to re-build or not to re-build

i have a 92 cherokee with a 4.0HO w/150.000m ive got a very loud rod knock problem, ive had people ask me how i got a diesle cherokee, ya ha ha.
im in the military and very short on cash, i know i need to do some thing soon should i have it re-built or take one out of a wrecked cherokee from a junk yard, all they do is a compreson check and note the miles on the motor.

i was also wondering why my PVC valve is filling my air box with oil on long trips. does everybody deal with this, i replaced it with a brand new one that has no moving parts. im tired of adding half a court every 100miles on long trips and when i get home i have to replace the air filter.

semper jeep

I can't say anything about the rod knock without hearing it, but the oil issue is a little easier...

It's not a PCV system, it's a CCV system. What's the difference? No valve to replace - and no valve to interrupt "oil flow" (atomised oil in the blow-by gasses) that gets replaced at intervals - usually when it gets filled up.

Take the CCV system apart (the two lines going into the valve cover) and blow them out with some carburettor cleaner, and then again with LOW-PRESSURE compressed air if you've got it. If not, keep up the carburettor cleaner until it comes out the other end fairly clear and you don't get any chunks anymore.

While you're at it, it's worth the effort to clean the baffle in the airbox (to keep oil drippage down) and blow out the baffles in the valve cover - so change your oil while you're at it (since it's going to collect solvent and crud.) Use carburettor cleaner to loosen everything up, and keep some pipe cleaners handy to break up the tough stuff.

It will probably take you an hour, including the oil change. Take your time - it will want some cleaning and some doing...

5-90

i ment the ccv, ive replaced the hose and that didn't do any thing i think it could be blow-by maybe

It's partly blow-by, and partly an accumulation of oil in the CCV system. Clean it out, don't just replace the hoses (especially the valve cover baffles...)

I wasn't sure if you'd meant "CCV" - most people call it "PCV" without thinking, and I find it usually serves me well to explain the difference. PCV = Postive Crankcase Ventilation - includes a PCV valve to prevent crankcase fires when backfiring through the intake (common on carburetted vehicles.)

CCV = Constant Crankcase Ventilation - always working. It's usually found on fuel-injected vehicles (like ours) with "dry" (no fuel) manifolds, because there's little to no danger of backfiring into the crankcase.

Anyhow, that's why the explanation. Clean out the baffles at both ends of the line, and you should notice oil contamination of the air filter dropping. It seems to want doing every 3-4 years, from what I've noted...

5-90

very well i have somthing to do this weekend, thanx

Look at it this way - weren't you due for an oil change anyhow?

That reminds me, I'm due to change oil in both of my DD's... Time to buy a case...

5-90

well not including all the oil i added last week driving to idaho and back, i changed it in dec.

Driving from WA to ID and back isn't that long a trip - I drive from here (San Jose, CA) to visit family (Lafeyette, IN - Monon, IN - Terre Haute, IN) and back at least once a year - which means I change the oil when I get there, and again when I get back!

Still, cleanup jobs like this will contaminate your oil fairly thoroughly, and you don't want to run oil if you get solvent in it. If you don't feel like changing your oil now, wait to do the job until you are ready (or just "reset" your "maintenance clocks" once you're done...)

5-90

In my experience, one of the culprits of oil in your airfilter is that the valve cover seal is leaking. The air comming in from the leak doesn't let the CCV system funtion properly. RTV is a good choice for seal material. I didn't have much luck with cork gaskets. I hear Fel-Pro or someone might have a combination rubber/cork gasket. That might do the trick. The other problem might be that your rings are bad. This would be tru blow-by. Still, try to get a good seal on the valve cover and clear the lines. Push a straightened paper clip or small drill up the rear tube to clear the port. You might also look at the big tube conversion on MAD-XJs site. It uses the later CCV tube (99+) and the related brass fitting. I also did this. I was loosing about a quart in 150 miles. I put on a 91-95 valve cover on an '88 motor. No oil in the airfilter after that.
Tom

VERY small drill - I don't recall the size offhand. If you can't find out, it's better to use a paperclip - that orifice helps to meter airflow.

I've had good luck with cork gaskets - but I also clean the surfaces well, coat the surfaces with LocTite #518 (Gasket Eliminator,) and I don't follow the FSM procedure exactly - but I do follow torque specs PRECISELY - if you don't, you'll crush whatever gasket you use...

75, did you have any trouble fitting the later valve cover to the RENIX block/head? Or did it bolt right on? How about air piping - any trouble there? I'm honestly curious - if nothing else, it's more "notebook" material, once I get re-organised... Brain trauma has a funny way of screwing up your systems (and yes, I'll be leaning on this for a few more months. I've got a lot of cleaning up do to from when I wasn't me for a couple weeks...)

5-90

I used a valve cover off a '95 motor I bought for the head. That head is on an '03 motor that is now in my '88 Comanche. I have the valve cover on the '88 motor though. It bolts right on. I wasn't the first to do it. I read it somewhere else. I used some type of fuel line or coolant tubing to adapt the front and rear lines. The The lines are a bit curved when you buy them from being on a rool. I used this to my advantage. The manifold port for the CCV line is farther forward on the Renix than the HO motor. I needed to cut the CCV line and use some fuel line to extend it. The 91-95 valve covers have a 90 degree elbow front and rear. They are suppose to help control oil spray btter than the Renix valve cover. I have seen some (in picutures) 95 cast valve covers that look to have the later 96+ grommets and elbows.
Tom

what i should do with the motor

you should re-build the engine and try to find a ho head along with tappet cover

40 extra hp from ho head

I had the same problem w/ oil coming out of the ccv into the airbox, especially on my last trip to moab. I had to reroute the line to a water bottle and it just puked the oil into that. The 20oz bottle was close to full every time i had to get gas.
When i got back from the trip, i replaced all the ccv system and that helped a bit, but oil was still getting into the air filter.
I was told to clean out my valve cover though, so I tried that and it made all the difference. I took off the valvecover, took off the rocker arms and cleaned everything out. I could not believe how much sludge was built up between the rocker arms. My engine has about 160k and it sure looked like the previous owner didnt know how to change oil. But if oil is getting into your airbox, i highly suggest you clean everything under your valvecover. All it cost me was time, valvecover gasket, oil, and an oil filter. Since I have done this, no oil has gotten into my airbox.

Hope that helps someone.

vbjornsson

If you can find a good deal on a used one, ie less that $500, or maybe 6, that has good front and rear seal and you can HOPEFULLY hear it run I think I might go that way, remove and replace is fairly easy. If you have some experience and the base auto-hobby shop is a good one I would take it in there to see how much damage your crank has from the knocking. If it looks ok, or if they have Pick a Part like those lucky rats in California where you can grab a good used one cheap you might get by with new rings, bearings gaskets and seals. A GOOD base hobby shop ( I have seen both kinds ) should be able to get the new stuff for a good price, check Autozone, NAPA or whoever you have out there too, price/brand shop everything the best your budget allows. If you can afford to, bore it, if not you can probably extend the life 50k to 100k by a simple rebuild depending on your driving style.

It is worth noting that a fresh cut 258 crank can be had (ask for an 88 model with serpentine belts) for about the same price as the 4.0 crank, find a set of rebuilt rods (PAW maybe?) and a new set of 4.0 pistons ( I like the Speed Pro hypereutectic ones, around $130 from Summit) have the machine shop lightly deck the block to restore the quench distance to around .040 and bore it and you are into a stroker for not much more than a normal overhaul. You would probably need to pirate some mustang injectors from the junkyard too. Still, could be done. Continuing to drive it knocking is a recipe for disaster though.

When I was in (Navy) you could usually find somebody transferring getting rid of a functional clunker for $50 to $300 bucks. You could always get a festiva or something else cheesy but functional to use until you get the XJ done and be able to get the same money right back out of it. With what an econo shitbox would save you in gas you might have an easier time getting the cash together for parts.

Oh yeah, have you listened around the block with a screwdrive handle? Could just be a broken rocker, bent pushrod or collapsed lifter. When you clean out the cover like 5-90 was saying check it all closely.

Check this out:

http://www.angelfire.com/my/fan/Catch_can.html

Might help with your blowby problem. Instead of the plug like he used you could install a small brass fitting in the bottom to screw a small valve in for draining it since it sounds like you'll be doing it a lot. He has a metric butt ton of other useful stuff on his site too.

Good Luck man!!! I remember too well how bad it sucks being broke back then.

buy a fire extinguisher and run it till it burns to the ground.

XJ's are expendable...

for 1500 for another one in good running condition, i wouldnt think twice about running one into the ground...

i have liability insurance and thats it...