Turner-2000TJ
NAXJA Forum User
- Location
- Kansas
Which is better? Ive been told the open cooling system is better. My 87 is a closed system but I have access to a complete open system from a 91. Should I go ahead and make the swap ?
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Closed vs Open cooling systems
- Thread starter Turner-2000TJ
- Start date
5-90
NAXJA Forum User
- Location
- Hammerspace
I have no idea how many times I'm going to have to beat this into the ground, but here's 3,467,201...
There is nothing intrinsically wrong with the RENIX "closed" cooling system. If the "closed" system idea is inherently worse, why is it picking up speed with OEM applications?
Considering I've got four RENIX rigs, and only one converted (and I'm honestly thinking of converting it back to closed system!) I can honestly say that all you need to do is maintain the thing as well as you normally would, make sure the system is flushed and coolant changed every alternate year, and keep an eye on the pressure bottle (keeping a spare around woudn't hurt - go to www.morris4x4center.com to order one - with cap - for about $22.)
The only real "issue" with the RENIX system is the radiator. From experience (and from talking to Jeep techs) the usual service life of the RENIX OEMR radiator is 120-170Kmiles, whether it came with the vehicle from the factory or you get it from Jeep. Replace the radiator with a Modine or a Performance Radiator replacement unit, and forget about it (I've got a Modine in daily service with 80K or so on it, and a Performance Radiator unit in service with at least 130K on it. Neither show any sign of trouble.)
Some of us "old hats" batted this one around for a while, and we decided it's an answer in search of a question. The whole craze probably started when someone was getting overheats (due to a failed radiator - see comments above) and just did the conversion while he was about it. Since it was a new radiator going in, he fixed the problem - there was just a lot of unnecessary work involved. Replacing the radiator witha quality aftermarket unit would have served.
Considering I've pulled the RENIX closed cooling system down to an operating temperature of 190-195 degrees Fahrenheit with only minor modifications, there really is nothing wrong with it - and converting it is an answer in search of a question, as I'd mentioned. My "closed" rigs run cooler than the one that was converted to "open!" Go figure.
Search for my other posts on the subject to attain enlightenment - I've covered this myriad times in the last several years, and I'm sure there are still a few posts somewhere around here. I've also worked up the FAQ article (currently in review - Mark?) that should get posted when it comes to pass that we get a FAQ section together...
5-90
There is nothing intrinsically wrong with the RENIX "closed" cooling system. If the "closed" system idea is inherently worse, why is it picking up speed with OEM applications?
Considering I've got four RENIX rigs, and only one converted (and I'm honestly thinking of converting it back to closed system!) I can honestly say that all you need to do is maintain the thing as well as you normally would, make sure the system is flushed and coolant changed every alternate year, and keep an eye on the pressure bottle (keeping a spare around woudn't hurt - go to www.morris4x4center.com to order one - with cap - for about $22.)
The only real "issue" with the RENIX system is the radiator. From experience (and from talking to Jeep techs) the usual service life of the RENIX OEMR radiator is 120-170Kmiles, whether it came with the vehicle from the factory or you get it from Jeep. Replace the radiator with a Modine or a Performance Radiator replacement unit, and forget about it (I've got a Modine in daily service with 80K or so on it, and a Performance Radiator unit in service with at least 130K on it. Neither show any sign of trouble.)
Some of us "old hats" batted this one around for a while, and we decided it's an answer in search of a question. The whole craze probably started when someone was getting overheats (due to a failed radiator - see comments above) and just did the conversion while he was about it. Since it was a new radiator going in, he fixed the problem - there was just a lot of unnecessary work involved. Replacing the radiator witha quality aftermarket unit would have served.
Considering I've pulled the RENIX closed cooling system down to an operating temperature of 190-195 degrees Fahrenheit with only minor modifications, there really is nothing wrong with it - and converting it is an answer in search of a question, as I'd mentioned. My "closed" rigs run cooler than the one that was converted to "open!" Go figure.
Search for my other posts on the subject to attain enlightenment - I've covered this myriad times in the last several years, and I'm sure there are still a few posts somewhere around here. I've also worked up the FAQ article (currently in review - Mark?) that should get posted when it comes to pass that we get a FAQ section together...
5-90
5-90
NAXJA Forum User
- Location
- Hammerspace
The system can be made to "burp" itself - that's why I drill thermostats. A search should turn up how to do that - I know I've covered it recently...
5-90
5-90
I drill mine too5-90 said:
Or just get an OEMR part that has the hole in the top already.
Anyway, I think we're both in agreement that the closed system functions as it was designed if you maintenance it. I think it has a bad wrap because at the very least it's 16 years old in any Jeep, and needs new parts.
5-90
NAXJA Forum User
- Location
- Hammerspace
You can get an OEMR, but you'll want to drill another hole in it - or just get a Stant or a Robertshaw at the local, and drill two holes.
One hole goes dead UP and the other dead DOWN - that way, you don't get "bubble lock" from two-way traffic through a single hole.
5-90
One hole goes dead UP and the other dead DOWN - that way, you don't get "bubble lock" from two-way traffic through a single hole.
5-90
lawsoncl
NAXJA Forum User
- Location
- North Idaho
Last year I was having lots of overheating problems in the 89 MJ. It was the original radiator with 190k miles on it. I had just replaced the bottle and cap 6 months earlier since the old one split open and left me stranded (guess it didn't like the -20F temp that morning). The cap and bottle I bought online were pretty poor quality. The cap would not stay tight and everytime it came lose the engine would boil over. I had tons of problems burbing even with a hole in the thermostat. If I didn't get it burbed by pulling the temp sensor in the head, it would boil over again and I'd be back to square one.
Since I was replacing everything anyway, I decided to switch to the open setup. I ordered a radiator for a 92 and converted everything. The open system runs a higher pressure (15 versus 6 psi I think) so burbing and boiling is much less of an issue. My temps are rock solid and with zero overheating since. I back flushed the heater core and ditched the vacumn valve as well. I went from slightly warm air at the vents to hot air. I attribute most of that to flushing all the brown crap out of the heater core, but the closed system lets a good portion of the coolant bypass the heater core. I think total cost to convert was $135 for the shipped rad plus about $15 for an overflow bottle and heater hose.
I agree with 5-90 that a closed system can be reliable. I think the new vehicles that are using a closed system are running higher pressures. If you're not overheating or having issues, I see no reason to convert. Doesn't someone make a metal replacement for the coolant bottle?
Since I was replacing everything anyway, I decided to switch to the open setup. I ordered a radiator for a 92 and converted everything. The open system runs a higher pressure (15 versus 6 psi I think) so burbing and boiling is much less of an issue. My temps are rock solid and with zero overheating since. I back flushed the heater core and ditched the vacumn valve as well. I went from slightly warm air at the vents to hot air. I attribute most of that to flushing all the brown crap out of the heater core, but the closed system lets a good portion of the coolant bypass the heater core. I think total cost to convert was $135 for the shipped rad plus about $15 for an overflow bottle and heater hose.
I agree with 5-90 that a closed system can be reliable. I think the new vehicles that are using a closed system are running higher pressures. If you're not overheating or having issues, I see no reason to convert. Doesn't someone make a metal replacement for the coolant bottle?
5-90
NAXJA Forum User
- Location
- Hammerspace
Yeah, but it's spendy. A dedicated replacement TIG-welded out of aluminum diamondplate. (?)
Eagle has had some luck with using a Moroso coolant surge tank (or similar) as I recall - maybe he'll chime in, or his posts on it are still here.
I've been getting my replacement surge tanks from Morris 4x4 Center - which is why I keep bringing them up. They're either OEMR or Omix-ADA (just as good,) and you can get them with the cap for something like $22-23. Cheap enough I can just replace them every four or five years, and keep a spare around anyhow.
Oddly enough, I ordered two tanks and two caps last time, since it added up to save a buck or so ordering separately rather than together (no, I don't understand it either - but dosh is dosh, and if I can save a buck here and there it will add up in the project fund...) and I ended up with two tanks and FOUR caps. So, I put a spare cap in the glovebox of each of the DD's. I don't understand it, either - but I'm not complaining.
I'll usually change the cap and tank at the same time, just to be thorough.
5-90
Eagle has had some luck with using a Moroso coolant surge tank (or similar) as I recall - maybe he'll chime in, or his posts on it are still here.
I've been getting my replacement surge tanks from Morris 4x4 Center - which is why I keep bringing them up. They're either OEMR or Omix-ADA (just as good,) and you can get them with the cap for something like $22-23. Cheap enough I can just replace them every four or five years, and keep a spare around anyhow.
Oddly enough, I ordered two tanks and two caps last time, since it added up to save a buck or so ordering separately rather than together (no, I don't understand it either - but dosh is dosh, and if I can save a buck here and there it will add up in the project fund...) and I ended up with two tanks and FOUR caps. So, I put a spare cap in the glovebox of each of the DD's. I don't understand it, either - but I'm not complaining.
I'll usually change the cap and tank at the same time, just to be thorough.
5-90
