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Build me a more effective shroud for the mechanical fan

maxbraketorque

NAXJA Forum User
Location
PDX
I picked up a 2000 XJ about a month ago and have been going through the vehicle to get things in good shape. Its quite apparent that the Jeep crowd is fairly polarized on the need for cooling system mods. My XJ is in pretty good shape, and even before I did a cooling system flush, its doing a good job of holding at 210F. The only time it drifts up a bit is in stop-n-go traffic where I've seen it hit 217F on the OBD-II scanner. I suspect that the mechanical fan clutch is somewhat worn, so I plan to replace it with a new XJ fan clutch.

Anyhow, I'd like a bit of extra headroom on cooling system capability, so I've done a bunch of reading on what people have done in the past. There are a ton of different ways to fortify the cooling system, but one thing that seems to have escaped any discussion in the last 10+ years is building a better fan shroud for the mechanical fan. Besides the fact that the mechanical fan shroud seems to become fairly fragile with age and therefore break easily, they do not fully encircle the mechanical fan which decreases the ability of the fan to suck air through the radiator. I suspect that a custom fan shroud that more fully encircles the mechanical fan, perhaps with a slightly tighter gap to the fan blades would significantly improve the cooling performance of the mechanical fan.

Would be great if one of the speciality vendors would make a nice replacement mechanical fan shroud. Besides fully encircling the mechanical fan, another nice feature would be to make it a two piece shroud so that the fan clutch can be more easily replaced. A two piece shroud may also be needed to even install an improved fan shroud. With how easily the factory fan shroud breaks, it seems like this would be a very popular item.
 
Yep, you're right about the shroud being ineffective. The sides and bottom
have a big gap, killing the shroud's effectiveness. I think a better shroud
would be a big help in slow traffic.

I'm going in a slightly different direction, by deleting the fan clutch and
replacing it with a flex fan and spacer. I plan to take temp readings at
the radiator center with both the stock fan and flex fan, to see if there's
any difference...
 
I can get behind this idea. I recently broke my mech fan shroud. I'd love an aluminum one that hugs the fan tighter to replace it with. Not sure that you'd be able to get too much closer with the clearance though because the fan is attached to the motor whereas the shroud is attached to the body.
 
I do write-ups all over the place. This is the same concept, just a little different execution. Just do some measuring and you'll get the exact shape you want.

For what it's worth, I don't have much of my original fan shroud left. It was all broken up when I bought the jeep, and I've never once overheated. I do lots of steep hills, slow movements, etc. I'm not saying you don't need a fan shroud though. Definitely build one if you have the spare time.
 
I do write-ups all over the place. This is the same concept, just a little different execution. Just do some measuring and you'll get the exact shape you want.

For what it's worth, I don't have much of my original fan shroud left. It was all broken up when I bought the jeep, and I've never once overheated. I do lots of steep hills, slow movements, etc. I'm not saying you don't need a fan shroud though. Definitely build one if you have the spare time.

Yeah, I found that custom shrouds have been made available for some other vehicles. I would make something myself if I had enough spare time, but no time for that kind of thing lately. Hoping a speciality vendor will run with it.
 
I got a '93 W/AX15
I bought a used XJ radiator off the C/L so I dunno what YMM it is out of
I will say it is much thicker than the OE one-- maybe a 3 row?
I do know the auto trans add a lot of heat to the rad.
So I am guessing it is out of a late model auto trans XJ

So my cooling system mods are
a) autometer electric temp gage---I do not trust the stock one
1) thicker 3 core rad'
2)eliminate both OE fans
3) two electric fans pulling
4) one fan pushing
Each of the fans is wired independently with separate temp sensors, relays and fuses
The pusher is wired to the "command A/C" switch so it comes on with the A/C
5) 1" spacers on the hood hinges to allow airflow out of the engine compartment
6) 3 layers of header wrap on the stock exhaust header
 
3) two electric fans pulling
4) one fan pushing
Each of the fans is wired independently with separate temp sensors, relays and fuses
The pusher is wired to the "command A/C" switch so it comes on with the A/C

The electric load must be horrible. I prefer a redundant system which factory provides, besides I don't have any room for a "pusher" under my grille.
 
I got a '93 W/AX15
I bought a used XJ radiator off the C/L so I dunno what YMM it is out of
I will say it is much thicker than the OE one-- maybe a 3 row?
I do know the auto trans add a lot of heat to the rad.
So I am guessing it is out of a late model auto trans XJ

So my cooling system mods are
a) autometer electric temp gage---I do not trust the stock one
1) thicker 3 core rad'
2)eliminate both OE fans
3) two electric fans pulling
4) one fan pushing
Each of the fans is wired independently with separate temp sensors, relays and fuses
The pusher is wired to the "command A/C" switch so it comes on with the A/C
5) 1" spacers on the hood hinges to allow airflow out of the engine compartment
6) 3 layers of header wrap on the stock exhaust header

I know that there are many options for replacing the mechanical fan with electric fans and these often seem to be referred to as shrouds, but I am talking about an improved shroud to be used with the mechanical fan.
 
Fill the gap between the shroud and fan with expanding foam or something of the sort and let-er-rip. Bounce the engine off rev limiter a few times to flex the motor mounts. The fan will self-clearance everywhere it needs the room and you'll have a more efficient shroud.

:D:D:D
 
Food for thought: I suspect that one of the reasons for the large gaps in the OEM shroud is to accomodate engine movement due to worn/failing engine or transmission mounts.

Even that's not always enough - just back in June, I was out on the trails with a group at NACFest, and one of the guys got stuck with his trans crossmember on a stump that was just tall enough to push the trans up a little. That was enough to shift the engine until the mechanical fan was hitting the factory shroud, but at first glance it sounded like fan-radiator contact (particularly since he had no efan and it chose that moment to boil over, further impersonating a breached radiator). He had factory mounts, and they were in decent shape.

Just something to think about - the engine/fan and radiator do not move as one in an XJ...
 
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