I6 engine for '91 XJ

[fatkid]

Ive tried everything to get mine running again and i still have problems. its over 200,000 anyway. im located in colorado please help!
thanks

[satan]

That engine is a tough one to kill -- what all have you trried (to make everything?)

There's quite a few yards that you could pull a runner from and many ways to rebuild yours...

Are you 100% sure you're not looking at a single-point-of-failure? like a sloppy PCM or something??

[fatkid]

ok i might have over exagerrated a bit but im at a loss. i keep getting a ridiculous amount of pressure in the coolant system ( for instance, ive blown up three resevoir bottles, and one radiator) the kicker is, when i run a block test to check for leaks, it comes up clean. other then that, i have ridiculous oil leaks coming from multiple places on the engine... as well as other issues that im drawing a blank about... im just skeptical to pulling the head off and replacing the gasket, in the hopes of it fixing the problem, when it might not... then i have the leaks to worry about and the final nail in the coffin is it has 200,000 on it. i know these motors run forever but thats risky either way... if you have any sugguestions i would gladly and appreciatively take them. thanks for all your help

[satan]

Hmm....
Interesting -- in 1991 the XJ SHOULD have an open cooling system (so blowing-up a catch bottle could be a challenge... the catch bottle is supposed to be open and vented to the atmosphere...

You do have a cap on your radiator, right?? (kinda like this one: ) http://www.partsamerica.com/product_images/aap/stb/11229.jpg

One thinner hose from the filler neck of the radiator to the bottom of the catch bottle (the hose may attach to a fitting where the bottom of the bottle is "ducted" into the bottle's fitting) - that hose sees VERY little pressure since it's mostly for vacuum (when the system cools, replacement fluid is drawn from the catch bottle... only occasionally with the cap burp enough to allow fluid to move from the rad to the bottle... This cap should take only 13PSI to release pressure into that hose... That is NOT really a "ridiculous amount of pressure" -- so I'd suspect other issues... Like the cap is bad/wrong (the 4cyl runs a 16PSI cap)...

If the radiator "blew up", then the cap (the pressure safety device in this system) failed to release for some reason. Fix that and replace the cap with a known good one before more damage ensues (certainly!)

Is there coolant in your oil or oil in your coolant (and/or ATF too)?
Do your plugs foul and/or smell (taste) sweet?
What's your compression testing like?

Probably the most important question:
When did this start?

Like was this just after a t-stat or w-pump change? or after a flush/fill or some other system part replacement (serp-belt change)?

Often the 4.0 is a victim of an air bubble behind the t-stat, which won't allow the t-stat to open as expected... then the system can really heat pretty quickly (insufficient coolant flow). Also, the XJ is a wide and short radiator; easily influenced by contamination in the radiator fins - made worse by having an A/C Condenser covering so much of the radiator trapping more mud and leaves (thought it sounds like you've just changed yours.)

Does your heater blow HOT and cool as commanded??

Leaks are as Jeep as a 7-bar grille... the 4.0 is designed to leak (or so it'd seem, Ha!) -- common 4.0 oil leaks are:

The valve-cover gasket (often the rear area - feel just below the cover on the back of the head for goo...)
The Distributor o-gasket (seal at the distributor to block mount)
The Oil-Filter Adaptor o-rings (yep right at the source of pressure, the 4.0 leaks - the adaptor is everything between the filter and the block and has qty=3 o-rings in it).
The oil pan gasket (most often from loose bolts that cause gasket failure -- or a few good rock hits - there's a newer style one-piece fully synthetic gasket that helps a lot!)
The rear main seal (yep ugly, but doable - before dropping time on the rear main - look for the other leaks -- there's a hole above the starter, about 1" in diameter that is not blocked-off, and many times the valve-cover, oil filter adaptor, and/or Distributor mounting leaks can 'get into' that ole and kinda impersonate the rear main leak)...


Your XJ is probably also dropping from the power steering pump (the cap and return lines are the usual suspects, and change/flush the fluid if you haven't already - chances are it's pretty near the oldest thing on the vehicle!)

Best thing on the leaks is to start somewhere... like a carwash and spray that engine clean (or cleaner)... and see what drops where and when...

Some leaks won't drop if the engine idles (valve cover, pan & dist) if all other things are nominal. The rear main drops when the engine runs... and ONLY when the engine runs, kinda like the filter adaptor (pressure leaks)... Valve cover drops at/after higher RPM operation which would cause the head draining to be taxed - raising the oil level at the rear of the rocker area enough to be above the gasket. Pan and Dist see a lot of "splash" - so when the crank is wetter and spinning faster -- the passenger side stuff sees this splash and can leak...

So, what's dropping where and when?

[fatkid]

no, its definately a closed system.... and i know this sounds lame, but i could be wrong on the year, i haven't even looked or thought about this thing in about six months and have gone through a bunch of cars since then, so i may be getting the year confused with another car, so i apologize. however, i AM 70% sure its a 91 but the more i think about it, it could be a '90. was there a big change in the design from '90 to '91? and i am 100% sure its a closed system.I cant go out and check cuz the car is at the shop i work/ worked at. ( someone crashed into the shop, and the shop is now condemned) i have a pressure cap on my overflow tank.

I bought this rig for $300 from a former co-worker of mine. he had the rig stolen from him for a few days, and when it had been returned to him by the cops, he had extreme overheating issues. he took it to a shop and they told him that it was most likely the head/ head gasket. but that it was no use replacing the head because he would have to do the bottom end. ( makes sense with the amount of mileage). so the guy offered it to me for $300. i came down to his house with my dad and checked out the rig, and felt as though it was a pretty good deal, all things considered, and if all else failed in fixing it, we could get a new engine at a junkyard for real cheap anyway. so i took it down to a very well known and trusted shop to see his opinion, and he felt all it needed was a radiator, an overflow tank, and a thermostat. we replaced all that, all of it from the factory. We have a pretty cool Snap-On tool at the shop that sucks out all the air in the coolant system, and then fills it with coolant, so there is very little chance that it has an air bubble.it ran for a few days but it then returned to the same problems, overheating, and blowing bottles up.

I have a manual transmission so there is no ATF in the coolant, however whenever i replace the coolant, a few days later, it is extremely dirty, its brown and black and is quite worrysome. it seems as though it could be oil, but, once again, i havent looked at this rig in six months, so alot of this is from memory.

We also replaced the spark plugs when we were replacing the radiator etc. and they were not oil soaked. in fact, they seemed quite clean and still in fairly good condition.

I dont have A/C but it doesnt seem to want to blow very hot in the winter.

And i will stick with my statement of a "ridiculous" amount of pressure for two reasons: the plastic overflow bottles would expand to twice their size before finally cracking, or " blowing up" and because of what happened to the radiator. on the radiator there are what i would call "seams" im not sure if thats right but oh well. these seams run down the four edges of the radiator. well these seams began to pull apart, until they finally broke and coolant went everywhere.

we also took a pressure washer to the engine while replacing all those parts, and it seems the worst place is definately the valve cover. it may also be coming from the distributor, and i will check into that. so much oil comes out of the valve cover that it actually covers nearly the entire engine so im not sure as to the under side of it.

another quite interesting place i am getting oil is in the air filter/air filter housing. i had just replaced the filter, and about three weeks later, i had opened up the housing to find that the filter was completely black and i had a strange "goop" in the corner where the hose from the PCV enters. this "goop" is brown and smells like oil. I call it goop because it has the consistency that is very similar pudding. this is an indication that i have blow-by and that the rings need to be replaced, does it not?

Once again, i thank you for all your help and the time and effort you are putting into my frustrating situation.

[satan]

the cooling system changed for '91 production (and the HO engine)... If you've got a bottle at the firewall with a plastic cap and some funky-*** plumbing (in constant circulation) it's an '87-'90 with a closed system...
... That had me confused (the open system has a cap on the radiator)

I won't offer too much of my opinion on the "cool Snap-on coolant sucker" (I wonder if they ever thought about the potential damage of drawing a vacuum backwards across a shaft-seal that's supposed to run with 15 or so PSI on the OTHER side) -- they really aren't too good at pulling all the air out... though it's a good start.

Dirty coolant prolly needs a good flush (like a chemical cleaning) to ensure that there isn't anything unknown happening. (you can take a glass jar of the nasty coolant and let it sit on a shelf overnight -- oil will float to the top).

on the leaks -- yeah - they leak ... Start at the top (valve cover) and work down -- it'll be easier to see what's leaking if you work that way, and the tasks seem to get a bit harder as you "go down" from valve-cover to rear main...

the oil in the filter is blow-by -- the Crank ventilation system on the '90 is pretty cool, but often fails to extract all the pressure that builds in the case (plus at 200K you're likely getting a fair amount of mechanical loss around rings and maybe even valve guides... That system is a CCV (like a PVC system, but there is NO one way valve - it's a Continuous Crankcase Ventilation system.

The fix for blow by is largely to be sure that the CCV stuff is running as well as it can, then look the other way! What's happening is that the fresh air intake for the CCV system (that 1/2" rubber hose that runs from the air cleaner to the hose junction to the front hole in the valve cover) is allowing OIL to pass from the valve cover into the air filter. Usually this is due in part to the rear vacuum source for the CCV system (the hard line from the manifold's vacuum tap to the rear hole in the cover) being plugged -- the "hole" in the vacuum source line is a "special" size that's intended to be a precise "vacuum leak" (really that thin hard hose just sucks air from your valve cover, which is re-filled by the big hose to your filter - bypassing the throttle body, direct to your intake -- just like a vacuum leak!) it's best to NOT open the hole you have much, but very advisable to clean and clear that vacuum line...

The other catch is what's inside of those valve cover holes... there's some baffles (hey - they're SUPPOSED to stop oil from getting out of the cover -- bet they're not working too well) inside the cover - over time, the baffles will get just NASTY and may even plug (think that the rear one has been drawing oil, vapor, and combustion gasses out of the cover for 16+ years -- it's dirty!) Again, a little surfing will turn up an article or two on cleaning the 4.0 valve cover (really, the baffles are held on on the inside with tiny screws... when you're pulling the valve cover to do the gasket... clean the crud out of the baffles -- and you can likely change the vacuum and source lines for the CCV at the same time (Checkers used to stock the lines in their HELP stuff, but I think they've stopped carrying the parts)...
- A few people forget that the vacuum tap and the intake manifold have also been sucking this oily-crap for years... a GOOD cleaning there may also help to increase the vacuum available to the CCV.
... that should make an improvement on your blowby (oil in air-filter), but it likely won't cure it. It's a symptom of an older motor (with leaky rings and such)... Surf some and you'll find more on the topic - there've been some creative work-arounds! Blow-by is worse with sustained low-vacuum high RPM runs (like a high-speed run up I-70 or whatever) -- with the vacuum lowered... and the crankcase pressures raised... somethings gonna go somewhere...

I'm thinking that there may be additional blockages or entrapped air in the cooling system of that thing. (or maybe just a simple t-stat issue like swap in a KNOWN good t-stat - preferably one with a punch hole (for burping air) -- and kinda start from there....

[fatkid]

which, in the end, basically brings me full circle to my original problem: i have an engine with 200k on it, very bad blow-by, and a seemingly incureable coolant system problem.

All of your sugguestions have been taken in with an open mind, and i cant thank you enough for them. However, attempting the procedures you have sugguested to me, only " might" fix the problem, and, in the end, i may still have a head problem.

I guess im at a loss for what to do next.

I suppose the next logical question is: what would you do? would you continue to spend time and money on this engine, or would you begin to look for another?

I would eventually like to add some performance parts to this rig; and to lift it and get big ol tires on it, just like everyone else.

Should i grab a new motor, and do a stroker upgrade that ive read so much about on this site?

im just not sure where to go next. i dont pretend to know everything about mechanics, and i CERTAINLY dont know everything about jeeps, but i do feel i know alot more about it then alot of my peers; i am only 18, for instance, and would love to learn more. this is one of the reasons that i have spent so much time on this site, trying to read up, and see if anyone has had the same problems i have, and to determine what the best course of action there is for me. any further advice would be greatly appreciated, and i thank you for all the advice youve already given me.

[satan]

True -- bear in mind that the cooling issue could be "external" to your engine (radiator, hoses, heater valves, etc...) -- but realy,

if you've got more money that time - a reman is the way to go (you can buy a running pre-90 for less)

If you've got time, and wanna "dig in" the 4.0 rebuilds prety easily... (pollu it - dissassemble it and run it piece at a time to your local machine shop... then get it all better and set it back in.!

The stroker optionis little more than a hotter rebuild - being a '90 it's a good year for that (controls are a bit more tollerant) - - You cna either strok wat you have (as in the rebuild with different parts) or buy a running core (You can find buildable pre-HO 4.0's on local boards and in local yards for the mid-$100 mark or so if you look.

All thinkg being equal, and if if time is not an issue, I'd go for a stroker (like a Hesco kit or ?? (some of the details on http://jeep4.0performance.4mg.com/stroker.html) the added oomph is nice to have, and, if you pay attention to detail, it'll still pass the Denver emissions tests. If you fear the emissions test, I'd just opt for a "stock" rebuild with a torquer style cam and a few goodies.

If you've got more time than money, then fixing and running what you've got may be better!