Cracked Flexplate Noise

[AZJeff]

2 minutes ago, cruiser54 said:

It's NOT flexplate. Did you tell us which oil and filter you're using? 

Mobile One 10w30 and a Mopar filter.

[cruiser54]

Okay. Let's do the test and see what happens. I have some ideas. 

[MiNi Beast]

3 hours ago, AZJeff said:

I get the idea of looking at the flex plate with my camera.  Once the engine cools, I will dive into that.  (Even though it never changes the noise between loading the engine versus no load.)

 

But on the lifter inspection, what are you suggesting I will see?  A pushrod flopping around under the rocker, or something else?  Wouldn't that be most likely detected by looking for lash to return very shortly after the engine is shut off?

push rods should be touching and yes not returning like others. 

do that cold test though per tests. I'm listening again and feel its a lifter for sure if not 2. thinking 4 and 6 are weak. 

[AZJeff]

22 hours ago, cruiser54 said:

Okay. Let's do the test and see what happens. I have some ideas. 

I did as you suggested, and recorded a cold start.  Here is the video (mostly for audio value).  As you can hear, there is virtually no ticking sound.

 

Then I shut it down, and waited about one minute, and did a restart.  The ticking starts up relatively soon after the restart, as you can hear.

 

[MiNi Beast]

yeah i still think lifter. pull valve cover and take a gander i reckon. 

[cruiser54]

Yeah, you could pull the valve cover.

 

I'd be more inclined to dump the Mobil 1 out in favor of Rotella 15-40.

[scaleless]

The zinc is critical, but definitely won't repair any existing damage.  A wiped cam is a wiped cam!

[cruiser54]

4 minutes ago, scaleless said:

The zinc is critical, but definitely won't repair any existing damage.  A wiped cam is a wiped cam!

Not sure it's a wiped cam just yet.

[AZJeff]

6 hours ago, scaleless said:

The zinc is critical, but definitely won't repair any existing damage.  A wiped cam is a wiped cam!

I used Mobile ONe in two XJ's I owned for many thousands of miles (here in PHX, the temperature endurance of synthetic is a significant bonus).   I never saw any cam issues.  Then again, I never had an engine with coolant contamination of the oil.

 

I will pull the valve cover, and I will measure the lift on each pushrod with a dial indicator, and compare against the shop manual spec.   I will report back in a day or so.

[cruiser54]

good plan

[AZJeff]

So I tried to measure valve lift at the valve spring retainer, but I could not get a good consistent spot with the tip of my dial indicator.   So...back to a more complex, but consistent approach:

 

1.  remove rocker bridge and the two rocker arms for a given cylinder

2. install dial indicator tip into hole on end of pushrod, and measure pushrod lift

3. multiply measured value above by 1.6 (the factory rocker arm ratio) to arrive at actual valve lift

 

Here is what I came up with, and it's not pretty.

 

Not a single pushrod lifts to the specified height, which means all the valves are not opening to the desired amount.  Even if the lifters themselves are clean and functioning normally, I think my camshaft may be toast.

 

Comments?

[scaleless]

The lift specs you posted are for 96 and up.  Earlier used .397 on both intake and exhaust, which most of your measurements are pretty in-spec for.  I think you just have an early cam in your engine, which shouldn't be an issue.  #6 intake seems pretty poor, though.  Isn't that where you said the noise seemed to be coming from?  Might be worth another measurement.

[AZJeff]

12 minutes ago, scaleless said:

The lift specs you posted are for 96 and up.  Earlier used .397 on both intake and exhaust, which most of your measurements are pretty in-spec for.  I think you just have an early cam in your engine, which shouldn't be an issue.  #6 intake seems pretty poor, though.  Isn't that where you said the noise seemed to be coming from?  Might be worth another measurement.

As my sig says, I have a 2000XJ engine/control system in my MJ, so the specs. I quote are for that year of engine (I have the Mopar shop manual for the 2000XJ).

 

However, you are correct in that my noise seems to be eminating from around #6.

[cruiser54]

You tested them more than once?

#6 at TDC, can you spin the intake pushrod?

[scaleless]

10 minutes ago, AZJeff said:

so the specs. I quote are for that year of engine

What I mean is the cams are to my knowledge interchangeable, and unless you built that engine by hand (and, really, even if you did) you probably can't be certain that the previous owner or builder didn't put an early cam in.  Given most of your numbers are evenly in-spec for an early camshaft, I think that's much more likely than the alternative.

[AZJeff]

19 hours ago, scaleless said:

The lift specs you posted are for 96 and up.  Earlier used .397 on both intake and exhaust, which most of your measurements are pretty in-spec for.  I think you just have an early cam in your engine, which shouldn't be an issue.  #6 intake seems pretty poor, though.  Isn't that where you said the noise seemed to be coming from?  Might be worth another measurement.

I acknowledge that I really don't know WHAT this engine is made from.  I know it has the late intake, and had the late head (the 0331 that cracks when overheated), but the cam/crank/pistons may be a mish-mash of stuff, for all I know.

 

I remeasured all the lifts again, and here is what I get:

[AZJeff]

19 hours ago, cruiser54 said:

You tested them more than once?

#6 at TDC, can you spin the intake pushrod?

When #6 is at TDC (verfied by copper wire into spark plug hole), the rods will spin, but not move radially at all (which should be normal, correct?)

[cruiser54]

The only one that seems out of spec is #6 intake. 

Maybe a bent pushrod? 

You can spin any pushrod that's on a cylinder when at TDC?

[AZJeff]

25 minutes ago, cruiser54 said:

The only one that seems out of spec is #6 intake. 

Maybe a bent pushrod? 

You can spin any pushrod that's on a cylinder when at TDC?

Cruiser,  I just went out and ran each cylinder through TDC, and confirmed that the pushrods spin (and do not appear to be bent) when in that position on each cylinder.  The pushrods were new when I put on the new head, so I don't "think" they could have gotten bent when I installed the new head and valve train.

 

When I did the head, I thought "don't mess with the lifters, since they are run in on the cam" and the old adage was "don't swap lifters between lobes, or put new lifters on an old cam".   (I realize this old adage is probably no longer applicable.)

 

When i cleaned the lifters, I did so in acetone, and I will admit, they were somewhat varnish coated, and were tough to get out of their bores with the normal lifter removal tool.  There was no scuffing or cupping on the bottoms of the lifters, and when peering down with a flashlight onto the lobes of the cam, I saw no signs of wiping on the cam (but of course, that wouldn't preclude lobe wear.)

 

Whaddya think?

[cruiser54]

start it with the valve cover off and poke around with a stethoscope.

[AZJeff]

9 minutes ago, cruiser54 said:

start it with the valve cover off and poke around with a stethoscope.

 

9 minutes ago, cruiser54 said:

start it with the valve cover off and poke around with a stethoscope.

Roger...standby

[AZJeff]

Well, I think I found the problem, or a least a major contributor:   Intake pushrods on #4 and #6 aren't gettting hardly any oil up onto the rockers.  I ran it for about 1 minute, and all the other rockers had plenty of oil accumulating in the low spots.   Those other two were damned near dry (other than what had splashed around prior to the valve cover removal.

 

I think a set of lifters are the order of the day, don't you?

 

[cruiser54]

are the pushrods clear? 

[AZJeff]

21 minutes ago, cruiser54 said:

are the pushrods clear? 

Clear?  Meaning free of obstruction and/or not bent?  Yes to both.

[cruiser54]

so, you can blow through the pushrods easily?