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Unread 05-28-2007, 07:39 PM   #1
Tomguy
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4.0 valve tap

So my 4.0 has seemingly out of nowhere developed a rather loud valve tap. I didn't notice it before (maybe because I have the windows up in the winter?) but here's the lowdown:

It seems to be the #4 intake (as best as I can guess). I didn't notice it in the winter when I was running 5w30. When I recently changed the oil (10w40 hi mileage) I didnt notice the tapping right away but maybe a week after (of course, I don't drive the Jeep that much).
The engine has 170k on it, and used 1qt of oil in the last 3000 miles (when using 5w30). I have put Mobil 1 in it the last few times.

It's quite harsh when "cold" (first started - but at 75+, it's hardly cold). It almost vanishes when warmed - so maybe the oil's too thick? I know that 170k isnt that high for a 4.0, so what can I do to ensure longer engine life? Should I grab a head (and maybe cam) off one in the junkyard and redo it, then put that on to replace mine? And if I do - what kind of head will fit? Any head from a H.O. 4.0? Or only ones in a certain year range... my engine is a '92. I'd like to get another 30k or more out of it! Even though my body may not last that long...

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Unread 05-29-2007, 12:09 AM   #2
KamekLocked
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If your going to start rebuilding parts of the engine you should rebuild it all. Other wise you end up with a rebuilt cylinder head (top end) and a bottom end with 170k on it.

The engine is already consuming oil so after a valve job, and having the cylinder head rebiult you will have increased oil consumption due to the higher compression ratio and higher vacuum the engine would have. This then allows more oil to be sucked past the worn piston rigns...

Do you mean the lifter is noisey???
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Unread 05-29-2007, 01:12 AM   #3
88_xj_hunter
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It may just be collapsed valve lifter (hydraulic check valve inside lifter body that keeps pushrod cushioned). If that is the case, then you will have to pull the head and then you can use a lifter removal tool to reach into the block and pull the lifters off the camshaft. Replace them all while you are in there since they're only about $3 each for stock (12 in all). A collapsed lifter will keep a valve from opening fully but does become less noisy as the engines warms and the oil thins out. A worn out camshaft will also give these symptoms. If that's the case, rebuild.
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Unread 05-29-2007, 01:48 AM   #4
Merovingian
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My '97 Cherokee Country has this same noise. A mech friend of mine listened to it and suggested Marvel Mystery Oil might help. What do you guys think? BTW, this is a daily driver that I don't plan to do any major engine work to. I only need to get 3-4 more years out of her then trade.
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Unread 05-29-2007, 12:02 PM   #5
jv3kxj
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You could also be hearing piston slap. It sounds a whole lot like valve train noise, and it goes away when it warms up. Lots of older Xj's have this noise, and it doesn't seem to have much effect on longevity. My 94 makes this noise, it has over 170k on it, and barely uses any oil between changes.
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Unread 05-29-2007, 08:24 PM   #6
Merovingian
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Thanks jv, I feel better now.
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Unread 05-30-2007, 07:36 AM   #7
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sometimes a small peice of drbris gets in the lifter, I had this problem on newer chrysler prouducts in the seventys, I changed the oil ( because the oil was wooped) and let it get good and warm, and then rev it quick almost full throttel, don't go too nuts, this will float the lifters the engine will stumble a little run a little rough for a few seconds, and then repump the lifters.

They used to take the cars back to the dealer and do a one lifter change, so they said, after I started doing this thats all they did afterwards.

I worked for Avis, and the chrysler newports with the 383's were big on this, saved the company a lot of money, I of couse got nothing....
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Unread 05-30-2007, 08:15 AM   #8
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Quote:
Originally Posted by 88_xj_hunter
It may just be collapsed valve lifter (hydraulic check valve inside lifter body that keeps pushrod cushioned). If that is the case, then you will have to pull the head and then you can use a lifter removal tool to reach into the block and pull the lifters off the camshaft. Replace them all while you are in there since they're only about $3 each for stock (12 in all). A collapsed lifter will keep a valve from opening fully but does become less noisy as the engines warms and the oil thins out. A worn out camshaft will also give these symptoms. If that's the case, rebuild.

BINGO

I've had two 4.0's and a 4.2 do this. It's an easy fix but will consume an entire weekend.

*Pull the head and remove the valves, de-carbon everything and Lap the valves with lapping compound (cheap and easy) This will re-seat your valves and get rid of any pitting while increasing compression.

*Buy a "top end gasket kit" from your local parts store instead of buying the head gasket and manifold gaskets seperatly..this will save you a ton of cash. This kit also come with new valve guide seals

* swap out the lifters, re-using your push-rods.....

Essentially you've just done a minor rebuild on the head. Unless there's damage to the valve guides you do not need to have them re-cut. Sometimes having the valves re-cut and not the pistons/rings is worse then not doing anything for blowby.

Nothing like a quiet running 4.0
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Unread 05-31-2007, 08:32 AM   #9
Tomguy
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Quote:
Originally Posted by XJH-007
Nothing like a quiet running 4.0
There is such a thing?
My manifold's been cracked about 5 years now!
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Unread 05-31-2007, 08:34 AM   #10
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Quote:
Originally Posted by Tomguy
There is such a thing?
My manifold's been cracked about 5 years now!

hahahahha....

Ebay, $65 to your door. It's a great time to change it!

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Unread 05-31-2007, 11:53 AM   #11
1990BlueXJ
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Quote:
Originally Posted by XJH-007
hahahahha....

Ebay, $65 to your door. It's a great time to change it!


Give us that Ebay link, cause I can't find it on Ebay that cheap.
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Unread 06-02-2007, 11:22 AM   #12
Tomguy
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Yeah, if you can tell me where to find a quality new manifold for $65 wiith shipping, I'd jump on it. Talk about a weekend project! Maybe I can get a can of R12 with it somewhere. I haven't recharged my AC (ever) and it's a little weak I think.
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Unread 06-02-2007, 02:31 PM   #13
n20jeep
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Quote:
Originally Posted by Tomguy
Yeah, if you can tell me where to find a quality new manifold for $65 wiith shipping, I'd jump on it. Talk about a weekend project! Maybe I can get a can of R12 with it somewhere. I haven't recharged my AC (ever) and it's a little weak I think.
skip the R12 and covert your system, it WILL be ALOT cheaper than recharging with R12
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Unread 06-02-2007, 05:27 PM   #14
Tomguy
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I don't see how a $25 can of R12 is more expensive than several bottles of R134a and the time and effort to change the dryer, and flush the system, and then have reduced capacity...
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