Need to Quiet Tapping Noise

Messages
4,437
Location
Guilford, CT
My uncle has a 1998 Jeep Grand Cherokee with the 4.0 I6. I'm not sure how many miles, probably around 180k. He said it recently developed a loud tapping noise, like it's in the valvetrain. He took it to his mechanic who tried to tighten up the rockers, but he said it's somewhere deeper in the engine. My uncle doesn't want to tear into the engine to fix it. He's decided to just run it till it blows. But in the meantime, he'd like to just quiet the noise. He knows additives aren't going to actually fix the problem. He knows it's going to blow sooner or later. He just doesn't want to hear the noise right now. Should he just use a thicker oil, or are there any additives you'd recommend?
 

Astro14

$100 Site Donor
Staff member
Messages
13,113
Location
Virginia Beach
If it's not in the valvetrain, then the tapping is fatal, and quickly so...like dozens of miles at best... You could try the thickest oil possible, like a 60WT racing oil...and if it quiets down, the engine might live a while longer...but every bearing knock I've ever heard is the harbinger of impending doom...
 
Messages
7,514
Location
North America
My 4.0s developed the lifter tick around 90k miles. If it's coming from the lifters, then it's no worries and I'd try 5w40 Rotella. If it's coming from the bottom end, then it is worse, may be bearings.
 
Messages
750
Location
MN
I'd say if it sounds like its in the valves, it's probably a lifter either stuck or collapsed. You might be able to free it with some MMO, seafoam or kreen. Maybe a few fills of Rotella.
 

JHZR2

Staff member
Messages
46,146
Location
New Jersey
Seriously, know that restore stuff? I found it and tried it (successfully) in my old bmw based upon TONS of good reports, all from the 4.0 community. Worth trying to clean the engine then give this a try. 4.0 engines like 40wts too.
 
Messages
258
Location
Western NY
When my Volvo 850 Turbo was clattering, I was worried the engine was on it's last legs. Desperate and not wanting to buy a new car, I decided to try some Sea Foam. I wasn't hoping for much but it actually worked. I added 1/3 can to the oil, 1/3 to a half-full gas tank, and sucked the rest through the brake booster vacuum line. I used a small funnel with an end smaller than the vacuum line, to make sure I always had some air going in to mix with the Sea Foam; I'm not sure if that even matter though, but I was afraid of damaging the engine with too much Sea Foam all at once. Poured it in, shut it down, let it sit for five minutes, then went for a drive. The noise quickly stopped. I drove around until the car stopped smoking, and parked it. Next day, noise free as well. In fact, it was fine until I got rid of it about two years later. I wouldn't use Sea Foam on a regular basis or just for the heck of it, but in this situation it might be worth a shot.
 

JHZR2

Staff member
Messages
46,146
Location
New Jersey
In the oil, I'd either start safe with kreen or MMO, or just go hard with b-12, with NO load on the engine. I went through the gamut.
 
Messages
1,121
Location
Hawkinsville Ga
Chris142 and Miller88 nailed it....broken piston skirt. It's a common problem on the 4.0 up until (I think) 2000 models. Mine has it but I baby it and feed it a diet of Rotella Triple T 15w40 which keeps the noise down. I am told they will run for quite a while like this as long as you keep the RPM's down.....ours has knocked for about 20k miles now.
 
Messages
693
Location
PA
They all tick, like the above said switch to a HDEO, I run 10-30 HDEO (rotella T5)and a HM 5-30 in the winter months. The piston skirt failure is not to common on 98's it was a 99-01 deal.
 
Messages
3,159
Location
Boston, MA
Originally Posted By: Kuato
My 4.0s developed the lifter tick around 90k miles. If it's coming from the lifters, then it's no worries and I'd try 5w40 Rotella. If it's coming from the bottom end, then it is worse, may be bearings.
+1 I have heard those engines do well with T6.
 
Top