I want to shoot my frankenjeep, running cold

[Pelican]

Beside the point, but the '84 and '85 2.5 was never a closed system. The pre-91 Renix 4.0 (and 2.5?) had the closed system.

I had the problem you are having with my 2.5 bought new in '85 that I had for ~20 years. I don't recall temps early on but in later years it was pretty much impossible to get the temp out of the blue area on the gauge with the OEM setup.

I finally replaced the mechanical fan with a single Flex-a-lite electric fan and controller. (I wouldn't think you would need a dual fan setup.) Always had a 195* stat and 16# cap. This helped get temps up to a reasonable figure but I'm in a much warmer climate than you to start with.

Thought I would throw this out. Perhaps some other thoughts later.

I will add that I never, ever had a problem burping the system or any need to go to any special lengths to do so. Also, when the heater control valve rusted up, I replaced it but agree with just removing the thing.

 

[1slowxj]

2 belts? your water pump turning the right way? they can be a royal pain to bleed ive had to jack up the pass side on mine to bleed properly before

 

[WarGin]

Beside the point, but the '84 and '85 2.5 was never a closed system. The pre-91 Renix 4.0 (and 2.5?) had the closed system.

I had the problem you are having with my 2.5 bought new in '85 that I had for ~20 years. I don't recall temps early on but in later years it was pretty much impossible to get the temp out of the blue area on the gauge with the OEM setup.

I finally replaced the mechanical fan with a single Flex-a-lite electric fan and controller. (I wouldn't think you would need a dual fan setup.) Always had a 195* stat and 16# cap. This helped get temps up to a reasonable figure but I'm in a much warmer climate than you to start with.

Thought I would throw this out. Perhaps some other thoughts later.

I will add that I never, ever had a problem burping the system or any need to go to any special lengths to do so. Also, when the heater control valve rusted up, I replaced it but agree with just removing the thing.

While this is kind of a relief to hear that someone else has had this problem, it sucks that you never really found a solution. I will remove the fan.
Right now it's a little cold to change thermostats outside, but ill do it one last time.
I've been at a loss for weeks as to what the hell is going on, the water pump which has already been ordered will be the last thing I do coolant wise.
This car seriously defies all logic sometimes. At least I guess I will never have to worry about overheating. Ever.

 

[yossarian19]

The fan clutch has never worked ever since I got the car, the fan spins with the engine at all times, from cold start.

As far as it goes, this is the intended function.
The mechanical fan will always turn when the engine is on. The clutch, if it is in good working condition, will have some drag to it. Meaning, engine off, the fan still has some resistance to turning. When the engine is up to temperature, that amount of resistance increases sharply (again, if the fan clutch is working properly).
In theory, you should not be able to over-cool the engine with a fan, as cool water will not be permitted to flow from a properly functioning thermostat.
The holes drilled in it are not helping things in this case. Depending on size, I'd even say they could be causing the problem.

 

[HappyDog]

The fan clutch has never worked ever since I got the car, the fan spins with the engine at all times, from cold start.

I'm not sure what you mean here. Does the fan run with full force and sound like a small jet on takeoff, or is it spinning but not making any wind noise?

If the former, and it continues to do it after you've driven a block or so, the clutch is defective in a rather unusual way -- usually they fail by never engaging the fan with full force when things get hot.

The reason the clutch engages solidly at first startup is the clutch uses a viscous coupling, and when the engine is off all the fluid drains to the bottom. When started cold, it takes my 2001 almost a block to get the fluid properly redistributed before the fan stops sounding like a giant wind machine. However, after that first block I never hear the mechanical fan again unless I'm going real slow up a steep hill, or I'm stuck in stop and go traffic on a real hot day.

If your fan is always blowing at full bore on a cold day that can cool the engine enough without even thinking about the radiator.

 

[WarGin]

I'm not sure what you mean here. Does the fan run with full force and sound like a small jet on takeoff, or is it spinning but not making any wind noise?

If the former, and it continues to do it after you've driven a block or so, the clutch is defective in a rather unusual way -- usually they fail by never engaging the fan with full force when things get hot.

The reason the clutch engages solidly at first startup is the clutch uses a viscous coupling, and when the engine is off all the fluid drains to the bottom. When started cold, it takes my 2001 almost a block to get the fluid properly redistributed before the fan stops sounding like a giant wind machine. However, after that first block I never hear the mechanical fan again unless I'm going real slow up a steep hill, or I'm stuck in stop and go traffic on a real hot day.

If your fan is always blowing at full bore on a cold day that can cool the engine enough without even thinking about the radiator.

The fan is ALWAYS turning full force. when the engine is off you can move it, with effort. if this is the problem then hallelujah, its comin off tomorrow as soon as im outta work.

 

[techno1154]

The holes drilled in it are not helping things in this case. Depending on size, I'd even say they could be causing the problem.

I agree here. Why two holes? A single 1/8" hole at the top is enough to allow any air in the engine block to move to the radiator and out to the over flow bottle.

I have yet get an after market thermostat form the discount parts places that work properly. I had the same problem as you in of all places Waterbury in the winter of 2001. Over cooling. The thermostat would open early then stay open thus allowing the engine temperature to stay at about 150 degrees. After that I only use the OEM (Chrysler) thermostat in my XJ. They already have a hole drilled in them and a little check ball installed to prevent reverse water flow. This hole should on the top or 12:00 o'clock position. No other holes are needed.

 

[djgrayxj]

Note from DJ
What is the part number of the 195 Degrees Fahrenheit Thermostat you are installing?

 

[Warlock1]

The heater control valve was rusted closed, now I have it open full time, capped off the vacuum. I'm reasonably certain that the heater hoses are correctly connected. Maybe I will try to delete the actuator completely.

Rusted closed, hmmmm.... I would have little faith in this heater control valve. I'd almost guarantee that is a part of your problem. New ones are relatively inexpensive, Rock auto has 2 listed for less than $14.

I will go back to advanced and get 3 more 195 degree thermostats (chances are at least one will work), and a cooking thermometer. If I'm pulling the housing off, again, it's gonna get the best thermostat outta what I got.

Good idea. I think this is most of your problem.

The fan clutch has never worked ever since I got the car, the fan spins with the engine at all times, from cold start. Does removing the clutch/fan involve needing to remove any pulleys? Or does it bolt to the shaft sticking off the pulley?

This might help in determining the state of your clutch fan.

Your mechanical (clutch) fan will always turn when the engine is running. To what extent, depends on its state of performance, good or bad.

A basic overview of the way a clutch fan works (viscous or hydraulic or hydrostatic) is kind if like a torque convertor, with a twist. The twist is that they are temperature and RPM sensitive. As stated in a previous post, when the engine is off, the fluid drains to the bottom of the clutch assembly. Then when you start the engine, the fan will turn at the (or very close to) the same speed as the input shaft speed (the shaft that is bolted to the driven pulley). After a few moments, the fluid in the clutch assembly will distribute due to centrifical force and the fan will slow its speed relative to the input shaft speed. This is why there is more fan noise when you first
start the engine.

Now, as your RPMs get higher, the clutch assembly will loosen up and eventually freewheel. It does this because, as an example, usually at higher RPMs, you are at highway speeds. At this point, the fan is really not needed for cooling purposes and also by the clutch assembly freewheeling, it frees up some horsepower for the engine by not having to turn that big fan.

Also, as your coolant gets hotter, like if you are towing or rock crawling, the air that is pulled through the radiator is heated by this action in turn heats up the clutch assembly and causes the clutch to "grip" firmer to the input shaft causing the fan to turn faster relative to the input shaft speed. This causes the fan to pull more air and become noisier, hence the "jet" sound.

When the engine is off and you grab the fan and try to turn it, it will turn but with some resistance, what you are feeling is the drag of the fluid in the coupling (clutch).

If your fan sounds like the "jet" all the time, especially in the extreme cold, I would say that it needs a new clutch assembly. Usually they fail in the other extreme (spin freely and don't pull enough air) but you never know.

So;
1- Thermostat.
2-Heater control valve.
3-Clutch fan.
I would say that either 1 of them, 2 of them, or all three are your problem.

 

[WarGin]

Ok so I got a Stant SuperStat, 195 degree, and tested it probably 50 times with a candy thermometer, 200 degree water and a bowl of cold water. Worked every time without fail. Also drilled a 1/16 hole at the top, because frankly every single person I've ever talked to advised to do this, and the stat still worked.
Installed it tonight, and attempted to remove the fan, didn't have anything that would fit between the pulley and fan clutch however, so I'll wait till I can borrow some tools to do that. Also messed with the control valve, didn't do anything at all.
Managed to get it running to 140-160 range for a bit, then dropped to 130.
Slamming face into the warm radiator.
So new plan
Remove fan permanently, get/borrow IR temp gun to verify temps, based on that maybe get a new guage.
On the subject of the heater control valve, is there a way to pipe the hose from the thermostat housing directly into the input of the heater core? And then output to the water pump? The input /output to the core is hoses clamped to the heater valve manifold thingy, would brass elbows or nipples with hose/hose connections work? Could probably even get away with threaded...
I really want to freaking get this to work,
At this point I've bled for heat, slipped on ice While burping and reflex made me grab for support and my hand found the 1200rpm vortex of doom behind the radiator. Got lucky with that at least...

 

[yossarian19]

F me...
Your water pump has a pipe running to the heater core and from the heater core, to the thermostat housing. Correct?
If so... the thermostat is bypassed by enough flowing water (maybe) to be over cooled by the fan & keep the engine from warming up. It's always got, say, one gallon per minute of super-chilly water flowing through it. Without the fan clutch stuck on that wouldn't be enough to keep it from warming up.
I'd never heard of it before and on a system without the bypass, I don't think it would be possible..... but yeah, the fan clutch is probably your problem. Use a screwdriver to wedge between the nut & fan clutch + a 13mm wrench, if it's the same as my 4.0 setup..

 

[WarGin]

Success!!
Well, kind of.
Kingkong pulled the fan off for me since my hand is a little f'd up, and we ran it, and FINALLY got it to operating temp. Yossarian, you're completely right, there was too much water going past the thermostat to the heater core. When we got the fan off and ran the car, we found that the heater core dropped temps by almost 20 degrees on its own. When it did get to "operating temp". We took it for a drive... And the temp dropped like a freaking rock.
It went from 210 to 130 in less then 3 minutes of driving 30-50 in cold ass weather ( I have no idea what the temp is right now but definitely teens if not less), sans fan.
So we got back and decided to see if it would heat up past operating temp. We left it running in the shop (door open of course haha) and checked on it every couple of minutes. Then I got distracted and he got distracted for like 5 mins. When we got back it was 240, so we shut her down, and I kid you not the block was like a freaking tea kettle, you could hear the coolant boiling like a mother, the engine was practically still shaking.
So I fired her back up and ran her around the block to cool it down. In 30 seconds or less I was at 200.
This car seriously defies all realities.
Ive never worked on a car that refused to heat up like this, and when it is heated up, even too much, you can cool it down by driving. It's mind boggling.
I've also never ever heard a block boil like that. Insanity

 

[8Mud]

Sounds a lot like my Renix 4.0. it would under cool and barley make it to 140 most days. Then it would occasionally overheat and spew, it seemed to happen fairly randomly. Turned out to be (mostly) a partially clogged radiator. I had some other issues like a pin hole leak in my radiator, a clogged heater valve and a cracked surge tank, I'm not sure if this contributed or not. It was mostly the partially clogged radiator that was causing most of my issues.

 

[yossarian19]

WTF.
Airflow while driving will cool things down, that makes sense. At idle, yeah, no airflow and things get hot. Sure. I still don't understand how with a known good thermostat it can be getting THAT cold. With no fan.
When did this madness start? Was there any recent work around the time it started? If so, what exactly? I'm trying to imagine what could be going on...
It seems like any airflow, at all, and the Jeep overcools. It does get up to temperature if you idle it, it'll even boil the coolant. The heater core drops temps by 20 degrees, which I've never seen happen - but it's evidently getting plenty of flow.
Air temperature shouldn't be relevant. Every vehicle I've ever been in, driven or heard of will get up to operating temperature in a Utah winter if you give it a moment, and will maintain that temperature on the freeway with a -20 F & 70mph air charge.
Coolant type / mixture... I can't think of a way it should do this, but lets put a pin on that
Water pump... I think it's been determined that you can't have too much flow, but I can't see how you'd run in to that in a practical way even if you could.
Yeah, I dunno man. This is a headscratcher for sure.

 

[Warlock1]

Success!!
So I fired her back up and ran her around the block to cool it down. In 30 seconds or less I was at 200.

Did it stay at 200 degrees or did you not drive it long enough to find out?

 

[WarGin]

Did it stay at 200 degrees or did you not drive it long enough to find out?

Dropped back down to 160 by the time I got back to the shop (maybe 3/4 of a mile loop).
Driving around today temp seems to have stabilized at 160ish when going under 45, 130 anything over 45mph. I guess I'll just have to get a piece of cardboard and find a happy equilibrium. And maybe finally throw on the E-fans I've had for 2 months.

 

[techno1154]

I may be wrong but I still think he is having a thermostat issue. The thermostat is designed to at the very least restrict the flow of coolant from the engine block long enough for the engine to get up to temperature before it opens and allow a partial flow in order to maintain optimum temperature. In this thread, the Stant thermostat opens wide when the temperature reach the designated target. after that it remains open thus allowing the engine to overcool. I had that same problem years ago in Waterbury, CT.

Everything the OP listed in his post I view as 100% accurate because I have experienced it exactly as he described it. And by-the-way, I was in Iowa in the winter of 2007. The OEM radiator fans on my XJ were replace by electric fans a few years before. My XJ will upward of 210 Degrees if allowed to idle long enough. Maintain upward of 40 MPH for 10 minutes when the ambient temperature is below 40 degrees and the temperature falls back to about 190 degrees as indicated on the Scangage but never below. And yes, a strong airflow across the cabin heater will drop the coolant temperature by maybe 10 degrees.

 

[WarGin]

The thermostat is not staying open, in fact it rarely opens at all.
I tested it 50 times, hot water (200) to cold water (room temp, probs 60)
And it opened, then closed, every single time. I actually bought 2, tested both, and took the one that opened/closed faster and installed it. It's not the thermostat.

I can only assume you run a 4.0, and not a carb'd 2.5 that puts out 120hp at best.
I think I just have too much cooling ability for the heat that my engine creates.
it too the better part of thirty (30!) minutes of idling in a heated shop before the thermostat even opened.

 

[yossarian19]

Are you sure you have the right radiator in this..? Is there a different / smaller radiator that you are supposed to have?
Still... it's hard not to keep looking at the thermostat. I mean, it's only job is to keep the engine up to temperature... and nothing else does that job, that I can think of.

 

[Warlock1]

it too the better part of thirty (30!) minutes of idling in a heated shop before the thermostat even opened.

Is this with the fan reinstalled?

You might be on to something Yossarian. Could you have the wrong radiator in there? Could that be a 4.0 rad?