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I am getting a noise that sounds like something hitting on something from the front of the engine. 98 Dakota 2.5 4 cyl. I recently put a new head, radiator, water pump and thermostat on it. Now I am getting this noise. A friend says its timing chain slap. It sounds like marbles rolling around inside a can.

What exactly is this and how do I determine it before I yank it apart again?

Also, number three cylinder exhaust side, when the rocker arm is tightened down there is no compression. For what ever reason when it is tightened down the valve is left open. I had to back off the bolt about a turn and a half to gain compression. This would not do because the bolt would just keep backing off. I put a spacer between the rocker arm and the head so that when its tightened it does not compress the spring and I get compression. I know this is not an ideal fix either. Any ideas?
 

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I am getting a noise that sounds like something hitting on something from the front of the engine. 98 Dakota 2.5 4 cyl. I recently put a new head, radiator, water pump and thermostat on it. Now I am getting this noise. A friend says its timing chain slap. It sounds like marbles rolling around inside a can.

What exactly is this and how do I determine it before I yank it apart again?
If it's timing chain related, there is no real way of determining without
pulling the timing cover off. What is the mileage on this 4 cylinder Dakota? On the 4 cylinder engine there is a timing chain tensioner that provides spring tension on the chain. If the chain and sprockets have excessive wear, then the tensioner spring can no longer have spring range to provide tension on the timing chain. As a result of this the stretched chain just clangs/slaps against it when running, because the chain is stretched now.
Looks like the chain and BOTH sprockets (cam/crank), may have to be replaced as a set. So perhaps that's what you are hearing, as the chain has stretched.
If the chain was kept taut by the chain tensioner..you would not hear that noise.

Also, number three cylinder exhaust side, when the rocker arm is tightened down there is no compression. For what ever reason when it is tightened down the valve is left open. I had to back off the bolt about a turn and a half to gain compression. This would not do because the bolt would just keep backing off. I put a spacer between the rocker arm and the head so that when its tightened it does not compress the spring and I get compression. I know this is not an ideal fix either. Any ideas?
Those are hydraulic lifters..and you probably have a collapsed lifter
on the exhaust valve, that if you tighten the rocker all the way down..
you are bottoming out and the valve spring is being forced open.

The lifter is supposed to be primed with oil even when the engine is
not running so that the hydraulic oil pressure builds up and takes up
any slack between the push rod and the valve rocker. Somehow it's lost
it's prime..would be my guess.

There is a procedure for tightening down the rocker arms and pushrods,
to avoid that. Sometimes you have to back it off (with the valve cover
off and the engine running for the lifter to "re-prime" with oil again.
If that doesn't work, then the seals inside the hydraulic lifter are worn
and the lifter will not prime..at that point..you have to replace the
lifter or lifters.

The other thing you can try is changing the oil to a heavier grade 20w-50
and see if that reprimes the lifter(s). You don't want to run on the heavier
grade oil to the next oil change..but just temporaily to prime the lifters, as the oil pump may build up a higher pressure to reprime the lifter in question.
If that trick doesn't work..the lifter (more than likely) will have to be replaced.
Note: new lifters HAVE TO BE PRIMED in oil first before installing.
 

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the truck has 123K miles on it. I put a mechanics stethoscope against the cover and can definitely hear the tapping noises there. I will pull it apart this weekend and check it.

I thought about the lifter also. How exactly do you replace the lifter? I have heard that there should be a plate on the side of the block to get to them but I don't have one. Someone else told me to use a strong magnet and pull it from the top then just drop it back into place. I have never had to replace a lifter before. Since they are cheap enough this is probably the way to go instead of constantly messing with the rocker arm.
 

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the truck has 123K miles on it. I put a mechanics stethoscope against the cover and can definitely hear the tapping noises there. I will pull it apart this weekend and check it.
With that many miles on it..you may as well get a new timing chain/sprocket set. Engine timing is very critical on a 4 cylinder engine..
as soon as the valve timing is off..you start to lose power. If you are
hearing tapping noises, the chain tensioner spring is at it's farthest
travel and can't compensate for the chain stretch anymore.

I thought about the lifter also. How exactly do you replace the lifter? I have heard that there should be a plate on the side of the block to get to them but I don't have one. Someone else told me to use a strong magnet and pull it from the top then just drop it back into place. I have never had to replace a lifter before. Since they are cheap enough this is probably the way to go instead of constantly messing with the rocker arm.
Generally you need a strong magnetic tool to pull it out..provided there
isn't so much wear around the part of the block (bore) that it sits in (similar
to the "wear ring" at the top of the cylinder block that impedes the
removal of pistons)... or a lot of varnish buildup in the bore itself, which
will impede the removal.

Here's a basic description of how to remove a lifter..
http://www.ehow.com/how_8034955_change-hydraulic-lifters.html

and you will need one of these telescoping handle mechanics magnets to pull
it out of it's socket.

http://www.tooltopia.com/se-tools-924.aspx?utm_source=nextag&utm_medium=cse&utm_term=SES924&utm_campaign=nextag_r1t's


There is also a special lifter extraction tool that you may be able to rent ( or borrow) from an auto-zone place? This tool actually has a spring loaded handle expanding "3 part bit" that grips the snap ring groove inside the lifter, made especially there to allow the lifter to be extracted.

Failing getting one of those above (special tool or magnet), take a machinists steel scribe, bend the end of it into a hook and grab the lifter under the circlip (retainer ring) that holds the little "piston" inside
groove and pull it out that way. (Cheapest solution if there is no other option).

Note: if you are removing lifters, pushrods..AWAYS mark the order (cylinder number) that these parts come from..if you are intending to reuse any.

Obviously if you are going to throw away the old part(s) and replace with
new parts, then you dont have to do that..but if you are removing 8 pushrods
and 8 lifters..make a cardboard holder for the pushrods so they can be
pushed into the cardboard in the order they come out as they should go
back where they came from.


Same for the lifters..if you are removing more than one..some kind of
wooden "rack" that identifies:
Cylinder #
Valve # (exhaust or intake) as each lifter will have some cam wear on it's
flat surface on the bottom..where the cam lobe contacts it.
 
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