Don't Fence Me In
Member
I originally posted about this over on /jeepforum/ and a friendly recommendation came through to seek out you folks. Said there was quite a wealth of knowledgeable people on here that would be more likely to steer me in the right direction, despite the fleeting connection between AMCs classic motor and the motors traditionally discussed here.
So, to go over the details:
I purchased a super nice '97 XJ Cherokee for a steal ($1k) about 6 years ago and has sat as a project car ever since, as I'm bad about getting to projects until I either need to use or move them. It was sold to me so cheaply (even totaled ones are about $3.5k here) because the guy told me he knew he had ruined the motor and he couldn't keep it just sitting there or it'd eventually get towed. Told me it had a cracked block and poured coolant out faster than you could pour it in and inevitably he had to drive it from Sacramento to Reno with no coolant, where it sat until he sold it to me. Did make it though.
So fast forward to recently when I decide to dig into it. Turns out the reason coolant would pour out faster than you could pour it in, was someone had stacked 5 or 6 paper gaskets on the water-pump. Figure I have nothing to lose, so I check the oil and it's clean, pour some water in it and fire it up. Pumping tons of exhaust into the cooling system, but no coolant into the bores or oil. In fact, runs quiet and downright smooth. Decide it's worth tearing apart and doing a real look at it.
Pulled the head and it was a total loss; no surprise there. Absolutely surprised the motor ran that well with that head though. Even more amazing it wasn't breathing any coolant; other way around. Cracked all the way stem to stern, between every valve and cylinder. Checked the deck on the block after cleaning it well; checked with a machinists straight-edge (certified .001 accuracy) on both sides, front to back and between the bores. For some reason I don't have a 1 thou feeler, but I do have a .0015 and it takes some finagling but at the worst spot, you can wiggle it through with some work and determination. No chance of it fitting under the straight-edge anywhere else. If I had to guess, I'd say it's right around .001 of actual gap--either way, still well within listed tolerance for deck flatness.
Then pulled the pan and checked the bearings; they look great for a motor with 250k, let alone one abused so badly. Good enough that I'd have no issue running them in a motor I relied on. Turned the motor over by hand and checked for any visually noticeable piston slap and everything was fine there. Cam lobes show no wear either. Can't easily check cam and crank endplay, but it seems to be fine (motor is still in the vehicle). Overall about inline with what I expect from these motors--very little to nearly no wear despite the mileage. The motors themselves only seem to accrue wear when something is actively wrong with them.
That said, I checked the bores and that's where I find an issue. Haven't checked taper yet, but I checked out-of-round, and every cylinder is within .0005 to .001 of roundness, except #2 which is .003 out perpendicular to the thrust surface of the bore. Every bore also has pristine cross-hatching except #2, which has perfect cross-hatching parallel to thrust (left-right of bore) but perpendicular, it's smoothly worn. When I say smooth, you can't catch anything with a fingernail and even the ball-point of my bore-gauge glides over with ease. Whatever happened to it, it wore well, just wore too much. If I had to guess, I'd say this is unrelated to the overheating--this is something the motor has been doing for a long time.
I've refreshed a few motors over the years, but I would not call myself a seasoned rebuilder, and this is the first time I've come across an out-of-round bore that has worn itself oblong in the wrong direction. Frankly, I don't know what to make of it.
I went into this project expecting to build a motor, but at the same time, I have all the parts already on-hand to just do a quick refresh, including a new head, some lifters, oil pump, etc, minus honing and rings because of #2. Can't hone a cylinder that far out. Or at least, you can, but you definitely shouldn't. Refresh vs rebuild at this point is the difference between nothing out of pocket besides odds and ends plus a few weekends, and a major time and money investment. Again, not that I wasn't expecting it to start, but there's a huge difference in cash and time investment there.
That's the end of the technical details. I'm a bit long-winded, I know. As a side tangent, the purpose for getting it back on the road now, is that I'm looking to sell my new car (Veloster N) and just commute with the Cherokee for now. It's fully loaded, has highway gears and despite needing a clean, is like new inside, so it makes a good candidate for driving to work and back compared to my other cars. Will get less mileage than the new car, but it can also take 87 instead of high-test. New car is going because it ran into some serious mechanical issues; dealer had a hard time getting parts for it, and despite getting it back, it still doesn't run right. What good is a 100k/10yr warranty if they fight you at every turn on it? I don't care what they say, fuel washing the rings won't get you a 35 psi difference in compression between cylinders and it certainly still wouldn't be down on compression after it's "fixed." Plus, I suspect we're all headed for some bad times in this country, and being my only debt, I'm tempted to do away with it anyhow, especially since I can actually make a profit given how topsy-turvy the market has gone.
As a final tangent, I don't know how much I believe the guy I bought the Cherokee from, driving Sacramento to Reno with no coolant, but I did have a '98 Wrangler I drove for over a year (unknowingly) without a water-pump. Didn't suspect anything because it never overheated. Only looked into it because it would get warm if I climbed a long, steep grade, but still wouldn't overheat. When I eventually pulled the pump, I found it had no impeller. Motor was keeping itself cool off just convection alone. Does make me wonder if he thought it had no coolant, as there is a level that will remain in the block, but won't get pumped out once the level is low enough. Bottom radiator hose was still full.
So, to go over the details:
I purchased a super nice '97 XJ Cherokee for a steal ($1k) about 6 years ago and has sat as a project car ever since, as I'm bad about getting to projects until I either need to use or move them. It was sold to me so cheaply (even totaled ones are about $3.5k here) because the guy told me he knew he had ruined the motor and he couldn't keep it just sitting there or it'd eventually get towed. Told me it had a cracked block and poured coolant out faster than you could pour it in and inevitably he had to drive it from Sacramento to Reno with no coolant, where it sat until he sold it to me. Did make it though.
So fast forward to recently when I decide to dig into it. Turns out the reason coolant would pour out faster than you could pour it in, was someone had stacked 5 or 6 paper gaskets on the water-pump. Figure I have nothing to lose, so I check the oil and it's clean, pour some water in it and fire it up. Pumping tons of exhaust into the cooling system, but no coolant into the bores or oil. In fact, runs quiet and downright smooth. Decide it's worth tearing apart and doing a real look at it.
Pulled the head and it was a total loss; no surprise there. Absolutely surprised the motor ran that well with that head though. Even more amazing it wasn't breathing any coolant; other way around. Cracked all the way stem to stern, between every valve and cylinder. Checked the deck on the block after cleaning it well; checked with a machinists straight-edge (certified .001 accuracy) on both sides, front to back and between the bores. For some reason I don't have a 1 thou feeler, but I do have a .0015 and it takes some finagling but at the worst spot, you can wiggle it through with some work and determination. No chance of it fitting under the straight-edge anywhere else. If I had to guess, I'd say it's right around .001 of actual gap--either way, still well within listed tolerance for deck flatness.
Then pulled the pan and checked the bearings; they look great for a motor with 250k, let alone one abused so badly. Good enough that I'd have no issue running them in a motor I relied on. Turned the motor over by hand and checked for any visually noticeable piston slap and everything was fine there. Cam lobes show no wear either. Can't easily check cam and crank endplay, but it seems to be fine (motor is still in the vehicle). Overall about inline with what I expect from these motors--very little to nearly no wear despite the mileage. The motors themselves only seem to accrue wear when something is actively wrong with them.
That said, I checked the bores and that's where I find an issue. Haven't checked taper yet, but I checked out-of-round, and every cylinder is within .0005 to .001 of roundness, except #2 which is .003 out perpendicular to the thrust surface of the bore. Every bore also has pristine cross-hatching except #2, which has perfect cross-hatching parallel to thrust (left-right of bore) but perpendicular, it's smoothly worn. When I say smooth, you can't catch anything with a fingernail and even the ball-point of my bore-gauge glides over with ease. Whatever happened to it, it wore well, just wore too much. If I had to guess, I'd say this is unrelated to the overheating--this is something the motor has been doing for a long time.
I've refreshed a few motors over the years, but I would not call myself a seasoned rebuilder, and this is the first time I've come across an out-of-round bore that has worn itself oblong in the wrong direction. Frankly, I don't know what to make of it.
I went into this project expecting to build a motor, but at the same time, I have all the parts already on-hand to just do a quick refresh, including a new head, some lifters, oil pump, etc, minus honing and rings because of #2. Can't hone a cylinder that far out. Or at least, you can, but you definitely shouldn't. Refresh vs rebuild at this point is the difference between nothing out of pocket besides odds and ends plus a few weekends, and a major time and money investment. Again, not that I wasn't expecting it to start, but there's a huge difference in cash and time investment there.
That's the end of the technical details. I'm a bit long-winded, I know. As a side tangent, the purpose for getting it back on the road now, is that I'm looking to sell my new car (Veloster N) and just commute with the Cherokee for now. It's fully loaded, has highway gears and despite needing a clean, is like new inside, so it makes a good candidate for driving to work and back compared to my other cars. Will get less mileage than the new car, but it can also take 87 instead of high-test. New car is going because it ran into some serious mechanical issues; dealer had a hard time getting parts for it, and despite getting it back, it still doesn't run right. What good is a 100k/10yr warranty if they fight you at every turn on it? I don't care what they say, fuel washing the rings won't get you a 35 psi difference in compression between cylinders and it certainly still wouldn't be down on compression after it's "fixed." Plus, I suspect we're all headed for some bad times in this country, and being my only debt, I'm tempted to do away with it anyhow, especially since I can actually make a profit given how topsy-turvy the market has gone.
As a final tangent, I don't know how much I believe the guy I bought the Cherokee from, driving Sacramento to Reno with no coolant, but I did have a '98 Wrangler I drove for over a year (unknowingly) without a water-pump. Didn't suspect anything because it never overheated. Only looked into it because it would get warm if I climbed a long, steep grade, but still wouldn't overheat. When I eventually pulled the pump, I found it had no impeller. Motor was keeping itself cool off just convection alone. Does make me wonder if he thought it had no coolant, as there is a level that will remain in the block, but won't get pumped out once the level is low enough. Bottom radiator hose was still full.
