Cooling Upgrade??

Well,
After going through my third pressure bottle on the XJ I've decided to overhaul and upgrade my cooling system from a closed system to an open system without the pressure bottle and just an overflow bottle and a cap.

Mine is a 90, the changeover year was 91, so some 91's had the closed system and some the open. So I bought a 92 radiator with the filler neck (cap) and a 92 heater control valve (vacuum activated). It completely eliminates the pressure bottle.

http://jeep.off-road.com/jeep/article/articleDetail.jsp?id=257864

It seems like a pretty straight forward install and I'm working off a writeup from another site. So, has anyone done this and if so are there any pitfalls I should be aware of.

Thanks

No pitfalls I can think of, it was one of the most helpful and straightforward things I've done to my XJ, there are fewer lines to put back in then you take out so it isn't that hard. I did it in a couple hours. After everything is out replumbing is simple if you have a cooling diagram. I can't find the site I used, it was from cherokee america I think, that doesn't sound right though. I'll keep looking.
Just make sure after you get everything in that you keep retightening all the clamps.
This is probably the best mod you'll do.

Found it.
http://www.olypen.com/craigh/rad.htm
Once you get everything out and put in the 4 way actuator the diagram will make more sense.
The one thing that took me forever was the inlet and outlet to the heator core were all rusty and felt like they were going to break and the hoses weren't coming off, other then that it was simple.

Actually this is a simple upgrade. Pay attention to the routing of hoses to the new heater valve. Make sure you get a radiator with metal tanks, not plastic.
Use a "lever-vent" radiator cap. Flush the system with the heater on before starting. (optional) If you have an auto tranny and do a lot of towing, or a lot of first gear, torque converter slippage situations, consider an auxiliary cooler install at the same time.

Hope these help...


I converted my 1990 XJ and love it, but my MJ is still the closed system and don't have any problem with it right now. With my Cherokee it was the same deal as you were having, seems like once I put the aftermarket bottle on, it was just never the same, so I said screw it. I think I'll leave the MJ until it starts giving me fits, then I'll worry about it. But as said before, it is fairly straightforward and relatively easy to do.

I put a 92 radiator into my 89 as well, after replacing the crappy plastic bottle 3 times. On the last time, the cap kept popping loose and letting the coolant boil over.

I recommend slitting the hoses that go onto the heater core with a razor and peel them off. That'll save breaking anything there. I didn't bother with the heater valve and plumbed straight to the heater core. The pink vacumn line had previously broken off at the firewall and was plugged with glue, so the valve was kinda pointless anyway. I had to heat the hose that goes onto the bigger of the two fittings with a hair dryer and bang a big socket into it to stretch it to fit.

I don't notice the air being any warmer in summer. The core gets blocked off so air doesn't go past it anyway. Plus the newer Jeeps don't even have one. You'll need to get an overflow bottle. I was thinking I'd need a big one since the level in the old football changed from near empty to near full from cold to hot. After the switch, it changes maybe 1/2-inch in the big ford bottle I mounted. In hindsigth, a 1-qt overflow bottle would have been plenty.

Oh, while you have the hoses off the heater core, take a garden hose and flush water back-n-forth until it runs clear. You'll be amazed the crap that comes out.

lawsoncl said:

Oh, while you have the hoses off the heater core, take a garden hose and flush water back-n-forth until it runs clear. You'll be amazed the crap that comes out.

Click to expand...

That reminds me I still have to do that :doh:
I took the overflow bottle out of a newer commanche, I haven't really had anything flow into it though, I don't know if thats so normal...
I think my max temp has been 195*, compared to my old off the gauge over heating and bubbling fits, god I hate that closed system.

OK gents,
I started this an hour ago and I'm half way through this project and have a couple questions. On the '90 radiator theres a sensor that screws into it between the upper and lower trans line. The wire goes to the harness for the aux. fan. On the new radiator there is no place for it to screw in.
Question #1 - Since it's a '90 and I'm going to a '92 system is there another place for this sensor to go? I've seen where the sensor is on the thermostat housing on newer (as in newer than '90) models.

Question #2 - If so, is the '92+ thermostat configuration the same as the '90 except for the sensor placement? And is this the sensor than, in fact, runs the fan or does it control something else?
I'd rather not direct wire the fan as my feeble mind could tend to forget to turn it on when it needs to go on. If you could help me out I'd appreciate it. This is the only glitch I've run into and my job is as good as done.

Sorry, but I really need to bump this as I need to figure this out this weekend. Helllp!! I won't do it again, Thanks

i ran into that same issue converting my '87 to a '95 system. i just cut the harness plug off of the old fan switch, soldered on two longer wires and ran them to a manual switch on the dash. everything still works the same(factory relay, etc.) it's just manually activated now. works just fine.

i just saw the 2nd question. i don't see any reason why you couldn't just buy a 92-up thermostat housing and lengthen the harness(reusing the factory plug, of course) and put the thermo switch into the 'stat housing.

Re: Cooling Upgrade?? UPDATE

So I went to the junkyard and found an intact t-stat with the right sensor port, robbed the wiring (the wiring was the biggest problem). Screwed in the new sensor and wired up the pigtail. Done.

Ten High said:

i ran into that same issue converting my '87 to a '95 system. i just cut the harness plug off of the old fan switch, soldered on two longer wires and ran them to a manual switch on the dash. everything still works the same(factory relay, etc.) it's just manually activated now. works just fine.

i just saw the 2nd question. i don't see any reason why you couldn't just buy a 92-up thermostat housing and lengthen the harness(reusing the factory plug, of course) and put the thermo switch into the 'stat housing.

Click to expand...

I do! I recently posted test data from mine that indicates that the T switch which activates the electric fan in the older jeeps (87-90) cuts on at 185 F and off at 170 F (+/- 2 F) as it sees the cooled water leaving the radiator bound for the engine and not the hotest water leaving the engine!!!! It's job (at least in the older models) is to insure that return coolant is cooled off enough to properly cool the engine at the design water flow rate.

So if you install the old style T-switch in the TStat housing where it never gets below 195 F, the electric fans will run all the time!

ParadiseXJ said:

OK gents,
I started this an hour ago and I'm half way through this project and have a couple questions. On the '90 radiator theres a sensor that screws into it between the upper and lower trans line. The wire goes to the harness for the aux. fan. On the new radiator there is no place for it to screw in.
Question #1 - Since it's a '90 and I'm going to a '92 system is there another place for this sensor to go? I've seen where the sensor is on the thermostat housing on newer (as in newer than '90) models.

Question #2 - If so, is the '92+ thermostat configuration the same as the '90 except for the sensor placement? And is this the sensor than, in fact, runs the fan or does it control something else?
I'd rather not direct wire the fan as my feeble mind could tend to forget to turn it on when it needs to go on. If you could help me out I'd appreciate it. This is the only glitch I've run into and my job is as good as done.

Click to expand...

Also the 92 sensor is a resistor that varies with tempurature used by the 92 PCM to measure temperature. It is not an on/off switch like the 87 one in the radiator.

Re: Cooling Upgrade?? UPDATE

ParadiseXJ said:

So I went to the junkyard and found an intact t-stat with the right sensor port, robbed the wiring (the wiring was the biggest problem). Screwed in the new sensor and wired up the pigtail. Done.

Click to expand...

Are you saying you're trying to use the computer sensor for the e-fan? If so that won't work, it's not that simple.

OK then, so here's what I did.
The sensor that was previously plugged in to the radiator was replaced with a different sensor and is now wired to the thermostat. Does that sensor run the fan or the computer? Is it a different sensor? How do I fix it and what type of sensor do I need?
I think that was my original question. That, and can it be done without re-inventing the wheel. This swap has been discussed so many times as being a piece of cake I just assumed it was just that simple. I've been wrong before, so could somebody educate me?

Don't use the computer to turn the fan on/off. Wire it to a manual switch and do it yourself.

I would also add the heater control valve is not necessary. If you used a plastic one, it is prone to breaking. You can just run straight hose to the heater core.

You could have converted you system to open by adding a pressure cap on the upper hose and you wouldn't have to replace your radiator or the temp sender.....sorry I know I'm a little late with this info.

ParadiseXJ said:

OK then, so here's what I did.
The sensor that was previously plugged in to the radiator was replaced with a different sensor and is now wired to the thermostat. Does that sensor run the fan or the computer? Is it a different sensor? How do I fix it and what type of sensor do I need?
I think that was my original question. That, and can it be done without re-inventing the wheel. This swap has been discussed so many times as being a piece of cake I just assumed it was just that simple. I've been wrong before, so could somebody educate me?

Click to expand...

First off if you are staying with the older computer system (Renix) and its coolant temperature system sensors then all we are talking about is the thermo switch that was in the radiator.

It is a simple upgrade if you do like the others suggested and use a dash toggle switch to turn the electric fan on when needed, but you said you want it to be automatic like before, operated by a temperature switch. Therefore you need to figure out a way to install or attach it (it being the old style thermal switch) to the new radiator if you want it to work like it use to work. Other wise expect problems as I said in the prior post.

The new style sensor (it is a sensor only located in the thermostat housing) simply reports a temperature reading (in ohms, resistance) to the computer, and the computer turns on/off a relay that then turns on/off the electric fan in the newer Jeeps. The new style sensor is not an on / off temperature switch like the one you had on the old radiator.

You will need to come up with a creative way to install that old switch on the new radiator. You might try having a radiator shop modify it, but that would require reomving it. I would probably try using some kind of metal epoxy to attach a threaded coupling to the radiator, that coupling would allow you to thread the old switch on, then just fill the coupling with some some high temp fluid or thermal grease to help the sensor get better thermal contact. Might want to leave a tiny (1/16th") breather hole in the top side of the threaded fitting so it does not pressurize and pop off the epoxy as the radiator heats up.

The rad needed replacing. Seemed like a good idea. If the valve breaks I'll bypass it then.

Is there another way to wire the fan besides a switch?

(Eric's information begins here: )
"Here's something I wrote up a while ago for someone describing tests for the sensors. I had done all these in hopes to find and eliminate the poor running I was experiencing. If you need anything to be clarified, let me know.....
Coolant Temperature Sensor (CTS)



So, is this the computer controlled sensor or what?

ParadiseXJ said:

(Eric's information begins here: )
"Here's something I wrote up a while ago for someone describing tests for the sensors. I had done all these in hopes to find and eliminate the poor running I was experiencing. If you need anything to be clarified, let me know.....
Coolant Temperature Sensor (CTS)

So, is this the computer controlled sensor or what?

Click to expand...

The computer does not control the sensor, it reads a variable resistance across the sensor which it converts into a temperature using a math formula. Then the computer uses that calculated temperature to control other things. In your case it uses the computed temperature to calculate a setting for the fuel injectors.

It is the location of the temperature sensor that your computer uses on your year model.