Mike1998XJ

That's a good point about the airflow Red Baron... I have been studying the Engine as it sits in the compartment as well as the shrouds. A few thoughts...
1. I would be surprised if the clutch fan actually cooled the Drivers side of the engine at all. I'm going to check the air flow tomorrow.
2. The engine is shoe horned in so tight it's nearly pressed into the fan and radiator. Most engine fans do cool the engine with airflow as well as pull air through the radiator. This design doesn't seem like it would allow the fan to efficiently blow air on the engine.
3. The back seal on the hood does not allow any place for air to escape. Obviously you wouldn't want to run without the seal. I think these guys that install vents or a hood with a rear facing functional cowl are on top of it for warm weather use. That way the air has a path for escaping.
4. If you compare the fan schrouds to other cars and trucks it seems like the designer was restricted by space limitations, which goes along with what your saying. In my research on fan schrouds part of their function is to channel air away from the radiator and also not allow the hot air to return to the radiator area. I'd like to run some smoke through there and watch the pattern of the airflow. Airflow that runs in a laminar flow pattern does a much better job of cooling objects than air that flows in a chaotic state. I propose we have the latter...
What your saying makes sense. Tomorrow I will do my test and see what else we can find out.
Watch out for the buzzards!

red91

I had a 66 ford PU with a300 six in it and used to haul wood, grain, dirt, stone, and all the inlaws furniture when they moved and did not have a fan or shroud for three years plus drove it to work every day never over heated once !!!

Also had a 71 f rd pu ( thats the way it was spelled any way on the hood ) with a 400 m in it did the same thing with that too I even drove into Toledo to go to work at Jeep to make these addictive little things we drive. Never over heated !!!
So before anybody flames me (either for building their Jeep or saying it's not needed ) it's as said before ; I didn't do any stop and go driving for extended periods except going down Central Ave. but even then you have 35 to 40 mph speed limit between lights. I also think those things had radiators that were larger than needed. If I had my way I'd be doin that ford taurus dual fan swap yep thats I'd be a doin!!!!

as I've read before if I had money and space to work oh yeah and skill love that

As another example of depending on your situation. I drove home once in 20 degree weather with no fan belt and no fan the thermosiphon effect was enough to keep it cool so it just goes to show ; you don't need none of it, all the time but, when you do !?!?!?

by the way Mike1998xj what I think you need is an air pitot tube like the aircraft engineers use it measures air velocity and pressure just the ticket I think

Mike1998XJ

Good post. I am real familiar with those Ford 300 straight 6's. Still have this 3/4 ton one sitting in my back yard! I drove it for 4 years gave it to my Son when he was 16 and he drove it until gas got too expensive 2 years ago or so. That was one of the best engines Ford ever built. You could camp out in the engine compartment!
That one had an unusual drivetrain. When you were in the sand in low-lock all 4 tires would spin. I miss it. I went from a 1999 Suburban to this Jeep after I sold my Boat. That Suburban got 15.5mpg driving around here and there and my Jeep only gets mid to upper 17's on the same route. The Suburban pulled 17's on the highway!
I miss that towing capacity and the room... But I still love these Jeeps, they have a lot of character!
Look for the air flow results tomorrow evening of the test I'm doing tomorrow.
Where the heck am I going to get a Pitot Tube??? Man you guys are tough! How about an easier request?
One question to everyone??? Why did Chrysler put the clutch fan on the passenger side when the exhaust and intake are on the Drivers side? Wouldn't it seem like a better idea if they weree reversed? Just a thought...I doubt we'll ever know the answer to that one!

JeepingDan

I'm running without a shroud or electric fan and no problems over heating.

Mike1998XJ

What state do you live in? Do you tow or 4 wheel it? I guess you must 4 wheel it from you picture... So yours never gets hot either huh? Interesting... Is your radiator newer?

red91

LOL yeah had to through that in there the pitot tube would be the cats meow on that test youcould move it around in the air flow and know just what kind of mass airflow you had at any given point on your radiator the only problem thogh would be finding one that you could calibrate for that low of a measurement.
personally I think they copied the 300 six to make the 4.0 L one thing most people don't know is that you can get more torque out of a straight six than a V6 or V8 of comparable displacement because of the power stroke overlap between the cylinders chevy and ford are finding that out in their diesels

red91

oh yeah I forgot concerning the location of the clutch fan I think it was just a question of ease of layout it was the only place they had room and still get the belt to line up just my guess

I need a signature line

ol"blue

Think of something that's important or relevant to you. Change it as often as the mood arises.

Mike1998XJ

Yep, When I worked at the old Federal Mogul then Asimco, we made the camshaft for the Dmax. That was one of my programs. The Dmax plant in Ohio is one of the nicest engine plants I've ever been in. The cam in those engines was one of the better designs I've ever seen. Very Robust.
I went in there one Friday after we had a quality issue and noticed this Japanese guy in a smock cleaning a machine... I asked someone who it was. We'll wouldn't you know it but it was the President of the Company. Every Friday they shut the line down and everyone no matter what their position is comes out and cleans the machines.
That's the Izuzu influence and part of the Toyota Production Systems principals.
Maybe GM and Chrysler will adopt those practices in the New World! It would do some of the execs I've meet over there some good!

Mike1998XJ

I suspect the shroud was one of those compromises... Where fit took precedence over function... If Jeeps were originally designed for 4 cylinders like someone said, they lost a lot of real estate by shoehorning the 6 in there. If there were 3 more inches between the engine and radiator so the Designer could fit a better shroud system in maybe overheating wouldn't be an issue...
The clutch fan hardly has any wall on the inboard side. There can be little or no air management taking place there.
Just my 2 cents... I'm still going to try and trace down anyone I can find at Chrysler that might know about this. Does anyone know if Chrysler had a similar sized and shaped fan shroud in that era? Most of the time when we designed anything we'd use an old design as a starting point. Maybe this fan shroud is the evolution or de-evolution of another shroud that had a more robust design? Just thinkin' out loud...

ol"blue

Wasn't this all done under AMC's control of the Jeep brand back then?

Mike1998XJ

OK. Just finished setting up for the test. Have both of them warming up to same temp in garage right now. Started at same time from cold. On a side note we'll see which one gets up to temp first.
I'm getting a little outside wind interference so going to have to close doors a bit for test. Don't want to kill myself.
Take a look at picture... Looks like the tissue was the way to go! Thanks whoever that was....
Going to take me until tonight to post rest of results. I have to go to a high school graduation party sometime today. Both Jeeps have heater controls in off position. Yes the tissues are being sucked into the grill by the fan... The wind is around 5-10mph from my left in this picture. Will close garage door in a minute.
Mike

red91

yeah but jeep had its own in house design engineers every thing was done at the old Toledo plant that they tore down not to long ago. When Chrysler bought it after a year or two all those engineers except for production engineers moved to the big house in Detroit so some may still be around

Mike1998XJ

Purpose:
This test was done to compare airflow on a 1999 (Purple) Cherokee without fan shround or electrical fan, to a 1998 (Red) Cherokee with a fan shround and electric fan. During this test the electric fan on the Red Jeep was not on. That is for another day.
When discussing the tissue pieces on the test fixture we will identify them as # 1-7 left to right. The rpm's the engine was operating at were saved in the picture name. Not sure if that will show in title. Tests were done at Idle and 1500rpm.
Test 1: During this test it was observed that the Red Jeep with the shroud and electric fan had more draw on the tissue with the test fixture positioned in front. It drew tissue pieces 1-5 towards it, both at idle and 1500rpm's.
The Purple Jeep had less draw on tissue #1 and virtually no draw on tissue #5.
A simple conclusion can be drawn from this: More air = more cooling. Shroud wins this test.
Test 2:
Test fixture was positioned in engine compartment. Obviously this would have more real world results with the hood closed. Since that was not possible, conclusions can still be drawn since test fixture was in same location on both Jeeps at same rpm's.
At 1500rpm on Red Jeep tissue 1-2 were hanging looser. One might draw the conclusion that this was due to the shroud routing the airflow back towards the engine in a more efficient manner. (More on that in Test 3). Since this is a simple test we must make several assumptions. One of those being that we must have some faith in the original Designers, the only logical conclusion is that the directing of this airflow is is a good thing for cooling and the design intent.
At 1500rpm on Purple Jeep tissue 1-3 were being drawn quite heavily towards the fan. One might argue that this is a favorable condition. We will have to discuss this one. Test 3 will shed more light on this.
Test 3:
Test fixture was positioned in engine bay. Both Jeeps at Idle. On Red Jeep tissue 1-2 were being blown back towards the front of the Jeep. Somehow the Shroud makes the air bounce off the firewall or create a low pressure causing these tissues to blow forward.
On Purple Jeep tissue 1-2 were being blown towards the firewall. Totally the opposite direction. The only logical conclusion I come up from this is to assume the shroud is directing the airflow properly and that the lack of a shroud is completely opposite from the design intent.

Test conclusion:
Results indicate the following:
1. Better air draw from the front when shroud in place.
2. Better air management in engine compartment per original design intent with shroud in place.
3. Clutch fan appears to have very little "airflow" cooling effect on the Driver side of the engine compartment. Of course it cools the radiator coolant that cools that side. One must conclude that without the electric fan the Drivers side of engine will run hotter than passenger side at low speed, high demand conditions especially if AC is run.
Further testing may include temperature measurement at various points on the cooling system and engine.
Thanks Guys!
Let me know what you think. It would only let me upload 5 pictures. The 6th picture is with the test fixture in the back of the purple engine compartment. I will post this picture right after I post this.
Mike

Mike1998XJ

Here is the final picture from the airflow test. This goes with test 3. Note the opposite movement of tissues.
By the way the pictures do not do this test justice. The tissues flutter so it's tough to capture the essence of the direction and the strength of the draw on them. If you were to see this in Person you would really be able to see a difference.
Gotta' fly... have graduation party to go to.
Mike