valve tapping in my 91 yj 4.0

last time i was out at rausch. when i followed nester up that big hill at the lake, my engine started tapping.it stopped when i got back on level ground. then i went through sunken treasure and it started tapping again when i let off the gas at high rpm, then stopped again....i have a dent in my oil pan, so i pulled it and the pick up tube is still in good shape, so it IS getting oil...WHAT COULD THIS BE AND HOW CAN I FIX IT (VALVE TAPPING?).SOMEBODY TOLD ME JUST TO PUT SOME OIL TREATMENT IN LIKE S.T.P... I DO NOT THINK THE VALVES ARE ADJUSTABLE

There is a tadpole in the oil pan and he keeps swimming in front of the oil pump and getting sucked into the screen. just hit a few bumps and it will shake loose.

You have hydraulic lifters so there is no adjustment.

What weight oil are you running? If 5w30 or 10w30 jump up to 10w40 and change your oil more often for awhile.

If it is a lifter then there is not a fix except for replacement of the lifters. Its a very easy job. I would run a compression test first to make sure there are no other problems and if everything tests good just replace the lifters. These 4.0's should go 200,000 easily...


When you heard the rapping were you just into the throttle hard? Hydraulic lifters are made to float away at high rpm instead of damaging the cam. My dad had a car with a Lt1 and he floated a lifter and it took awhile to settle down. We were ready to pull them and a dealer said give it some time and see if they return. Once it went away the lifter never made another noise.

thank you for the info., i will change the oil and put treatment in, also get rid of the tadpole that is swimming around in my oil pan , i only have 80k miles on this engine, but it has set awhile before i got it back. hopefully the tapping will disappear like you said, if it does not, i will take it to the next level. thanks.............question? will this kind of tapping hurt the engine if it keeps happening occasionally

You just gave more info... Sitting...

I sold my Dad a 97 Silverado back in 02 and since then he has put like 8000 miles on it. Last year I went to start it and I got the tapping out of that for awhile. This was my truck and I know how it was taken care of and the oil changing was not an issue. Its kind of funny but I really believe letting a car sit does more harm than driving it. Just like the other car he had that he floated a lifter on. Since retirement they do not drive their cars much..


That is why I switched his truck to 10w40 and it hasnt done it since. I have to take the truck every 6 months and change the oil and he usually has less than 1500 miles each time I change it. He has a new Buick now and the dealer has been changing it for the warranty deductible.

If the lifter is bad it will eventually collapse.

Just keep an eye or EAR on it and see if it gets worse.

You are not using synthetic are you? I wouldnt!!!

no, i am not. i will change it with 10w40 and see what it does on the next run i go out on. meanwhile i have a rear locker and a front pull down winch cable to fix. thanks for the info

more problems, i put a mech. guage on my oil pressure. it was reading 20 to 50 lbs (good). but when i let it run for about 45 min. and went back and checked it was practically 0 lbs at idle and 20 lbs reved up. can this be an oil pump problem or do i need a rebuild. what should i do, also at 220 temp. steady

vonsjeep wrote:

more problems, i put a mech. guage on my oil pressure. it was reading 20 to 50 lbs (good). but when i let it run for about 45 min. and went back and checked it was practically 0 lbs at idle and 20 lbs reved up. can this be an oil pump problem or do i need a rebuild. what should i do, also at 220 temp. steady

was this before you changed oil or after you put in the 10W40. If you drop the oil pan to change the oil pump you can check for a loose bearing cap at the same time.

Correct me if Im not thinking but i dont see where anything but the pump could make you loose oil pressure. If the rings are worn then you would loose compression but not pressure, right???

After it has cooled down try it again.. Also do a compression test and get us the numbers on each cylinder. If they are close then I think just a pump problem.

I will ask around today...

I have a compression tester if you need it.

Is it smoking or anything or just loosing pressure.

I would think a loose crank bearing would cause loss of oil pressure. Spin a bearing and sometimes it seats? This would not effect cyllendar compression. If you have a loose bearing and it spins causing you to loose oil pressure then I could see how the valves might start tapping, lack of oil getting to the hydraulic lifters.

Mine was doing the same thing last winter with about 115K on the motor. I changed the oil to 10w40 and ran a can of sea foam cleaner on some 93 oct. and the oil pressure issue went away and the taping stopped. Did the same thing in the grand cherokee too and it improved the MPG

Hmmm...the sea foam thing is interesting. I've heard and read mixed results.

never heard of sea foam, can you get it at auto parts store, also the engine is strong and does not smoke. i ordered a pump today and i will check my bearing caps also when i put it in. what are they suppose to be torqued to when i reinstall ?..thank you all for the input, i believe my brother has a comp. tester. also is 220 temp normal for these engines.

here http://jeephorizons.com/tech/99_40l_torque_specs.html

check this out also
http://www.madxj.com/MADXJ/technical/technicalfiles/SRengineBearings/enginebearings.htm

Well for 8 bucks what did I have to lose? yeah you can the sea foam from the parts store and you run it in the with the gas.

great info, thanks here are some pics of my connecting rod bearings and my main bearings 1617][/URL]

i was able to move the crankshaft up and down (almost not noticeable) but i did not think that i should see any movement in it by pushing and pulling up and down on the front flywheel

i got my bearings in and the rod bearings do not have a groove in them, the main bearings do

I believe the rod bearings are lubricated by splash when they descend into the oil?

well, i replaced my bearings and i am getting 5 lbs pressure hot and 40 lbs when i rev up about 20 lbs at a high idle. that is acceptable for me, but my oil pan is leaking, it is almost pouring out of the seal right at were the pump is located, i think the oil pump is not seated right and it is blowing oil at the silicone gasket i made causing it to penetrate through and leak, the pump did not have a gasket in the box and the sales clerk did not know anything , he said to put it on with out a gasket, what should i use for a gasket if any (the old one had a very thin paper gasket on it) . i have to pull the pan back off again now and fix this problem. when i look at it while the engine is running the oil looks like is is coming out with force (it is bubbling as it comes out). it does not leak while the engine is off

did the old pump have a gasket?

I have some really good gasket material if you want to make one..I got it to make axle flange gaskets and it worked great.

I would check with another retailer and see if it was supposed to come with a gasket.. I can check for you in the morning if that helps..

it had a paper thin gasket on the old one. do you think the stuff you have will work, if so i can pick up a peice of it, i plan on doing the job sunday. maybee come get it saterday around 1:30 to 2:30

I just checked and the pack is in my truck.. I have a couple different styles and thickness'es you can choose from.. I will be working if you want to stop by there. Sears White Marsh auto center..

ok i will stop in about 1:30 saterday at sears

i put a new gasket on the oil pump today donated to the cause by matt. thanks. and i buttoned up the oil pan again, i am going to wait and give the silicone time to cure before i put any oil in and start it up. then i should be done with this issue. thanks everyone for all the input