Wg 4.0lt engine rebuild

[Hobtech82]

Seems that I have a knock in my engine which has worsened and looks like a piston skirt failure? Has anyone got any use resources on rebuilding a 4.0 engine? I was going to put a kit through it but would be good to has some extra knowledge of things to be aware of.
Or should I just order this book from eBay and wait a month before I start? Cheers https://rover.ebay.com/rover/0/0/0?m...2F131316657272

[cherokee94nz]

Plenty of cheap 2nd hand motors about, just look at shaping out motor for a good one. Spending heaps on motor will not increase value of Jeep.

[Jonny Jeep]

I've just replaced pistons, cam, lifters, pushrods and rockers on my 97 TJ that lost a piston skirt at just shy of 192K miles.

I'll get back to this later. The sun is shining over here in blighty and I have the day off work to go drinking with friends so that's all for now.

[Jonny Jeep]

I have no idea what a used motor costs over there so can't comment on that option, other than ask what would you trust more, a used motor of unknown history, or your own rebuilt motor with whatever history you know?

I've had my 97 TJ since 2000 and picked it up with 36k miles on it. So 19 years and 156k miles/250k km with me behind the wheel, and maintaining it. For me it wasn't about increasing value of the vehicle just getting back on the road as soon as I could with a known good engine. If I'd gone the second hand engine route I'd have felt the need to rebuild any used engine before fitting it anyway.

I don't know how good the book is you've linked but I used the Factory Service Manual (FSM) as my guide. There are copies floating about the internet.

If it is just a broken piston skirt then I'd do as I did and replace the lot. I only had one piston with a broken skirt I found three or four more had cracks in them so won't have been too far behind. Obviously, the head needs to come off and the oil pan needs removing to get any broken pieces out so Full gasket sets are needed. I bought Fel-pro gasket sets and Engine Tech pistons and rings from rockauto.com

Since my engine had been seeming to develop a bit of a flat spot in the mid-upper rev range i decided to also replace the cam and lifters too. Buying the Melling set, again from rockauto. I also decided to replace pushrods and rocker arms. With a new cam, the distributor (or OPDA) drive gear should be swapped too. I'd forgotten to look at my distributor, or order a new gear so I ended up buying a new distributor in the UK as my old one had play in the shaft. I used my original sensor in it, rather than the new one that it came with.

When honing/deglazing the cylinder walls I didn't remove the crank. What I did to stop any crap getting to the crank was chop down the broken piston halfway through the gudgeon pin holes, remove the rings and drill a hole in the center where I fitted a small bolt for getting it in and out of the cylinders. I smeared a ridge of vaseline around the top of the piston and dropping it into the cylinders I then smeared the vaseline around the edge to completely fill the gap. After honing, the cylinder walls were wiped clean before the piston was pulled out and any vaseline left was also wiped up.

With the head being off, I borrowed a valve spring compressor and removed a couple of valves. I decided they would all get ground and lapped while I was waiting for parts to arrive. Having a right angled air drill with push button reverse, and air limiter on the input to keep speed down, made that job a lot quicker and easier than it would have been doing it entirely by hand as the valves and seats needed a fair bit of grinding.

I'm lucky to work in a maintenance department, and luckier still that I was able to borrow a car from work that doesn't get used much for the time the TJ was off the road. I'm a welder/fabricator rather than a fitter but I do have a bloody big pretty well stocked tool box. Having an engine hoist available saved the heavy work of lifting the head off and on the engine. Even with what there was available I needed still more tools, like a piston ring compressor and cylinder hone/deglazer and a half inch 12 point deep socket for the head bolts. I already had 1/4", 3/8" and half inch torque wrenches and they all got used as everything got torqued to spec.

My exhaust manifold had a few hairline cracks appearing in it so I could have welded them but decided to braze them instead. Time will tell how well that works.

If doing it yourself, how involved you want to get is up to you. The minimum you'd need to do is replace the broken piston, but as noted if one is gone others are likely to be not too far behind so worth doing all of them.

I was going in work up to a couple of hours early most days and working on it during my breaks. I was then in Saturdays and Sundays too. I ended up taking it off the road when I got to work on a Monday and driving home in it two Sundays later just after 9pm. I was exhausted at the end of it, but driving to work the next day with the sun shining and the sunrider top open it felt bloody fantastic.

Driving it, with no more ticking or knocking noises, and so a relatively quiet engine was, and still is, incredibly satisfying. 800 miles on it so far and the engine is still loosening up. The engine's still really tight and I reckon my fuel consumption has taken around a 5% hit.

That's a bit of long read but might give you some idea of what's involved. It's up to you which route you take. But a good start point would be removing the oil pan to confirm whether a piston skirt has in fact broken or removing the rocker cover to see if any rockers are loose which would indicate a sticking lifter.

All in with shipping and VAT on parts, and the extra tools I bought, I reckon my total was around £850 in cost. A used engine over here would have been at least half that amount, but as I've said, I'd have felt the need to rebuild any used engine anyway.