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What are tappets? What is their function? How long are they suppose to last (in a XJ)?

I was at a gas station one day and the person who worked there metioned to me that my tappets are noisy and it might be a problem...my jeep cherokee is 1997, 4.0L...seems to be far to early to have "tappet" problem...even though i don't know what they are...i mean aren't these engines suppose to be tough and last a long time?

thanks in advance...
 

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The tappets or the more commonly know "lifter" is a part of the motors valve system. The lifter rides on the cam and with the aid of rocker arms, push rods, and springs opens and shuts your intake and exhaust valves. Sorry but I can't tell you how long they should last in a Jeep, I'm sure that someone from the Jeep forum could help you with this though.
 

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Silverback
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Lifter noise is pretty common with the I-6. How bad is it? Are you running synthetic oil, or dino? How often do you change the oil/filter?

Hopefully, with a '97 the issue is somewhat correctable - depending on the mileage, one wouldn't expect a worn cam to be the culprit in your case.

These engines run HOT! I've never had a vehicle that cries out for synthetic oil like my 4l I-6. I know the owner's manual says that "it's normal for steam to rise off the hood of the engine", but I swear we could use the hood as a griddle and avoid those McD's Big Breakfasts altogether :D (and the temp gauge continues to read "nominal" - a nice steady 210*).

Noisey tappets can mean lack of proper lubrication. If you've run dino and have missed the odd oil change, there could be sludge build-up fouling oil delivery resulting in additional noise.

I changed over to synth at 5,000 km's (from new) and lifter tapping hasn't been much of a problem....., though maybe that's because I was so used to it - our '75 Scout II had the same noise, but a lot worse at 100,000 miles (the 350 V-8 sounded like a diesel).

Depending on your mileage you may want to consider changing to synthetic. Realize that its detergent properties will loosen sludge and perhaps clog your filter, so change the filter after you've gone 500 km's or so. Also, if you've got a fair amount of build-up, your gaskets may have dried out and cracked, so once the sludge is removed you could end up with a few oil leaks.

There are engine flush products that might help - you can do this next trip through Mr. Lube/Jiffy/McLube etc etc (or yourself if you do your own oil changes).

Hopefully Dan B will see your post and give you the inexpensive route to go - he's clever with this sort of thing.
 
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