Rocker arms

I just got a 98 xj and was told that the noise I am hearing is a broken rocker arm. I want to go ahead and replace all of them, I'm sure the ones that are in there are stock. What are the best kind to get or does it really matter? My husband showed me some and said thats what I should get, but sence it is my jeep I thought I would do some asking around.


***SORRY IF ANYTHING IS SPELLED WRONG***

~*~Babydoll~*~

My xj is an 89 not a 98, sorry

Are you sure it is a broken rocker arm? I have seen quite a few broken valve springs on older XJ engines. Have you removed the valve cover and checked for sure yet?

Bryan

It's more likely that you have a bad hydraulic valve lifter :wave1:

Are you mechanically inclined and not afraid to get your hands dirty? You can pull the valve cover with only about 8 bolts. From there you can see the rockers and valve springs. You should be able to spot any broken springs or rockers. You can even start the engine without the valve cover and find the offending cylinder either by sight or by putting your hand on the rockers as they tilt back and forth. The one that is making the noise will have a very rough action with a decided knock.

The only problem with replacing the lifter is that on the 4.0L, unlike its baby brother the 2.5L, you have to remove the head to get to the lifters. Can't understand why they had to do it that way when the 2.5L shares the same bore, stroke, valves, springs, pushrods and lifters.

You don't have to pull the head to replace the valve spring. If the spring is the problem, come back on this board and some of us can explain a couple of ways to change a valve spring without pulling the head.

The stock rocker arms on my '88 have gone 240,000 miles, and I've seen them go over 300,000. It's unlikely that you have a broken rocker arm -- if you did; in addition to a noise you would be running on 5 out of 6 cylinders (or 3 out of 4) and have a serious skip.

However, if it is a broken rocker, the easiest and least expensive replacement is another factory rocker arms. Mopar Performance sells roller rocker arms for the XJ, but they are extremely pricey, and don't provide any significant advantage for a street or trail Jeep.

Ok guys! When I start her up there is a knocking and when I speed up it gets faster and loader. When I open the hood while it is running the back spark plug is shaking really back with the knocking. The guy I got this xj from thought the motor had seazed. I was told by the guy that lived next door to this other guy that it is a rocker arm. I'm not all smarts on this stuff, but I do want to get in there and get my hand dirty working on it.

Ummm, if you have a shaking spark plug, it is loose - as in "ready to fall out" loose. Tighten the offending plug and test drive it. If just the plug wire is shaking, that just means your motor isn't running smoothly. Does it run/idle smoothly?

Jaredatriot:

dirtswoman said:

Ok guys! When I start her up there is a knocking and when I speed up it gets faster and loader. When I open the hood while it is running the back spark plug is shaking really back with the knocking. The guy I got this xj from thought the motor had seazed. I was told by the guy that lived next door to this other guy that it is a rocker arm. I'm not all smarts on this stuff, but I do want to get in there and get my hand dirty working on it.

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Got a mechanic's stethoscope? If not, you can use a length of garden (or heater, or washing machine) hose. Listen through the hose and try to isolate where the knock is coming from, or at least where it sounds the loudest. If it sounds louder toward the bottom of the engine, it could be a worn or spun connecting rod bearing. (This is where the comment that the previous owner though the engine had siezed gets me thinking.)

If the noise sounds like it's coming from the valve area, it's probably time to get dirty and remove the valve cover to see just what's going in on there. Possibilities include broken rocker arm; bent pushrod; bent valve; broken valve spring; collapsed lifter; and probably a few more I can't think of at the moment.

Get that spark plug wire seated properly. Maybe it's the onlyproblem

thanx for all the info. i will be assisting her with these repairs. i tried getting the spark plug wire seated, but it din't feel right.
i was looking at using roller rockers, i believe i saw some in either jegs or summitt, if it is indeed a broken rocker arm. it may be a bit before these repairs get done, just because i have a dana60 sitting in the garage right now waiting to be put under my 82 waggy (i'm having a hard time finding the brake lines and wheel studs i need to replace)

truckerdirt said:

thanx for all the info. i will be assisting her with these repairs. i tried getting the spark plug wire seated, but it din't feel right.
i was looking at using roller rockers, i believe i saw some in either jegs or summitt, if it is indeed a broken rocker arm. it may be a bit before these repairs get done, just because i have a dana60 sitting in the garage right now waiting to be put under my 82 waggy (i'm having a hard time finding the brake lines and wheel studs i need to replace)

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I don't wish to appear rude, but this will probably seem that way anyhoo: Whose money is paying for these roller rocker arms, yours or hers? Roller rockers arms don't provide any tangible benfit in an engine that's operated at the kind of RPMs seen in street and off-road vehicles. The 4.0L is redlined at 5,000 RPM, which is below the speed where you'd see any benefit from rollers anyway.

Considering that a full set of roller rocker arms for a 4.0L will cost between $500 and $800, whereas a replacement stock rocker arm might cost $5 to $10 -- I respectfully suggest that you have a serious discussion about the wisdom of using roller rocker arms in a 6-year old Jeep that's probably never going to see superspeedway duty.

That's IF[/i] diagnosis confirms the problem to be a broken rocker arm.

Basically you have an unknown vehicle that needs to be baselined.
The very first thing I would do is a complete tune up, using factory jeep plugs, cap, rotor and wires. Don't bother with fancy high performance wiring and miracle spark plugs, jeeps run better on the stock parts anyway, you don't have an engine that revs 10grand and does 9 second quarters. New air cleaner, oil change with a good filter, I use Mobil-1 and K&N filters normally but I also run Mobil-1 oil and have for the past 180,000 or so miles, stay away from fram, Purolater is OK. Once I did all that I would then see what you have, if it is from a collapsed lifter the mobil-1 or castrol syntec will clean it out in a couple hundred miles and if I remember correctly most PX's carry castrol syntec for a good price, some carry Mobil-1 at normal retail so the castrol is a better deal, both those oils are high detergent and will clean out sludge. We run Mobil-1 in all three of our jeeps, one XJ and two TJ wranglers.
About that time I would also do a cooling system flush, put in a new thermostat and refil with 50/50 coolan/distilled mix of coolant. I would also do the diffs, transfer case and maybe the tranny too.
Use the base auto hobby shop, they usually have some of the equipment that makes jobs like this easier and you might get lucky and they may have a coolant system change machine, lifts for sure to make changing the diff and Transfer caes fluids easier anyway...

Trucker -

I just saw the wife's intro post on Non-Tech. On that forum she wrote the ailing XJ is an '89, in this post she said it's a '98. If it's an '89, going roller rockers will mean the rocker arms are worth about three times as much as the entire Jeep. If it is a blown rocker, just toss in another stocker and button it up.

it's an 89, not 98 as she originally posted here. actually, the second post in this thread is from her stating that she mistakenly put 98 instead of 89 in the original.

richp, thanx for the advice. i do not and will not use teh hobby shop here at elmendorf, but i may eventually use one at our neighboring army post. also, she doesn't yet have a transfer case, or front diff, since this is only a 2wd model, for now.

truckerdirt said:

it's an 89, not 98 as she originally posted here. actually, the second post in this thread is from her stating that she mistakenly put 98 instead of 89 in the original.

richp, thanx for the advice. i do not and will not use teh hobby shop here at elmendorf, but i may eventually use one at our neighboring army post. also, she doesn't yet have a transfer case, or front diff, since this is only a 2wd model, for now.

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2WD in ALASKA, geeze what did the original owner do or who'd he piss off to get transfered from mcdill to elmendorf The only place I ever saw 2wd XJ's was out of florida.

I'd advise you look at a traction device for that rear diff like an auburn or trac lock for the winters up there cause I know how mine handles in 2wd with even light dusting of snow here in Pa. I'm curious how it will handle now that I have the auburn in there, got it last month and it's pretty cool off road..

There have been a few that have done the conversion, all the mount points are there, all you need is a donor vehicle, try to find one without the vacumun disconnect front differential, 91 and newer I think. Grab all the parts including linkages, front springs and even the console.
I saw one really determined guy up here do one in a weekend but he also had the donor 30 ft away, was a rollover 95 and his was 95 he picked up here originally from florida.
I am serious about the stock parts though, don't use any fancy stuff till you find out whats what, the XJ's run just great on dealer supplied Champion plugs and Mopar does have an 8mm high performance plug wire thats about $10 cheaper than the stock OEM plug wires, just one of those strange things.
Also anytime you take a bolt off put antisieze on when reassembling. Buy a case of powerblaster and soak any planned parts removal about a week ahead of time. Use dielectric grease on all electrical connections including the plugs and cap. If you clean the throttle body out with a spray cleaner keep the cleaner off the plastic sensors in the throttle body or you will be replaceing a throttle position sensor and MAP sensor in short order. Better to remove the throttle body and clean it on a workbench, takes 10 min off and 15 back on, take a picture or make a drawing of what goes where...
If you pull the valve cover have a shop vac handy, if there is alot of sludge build up in there the stuff will break loose, use the shop vac in one hand an a plastic scraper in the other in tandem, you don't want those small pieces of sludge getting down into the return passages and into the oil pan where they can block the oil pump pickup... It is also a good time to clean the CCV system, specially if you have any oil in the air filter, if so you will need to either clean or replace those CCV parts and tubes... Thats about all I can think off off hand, any more questions feel free to ask.
Alot of the stuff can be found with the search function about specific questions though there is alot of stuff to sort thru. Another good thing is to find a Factory Service Manual, they are worth their weight in gold. The chiltons and Haynes manuals are pretty much a waste of money. The FSM's are the size of a city phone book and just cover YOUR year and your model, not 10 or 12 years and 8 different models. Sometimes you can find them on Ebay, I have two, one for the XJ and one for our two TJ's.

thanx again. we were told that this xj originally belonged to the state forestry department; but that is hard for me to believe right now. also, i have 2 copies of teh fsm in pdf format; i just need to look through them to see if they are missing much info.