Over Flow Tank......

[chuy79]

What does it mean when I'm at red lights ( or any stopping point) after a good hour of driving and I can hear the coolant bubbling and start coming out of overflow tank??? Does not do it all the time.....not a mechanic so I need some options on how to fix this..easy fix or not?

[yellaheep]

Are we to assume you have warning lights in the dash and not gauges?  If it's getting hot and your temp light isn't going on, this is something you'll definitely want to address sooner than later. 

 

Generally speaking, it's the result of that expansion tank on the firewall developing cracks and not holding pressure - which the cooling system needs to function properly.  No pressure means it'll over heat and bubble up all hot and angry like that. 

 

But other things with the cooling system can also cause this - leaking radiator, bad hoses, stuck thermostat, inoperable fan clutch or auxilary elect. fan......... best to get with a club member to look at it, or take it to the mechanic's shop. 

 

I'd strongly urge you to also have the temperature sensor replaced as a matter of maintenance so you have piece of mind that the sensor and warning light are functioning properly.

[64 Cheyenne]

You need a new pressure bottle.

The cap needs to fit TIGHT, no leaks

If there is no pressure in the system (or any leaks for that matter), then the coolant "boils"at a lower pressure.

You can't Jerry rig a pressure bottle it needs to be converted or replaced.

Search "closed to open cooling system conversion"

 

http://www.ebay.com/itm/87-88-89-90-JEEP-CHEROKEE-COOLANT-BOTTLE-RESERVOIR-TANK-/350732444581?pt=Motors_Car_Truck_Parts_Accessories&fits=Year%3A1989|Model%3ACherokee&hash=item51a94863a5&vxp=mtr

 

Before it goes much further, you should probably state year and engine to make sure the pressure bottle is where to start.

As stated above there can be many contributing factors, but the bottle is where I would start if it has one.

[Eagle]

What year MJ and what engine? If it's an 87 through 90 4-liter, the bottle is not an overflow, it's a pressurized tank. Overflowing could mean the cap doesn't seal tightly (very possible), or it could mean the tank is overfilled. The colling system with the pressure tank doesn't have any overflow provision, so there has to be somewhere for coolant to expand when it gets hot. The coolant bottle on the firewall should be filled halfway when cold -- no higher, and definitely not "full."

[chuy79]

Thanks gentlemen..... its an 88 4.0L with dummy light cluster....question? People at work are telling me to remove thermostat- is this a good idea or bad?

[chuy79]

This is my first ever jeep product to own so I'm not familiar with the setup...if you know what I mean.

[Eagle]

Removing the thermostat is a bad idea. People who suggest things like that don't understand that the purpose of the thermostat is to keep the temperature UP, not down. If the engine runs too cold, it doesn't run efficiently. With the Jeep RENIX injection system, too cold means the ECU never switches from "warm-up" mode to "run" mode, so you'll always be running rich and wasting fuel.

[battleborn]

I agree removing thermostat will prove nothing unless your able to see a specific failure. If you know someone that has a non-contact tempature gun you can take a tempature at the thermostat housing when your condition has been duplicated, this way you would know if your cooling system is overheating. I would start with the expansion tank first, mine had the exact same issue as yours is having know. Installed in-line filler neck into upper radiator hose converting it into an open cooling system. Summit Racing carries this part P/N# HRE-3423. Then the expansion tank would serve as an overflow tank at this point. The expansion tank is a poor design and I have had nothing but trouble with it since I have owned this truck. I would also give strong consideration to installing gauges into your vehicle if warning lights are all that the vehicle is equipped with. Autometer makes A-pillar gauge mount P/N# 15210 that will except 2 1/6" gauges. Never rely on warning lights to illuminate, possibly by then it will be to late. Gauges would allow you to see pending issues and allow correction before a catastrophic failure. Inline, rather they be diesel or gas engines are absolutely the wrong type of engine to overheat due to the way coolant circulates and length of the cylinder heads.

[Eagle]

The concept of the expansion tank and "closed" system is not a bad idea. Several other manufacturers were using it at the same time Jeep first used it ('87 thru '90), and Jeep went back to it with the Liberty. The problem with it as executed on the '87 - '90 XJ and MJ is that they used a plastic cap on a plastic bottle, and plastic is not particularly stable as temperature changes. One of the favored "fixes" for the XJ & MJ has been to get expansion tanks from Pontiacs or Dodges in the junk yard. These have "real" pressure caps on them. Not knowing about that, I replaced mine with an all-aluminum surge tank my Moroso, which uses a standard radiator cap.

 

Back to the original question: If your truck still has the original radiator, most likely it's plugged and not providing much cooling in summer weather,. My '88 XJ (the one I bought new) is currently on it's third radiator.

 

BTW - just adding a filler neck in the radiator hose doesn't make the original surge tank into an overflow tank. It'll still be part of the pressurized system. An "overflow" tank is outside of the pressurized system, and separated from it by the radiator cap.

[Keyav8r]

My '05 Silverado has a closed loop cooling system, as did my '01 Sierra, as does my wife's '12 Mazda6. Never had a cooling problem with any of them. Replaced a water pump in each, but that's a normal wear item when you put 200,000 miles on a vehicle.

[cruiser54]

Go to Napa and buy a 703-1396 cap for that bottle. Seals tighter and holds a bit more pressure. Leave the stat alone. For less than $10, you could have this problem licked

[rocks91mj]

You can get a overflow tank off a 91 or newer xj or mj  and a new rad, sounds like you may need one anyway and then replace all your other stuff. thermostat, hoses, rad cap, water pump, heater hoses, and check your fan clutch for proper operation. Also need to make sure your temp gage is working or light , if you do not see it turn on red when you turn the  on key before you start the engine it's not working. Will also need a overflow hose to the tank from the new radiator. Good luck! hope this will get you started. I just bought all the same parts minus the tank, 91 has one. I spent $220 approx., $108 rad, $27 pump ,$10 thermostat, $5 cap, $50 in hoses, $12 hose clamps, and lets not forget the state so that's about it.