Hypoid
June 30th, 2012, 12:57 PM
From '87 to '90, Cherokees and Comanches used a closed cooling system. For the uninitiated, this system used a sealed reservoir that sits high in the engine compartment, above the engine and radiator. Unlike systems that have two way radiator caps, and recovery tanks, the closed system remains sealed. It does not cycle fluid in and out of the cooling system. It keeps a pocket of air in the reservoir, that compresses as the coolant expands during the thermal cycle.
The problem with the reservoirs, like any other part, is that years of thermal cycles wear them out. Sadly, the aftermarket produces an exceptionally shoddy replacement: The bottles are thinner, the caps that come with the new reservoirs are too flimsy. The aftermarket replacements are not worth installing!
The search for solutions turns up and overwhelming number of conversions to an open cooling system. People are so frustrated with the RENIX reservoir, that they condemn the closed system outright. They spend a few hundred dollars changing out radiators, hoses, thermal switches, and install a recovery tank. I'll be the first to admit that I am frugal. I kept searching for solutions that do not involve hundreds of dollars. After all, when the closed system can hold pressure, it works!
What I learned, is that the closed system operates around seven PSI, because the air in the top of the reservoir can compress. My first thought was of changing out the old heater core, it might be the same age as the vehicle. Replacing the heater core involves removing the dash, I'd rather not. Another point of discussion, is that closed systems are still used in new cars today. In fact, automakers never abandoned the system, junkyards are filled with OEM reservoirs. Armed with that information, I picked a reservoir from a boxy looking Volvo. To make it fit, I bought another $12 worth of hardware.
Time for pictures! :D
The stock configuration:
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF027a.jpg
The Volvo bottle looks a little different, those dimples are fused together in the middle:
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF028a.jpg
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF029a.jpg
Since the top hose is much smaller in diameter, I bought a 5/8" x 3/8" NPT nipple, and a brass adapter:
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF031a.jpg
This is the second swap I've done. The first time, I was concerned about the hood hinge hitting the lid on the bottle. This time, I cut another hole in my bracket, to see how it would clear if I switched the mounting end for end. I did not take a picture of the alternate mounting, but the small nipple stuck out enough to make the original mount look better. Also, you can see my relocated vacuum reservoir. :)
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF033a.jpg
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF034a.jpg
The Volvo reservoir in it's new home. I stuck the extra section of hose under the tie down to keep it snug on the bottle. As you can see, the bottle will bulge a little at the system's operating temperature. After installing the first reservoir last winter, and running this one for a month or so, I am happy with the results. Time will tell if the old junkyard part, is more reliable than the cheap, aftermarket replacement.
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF036a.jpg
The problem with the reservoirs, like any other part, is that years of thermal cycles wear them out. Sadly, the aftermarket produces an exceptionally shoddy replacement: The bottles are thinner, the caps that come with the new reservoirs are too flimsy. The aftermarket replacements are not worth installing!
The search for solutions turns up and overwhelming number of conversions to an open cooling system. People are so frustrated with the RENIX reservoir, that they condemn the closed system outright. They spend a few hundred dollars changing out radiators, hoses, thermal switches, and install a recovery tank. I'll be the first to admit that I am frugal. I kept searching for solutions that do not involve hundreds of dollars. After all, when the closed system can hold pressure, it works!
What I learned, is that the closed system operates around seven PSI, because the air in the top of the reservoir can compress. My first thought was of changing out the old heater core, it might be the same age as the vehicle. Replacing the heater core involves removing the dash, I'd rather not. Another point of discussion, is that closed systems are still used in new cars today. In fact, automakers never abandoned the system, junkyards are filled with OEM reservoirs. Armed with that information, I picked a reservoir from a boxy looking Volvo. To make it fit, I bought another $12 worth of hardware.
Time for pictures! :D
The stock configuration:
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF027a.jpg
The Volvo bottle looks a little different, those dimples are fused together in the middle:
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF028a.jpg
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF029a.jpg
Since the top hose is much smaller in diameter, I bought a 5/8" x 3/8" NPT nipple, and a brass adapter:
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF031a.jpg
This is the second swap I've done. The first time, I was concerned about the hood hinge hitting the lid on the bottle. This time, I cut another hole in my bracket, to see how it would clear if I switched the mounting end for end. I did not take a picture of the alternate mounting, but the small nipple stuck out enough to make the original mount look better. Also, you can see my relocated vacuum reservoir. :)
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF033a.jpg
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF034a.jpg
The Volvo reservoir in it's new home. I stuck the extra section of hose under the tie down to keep it snug on the bottle. As you can see, the bottle will bulge a little at the system's operating temperature. After installing the first reservoir last winter, and running this one for a month or so, I am happy with the results. Time will tell if the old junkyard part, is more reliable than the cheap, aftermarket replacement.
http://i232.photobucket.com/albums/ee120/Hypoid/Jeep%20stuff/Reservoir/JEEPSTUFF036a.jpg