Bought a boat, now what?

99 Sport, 5.5" lift, 31", aw4, 3.55

So I bought a boat and am towing it around. I know my XJ is under geared (should be 4.10 for 31", thinking 4.56 so I can throw 33's under it). If I tow the boat for a while the temp starts to spike. Everything in the cooling system is stock. Thoughts on items I should upgrade? I'm thinking a trans cooler to start... And go...

Add a trans cooler. Engine cooling, not much you can do except add an oil cooler and upgrade your radiator. How heavy is the boat? under 2k pounds I think all you need is a trans cooler and different gearing once you get bigger tires.

I tow with my LS powered XJ. Heat was always a problem. I know a thing or two about getting the 4.0 as well too run a bit cooler under extreme load. Honestly, start with an upgraded trans cooler.

clydefrog said:

Add a trans cooler. Engine cooling, not much you can do except add an oil cooler and upgrade your radiator. How heavy is the boat? under 2k pounds I think all you need is a trans cooler and different gearing once you get bigger tires.

I tow with my LS powered XJ. Heat was always a problem. I know a thing or two about getting the 4.0 as well too run a bit cooler under extreme load. Honestly, start with an upgraded trans cooler.

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Sounds great, I was already leaning that way to begin with, just wanted to know what the peanut gallery would say. Boat is about 2,500 lbs, so it's not extremely heavy. However, being under geared already makes my XJ sluggish. I'm considering putting 4.56 gears in it so I can run 33's.

Do you think an upgraded fan clutch is a good idea? I think I need to replace that anyway.

Are you using overdrive?

My XJ has stock gears and 32" tires. I keep the shifter on 3, cruise at 2500 RPM with my trailer, no problems with overheating.

Start by reconditioning the cooling system. Flush the cooling system, replace the wear items. Thermostat, hoses (good to do while you're in there), water pump (probably about due), look inside radiator for scale (after the flush), and replace the fan clutch. From there, install a trans cooler - bigger the better. I would suggest you bypass the trans cooler in the radiator to avoid dumping the heat from the trans into the coolant. Install a gauge on the trans temp and track that. If the trans starts running below 150 after the cooler install, add the radiator cooler back in to keep the trans fluid warm.

If you plan on towing it alot you might want to step up to 4.88 instead of 4.56. Your not going to be doing much over the speed limit on the freeway and it will help better in traffic.

Great info, for the record I have done some reconditioning to the cooling system, but it appears so far that it's not enough. I cleaned the system quite a bit and replaced the radiator cap. Definitely looking to do some upgrade/reconditioning to the system. Something tells me that I have tons to do.

I think the real issue is not really related to towing anything. It's quite hot here right now 95* and if I run my ac it starts to heat up. Once the system gets to 220* the radiator cap starts to port fluid out the top. At times it becomes significant. I'm nowhere near overheat as the temp doesn't go any higher than 220*. I replaced the cap about a month ago when this first happened, and I thought I had it fixed. It happened again today. It's not going into the overflow bottle. I know the overflow line is not clogged, because it will suck fluid out of it during normal operation.

If I have the AC on during normal conditions I have no issues. It only pushes fluid out if I'm moving slowly or not moving at all while the AC is on.

Has anyone else had the radiator port fluid out of the cap when it's nowhere near overheat?

I have a couple ideas:

1) The electric fan is not operating correctly. When I messed with it today, as soon as the temp got to 220* I noticed seeping from the radiator cap, but the fan was not on. I had the AC running.

2) The viscous fan clutch needs to be replaced. I'm doing this regardless, but I'm considering an "upgraded" ZJ HD clutch. The big issue here is the my clutch is held on by 4 bolts at the engine. The ZJ clutch connects by a large nut on the post.

3) I cleaned the system before the winter with baking soda and vinegar and cleaned a ton of stuff out of it. However, I think I need to perform a chemical flush. Thoughts on doing this? I've read so many things on the pros and cons, what have you all run into doing this type of flush. How long have you left the chemical flush in the system.

I think that's it for now.

I am thinking that if the AC is on, the Auxiliary Fan should be on.

Hypoid said:

I am thinking that if the AC is on, the Auxiliary Fan should be on.

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That's what I was thinking as well. I did read that it won't come on till the temp hits 220* on a 98-01 XJ.... Not quite sure what to believe...

I'm not well versed on those years, but, yeah.

Vernicious said:

I think the real issue is not really related to towing anything. It's quite hot here right now 95* and if I run my ac it starts to heat up. Once the system gets to 220* the radiator cap starts to port fluid out the top. At times it becomes significant. I'm nowhere near overheat as the temp doesn't go any higher than 220*. I replaced the cap about a month ago when this first happened, and I thought I had it fixed. It happened again today. It's not going into the overflow bottle. I know the overflow line is not clogged, because it will suck fluid out of it during normal operation.

Has anyone else had the radiator port fluid out of the cap when it's nowhere near overheat?

I have a couple ideas:

2) The viscous fan clutch needs to be replaced. I'm doing this regardless, but I'm considering an "upgraded" ZJ HD clutch. The big issue here is the my clutch is held on by 4 bolts at the engine. The ZJ clutch connects by a large nut on the post.

Click to expand...

I'd test your existing radiator cap, but it should be going to the overflow bottle. Do you have 50/50 antifreeze? IT shouldn't be boiling over at that low a temp, unless the radiator cap isn't allowing the system to build pressure.

Sounds like you're looking at the wrong ZJ fan clutch. You want a ZJ fan clutch, regular, not heavy or extreme duty, from a 4.0L 96-98-ish ZJ. they have the same bolt pattern as the XJ. You're not likely to fit the extreme duty fan clutch due to the extended cooling fins on it. Radiator contact is not a pleasant thing.

David Bricker / SYR - TUS

David_Bricker said:

I'd test your existing radiator cap, but it should be going to the overflow bottle. Do you have 50/50 antifreeze? IT shouldn't be boiling over at that low a temp, unless the radiator cap isn't allowing the system to build pressure.

Sounds like you're looking at the wrong ZJ fan clutch. You want a ZJ fan clutch, regular, not heavy or extreme duty, from a 4.0L 96-98-ish ZJ. they have the same bolt pattern as the XJ. You're not likely to fit the extreme duty fan clutch due to the extended cooling fins on it. Radiator contact is not a pleasant thing.

David Bricker / SYR - TUS

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Good deal, I was looking at the 99 ZJ fans (same year as mine), guess I'll back those years down a little. This is one piece I was looking for. Thanks!