Upgraded to WJ Pump, won't stop leaking

I picked up a WJ pump and swapped it in my 97. The WJ pump has two return fittings on the reservoir while the XJ only has one. Everything I read said to cap the smaller one higher up on the reservoir and use the bigger fitting on the bottom of the reservoir. Well the pump works fine, Jeep drives fine, but the fitting I capped won't stop leaking! I used a vinyl universal cap I found in an assortment over by the vacuum section where you also find the rubber caps for capping off things like this. Normally I use rubber but I have had the rubber ones dry rot and go bad sooner than I would have liked so I figured I would get more life out of the vinyl ones. Well I capped it off and even put a small hose clamp on it to secure it and the darn thing leaks! I even tried replacing it with another one and it still leaks! Anyone else had this fitting leak? It leaks pretty good too, I usually have a 3"-4" diameter spot underneath the Jeep in the mornings when I come out to go to work.

Are you sure the reservoir isn't cracked at the fitting?
There isn't much pressure on the fitting, did you use a hose clamp on the cap?

lazyxj said:

Are you sure the reservoir isn't cracked at the fitting?
There isn't much pressure on the fitting, did you use a hose clamp on the cap?

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I am pretty sure its not cracked at the fitting but I will be double checking when I go to fiddle with it again. I also replaced the cap once already thinking I messed it up clamping the hose clamp too tight. I clamped it with only a little pressure and it still leaked, so I tightened it more but not as much as the first time and it still leaked. I was planning on taking the time to fool with it yesterday after I replaced the frame end bushing on me Iron Man 4x4 Fab track bar but I quickly found out that the bolt had froze in the sleeve in the axle end and I got to a point where I had no choice but to cut it out and destroyed the bushing and sleeve along with it. Now my Jeep is down until he can ship out a new axle end bushing, bolt, and sleeve.

I did this swap too but I capped the lower one. I capped mine with about 3" of transmission line, a bolt and then hose clamps. I have a super small leak that I just need to adjust but nothing that is crazy. My understanding when I did the swap is that the lower one was for a cooler line and the top was the true return line. So it may be that it's routed incorrectly and creating additional pressure thus creating a leak. I could just be entirely off though.....

smokeyyank said:

I did this swap too but I capped the lower one. I capped mine with about 3" of transmission line, a bolt and then hose clamps. I have a super small leak that I just need to adjust but nothing that is crazy. My understanding when I did the swap is that the lower one was for a cooler line and the top was the true return line. So it may be that it's routed incorrectly and creating additional pressure thus creating a leak. I could just be entirely off though.....

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See everything I read said the lower one was the one to use. Everyone said that when they used the smaller upper one the pump was really loud and whiney and that the lower one has a special piece in it to stop cavitation inside the pump. I was going to do what you did with the lower one but with the upped one. I hope its just that the cap can't handle it.

I have not done this swap but have found that the thin caps dont like heat and leak easy. With most things like that i will run a short hose (gas line) and use a capping bard or a female bard with a cap. Oh and hose clamp and it stays dry for years.

Ben824 said:

See everything I read said the lower one was the one to use. Everyone said that when they used the smaller upper one the pump was really loud and whiney and that the lower one has a special piece in it to stop cavitation inside the pump. I was going to do what you did with the lower one but with the upped one. I hope its just that the cap can't handle it.

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The only thing I read about whine or the pump being loud was when people didn't swap out the fitting on the high pressure line. Try it out and see. :cheers:

Ok I used a small piece of hose and put a bolt in the end of it and clamped both end of the hose and viola! Leak is gone. I was just surprised that that little cap didn't hold. I didn't think there was that much pressure in the reservoir but I guess there is. Anyways the leak has completely stopped. I can definitely tell there is an improvement to the ease of steering. Not night and day but its there. I didn't drill out the XJ fitting that I swapped over like many other have tried. I read that someone had tried several fittings, drilling them different sizes, and he said to drill it out to match the WJ fitting it way too large and he believes it causes the pump to cavitate. So he tried different size holes until he got the right size that gave a boost in flow but not so much that it caused the pump to cavitate and whine. I can't remember what size was the sweet spot but I will find the post that I read it in and give it a try and report back.