Maveric Posted June 2, 2008 Share Posted June 2, 2008 hey yall, just posted a short while back on what i need to do to install an open cooling system. well i seem to have run into a wee bit of a problem. here's what was connected to my fan. here's what was connected to the radiator sensor, its near the fender well. here's the plug on the end of the radiator. and here's the radiator with a sensor. here's the questions i have, is this inportaint? is it for the electric fan? why does my dads have his running straight from fan to thermostat? what will happen when i get a 91+ new radiator (open system) do i need to reroute this plug? can i install it on the radiator? seems like the three core my dad has replaced his with, you can't so i need someone with mechanical knowledge. Link to comment Share on other sites More sharing options...
Pete M Posted June 2, 2008 Share Posted June 2, 2008 Unfortunately I won't be of much help here. I wired my fan through a relay to a switch in the cab. Another choice would be running it thougha relay to a switched hot lead so it just came on with the truck. Link to comment Share on other sites More sharing options...
BLHTAZ Posted June 2, 2008 Share Posted June 2, 2008 This is exactly the issue I was trying to warn you about when I said that I would NOT recommend doing it this way. I worked for several weeks to find a solution to the issue. If you look back at the links to my conversion threads that I posted in your previous thread about this you will find the solution that I used. It is the switch that controls your electric fan. Most people just run wires in to the dash and hook up a manual switch to turn it on when needed, but I wanted mine to work on it's own as intended so I went through hell and back to make it work. Here is my thread on the electric fan nightmare... http://comancheclub.com/forums/viewtopi ... conversion Link to comment Share on other sites More sharing options...
Pete M Posted June 2, 2008 Share Posted June 2, 2008 Most people just run wires in to the dash and hook up a manual switch to turn it on when needed, Through a relay! Run it through a relay. :D Link to comment Share on other sites More sharing options...
BLHTAZ Posted June 2, 2008 Share Posted June 2, 2008 Most people just run wires in to the dash and hook up a manual switch to turn it on when needed, Through a relay! Run it through a relay. :D Guess I shouldn't ASSume anything ;) :cheers: . Link to comment Share on other sites More sharing options...
Eagle Posted June 2, 2008 Share Posted June 2, 2008 BLHTAZ is correct, and this is the reason I also advise people against rushing into the "open" cooling system conversion. You create a lot of problems, yet the "open" radiator has exactly the same core so it doesn't cool any better. This is one of those things that someone once posted was a good idea, and it has now achieved urban legend status that this swap is a "must do" "upgrade" for the early XJs and MJs. I assume you have already bought the new radiator, so you're stuck with it. My suggestion would be to buy a toggle switch and run the aux fan manually. That 2-wire connector coming out of the old radiator is the control switch. If you're sure you'll never need it, you can cut the wires off that and use them to run to the switch on the dashboard. If it were me, I'd save that sensor and just go to the auto parts store and buy a matching connector to use for the switch wiring. Of course, if was me I wouldn't have a radiator that doesn't have that bung. When I replaced the radiator in my '88 XJ last summer, the shop ordered the wrong year and the one that arrived had a filler neck, and no bung for the aux fan sensor. Once I pointed out that it wasn't the right one for me Jeep, the shop sent it back after I declined an offer to take it at their cost. IMHO, this is one of those changes that has no valid reason for being done. Yet no matter how many times the explanation gets posted why it's NOT a good idea -- somehow it seems people only see the articles advising that it's an essential upgrade -- and then they encounter the same problems that have been written up a thousand times and wonder how to solve it. Link to comment Share on other sites More sharing options...
Pete M Posted June 2, 2008 Share Posted June 2, 2008 Yeah, when I say I prefer my radiator with the cap on it (not the full out conversion, just the later model radiator), I forget that my truck had that sensor in the radiator hose (which is apparently pretty odd). Link to comment Share on other sites More sharing options...
Motion Offroad Posted June 2, 2008 Share Posted June 2, 2008 Buy a HO t-stat housing with the bung in it. Buy the correct sensor for the t-stat housing and extend the wires to the new sensor. Works well and total cost is about $25. Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 2, 2008 Share Posted June 2, 2008 Well, since my 91 already had the open system, I'll obviously keep it. The main advantages of the open system are that "burping" the system is much easier, and the coolant system pressure is not extended to the bottle. Both of these issues can cause problems with the closed systems. But it doesn't cool the engine any more effectively IMHO. Link to comment Share on other sites More sharing options...
Maveric Posted June 2, 2008 Author Share Posted June 2, 2008 sounds like if i got the t-stat housing from a 91 or newer jeep, and some wire (while I'm at the junk yard why not) i can solve it? Link to comment Share on other sites More sharing options...
HOrnbrod Posted June 2, 2008 Share Posted June 2, 2008 sounds like if i got the t-stat housing from a 91 or newer jeep, and some wire (while I'm at the junk yard why not) i can solve it? Yes, in a way. The 91+ stat housing will give you a bung hole for your new temp switch in which you can screw in your new switch to replace the temp switch in your old rad. The 91+ stat housing used a thermo sensor which fed a variable voltage to the ECU. So you can not use this ECU sensor. The ongoing problem is finding the correct switch to use in the stat housing bung. There are many many threads out there as to the correct temp switch to use. I can not recommend one since I opted to go with the Spal PWM controller that uses an existing engine sensor input; maybe Taz can chime in how he solved his temp switch selection, I don't remember. Make any sense? Link to comment Share on other sites More sharing options...
Maveric Posted June 2, 2008 Author Share Posted June 2, 2008 could i run a jumper on the ecu plug to where the fan runs all the time when i start the truck up? i don't think it would harm anything the alternator would generate enough power to keep the fan going constantly, then it would remain super cool. Link to comment Share on other sites More sharing options...
Eagle Posted June 2, 2008 Share Posted June 2, 2008 could i run a jumper on the ecu plug to where the fan runs all the time when i start the truck up?i don't think it would harm anything the alternator would generate enough power to keep the fan going constantly, then it would remain super cool. Yes, you can. Except you wouldn't jumper the ECU. On your year, the ECU has nothing to do with controlling the fan. That plug where the two leads from the radiator connect? Just jumper the two terminals of that connector and your fan will run constantly. This one: Why run the fan when it isn't needed? Your vehicle already has a relay for the fan. All you need is a toggle switch and a few feet of 14-gauge wire. You can leave the fan running all the time if you wish, or leave it off most of the time. Remember, the vehicles sold w/o a/c didn't have that second fan, and they had radiators with one less row of tubes. Most of the time you simply don't need the auxiliary fan. It won't stay "super cool" even with the fan running 24/7, because the thermostat will just close and keep the temperature up to 195 anyway. I just read your initial post (in this thread) again -- am I correct in understanding that you did NOT buy the new radiator yet? If not -- why not just make life easy and buy the correct radiator for your vehicle? Link to comment Share on other sites More sharing options...
Maveric Posted June 2, 2008 Author Share Posted June 2, 2008 well foolish me...didn't check to see why I'm heating up so much....I uh....flushed the radiator and water flows through it nicely, its the thermostat that needs replacing, least i think so ill check it later today, in any case no i didnt buy the radiator yet, thank god, but yall are a big help for even foolish people like me. Link to comment Share on other sites More sharing options...
BLHTAZ Posted June 2, 2008 Share Posted June 2, 2008 Buy a HO t-stat housing with the bung in it. Buy the correct sensor for the t-stat housing and extend the wires to the new sensor. Works well and total cost is about $25.I thought that too, but it's not correct. That may work for a '91+, but on the Renix....it's a direct connect switch, not a sensor and it does not work because you can not find a "switch" with the correct temperature range to run the fan. Believe me...I spent weeks looking for this and talking to companies that make fan controlers and they all said that it doesn't exist. The t-stat housing stays too cool being right behind the mechanical fan so the one switch that is out there (for an old Corvette) will not turn the fan on until the engine is over 230 degrees. Maveric...I hope it is just a t-stat and it stays simple. You can change to an "ope style" system...just do it without changing the radiator as show in the other threads ;) . Link to comment Share on other sites More sharing options...
Eagle Posted June 2, 2008 Share Posted June 2, 2008 I thought that too, but it's not correct. That may work for a '91+, but on the Renix....it's a direct connect switch, not a sensor and it does not work because you can not find a "switch" with the correct temperature range to run the fan. Believe me...I spent weeks looking for this and talking to companies that make fan controlers and they all said that it doesn't exist. The t-stat housing stays too cool being right behind the mechanical fan so the one switch that is out there (for an old Corvette) will not turn the fan on until the engine is over 230 degrees. A long time ago somebody on the NAXJA forum posted that there's a Honda temp sender that works as a switch rather than a variable resistor. I never followed up on it because I prefer the surge tank approach, but I wondered if you checked with any Honda dealers you might have professional contacts with. Link to comment Share on other sites More sharing options...
BLHTAZ Posted June 2, 2008 Share Posted June 2, 2008 I can check with them, but the problem may still be the same...Heat Range... The adjustable set up that I am using now had to be set at it's lowest setting to get it to come on when I needed. Link to comment Share on other sites More sharing options...
Maveric Posted June 3, 2008 Author Share Posted June 3, 2008 theres threads about converting closed to open without changing the radiator? where? any links? i can't seem to find them. Link to comment Share on other sites More sharing options...
BLHTAZ Posted June 3, 2008 Share Posted June 3, 2008 I don't know that there is a complete thread about it, but if you look at page 4 of this thread you will see the Moroso tank that Eagle used to do just that... http://comancheclub.com/forums/viewtopi ... conversion Link to comment Share on other sites More sharing options...
Eagle Posted June 3, 2008 Share Posted June 3, 2008 Moroso also makes a funky thing that's basically a length of pipe with a radiator fill neck in it. It costs a lot less than the tank I used. You just cut the upper radiator hose, insert this "thingie" into it, and clamp the two sides of the cut hose onto the ends of the pipe. Voila! Instant open system. I think Summit Racing carries that part, too, but I don't have a part number. Link to comment Share on other sites More sharing options...
Maveric Posted June 4, 2008 Author Share Posted June 4, 2008 whats it look like whats the part number? link? whats pete talking about in http://www.comancheclub.com/forums/view ... hp?t=10145 this thread? sounds like he converted to an 'open' system without converting to an open system? pete whatcha talking about? Link to comment Share on other sites More sharing options...
Pete M Posted June 4, 2008 Share Posted June 4, 2008 I bought a new radiator from a later model XJ (open system). But I didn't convert mine to open. I just added a radiator with a radiator cap in it. I skirted the e-fan issue by running power for it though a relay to a switch in the dash (actually, I think it's in the overhead switch panel). And every time I recommend the rad w/cap, I forget all about the loss of the e-fan switch in the old radiator. :roll: See the radiator cap? Link to comment Share on other sites More sharing options...
Eagle Posted June 4, 2008 Share Posted June 4, 2008 There is a company making a radiator that has both the filler neck and the bung for the aux fan switch. Unfortunately, I don't know who it is. I do know that it is NOT GDI (Go Dan Industries), because that's the brand I bought and the first one that came in did not have a bung. If it did, I would have taken it. Link to comment Share on other sites More sharing options...
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