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Intermittent Lifter Knock - Need Advice

Sleepydog

NAXJA Forum User
Location
Clarksville, TN
I've got an intermittent lifter knock/tap in my 1990 MJ (165k miles). It runs great, keeps good oil pressure, no cooling problems...

I took it to the Dealer for diagnosis of the knock/tap sound - sure enough they confirm it is a lifter, and they want $800+ to replace them!!

If I just decide to live with the lifter tapping, will I risk additional damage? I tried seafoam through the TB and the crankcase, buth that has not eliminated the tapping either.

Any thoughts or suggestions are appreciated.
 
Try replacing a quart or two of your regular oil with 40W or 50W racing oil, and see if that doesn't quiet it down. Most lifter noise I've dealt with is caused by the inability of the lifter to stay "pumped up" - heavier oil will help this.

I'm assuming you have a 4.0 in your MJ - that price wouldn't be too far out of line. The head has to come off of a 4.0 to change lifters...

Oh - NOTHING you put down the TB will help. Don't bother - it's going to be something to do with the oil or the lifters proper...

Where are you, anyhow? I'm getting my garage cleaned up to the point where I'll be able to start taking in work soon....

5-90
 
5-90 said:
Try replacing a quart or two of your regular oil with 40W or 50W racing oil, and see if that doesn't quiet it down. Most lifter noise I've dealt with is caused by the inability of the lifter to stay "pumped up" - heavier oil will help this.

I'm assuming you have a 4.0 in your MJ - that price wouldn't be too far out of line. The head has to come off of a 4.0 to change lifters...

Oh - NOTHING you put down the TB will help. Don't bother - it's going to be something to do with the oil or the lifters proper...

Where are you, anyhow? I'm getting my garage cleaned up to the point where I'll be able to start taking in work soon....

5-90

Yeah, its a 4.0. I'll try the heavier oil...I'm in Clarksville, TN - Thanks for the fast response.
 
5-90 said:
Try replacing a quart or two of your regular oil with 40W or 50W racing oil, and see if that doesn't quiet it down. Most lifter noise I've dealt with is caused by the inability of the lifter to stay "pumped up" - heavier oil will help this.5-90

Not trying to hijack Sleepydog's thread, but I'm going thru the same problem w/my '88. I did the whole detergent thing where you dump a quart of this engine cleaner stuff (can't remember the brand) run it about a half hour or so and then change the oil. Didn't really help. It gets worse when I get close to an oil change. 5-90, should we use straight 40 or 50 wt oil or should it be like Castrol's 5-50wt? It get's pretty cold here in Wis and the oil gets pretty thick when you first start it anyway.

Thanks for the thread-ride, Sleepydog

Steve
 
Straight - you'll usually find it as a "Valvoline Racing Oil." I'd not change more than a third of it to the heavier stuff, and a pint or so of Marvel works wonders for cold weather viscosity (I used to run 50W in my Bug year-round in Lafayette, IN. Marvel helps.)

Most lifter clatter I've had the misfortune to encounter came from one or more lifters that simply could not maintain the internal oil volume they are designed for (that's what makes the valvetrain self-adjusting) and they'd "go flat." The heavier oil helps for a while, but plan on replacing the parts. Before you get started on the job, check the head bolts on the driver's side for paint marks. If present, get a new set of head bolts as well as the head gasket kit and lifters. 4.0 head bolts can only be torqued twice before failure, they are "torque-to-yield" types. This is per the FSM and the aftermarket manuals...


Try not to let this go too long - lifter clatter is caused by the excessive lash in the valvetrain, which results in valve slamming as well. Valves are pretty tough, but it would suck to have one fail into the cylinder... You'd probably also blow a hole thru the valve cover if the valve head lets go...

5-90
 
Thanks, 5-90. You've saved me again. I will 'doctor' the oil the way you described and I plan on changing the lifters this spring. I think the motor is worth the work. I've only got 115K on it and it doesn't smoke or hammer although I do have to add a half a quart or so to it if I do alot of highway driving before the 3k oil change mark.

Thanks again! :wave:
 
5-90
Im not trying to hijack here so sorry, but I'm experiencing lifter noise as well. I was told its pretty normal, but it bothers me. Mine is only at idle and not at all when driving. Should I worry about it, or just wait till its gets worse. I don't use any oil and I only have 85K on it, but its done it since I bought it used 10K ago. I tried running 20-50 in it instead of 10-30 and it didn't make any difference. I think I may try your suggestion of a quart of straight 50 weight to go with my 10W-30.
Thanks :D

Oh yeah, I forgot a very important part, It only does it once its warmed up. I have no lifter noise at all at start up.
 
Makes sense - the "viscosity improvers" in multi-grade oil are designed to try to thin it at lower temperatures and thicken it in higher - but this does not always seem to be so. Anytime I've had anything like this happen, I'll run a heavy "straight-weight" oil until I can get around to changing the parts.

Sometimes, if I catch it just as it starts, running the heavier oil seems to "save" the parts if I don't use it the next time. I still plan on replacing lifters when that happens, tho.

A little clatter at startup is a farily common thing, but it should go away within a minute or so as the oiling system develops pressure. Any longer than that, and you should start thinking about changing lifters...

5-90
 
Well, my lifters only make noise at idle and not at all when driving or anytime the rpms are over about 1200 or so. You still think I should replace them? Its been doing it since only had 70K miles on it and its been very well taken care of. Maybe I've been misinformed, but I was told not to worry too much about it, its a Jeep and a lot of them do it and if its starts doing it while driving then replace them. I'm just asking because I was told differently by my father's friend who is an ex Jeep mechanic.
Thanks :D
 
Make sure it's lifters and not the injectors, they make a clicking noise also.
 
I'll check that out, but I don't think thats it. I'm also going to run a high detergent oil through it like you suggested in another post.
Thanks
 
Crash course in hydraulic valve lifters.

WAAAAY back, all engine had mechanical valve lifters, or "tappets" (which is why the guys on Car Talk call themselves the Tappet Brothers). They had to be adjusted periodically, when the engine was hot. Not rocket science, but a messy, nuisancy job that lots of owners never had done.

Along about the mid-1950s the manufacturers came out with hydraulic lifters. The deal with them is that they are self-adjusting. Inside each one is a spring and a check valve, beneath a plunger which is what actually contacts the bottom end of the pushrod. When you fire up the engine, oil pressure is supposed to push the plunger up and maintain it in contact with the pushrod, while providing enough pressure to lift the valve by the specified distance.

Hydraulic lifters fail in two modes: either the check valve goes bad and they bleed down too fast, or the oil feed orifice gets clogged and they don't get enough (or any) oil. If the latter happens, the plunger doesn'tride high enough to keep the pushrod in contact with the rocker arm when the lifter is at the low point of its travel, and the "tick" you hear is when the pushrod starts to move up and makes contact.

If it's happening all the time, eventually it can cause wear on the cam and the rocker arms. If it only happens when the engine is cold, or only at idle, it's probably not worth replacing the lifters. The reason that job is so expensive at a dealer is simply that on the 4.0L you have to remove the head to replace the lifters.

Heavier oil will address the problem if it's a case of the lifters bleeding down too quickly, but will not address the problem of dirt. You need a cleaner to have a prayer of fixing it that way. I like Marvel Mystery Oil for that purpose. The directions are on the can. If you have noisy lifters, you want the "purge and clean" dose, not the normal "I do this at every oil change" dose. It's not guaranteed to work, but it often does. Sometimes helps to combine the Marvel purge with a bit of Mexican tune-up -- run it up to high RPM for several seconds. I prefer to do this in 2nd or 3rd gear on the road as opposed to in neutral in the driveway,but that's personal preference. The idea is to maximize the oil pressure so any specs of dirt can be pushed through and out of the lifter passges.
 
Thank you very much Eagle, that was very informative. You are very knowledgeable and I always trust your recommendations. According to your respsonse I think I have a blocked oil passage and can address the problem with a good engine cleaner like the Marvel's Mystery Oil you suggested. Thats too funny, my dad, an old gearhead, has been suggesting this all along. I guess I should listen to pops more often. :D
 
Yea, its pretty amazing how much smarter we parents get as you kids age :D
 
I also really appreciate the info. I've been having some lifter noise for a few months now and it seems to get louder and louder. It's a little depressing cuz I just had a new longblock 4.0 put in it by the dealership. Well, at least it's still under warrenty! :)
 
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