90 XJ tapping/ticking from valve cover

When I start this thing its quiet, but after driving it around and the oil I suspect gets warmed up there's a ticking coming from the valvecover area, maybe under it. I can't feel the ticking but just hear it. Usually when the oil gets hot and I notice the pressure drops while idling. I know the oil is thinning when it gets hot so maybe the oil pump could use replacing? Or should I do some work on the valve/lifters/whatever? I have tools and if its something that I may be able to tackle if I get the right manual I would like to do it myself. I will buy tools if I need to.

The engine has 150,000 miles on it, and I dont think its had any major work done to it. Could I maybe put a thicker oil in it to silence the ticking? Could someone out there let me know what all these things would do and suggest others I might try? Other than the ticking it's perfect, although it tends to idle around the 250 rpm mark when at a stoplight after it's all warmed up.

Oh and it's hot in florida

Troy

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Troy
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What weight oil does it have now? How long since it's been changed? What are the pressure readings idle/2000rpms hot/cold?

Carl

Reply to
Carl

Fist thing that is wrong is the idle speed. Idling an engine that slow is bad. Many engine components rely on oil splash for lubrication. The camshaft, timing chain, and valve springs are the most critical. I mention valve springs because they need oil splash for cooling. You compound the problem if you do indeed have a low pressure situation at idle. I would suspect that the Idle Air Control valve may be the culprit. These tens to get carboned up over time. It is easy to pull the valve and clean it. Also check the electrical connections to the valve, they may be corroded as well. To clean the valve, you just need a can of fuel injection compatible carb cleaner. there is a plunger that controls the valve, and it needs to operate freely for the valve to work properly.

The ticking is more than likely something in the valvetrain, but could also be a piston pin, or less probably a rod bearing. Usually you can tell if it is a piston pin by starting the engine with the plug wire from the suspect cylinder disconnected. If it is a pin, the noise with decrease noticeably without the plugwire hooked up.

I would most likely suspect a lifter is bleeding down when the oil gets hot. Not much to do about it other than replace the lifter(s). Using heavier oil may patch the problem for a while, but more than likely it will resurface later as things get worse. There are downfalls to using too heavy an oil, but going up one range should be fine considering you're in a hot climate. First thing you need to do is fix the idle speed issue, as I would imagine using heavier oil and idling that slow will cause even more problems related to the parts needing splash oil for lubricant.

Chris

Reply to
c

I changed the oil a couple weeks ago with 10w30 and immediately noticed the ticking once it warmed up. I suspect the oil before I changed it hadn't been changed in over 3000 miles, it was black. The previous owner probably didnt take care of it when he got his grand cherokee to replace it. When cold at idle the pressure it high, I forget the exact space but its on the high side. Gets higher when I am driving, that's why I think its the oil getting hot and thinning out because once it gets fully warmed up it drops quite a bit.

I am going to be home tomorrow so I will take exact measurements while cold and hot, and how long it takes to do its thing.

Troy

Reply to
Troy

Yeah it gets idling so low after getting fully warmed up that sometimes I just knock it into neutral so it doesn't stall out... it stalled out once a week ago but hasn't since, but I haven't given it the chance.

A few connections were cruddy when I got the thing, I will clean/check all the connections you mentioned

I've never done this, but to find out which lifter or whatever exactly is ticking, am I able to run the engine with the valve cover off? I realize that must sound like a stupid question to a mechanic type who has done this kind of work before, but I don't know because I've never done that before. I don't know if the oil splash is strong enough to shoot out, or even where the oil splashes from.

I'll save the thicker oil for last maybe, but what would be the next step up from 10w30? I've seen 20w50 oil in the store before, but I dont know if thats the next step up. All the vehicles I've owned run 10w30 so I've never had to use thicker but it was suggested by a neighbor. (not a mechanic, I trust you guys more)

Troy

Reply to
Troy

Next step up is 10w40, but you really need to fix that idling problem. If it comes down to it 20w50 can do a world of good in a tired engine, but a healthy engine shouldn't need it. I've had engines where I ran

20w50 AND STP... needless to say they weren't healthy engines!

You don't want to use STP in a healthy engine, but it can work miracles in a sick one. I used to have a 57 Studebaker Pelham (2 door wagon), with a tired flathead six. That engine would smoke, make ugly noises, had no pep (not that a 170 cid flat head six had much at best!) and the oil pressure light would come on at idle. With STP it would smooth out, quiet down, the oil pressure would come up, it would stop smoking, and got peppier.

But again, before you play with oils get your idle speed taken care of.

Jeff DeWitt

Reply to
Jeff DeWitt

I'll second what Jeff said. Get the idle issue taken care of first. How loud is the tapping/ticking? You can add no-smoke or STP oil treatment to the oil. I had a Toyota 22RE that had 215,000 miles on it. Burned a little 10-40 so I put 20-50 in it and had no more burning issues, and the oil pressure came up quite a bit.

You can run the engine with the valve cover off, but it will be very messy. Overall, I wouldn't be too worried about the tapping/ticking sound unless it was very loud. 150,000 miles is nothing to worry about with a 4.0. I would not hesitate to buy a Cherokee with 150,000 miles on it.

Carl

Reply to
Carl

You get ticking because you have no oil pressure because your idle is too low. Likely no need to open anything up.

I find a spray electronic contact cleaner clean on all the plugs and sockets, especially around the throttle body does them wonders.

Same for cleaning out that idle air passage.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

I was under the impression that the ticking happened all the time when the engine was hot, not just at idle. Maybe I assumed something I shouldn't have, but if the ticking is just at idle, then Mike is right, you probably don't need to open the engine up. Definitely fix the idle problem first.

Chris

Reply to
c

Yes the ticking is all the time, its just when its hot and idling its somewhat loud, enough to where people ask me why it's ticking, and as I am driving the oil pressure raises a bit, but if I stick my head out the window I can still hear the ticking, but faster and not as loud.

I will try to get the idling problem sorted out first, maybe its so low that it isn't lubing up whatever is making the ticking sound to begin with.

Troy

Reply to
Troy

Do you have an oil pressure gauge? It would be interesting to know how the oil pressure is doing.

Jeff DeWitt

Reply to
Jeff DeWitt

Nope sorry I dont have an oil pressure gauge... but I will buy one soon as I get the money. Where does this gauge hook up on the engine? I've never seen or used one.

Today I wrote down the measurements on the gauges: When cold, at idle: ~750 rpms in park, pressure from the gauge read ~50 When cold, at 2000 rpms driving: oil pressure on the gauge read ~58

When hot driving home: Idle ~250 rpms (yeah I gotta fix that,working on it) and pressure from the gauge read ~20 Driving at 2000 rpms the oil pressure gauge read ~30

I didn't get a chance to clean the connectors n such today, but what exactly controls the idle speed? The TPS? I plan on taking alot of stuff apart tomorrow and cleaning and reassembling it all.

Troy

"
Reply to
Troy

OK, now I'm officially confused. You don't have a gage but your giving pressure readings, are those from the gage in the instrument panel?

Assuming that's the case those sound like reasonable readings to me.

Thought occurred to me, if it's got 150,000 miles and the oil was pretty much black you may have a lifter that's sludged or varnished. I believe those things have pretty small holes and if they get clogged the lifter isn't going to work properly and it's going to click.

If it was mine, the oil pressure is OK and the engine seemed to be running pretty well and it's just a tap or a click from fairly high up in the engine I think I'd just drive it, making sure to change the oil regularly, maybe even a bit more often than normal.

With a bit of luck the problem may fix itself with that treatment, if it doesn't than you might try flushing the engine with some Rislone or something similar.

But fix the idle first!

Jeff DeWitt

Troy wrote:

Reply to
Jeff DeWitt

Heh well yeah there's an oil pressure gauge on the instrument panel, I was somehow thinking you were meaning an external gauge that I would temporarily hook up for a more accurate/scientific measurement. Oops

I will try to find out how to fix the idle and let ya'll know what's going on with it afterwards.

Troy

Reply to
Troy

Every six to ten months I get ticking. For a long time I thought it was lifters or exhaust noise. It drove me nuts not being able to find the root cause. Then one day I was reading a thread about carbon deposits not allowing valves to seat properly. I contemplated using ATF but settled on 12 oz of water poured down the throttle body just fast enough to make the motor start to stumble. Lot's of white smoke out the back for a few minutes but it stops it (the ticking) almost immediately. Lasts for a good long time. I think my Jeep runs a llittle lean. Maybe it's just that simple for you too?

Brian

Reply to
jamiecarson

Another thing that causes a ticking is the notorious cracked manifold. That can imitate a valve tick that happens as it warms up.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail >
Reply to
Mike Romain

Could it also be some sludge or dried oil crud floating around in the oil pan? Or even blocking the oil return holes in the cyl. head. When you first start it this debris is in the bottom of the oil pan and the oil pump pickup screen is clean. Then as you drive it around the debris moves around and starts clogging up the screen and oil begins to stop flowing to the rest of the engine.

I changed the valve cover on a '93 XJ 4.0 and the debris around the valve springs was super thick. I plugged the oil return holes, scraped the debris off and blew it away with some compressed air. Owner was quite pleased and said the engine was running smoother and quieter. Of course I changed the oil too and hoped any debris down in the pan area came out.

Maybe some engine flushing and frequent oil changes make help! ;-)

Just a thought!

Reply to
One out of many daves

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