Need help with the coolant.

[Eagle]

The fan clutch should move *somewhat* easily when cold, and it should NOT move easily when hot.

 

The simplest end-user test for the fan clutch is a traffic light. If the truck holds normal temperature when you are moving but starts to heat up when you stop at a long light -- then cools right back to normal when you start moving again ... the fan clutch isn't spinning the fan fast enough to be doing any work.

[chicofuentes0224]

Well if it's boiling out, ya your overheating. Let us know if the fan clutch was the prob then. Good luck :cheers:

[chicofuentes0224]

The fan clutch should move *somewhat* easily when cold, and it should NOT move easily when hot.

 

The simplest end-user test for the fan clutch is a traffic light. If the truck holds normal temperature when you are moving but starts to heat up when you stop at a long light -- then cools right back to normal when you start moving again ... the fan clutch isn't spinning the fan fast enough to be doing any work.

 

So Eagle, mine moves easily after it's hot. Not as easy as when it's cold but still easy. I guess it's bad. However my temp doesn't go up at a light. It goes up while driving around town and drops back down when I stop at a light. Could the fan-clutch cause this to happen? I pulled out the laser thermometer again and ran a couple tests. While my gauge reads probably somewhere between 215 and 225 it never hits 225. I aimed the laser at all the different places I could think of and right where the sensor is by the VC is where it almost matches my gauge. Everywhere else though it reads anywhere from 170 to 200. I thought my gauge was just wrong because it never overheats but now I'm secondguessing myself. I've changed the thermostat, fan temp switch/sensor, plastic expansion tank, and the PO put a new radiator in. The fan works but it doesn't turn on until the gauge reads close to 220-225. That's why I always thought the gauge was off. Is it normal for it to turn on that late? So should I just go ahead and change my fan clutch and does anyone have a good set of instructions on how to do it? Oh I've flushed the coolant and replaced and bled the air bubbles too. What da ya think?

[Eagle]

However my temp doesn't go up at a light. It goes up while driving around town and drops back down when I stop at a light. Could the fan-clutch cause this to happen?

Nope. A bad fan clutch would not result in that behavior. A bad fan clutch doesn't move enough air to remove the heat from the radiator. A vehicle moving at 25 or 35 MPH pushes air through the radiator and doesn't need the fan -- that's why we have fan clutches, to essentially make the fan NOT work when it isn't needed.

 

I pulled out the laser thermometer again and ran a couple tests. While my gauge reads probably somewhere between 215 and 225 it never hits 225.

 

Get serious. The Jeep temp gauge isn't calibrated in a linear scale, it's logarithmic. The low mark is 100, straight up is 210 (that's a delta of 110 degrees), and the top end is 260 (that's a delta from the mid-point on the gauge of only 50 degrees). Ain't nobody got any idea where on that scale 215 or 225 is.

 

I thought my gauge was just wrong because it never overheats but now I'm secondguessing myself. I've changed the thermostat, fan temp switch/sensor, plastic expansion tank, and the PO put a new radiator in. The fan works but it doesn't turn on until the gauge reads close to 220-225. That's why I always thought the gauge was off. Is it normal for it to turn on that late?

 

That's not turning on late, that's turning on when it's supposed to turn on. The aux fan isn't for normal cooling, it's to prevent OVERheating. It doesn't turn on until the temperature gets above the normal operating range.

[mvusse]

And on a closed system under 13 pounds of pressure, a 50/50 mix of coolant and water will not boil until it gets to 260 degrees.

[Eagle]

And on a closed system under 13 pounds of pressure, a 50/50 mix of coolant and water will not boil until it gets to 260 degrees.

Nyuk, nyuk -- A 50/50 mix under 13 psi won't boil until 260 degrees with an open system, either. :D

 

But -- different parts of the engine see different temperatures, and all it takes is one hot spot to create localized boiling, which then raises the pressure throughout the entire system and can cause boiling over even if the gauge doesn't show an overheating condition. Although I believe that spot on the back corner of the head was selected for the sender because it is normally one of the hottest parts of the engine.

[HOrnbrod]

That's not turning on late, that's turning on when it's supposed to turn on. The aux fan isn't for normal cooling, it's to prevent OVERheating. It doesn't turn on until the temperature gets above the normal operating range.

 

217*F to be exact if it's working as designed.

[chicofuentes0224]

So should I change out the fan clutch?

[mvusse]

And on a closed system under 13 pounds of pressure, a 50/50 mix of coolant and water will not boil until it gets to 260 degrees.

Nyuk, nyuk -- A 50/50 mix under 13 psi won't boil until 260 degrees with an open system, either. :D

 

Ummm, in an open system, the overflow bottle is not pressurized, but the rest of it is still a "closed system" pressurized to 13 psi. If a cooling system would truly be open, you wouldn't be able to pressurize it. :D

[JohnQ]

I had a pressure test done on my coolant system today. They told me my radiator was leaking, allowing air into the system.

 

So on my way home in 90+ degree weather with my heater on full blast, I stopped at an auto parts store and picked up a 92 radiator. I don't have extra money for a nice radiator so this will have to do for now. What else do I need to get? I know I need a heater control valve, from what I have read, but I can't find a real detailed write up for the conversion. I don't even know what the heater control valve looks like. Does anyone have any pictures that show exactly what I need to do with the hoses under the pressure bottle?

[BLHTAZ]

I did this conversion a while back and knowing what I do now...I would not have done it this way (changing the radiator).

 

Here is my thread about the biggest PITA of the change... the electric fan operation... http://comancheclub.com/forums/viewtopi ... conversion

 

Here is my thread on the conversion itself... http://comancheclub.com/forums/viewtopi ... conversion

 

You will need the heater hoses and control valve to fit the later model as well. You will also need to figure out an overflow bottle.

[JohnQ]

I did this conversion a while back and knowing what I do now...I would not have done it this way (changing the radiator).

 

Here is my thread about the biggest PITA of the change... the electric fan operation... http://comancheclub.com/forums/viewtopi ... conversion

 

Here is my thread on the conversion itself... http://comancheclub.com/forums/viewtopi ... conversion

 

You will need the heater hoses and control valve to fit the later model as well. You will also need to figure out an overflow bottle.

 

Do you have a picture of the heater control valve and the hoses going to it?

[BLHTAZ]

This is a pic out of my computer at work. I don't have any good pics of just the valve in my truck.

 

[Eagle]

I did this conversion a while back and knowing what I do now...I would not have done it this way (changing the radiator).

 

Here is my thread about the biggest PITA of the change... the electric fan operation...

 

That's why I advocate just replacing the plastic surge tank with a Moroso surge tank, and keeping the original style radiator. Everything else works as it always did, plus you even gain a bit of coolant capacity.

[BLHTAZ]

I knew you would come around sooner or later Eagle. I told them that you had a much simpler solution, but I could not remember where you got the tank from :cheers: .

[Eagle]

Summit Racing has it. Moroso part number 63650 for the cheaper one with the stamped filler neck, or 63651 for the one with the machined billet filler neck.

 

It needs a couple of elbows from a plumbing supply house and it's good to go. Uses a standard radiator cap. I'm using a STANT brand with a lever, but the lever is optional.

[JohnQ]

Well for less than $200 I am currently without an over heating issue! :D

 

Switched to an open system with all 92 XJ stuff.