WJCO's Build Thread, 1999 WJ

Did a cooling system flush today. Engine has been running about 230 since the MSV trail. It only does it at low rpms. Fan clutch didn't fix it. I've already cleaned out the radiator fins which weren't that bad. Coolant today was beautiful, clean system.

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After the flush, still doing it. It seems like the electric fan isn't running strong enough. I ordered a relay as these are known to have a ton of problems. If that doesn't fix it, I'm guessing it's the fan motor. Radiator itself isn't that old and thermostat and water pump are newer as well.
 
Tanktitan said:
Help me understand something. I would have thought that if I had no gear oil leaks, water could not get in. But as I think about it now, you do have higher external pressure under water. Any guidance on when to be concerned; that is, how long under water, how deep, etc., or is there some other way water gets in?


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I have also read on the internet (scary I know) that when a hotter gear box contacts cooler water during a crossing, the metal shrinks just enough to allow water to bypass the seals. Not sure if that's true or not, but theoretically, it could make sense.
 
WJCO said:
I have also read on the internet (scary I know) that when a hotter gear box contacts cooler water during a crossing, the metal shrinks just enough to allow water to bypass the seals. Not sure if that's true or not, but theoretically, it could make sense.
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That actually sounds plausible. Add to the list of things to do: maintain seals and bolt torque. Be nice if someone in the trade could do some dye testing and make assurances or suggestions.

I did find Eddie's breather hose extension thread: https://wayalife.com/showthread.php/5197-Jeep-JK-Wrangler-Axle-Breather-Hose-Extension

What I have attempted with my build is to have a Jeep that I can drive for a thousand miles on highway, that performs superior off highway, and takes me back on highway with no regard to what I have done off highway. All of your comments have been helpful in that regard. Thank you.


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WJCO said:
I have also read on the internet (scary I know) that when a hotter gear box contacts cooler water during a crossing, the metal shrinks just enough to allow water to bypass the seals. Not sure if that's true or not, but theoretically, it could make sense.
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It is absolutely true, in my opinion. It cost me two pinion seals. This first was a spring run on a hot day, diff was getting worked hard, and there were a couple water crossings. After the run, I had milk seeping out of the front pinion seal, and a diff full of it. The next spring, same trail, rear diff this time. The front did not in part likely due to my use of rtv when I installed the replacement.
No leaks ever before, and breathers were clear both times. Hard worked diff hitting damn cold water was my only thought.

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WJCO said:
I have also read on the internet (scary I know) that when a hotter gear box contacts cooler water during a crossing, the metal shrinks just enough to allow water to bypass the seals. Not sure if that's true or not, but theoretically, it could make sense.
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It's not that the metal expands and contracts with heat differential that is the problem...it is the airspace inside that heats up and expands...then suddenly cools in a water crossing creating a vacuum condition that wants to suck water in. ARB sells a diff breather kit that prevents this pressure differential from occurring, with enough tubing and intakes for up to four drivetrain components to be attached and located much higher than where normal breather tubes are located. I've installed these in both my Brute & Jk6...I've had the Brute in multiple water crossings and have found no water intrusion in any of the diffs or transfer case during normal maintenance fluid changes


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My cooling system issue is definitely something with the electric fan. When I first bled the system, I could actually see the electric fan turning and almost see the blades themselves. After a second test drive and a re-bleed to make sure air was out, when I look at the fan, it's spinning so fast that the blades aren't visible and it is much louder. So I'm hoping the relay fixes it. If not, it looks like I'll need a motor.
 
Brute said:
It's not that the metal expands and contracts with heat differential that is the problem...it is the airspace inside that heats up and expands...then suddenly cools in a water crossing creating a vacuum condition that wants to suck water in. ARB sells a diff breather kit that prevents this pressure differential from occurring, with enough tubing and intakes for up to four drivetrain components to be attached and located much higher than where normal breather tubes are located. I've installed these in both my Brute & Jk6...I've had the Brute in multiple water crossings and have found no water intrusion in any of the diffs or transfer case during normal maintenance fluid changes


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I will trust your advice with underwater pressure differentials based on your previous line of work :D Do you happen to have a link or description on this part? I would love to add it on. :thumb:
 
Brute said:
It did for mine...I guess it all depends on where you mount it


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Thanks. Scientifically this does make sense. I've always changed my fluid after crossings and never had evidence of water in the differentials. But this last time, the tcase was pouring out when i pulled the fill plug and was really thin, and I just changed fluid last year and know that it was not overfilled, so I'm thinking some water got in there. For less than a hundred bucks, this seems like a good ideal. Where did you mount yours (on the jeep)? Just curious.
 
Changed out my trans fluid and filters today. No water there, so that's good. I wanted to change it for PM anyways.

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WJCO said:
Changed out my trans fluid and filters today. No water there, so that's good. I wanted to change it for PM anyways.

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I don't think I would have the guts to open up my transmission pan quite yet, maybe some time down the road. Question though, don't you have to go to a trans shop or a dealer to do a complete flush. I remember reading that somewhere.


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VeruGE*144 said:
I don't think I would have the guts to open up my transmission pan quite yet, maybe some time down the road. Question though, don't you have to go to a trans shop or a dealer to do a complete flush. I remember reading that somewhere.


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It's just like pulling a diff cover. Just make sure you have the right type of fluid and know how to check the proper level when refilling it. Any shop with a flush machine can do it, but I would trust a dealer more because they'll likely have the knowledge of the correct type of fluid. I myself would only do a flush if the trans has been flushed every 30k or sooner. Flushes can have some risk especially on higher mileage vehicles. We bought this at 136k, so I just do a drain and fill every 10k or so (not a daily driver so that's usually a couple of years apart). I think this is the first time changing filters on it for me.
 
WJCO said:
It's just like pulling a diff cover. Just make sure you have the right type of fluid and know how to check the proper level when refilling it. Any shop with a flush machine can do it, but I would trust a dealer more because they'll likely have the knowledge of the correct type of fluid. I myself would only do a flush if the trans has been flushed every 30k or sooner. Flushes can have some risk especially on higher mileage vehicles. We bought this at 136k, so I just do a drain and fill every 10k or so (not a daily driver so that's usually a couple of years apart). I think this is the first time changing filters on it for me.
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Additional comment from my end is make sure not to over torque the bolts. I learned the hard way on my oil pan
Have to get to it one day no leak yet after stripped bolt head:)
 
So I'm hoping a new fan relay will fix my fan issue. These are known to have problems. Come to find out, the engineers thought it would be a good idea to put this in a location that is only accessed by removing the entire front bumper, grill, and headlight reatiner. And in my case, the winch and brush guard first. Luckily, the internet had a well-documented way to do this that is much easier. I got to the relay in less than five minutes literally.

Pull the right headlight, cut an access hole with a dremel in the plastic headlight support, and there it is. After changing the relay, I just have to glue or tape up the hole and it isn't visible. If this doesn't fix it, I'll probably need a fan motor.

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New relay in and hole sealed up. Hope it works.

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WJCO said:
So I'm hoping a new fan relay will fix my fan issue. These are known to have problems. Come to find out, the engineers thought it would be a good idea to put this in a location that is only accessed by removing the entire front bumper, grill, and headlight reatiner. And in my case, the winch and brush guard first. Luckily, the internet had a well-documented way to do this that is much easier. I got to the relay in less than five minutes literally.

Pull the right headlight, cut an access hole with a dremel in the plastic headlight support, and there it is. After changing the relay, I just have to glue or tape up the hole and it isn't visible. If this doesn't fix it, I'll probably need a fan motor.
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Wow, that does look hard to get to. I'll have to make a mental note in case mine ever has trouble.

Hope it fixes it for you!
 
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