Which CSF Radiator for Renix conversion is best

I DO NOT want to convert my electric fan to a manual switch. I want to be able to leave it as factory to cycle on and off at the factory temp. settings. That being said...which scenario would be best?

OPTIONS
1. Use the 1992 radiator with radiator cap, and someone tell me a solution for the temp sensor? I know it can't go the the thermostat housing, because the water temps are different at that point, so the temp switch wouldn't react to the correct temperature.

2. Use the 1988 radiator which has the threaded hole for the temp sensor, and use the Dakota "in line" radiator cap to convert it to a true open system.


Here are the radiators in question from Radiator Barn...

CSF2671 - 1992 All Metal 3-row Heavy Duty open system with pressure cap


CSF2572 - 1988 All Metal 3-row Heavy Duty closed system Renix style.

Any help would be appreciated.

Jeff C.

Is there a better forum to post this question on? I've not received any feedback on the last two threads I started, and I could really use some help. I've searched and read many threads, but none seem to answer my question.

Thanks...

imajeepnut said:

I DO NOT want to convert my electric fan to a manual switch. I want to be able to leave it as factory to cycle on and off at the factory temp. settings. That being said...which scenario would be best?

OPTIONS
1. Use the 1992 radiator with radiator cap, and someone tell me a solution for the temp sensor? I know it can't go the the thermostat housing, because the water temps are different at that point, so the temp switch wouldn't react to the correct temperature.

2. Use the 1988 radiator which has the threaded hole for the temp sensor, and use the Dakota "in line" radiator cap to convert it to a true open system.


Here are the radiators in question from Radiator Barn...

CSF2671 - 1992 All Metal 3-row Heavy Duty open system with pressure cap


CSF2572 - 1988 All Metal 3-row Heavy Duty closed system Renix style.

Click to expand...

Option 1: You can't just put a sensor in the t-stat housing, not from a Jeep anyway, and expect it to do anything at all, because it's a SENSOR not a SWITCH. The RENIX switch in the radiator bung has a specific purpose...it won't turn on the fan as is.
You could put an adjustable temp switch in the t-stat housing from a GM/Corvette engine. Remember the terminology. The sender for the gauge, the sensor for the ECU, the switch for the fan. Up to 95 or 96 there are only the sender and the sensor, the switch is in the ECU. The switch, sender and sensor are all the same unit in 97+.

Option 2: This is the way alot of guys have gone but not acceptable, for me anyway.

Option 3: Some of the CSF radiators DO have the bung for the switch. Call them and ask if they stock such an animal. My buddy got a 92+ radiator with a bung...it was covered with a slug/plug, like a knockout in an electrical box.

Option 4: Just bite the bullet, throw caution to the wind and wire in a switch on your dash through the fan relay and only use it when under extreme conditions...the e-fan will still cycle on/off with the A/C.

Thanks for taking the time to offer your suggestions... I did call one of the vendors and asked about the CSF '92 and up having the threaded bung, but they didn't know I may try to call CSF directly and see if I can get any help there. I'll let you know what I find out.

My local radiator shop said they could sweat the threaded bung in the metal tank if it didn't come with it. They said they have done it quite often. That at least gives me an option if the CSW doesn't come with one.

I think the closed system is far superior to the open system, as it operates at lower internal pressures, and is easier on the radiator joints and hoses, seals etc.

I gave up and went to an e-fan toggle switch, mine is on all year, except the winter. The problem with the renix switch design for the E-fan, is once the flow slows down going through the radiator (slow clogging process....), the inlet side gets hotter, and the outlet side gets colder, and delays turning on the E-fan, and the engine slowly gets hotter and hotter as the months and years pass. That is why the HO models moved the temp control sensing point to the T-Stat housing.

The only reason I use the inline filler neck on my renix inlet upper hose, is to make filling the radiator (getting all the air out) fast and and easy. Then I use an 18 lb cap that never opens, and keep the plastic bottle and 16 lb cap on the bottle, which also never opens unless you hit about 250-260 F, which mine never does, so it is truly sealed!!

i have done the conversion you are doing. none of the csf radiators have a bung for the temp sensor. a friend of mine found me a Aluminum single row 1 1/2 inch core high effiencey radiator. it has the bung for the fan temp sensor.this is the only radiator i have found that has the bung in it. unless you have a custiom one made.i couldnt get anyone where i live to make me one. they all said they cant due to enviro laws here in so. ca.when i did my conversion i also removed my bottle and the factory heater valve and used a 96 heater valve and found the Jeep would run hot about any out side temp of 90 or engine speed about 2500 rpm. after some research i found the factory heater control valve has a restrictor in the by pass circuit.so when the valve is closed and not going throught the heater it would by pass into the bottle at a low flow.using the 96 valve caused too much hot coolant flow back to the engine. to fix that i went and got a renix 87 to 90 heater valve reinstalled it . where the other hose would go into the bottle i installed a heater t. so when the heater valve flows throught the heater i have good flow good temp. when the valve is closed it by passes at the heater valve restriced and the temps are back to normal. the renix is touchy

jeeptec said:

when i did my conversion i also removed my bottle and the factory heater valve and used a 96 heater valve and found the Jeep would run hot about any out side temp of 90 or engine speed about 2500 rpm. after some research i found the factory heater control valve has a restrictor in the by pass circuit.so when the valve is closed and not going throught the heater it would by pass into the bottle at a low flow.using the 96 valve caused too much hot coolant flow back to the engine. to fix that i went and got a renix 87 to 90 heater valve reinstalled it . where the other hose would go into the bottle i installed a heater t. so when the heater valve flows throught the heater i have good flow good temp. when the valve is closed it by passes at the heater valve restriced and the temps are back to normal. the renix is touchy

Click to expand...

That is VERY interesting!!!!

I never once considered the bottle bypass issue and how it might affect heating in the cabin and overheating in the engine!!!!!

That flow rate could be a major issue. It also might explain why my 89 has better heat in the winter (it has the valve) and my 87 barely heats at all. Also as a radiator's tubes slowly clog, the water pump just pushes the water in a different circle, not through the radiator, but in a bottle to engine to bottle circle building up heat, with out sucking the lower radiator hose collapsed or blowing up the upper radiator hose!!!

That explains a lot of Jeep cooling system anomalies I have seen, and never figured out.

Does every one else understand what he said?

Note to the OP, the 87 (at least mine?) did not have that heater valve, it had a T built into the hose assy. I think the valve was added in 88 or 89?

I don't know if/when it was added, but I'm reasonably sure it was deleted for 1996.

As far as RENIX, I've removed the heater control valve with good results on my 87 and 88 (87XJ/242/AW4/NP231/D30/D35/3.55, 88XJ/242/BA-10/NP231/D30/D35/3.07,) and I didn't have any trouble. Just replace them with fabricated T fittings (on my 88, I went and fabbed up replacement heater lines out of copper - as some people here know,) and you should be good.

The idea of the heater control valve is to cut off the flow of hot coolant through the heater core, typically before the engine heats up or when the aircon is on (to reduce thermal demand on the aircon system.)

I prefer keeping coolant flowing through the heater core, because letting it sit can contribute to corrosion - circulating it helps keep that from happening.

As far as the "football" on RENIX, it's just a pressurised volume tank (which is why you don't fill it all the way up!) On the more common "open" system, the radiator cap is a two-way valve - an outlet valve that opens at the specified pressure (8-16psig, usually printed on the cap) to allow coolant out as it expands, and an inlet valve (typically -0.5psig) to allow the suction created by the coolant contraction to draw coolant back from the overflow tank (this is why the hose that connects to the radiator neck attaches to the bottom of the tank.)

The outlet valve is tested using a pressure tester, the inlet valve is tested by merely prying up with a knife point or a small screwdriver, just to make sure it moves fairly freely.

For "closed" systems, the radiator pressure cap is a one-way pressure valve - outlet only, no inlet.

Interestingly, the unpressurised overflow tank, if constructed using a conventional neck, can have an "open" overflow tank added as well - but it's probably not necessary.

I've always bypassed the HCVs myself with excellent results.

Thanks for checking in and posting.

But I think you two missed my point. When servicing a cooling system, we know how to do it right, and while using a T (no valve, and no restrictor) is not, and has not been a problem for us....

as the working system ages, and the newer cores on these radiators with their narrower tubes, slowly build up a little scale and the flow through the radiator slows down, the pump does not work harder to push the coolant through the radiator (like we think it would), it instead, bypasses the radiator, goes through the bottle, back to the pump, and does not get cooled!!!! This may be worse at elevated rpms or at idle.

That is the point I was trying to make. The HO design, with a heater valve, lets the full force of the pump push on the radiator inlet side on the HO cooling systems, as there is NO BYPASS, no T, and no Renix bottle (another bypass for the pump)!!!!


So my thought is, as the system ages, it might be useful to restrict (reduce the flow or cut it off temporarily) the entire by pass flow rate through the bottle (or heater core if one has no valve) in the summer, or in heavy special load conditions, like steep grades while towing or rock climbing?

Doing so in the hottest summer conditions or peak loads, might keep many of them from marginally overheating.

I think I now better understand the more complex CLOSED cooling system routing I am seeing on newer closed coolant systems, like my ford and saturn.

1. So how would you restrict the flow through the heater core without the vacuum valve?

2. Seems like dropping the valve altogether, as posted in many threads, might in fact be better on the heater core. The heat transfer to the cab should be minimal as the heater "flap" wouldn't be open during the summer. Correct?

Thoughts?

So what if I just get the '88 CSF radiator with the original threaded bung...and install the in-line Dakota filler cap, or some other brand? I don't see a reason for it not to work... you'll have a filler cap, overflow tube, bottle....open is open right? The filler neck/cap on the inlet hose side will be higher than the OEM position of the '92 radiator.

cruiser54 said:

I've always bypassed the HCVs myself with excellent results.

Click to expand...

I bypassed mine went I went open system. just two hoses into the core.

I don't have an e fan either.

My wife's 88, with whatever radiator came with it 2 years ago, with the HCV removed, not new water pump, factory 195 thermostat and running the AC all the time in summer in slow speed traffic around town, never gets hot or near hot.

imajeepnut said:

1. So how would you restrict the flow through the heater core without the vacuum valve?

2. Seems like dropping the valve altogether, as posted in many threads, might in fact be better on the heater core. The heat transfer to the cab should be minimal as the heater "flap" wouldn't be open during the summer. Correct?

Thoughts?

Click to expand...

Only if the heater flap (damper door, LOL) works and seals well. If there is any control or vacuum or valve door operator problem, it is PITA not being able to turn the flow off to the heater core in 100 F weather. Ask me how I know? LOL

In Houston, the heater core gets used in summer too, when it rains and humidity spikes, using defrost with AC on cool.

My heater cores are 1987 and 1989 OEM. 278,000 miles on one. The newer heater cores and evaporators are junk from what I hear.

In the past, other vehicles, and my 85 jeep, I used a brass gate valve. Manual override, LOL!:laugh3:

imajeepnut said:

So what if I just get the '88 CSF radiator with the original threaded bung...and install the in-line Dakota filler cap, or some other brand? I don't see a reason for it not to work... you'll have a filler cap, overflow tube, bottle....open is open right? The filler neck/cap on the inlet hose side will be higher than the OEM position of the '92 radiator.

Click to expand...

There was a recent discussion on this here. Turns out the inline filler cap is OK for the Renix closed system. I have one, has worked flawlessly for 3 years now.

BUT, for an open system, if and when the radiator clogs up enough, the radiator inlet side reaches a much higher system pressure than the outlet side on an open system, due the pump sucking on the outlet and pushing on the inlet, so pump pressure adds to the coolant temperature driven pressure on the inlet side to the radiator and can open the inline filler cap sooner than it would on the low pressure side.

That would be more of an issue in summer with no flow through the heater core!!!!!

cruiser54 said:

My wife's 88, with whatever radiator came with it 2 years ago, with the HCV removed, not new water pump, factory 195 thermostat and running the AC all the time in summer in slow speed traffic around town, never gets hot or near hot.

Click to expand...

OK, cough it up, disclose the secret, what radiator was on it, a Cummins diesel big rig? LOL Or was it AC on in the winter blizzard, LOL!

Mike...My plastic tank radiator has been in my XJ for some 14 years now...ever since I put the new Jasper engine in. I haven't had the first bit of trouble with it...nor any sign of reduced flow....until my surge tank cap started failing. The radiator itself is clean, as is the block. I know you get "some" buildup over time, but all-in-all it has been a great setup. SO...if it takes 14 years for this new radiator to show signs of clogging...it'll be time for another one all over again. I'm thinking to myself...get the '88 CSF, use the inline filler cap, run it for 10 or so years and change the hoses along the way and I should be good. Sound like a plan??

BTW... I'm thinking of starting a new thread and calling it Renix Rejuvenation...or something. I'm taking pics of everything as I tear it down...from hoses, vacuum lines, rocker arms...you name it. I'm replacing every sensor in sequence, and checking all my wiring as I go. Once I start the thread, I'll be posting more questions when I hit a wall on something. I'll be starting with the mechanics, and moving on to suspension, and then an interior refresh. It should be fun...slow, but fun! My plans are to outfit the "new" Renix XJ as an Expedition rig for my family to enjoy. I have plenty of pics too, we all love pics!

Here's what I'm starting with...all over again...

The heater blend door is cable operated and easily adjusted from under the passenger side dash. 3 minute job.

I was just looking on the CSF site...in their catalog. They have the "economical" aluminum 1 row with plastic tanks, with filler neck, and what looks to be the bung for the temp. sensor. Their part number is #3251. Has anyone used this radiator before? I know it has the plastic tanks, but my other one lasted many years. I'm waiting for a CSF tech to call me back to confirm.