad itself, a closed system would be no cap on rad, but on the reservoir.

[Blaine B.]

This is an open system, and a 1995 XJ. Like I said the thermostat is good, I tested it, and it is new as of July 4th 2006. I had the "pressure" release cap purchased on the same day. I replaced it with the "normal" cap today from AutoZone. What is the difference between the two in terms of automatically operating, besides the fact that the "pressure release" cap can also be manually opened?

Also, checked the oil. Amberish color, not milky at all, looks like how it did when I put it in three or so weeks ago.

Lastly I got some of that Prestone radiator cleaner/flush. Once I am 100% done flushing I'll add some of that Prestone anti-rust stuff too.....thanks!

[xjbubba]

The cap used on a modern CLOSED coolant system has two functions: allow coolant to be released as the coolant expands normally with normal engine operation (the closed coolant system of the older XJ had a pressure bottle with an air cushion to absorb this normal expansion and contraction), and an internal vacuum actuated valve to allow the coolant that was subsequently stored in the expansion tank (recovery bottle) to be sucked back into the radiator as the system cools and the coolant contracts. The wrong cap can act as a one-way pressure relief valve--always letting the coolant to escape when it expands, thus eventually resulting in low coolant as the recovery bottle fills and eventually overflows. Radiator caps meant for old style open coolant systems only vent either on to the ground, or into a "catch can". In the "olden days", you didn't fill a radiator all the way to the top. It needed an air cushion to handle the normal expansion of the coolant. Modern closed systems are filled to the top and depend on the external expansion tank to catch the expanded coolant. caps for both types of systems are available, and it's easy to buy the wrong one. Caps also come in a number of different pressure ratings, for either type.

[Blaine B.]

They only had 2 listed at AutoZone for my Jeep, the pressure relief type I bought before, and the normal type I bought today. 13 PSI is the pressure rating on the caps, and my radiator is from AutoZone too (so I'm pretty sure the caps are made for that specific radiator).