cooling upgrade

Hi all, I have a couple of questions and hopefully someone can help. First off, I have a 99 XJ, I6 4.0CL. I will be moving soon from Elmendorf Air Force Base to Eglin Air Force Base (Alaska to Florida) and hauling a trailer so I am planning a trans cooler possibly. I am working on a cold air intake to replace the stock air box. I would like to get rid of the engine driven fan and stock electric fan and replace it possibly with dual electric fans. Is it just that simple? Do I need a new thermostat, water pump, lots of wiring? And, is it all worth it? Will I gain much HP? More gas efficient? And if so, what brands can you all recomend as I know nothing of how much CFM's my stock fan's push, pull, whatever. Any advice would greatly be appreciated

CrewDawg said:

I would like to get rid of the engine driven fan and stock electric fan and replace it possibly with dual electric fans.

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Why?

Rev

Becuase I heard that upgrading fans can be one of the most beneficial upgrades in increasing performance. Am I wrong?

It can be, but it's not usually - for us.

The XJ runs rather warm, and has a difficult time cooling everything once you've started swapping parts (low grille and nasty wide radiator.) Most people who switch to dual electric fans end up going back.

With that in mind, since you've got a known towing jag coming up, here's what I'd do...

1) Install the transmission cooler. Remove the "internal" cooler from the circuit and go with the external only. You can replumb the "internal" cooler later, or just add a thermal bypass valve (from B&M and maybe a couple other outfits) which do the same thing but still keep the thermal load off your coolant.

2) If you haven't done a flush recently, do so - the refill with about 70-30 rather than 50-50. The extra water will help you cool more, since water is a more efficient heat transfer medium than ethylene glycol (and a bottle of Redline Water Wetter won't go amiss, either.)

3) Consider adding an engine oil cooler - that will also help remove some heat from the engine - by using another fluid. Oil contacts pretty much everything, and picks up a fair bit of heat on the way back down the side of the head (and from friction in the valvetrain and camshaft running gear.)

4) If you don't know how old it is, you might want to replace your fan clutch - they have a service life of about five years before the viscous coupling starts to fail. Actually, I'd take it to the hobby shop there (they still have an auto hobby shop, right?) or have one of the machinists on base (they bloody well should still have those!) and have two or three holes drilled in a pattern near the centre (180* or 120* apart) to accept a set of small bolts - say, #10 or 1/4" at largest. You're trying to "pin" the hub to the housing, and make it a solid part for the duration of the trip. The power loss is minimal, you probably won't really notice while you're driving. Replace it when you get to Florida - use a Hayden thermal unit.

If you're dead set on going to all-electric fans (a mod I usually suggest for bracket racing and such - where consistency and power are key,) make sure you get fans that pull at least 2500cfm - EACH. These are going to be brutes - big, noisy, and hungry. Like I said, the 242 likes a lot of cool air...

Sounds like a fun trip - you coming down the Al-Can? I got to drive on convoy once to Elmendorf - then I had to follow the load to Shemya. Glad I don't have to do that again...

5-90

5-90, thanks so much for the advice, I'll take it. I didnt really understand 1. at all or most of 4. but ill try and make sense out of those later. Yea, I'll be driving the Alcan (in Nov, ouch) with a dog, 2 cats, and complaining wife! And the 5x8 trailer in tow. Sounds like your an AF vet, what years? I've never been to Shemya and didnt think you could drive it, isnt that like the last damn island out on the aleutian chain? Anyways, thanks again for the advice.

Yeah - get on the boat with the CONEX boxes and enjoy the ride. Ugh. Just following orders - follow the load until it's signed for.

USAF/SOCOM, 6/1989-6/1995. Home-stationed here in CA (grew up in IN.) At least you won't have to listen to your kids - too bad your wife doesn't travel well (mine does! :kissyou: )

1) The "internal" tranny cooler is the one that's already in the radiator - if you follow the lines up from the transmission to the radiator, you'll follow them right into the cooler. It's a hollow cylinder in the radiator tank.

They put it there both to cool the fluid (from about 230* to about 210*) and to heat it to operating temperature quicker (from ambient to 190* or more.) You aren't going to harm anything by taking the internal cooler out of the circuit and going with the external unit only - and you'll be able to cool your transmission off more. If you were going to tow regularly, I'd highly suggest a transmission fuild temperature gage, and take the temperature before the fluid gets to the cooler, not after. (Ideally you want both - that will tell you if the cooler's clogged. But, pre-cooler temperatures are closer to actual operating temperatures, and spikes in temperature are pretty reliable indicators of problems. Since you're driving the Al-Can, install the gage. It can get lonely out there...)

4) The fan clutch is actually a viscous coupling that is thermally activated (uses a really thick fluid that is supposed to get thicker with heat.) This fluid has a shortish service life - say, five years or so. I tend to write the date I replaced mine on the body of the new cooler to help me keep track (four XJ's.)

The idea of "pinning" the fan clutch is to make the fan "always on" - the fan clutch is a variable coupling, and it never reaches 100% power transmission (I think it peaks around 80%.) You want to use two or three bolts for balance, to reduce stress on the bearing behind the fan. If you don't know how to set up a hole pattern, a machinist on base (check the aero shops) can do it for you in about 15 minutes - show him my first post and he should get the idea. This will keep the "string-driven thing" on all the time, which will help both your engine temperatures and your transmission temperatures (the tranny cooler mounts on front of the radiator, and uses the same fans.)

Most people who hear about "going solid" at the fan clutch fear some great power loss, but it's a non-issue for engines like ours in street vehicles or off-road vehicles - and I'd sooner have a solid mechanical primary fan than an electrical off-road. There's no real useful reason I can think of for going with electric fans only in our applications - I save that for racing vehicles (I might do it with Project: REDSHIFT, but I haven't decided yet.)

With the 99, you should have the dual diaphragm booster, which will give you better brakes. Check your brakes a month before you go - if the look a little worn, change them then! There's a "break-in" cycle for brakes - heat them up too much too soon, and they're history. Not the sort of thing you want to have happen with a trailer... You're also due for a fluid change - or at least a thorough bleeding - but you'll have to check your user manual for that (I haven't gotten an XJ w/ABS - yet.)

If you have any more questions, feel free to ask! We do what we can...

5-90

4) The fan clutch is actually a viscous coupling that is thermally activated (uses a really thick fluid that is supposed to get thicker with heat.) This fluid has a shortish service life - say, five years or so. I tend to write the date I replaced mine on the body of the new cooler to help me keep track (four XJ's.)

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I have always been confused about that, That may be how a thermally activated clutch works the don't have a thermo valve, but the ones with the spring in the front work a little different.

The fan clutch is a small fluid coupling with a thermostatic device that controls a variable-speed fan. The fan clutch ensures that the fan will rotate at just the right speed to keep the engine from overheating, and reduces drive to the fan when it is no longer needed. The fan clutch has a fluid coupling partly filled with silicone oil designed for just that purpose. If the temperature of the air passing through the radiator rises, the heat alerts a bimetal coil spring to "uncoil" or expand. When it expands, it allows just a little more oil to enter the fluid coupling, so the fluid coupling starts to rotate the fan. If the air coming through the radiator is cool, the opposite happens; the coil spring contracts, the oil leaves the fluid coupling and the fan slows. Slowing the fan when it is not needed reduces fuel consumption, makes less noise and saves engine power. Sometimes a flat bimetal strip spring is used instead of a coil spring; it bows out and in when the temperature rises and drops, letting oil in and out of the fluid coupling.

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langer1 said:

I have always been confused about that, That may be how a thermally activated clutch works the don't have a thermo valve, but the ones with the spring in the front work a little different.

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Those use the differing expansion rates of the metal springs to control the rate of spin the fan maintains. Like 5-90 I trust the solid fan over either system.

Sarge

CrewDawg said:

Hi all, I have a couple of questions and hopefully someone can help. First off, I have a 99 XJ, I6 4.0CL. I will be moving soon from Elmendorf Air Force Base to Eglin Air Force Base (Alaska to Florida) and hauling a trailer so I am planning a trans cooler possibly. I am working on a cold air intake to replace the stock air box. I would like to get rid of the engine driven fan and stock electric fan and replace it possibly with dual electric fans. Is it just that simple? Do I need a new thermostat, water pump, lots of wiring? And, is it all worth it? Will I gain much HP? More gas efficient? And if so, what brands can you all recomend as I know nothing of how much CFM's my stock fan's push, pull, whatever. Any advice would greatly be appreciated

Click to expand...

I would also plain on takeing the Northern route, less mountains, cooler temps, no desert.

langer1 said:

I would agree with just get rid of it, accept he's going to Alaska and there anything that helps your engine to warm up should not be removed IMHO

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Check again - he's going FROM Alaska TO Florida - not the other way 'round. Eglin is, as I recall, in the Florida panhandle. (Whenever I had to go to FL, it was usually to MacDill.)

If he were going UP the Al-Can and into Alaska, I'd have handled suggestions differently. Coming down the Al-Can with a load? I'd sooner have an engine that runs a little cool - by the time he gets down this way, that little problem will be self-correcting.

5-90

CrewDawg said:

Becuase I heard that upgrading fans can be one of the most beneficial upgrades in increasing performance. Am I wrong?

Click to expand...

Yes ... you are wrong.

More precisely, what you heard is wrong. If it ain't broke, don't fix it.

I stand corrected, by a spacer and just remove it.

Thanks guys, I sure appreciate all the advice. I'll let you all know how it goes, I'll be leaving Nov 1. And taking a piss on the "welcome to Alaska" sign on my way out!