Long time reader of this forum, but this is my first post. I need to replace the exhaust manifold on my 99 XJ. It's been sputtering and I found a good size crack in the manifold. Question: What else should I repair/replace/clean while I have all of those parts out? My XJ is approaching 300,000 miles and other than the crack in the exhaust manifold, it runs great. I have kept up with routine maintenance for the life of the car (all the basic stuff, oil, transmission filter, spark plugs, filters, distributor, starter, radiator, fuel injectors, belt, fuel pump, rotors, pads, etc...), but I have never gone deep into the engine bay. I feel like it's about time for some major preventative maintenance, and this is the opportunity. I'm already planning on cleaning the intake manifold, but what else can I do in that area? Maybe pull the cylinder head, clean it and replace the gasket? I'm open to any ideas. Thank you.

 

Degrease/clean the engine block, replace any seaping power steering lines, inspect/potentially replace the freeze plugs in the side of the block

 

The only thing I definitely would replace (unless done within last few years/50k miles is the LH engine mount

LH mounts always wear much faster than RH, as they are under compression (and near exhaust heat in an XJ)

It is not very easy to replace one, but with exhaust out, its a snack

wear on LH mounts is so pronounced, I just replace it and leave the RH, unless they are very old (which is both visible for inspection, and easy)

best practice would be do both as a pair

same deal for trans mount, much easier with exhaust system displaced

I would not take the head off. That is inviting shipwrights disease. Unless you want to budget for a complete head rebuild

 

love this - very true

 

I would also use heating and cooling to get the nuts, or bolts out in this situation, I use a butane torch

Sure, it takes a bit longer, but snapping one off is a distinct possibility

I use a lot of penetrant, be careful, it catches fire

 

When I got my '99 I had a similar issue. I took the opportunity to pull the head which made getting the exhaust and intake manifold off much easier. It also allowed me to inspect the head and pistons to make sure nothing looked badly worn. Purchased a fresh set of head bolts and a new exhaust header, Then I started replacing gaskets including the head gasket. I also generally cleaned everything up, because with 220k+ miles the engine was leaking everywhere. Anyway this snowballed into me basically replacing every single engine gasket on the 4.0 and discovering loose bolts, worn parts etc. I also replaced the balancer and timing chain since I had it all off anyway. I ended up doing a mini engine overhaul and using a gallon of Simple Green in the cleaning process. I guess it depends how deep into this you want to go and how much downtime you can afford to have.