XJ overheated

I was sitting in the drive thru @ sonny's and all of a sudden i saw steam pouring out where the overflow canister is and coolant all over the ground. When i got out and popped the hood- no busted hoses, no obvious origin of the leak. Any ideas? (by the way, i have idiot lights and it never lit up)

radiator cap failure. known problem area on XJ's

I guess you mean the cap on the bottle?, its a closed system- 88'

Coolent should never exit that bottle, there is no overflow.

If the coolent came out the cap, replace it.

Rev

thats the only place i can guess that it might of come from, none of the hoses are cracked or busted....?

No, I actually meant the radiator cap. Sometimes the gasket will fail but is not noticable until something like an overheat happens. Only a few bucks at your local parts store.

tupton said:

No, I actually meant the radiator cap. Sometimes the gasket will fail but is not noticable until something like an overheat happens. Only a few bucks at your local parts store.

Click to expand...

You do know there is no radiator cap on a 88?

Right?

Rev

Mine did the same thing once. It turned out to be a tiny crack in the bottle. replaced the bottle and no more problem. Check to see if you have the same delima. My crack was not noticeable until it was heated up. Took about 30 min in my driveway to visually recognize the crack.

Rev Den said:

You do know there is no radiator cap on a 88?

Right?

Rev

Click to expand...

So what does the '88 use for pressure relief? When a radiator or cooling hose burst, it is nearly an explosion, NOT to mention the dangers of superheated liquid being sprayed everywhere. Ralph Nader would be doing back flips, if someone was dumb enough to produce a vehicle with NO pressure relief for the cooling system.

Are we getting terms confused? Pressure Relief Cap, a.k.a. Radiator Cap (because its usually on the radiator), which some people still call it a Radiator Cap no matter where its placed on the system, others just call it a Pressure Cap.

BTW, has anyone tried to fit a metal tank in replace of the plastic bottle for closed cooling systems. I would think a good metal tank would be far less likely to crack than plastic under that heat and pressure cycling.

Academic Bickering Aside, if your system has some sort of pressure relief valve, like a Pressure Relief Cap (A Radiator Cap installed in a different place) I would look at replacing it. They are cheap and often fail after a couple of years. If the Pressure Cap malfunctions, it could hold a much lower pressure in a perfectly good system, which will allow the coolant to boil at a much lower temp, and once the coolant starts to boil it will force its way out past the failing Pressure Cap. In this case, a new Pressure Cap is all that is required to return the system to perfect function.

Also pay heed to the advice about cracks and leaks, they will have the same effect and can be difficult to find. Some cracks or leaks, will still seal up to a certain pressure, then start to leak once the coolant starts to get warmer and build pressure in the system, and the results can be the same as the bad Pressure Cap. The coolant boils way to early (at a lower temp because the pressure is lower) the rapidly expanding steam forces itself and coolant with it out the leak.

I'm with mikeforte - tanks I've used only last about 4-5 years and it's often very hard to tell it's cracked without pressure on the system.

When refilling closed systems, remove upper hose from thermostat housing and pour coolant into radiator with tank cap off, vehicle level. This will reduce or eliminate air trapped in the system. Pouring slowly until level rises from the bottom of the tank to full line. Reconnect hose and heat engine/system to full pressure, inspect for leaks.

mikeforte said:

Mine did the same thing once. It turned out to be a tiny crack in the bottle. replaced the bottle and no more problem. Check to see if you have the same delima. My crack was not noticeable until it was heated up. Took about 30 min in my driveway to visually recognize the crack.

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do parts stores generally carry the bottles?, or does it have to be ordered?

I believe one of the guys running an earlier XJ told me you can buy an aftermarket bottle that's much thicker and will last a lot longer than the stock one, but it's pricey. Maybe one of the Renix guys can help you out with getting one of these bottles, or Google it.

There are $25 bottles out there if you can wait for mail order and/or auto parts stores often have 'em in stock for not much more. I think I paid $60-$80 from dealer last time since I was SOL and needed to get it going that day. I'm on my 3rd bottle in almost 10 years and I'm starting to think converting to open system might be better and cheaper in the long run?

Rick,
Yup...pressure cap, YOU may know what you were talking about, but not everyone on here does.

AND as I said...if it leaked around the cap....replace it.

I am on my second bottle in 16 years, there is NO NEED to replace the "closed" system to an "open" one.

Lots of info here...
http://www.naxja.org/forum/search.php?searchid=1498721


Rev

True, there is no NEED to replace the closed system, but, I found it much better to have the open system (just my preference). It is pretty easy to do and is a good excuse to buy a newer style radiator.

Rev Den said:

Rick,
Yup...pressure cap, YOU may know what you were talking about, but not everyone on here does.

AND as I said...if it leaked around the cap....replace it.

I am on my second bottle in 16 years, there is NO NEED to replace the "closed" system to an "open" one.

Lots of info here...
http://www.naxja.org/forum/search.php?searchid=1498721


Rev

Click to expand...

I never said NEED, I said "may be better" - I used to be like you but if I'm forced to change another bottle in the next 5 years the next radiator will be an open design.

It isn't a hard conversion. You can convert to open using the same closed radiator - just get a different overflow bottle, cut your upper radiator hose, and clamp in a radiator cap "T" connection.....

That's probably the cheapest way to go and still have an "open" system.

A lot of the newer cars, that have WEDGE shape, with the diving nose, the radiator is lower than the engine and the highest point of the cooling system is no longer at the top of the radiator. They have the "Pressure Cap" mounted either on the engine or on a "T" connection like you describe.

The engine mounted "Pressure Cap" usually is a modified thermostat cover that has a neck and lip to screw on the pressure cap.

The "Pressure Cap" can really be anywhere in the system, but its wise to have it at, or near, the highest point of the system because you want the air/steam to collect there. A closed system just puts the pressure cap on top of the reservour and turns into an expansion tank on the pressure side of the system.