Whitaker717 Posted January 10, 2023 Share Posted January 10, 2023 Hi guys title says it all. I am at a crossroads with the Comanche. I have about 20k and a second used engine in him. I have been chasing a rear main leak for months. It’s at the dealership for the umpteenth time getting looked at. They are telling me it is either crank walk or crankshaft is scored. They are recommending either a crankshaft replacement or new engine. So I pose the question, what is the best and cheapest way to go. I can’t really afford a new engine right now. I’m not sure what to really do. I have spent at least 20k on this truck and know I won’t get my money back out of it. Any input, ideas, suggestions are welcome. Yes it’s the rear main too. Everything and I mean everything else has been fixed on it. Thanks guys Link to comment Share on other sites More sharing options...
acfortier Posted January 10, 2023 Share Posted January 10, 2023 Are you taking it to a CDJR dealership? Honestly, I'd find an indy who is familiar with this era of vehicle. They probably have kids who were born after the Comanche was discontinued. Hell, the XJ stopped production in 2001... 22 years ago. You've spent $20K on fixing your Comanche? Holy smokes. And, if I'm understanding your post correctly, you've put in a replacement engine, that is leaking from the RMS? But they've diagnosed it as crank walk or the crank is scored? Have they dropped the oil pan? I mean, if that diagnosis is correct, the cheapest option would be putting in another used engine, probably from a junkyard. But it seems like you've found out (since you're on your second engine, which I assume is from a junkyard) that they don't always work out. Comanches, although rare, aren't an investment. It's really up for you to decide how much you want to put in to it before it's not worth it to you. Link to comment Share on other sites More sharing options...
Andy in Pa Posted January 10, 2023 Share Posted January 10, 2023 I have known people that have chased that rear main seal leak, and finally just decide to live with it. If that is the only thing wrong with your MJ, I say you have invested plenty, and now its time to drive it and enjoy it. If you look under almost EVERY other XJ, MJ, ZJ, or TJ with that motor, with over 100kmiles, they are either extremely lucky that the RMS is not leaking, or, like 90% of them, they leave a few little oil drips from their RMS. Link to comment Share on other sites More sharing options...
Whitaker717 Posted January 10, 2023 Author Share Posted January 10, 2023 3 hours ago, Andy in Pa said: I have known people that have chased that rear main seal leak, and finally just decide to live with it. If that is the only thing wrong with your MJ, I say you have invested plenty, and now its time to drive it and enjoy it. If you look under almost EVERY other XJ, MJ, ZJ, or TJ with that motor, with over 100kmiles, they are either extremely lucky that the RMS is not leaking, or, like 90% of them, they leave a few little oil drips from their RMS. I don’t mind living with it but it’s leaking about a quart of oil a week. That’s a lot to me. Link to comment Share on other sites More sharing options...
Eagle Posted January 10, 2023 Share Posted January 10, 2023 A quart a week is a lot. How did this dealership diagnose crankshaft walking? If that's really happening, how long ago was the rebuilt engine installed? A new or newly-rebuilt engine should not have that -- so I'd look into whether it's covered by whatever warranty you got with the engine. If it's a scored crank -- one of the "name" gasket and seal companies (FelPro, maybe) makes a rear main seal for the Jeep 4.0L engine with a double wiper lip -- precisely to address this issue. I would try that first. Looking at alternatives, I think that almost has to be the cheapest thing to try first. Link to comment Share on other sites More sharing options...
ghetdjc320 Posted January 10, 2023 Share Posted January 10, 2023 Did they pull the bearing cap to inspect the crank? Just wondering how they came to that conclusion and what data they provided to back up their assumption? Link to comment Share on other sites More sharing options...
Whitaker717 Posted January 10, 2023 Author Share Posted January 10, 2023 54 minutes ago, Eagle said: A quart a week is a lot. How did this dealership diagnose crankshaft walking? If that's really happening, how long ago was the rebuilt engine installed? A new or newly-rebuilt engine should not have that -- so I'd look into whether it's covered by whatever warranty you got with the engine. If it's a scored crank -- one of the "name" gasket and seal companies (FelPro, maybe) makes a rear main seal for the Jeep 4.0L engine with a double wiper lip -- precisely to address this issue. I would try that first. Looking at alternatives, I think that almost has to be the cheapest thing to try first. The service lady said the tech said it could be either crank walk or a scored crankshaft. I would have thought after the first seal they would have checked that stuff. Now they are fighting me on it. The used engine was out in last January. It had 141K miles on it. I believe it was a 90 day warranty. I will look into a double wiper seal. I would like to try on my own before I give up on it. Can you find a link for the seal? Link to comment Share on other sites More sharing options...
Airborne Janitor Posted January 11, 2023 Share Posted January 11, 2023 1 hour ago, Whitaker717 said: The service lady said the tech said it could be either crank walk or a scored crankshaft. I would have thought after the first seal they would have checked that stuff. Now they are fighting me on it. The used engine was out in last January. It had 141K miles on it. I believe it was a 90 day warranty. I will look into a double wiper seal. I would like to try on my own before I give up on it. Can you find a link for the seal? FelPro BS40612 2 piece seal https://amzn.to/3vVvxbI Link to comment Share on other sites More sharing options...
fiatslug87 Posted January 11, 2023 Share Posted January 11, 2023 This is an interesting post: Link to comment Share on other sites More sharing options...
Whitaker717 Posted January 11, 2023 Author Share Posted January 11, 2023 3 hours ago, ghetdjc320 said: Did they pull the bearing cap to inspect the crank? Just wondering how they came to that conclusion and what data they provided to back up their assumption? That’s the problem. They are assuming that I think. They have put 3 seals in. I’m not sure how they didn’t check that after the first seal. That’s what aggravates me. I’m hoping they figure it out for me. That will be a big factor in what I do with it. Link to comment Share on other sites More sharing options...
Pete M Posted January 11, 2023 Share Posted January 11, 2023 this is why I don't let other people work on my stuff. especially not 3 times. I don't need to pay someone else to fail at a job. I can do that all on my own. Link to comment Share on other sites More sharing options...
Smokeyyank Posted January 11, 2023 Share Posted January 11, 2023 54 minutes ago, Pete M said: this is why I don't let other people work on my stuff. especially not 3 times. I don't need to pay someone else to fail at a job. I can do that all on my own. Hahaha, same. Link to comment Share on other sites More sharing options...
Romain Posted January 11, 2023 Share Posted January 11, 2023 I was losing a quart per tank of gasoline from bad valve stem seals. Once I replaced them, it’s all good. The inspection was easy. You could see the seals riding high on the stems. Link to comment Share on other sites More sharing options...
Whitaker717 Posted January 11, 2023 Author Share Posted January 11, 2023 11 hours ago, Pete M said: this is why I don't let other people work on my stuff. especially not 3 times. I don't need to pay someone else to fail at a job. I can do that all on my own. Been there done that Pete. It’s the only job I had to throw in the towel on. I hit the old pan out but couldn’t get the new one back in. Link to comment Share on other sites More sharing options...
Pete M Posted January 11, 2023 Share Posted January 11, 2023 shoulda just asked. plenty of us have been through that and found solutions. Link to comment Share on other sites More sharing options...
Whitaker717 Posted January 12, 2023 Author Share Posted January 12, 2023 11 hours ago, Pete M said: shoulda just asked. plenty of us have been through that and found solutions. Now you tell me Link to comment Share on other sites More sharing options...
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