Jeep coolant temperature help

[THEFERMANATOR]

I've got a 97 4.0L out of a CHEROKEE that has about 70K miles on it, and I can't give the dam thing away. Tried with a few people and everybody laughed at me. Things hardly ever blow an engine unless you run one hot.

[Destroyer]

Originally Posted by THEFERMANATOR

I've got a 97 4.0L out of a CHEROKEE that has about 70K miles on it, and I can't give the dam thing away. Tried with a few people and everybody laughed at me. Things hardly ever blow an engine unless you run one hot.

Ferm, I just might need that engine. My 98 Cherokee ran super hot due to loss of coolant, and now it has low compression in 3 cylinders. (2,3, and 5) I know it;s my own damn fault for running it hot, but I was in a bad spot on the freeway and really didn't have a choice. Anyways I suspect a blown head gasket caused the initial coolant loss. I won't know till the spring when it's warm enough to work on it outside what the total damage is. I'm thinking a head gasket and probably broken rings. But if it's anything more than that a transplant may be necessary.

[THEFERMANATOR]

Originally Posted by Destroyer

Ferm, I just might need that engine. My 98 Cherokee ran super hot due to loss of coolant, and now it has low compression in 3 cylinders. (2,3, and 5) I know it;s my own damn fault for running it hot, but I was in a bad spot on the freeway and really didn't have a choice. Anyways I suspect a blown head gasket caused the initial coolant loss. I won't know till the spring when it's warm enough to work on it outside what the total damage is. I'm thinking a head gasket and probably broken rings. But if it's anything more than that a transplant may be necessary.

Yep, sounds like some broken rings. Problem is the newer 96+ metric hyperautic pistons seem to crack a lot more so than the early style cast pistons did when run hot. I've scrapped out a few, and the 96+ engines seem to have cracked pistons in them when run hot whereas the early cast pistons would be fine.

[Destroyer]

Originally Posted by THEFERMANATOR

Yep, sounds like some broken rings. Problem is the newer 96+ metric hyperautic pistons seem to crack a lot more so than the early style cast pistons did when run hot. I've scrapped out a few, and the 96+ engines seem to have cracked pistons in them when run hot whereas the early cast pistons would be fine.

Ugh. Never thought about cracked pistons. Figured that since I still had compression of 75 and above on the bad cylinders that I had not melted a hole in them... One more thing to look at. Still, with the pistons out to look at the rings replacing the piston itself should not be a problem.

Now it gets down to the "do I do the necessary work on the present engine or do I do a transplant?" question. <sigh>

[THEFERMANATOR]

Originally Posted by Destroyer

Ugh. Never thought about cracked pistons. Figured that since I still had compression of 75 and above on the bad cylinders that I had not melted a hole in them... One more thing to look at. Still, with the pistons out to look at the rings replacing the piston itself should not be a problem.

Now it gets down to the "do I do the necessary work on the present engine or do I do a transplant?" question. <sigh>

The 96+ engines I had would crack between the ring lands when run hot. And you need the special fixture to change them out. The pistons where the rods go in is angled but the rods are flat, so you have to have the tool to hold the rod to press them out. 87-95 engines were flat in the piston where the rod went, and the rods were flat so you could just support the piston and press them apart. Just one more reason I like the 91-95 engines. Now if you find a 93-94 grand Cherokee short block to drop in, you will have a screamer on your hands. 93-94 grand Cherokees had a much more radical duration to the camshaft and held the valves open longer. 96+ engines made there power with hotter tuning, 91-95 engines did it with a better cam. Put a 91-95 cam in a 96+ truck and you will notice a difference. I put a 93 cam in my 88 and it woke it right up. Put one in a 96 and that sucker flat out MOVED! Then again these were just budget builds because I had the 93-94 grand Cherokee cams in the shop.

[smokeonthewater]

hmmmm sooo a 93-94 grand cherokar cam in my 95 YJ w 230k miles.....

[smokeonthewater]

WHOOPS just realized you gotta pull the head to get to the lifters!... UGH I wish I had that free 70k engine to swap in with a new comp cam n a couple other goodies

ever get near Louisville? :D

[Destroyer]

Originally Posted by THEFERMANATOR

The 96+ engines I had would crack between the ring lands when run hot. And you need the special fixture to change them out. The pistons where the rods go in is angled but the rods are flat, so you have to have the tool to hold the rod to press them out. 87-95 engines were flat in the piston where the rod went, and the rods were flat so you could just support the piston and press them apart. Just one more reason I like the 91-95 engines. Now if you find a 93-94 grand Cherokee short block to drop in, you will have a screamer on your hands. 93-94 grand Cherokees had a much more radical duration to the camshaft and held the valves open longer. 96+ engines made there power with hotter tuning, 91-95 engines did it with a better cam. Put a 91-95 cam in a 96+ truck and you will notice a difference. I put a 93 cam in my 88 and it woke it right up. Put one in a 96 and that sucker flat out MOVED! Then again these were just budget builds because I had the 93-94 grand Cherokee cams in the shop.

Well, hopefully I'll just find some cracked rings and that will be the end of it. If I have to press out the wristpins I'll talk to one of my friends who works for Chrysler and see if he has the tool that I can borrow. Or if it's really damaged I'll say the hell with it and go the transplant route. I know this guy that has a 97 4L engine with about 70K on it that he can't give away.... And I'm thinking I can buy it from him. Only problem is I'll have to drive to Fla to get it.. but I've done that before so it's no big deal.