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99 Chrystler 3.8L Engine Knock - HELP~

26K views 25 replies 14 participants last post by  sideburns2009 
#1 ·
Hi all:

I am a new member and a new Chrystler Town and Country owner... a nice ride leather heated seats very nice. I'm impressed, never had one before.

I have a problem, the engine knocks, raps, it sounds like in the tappet area a distinct knock. It's not at the rocker arm area, too heavy a sound, it goes down the road nice doesn't skip or smoke, just knocks.

Today I tore it down, heads off, oil pan off... all the roller lifters look great, they all move like the same amount, the pushrods are fine and the rockers.
I checked each connecting rod bearing*(it's got 162,000 miles on it) all the bearings are intact, wear is evident for sure but not so you would hear a knock, I expected to find one spun.
Now I''m at a loss, I've looked at all the likely suspects and stilll no smoking gun~!

Any thoughts will be greatly appreciated... I heard that the cams break on some of these... if the cam was broke it wouldn't run very well...

HELP>>>

:(
 
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#2 ·
Geez, I wish you'd found us before you tore your motor down. The fact of life is that pretty much all of these motors knock to a certain extent, our 1998 3.8 is no exception. This issue has been discussed a time or three around here and if I remember correctly the popular consensus is that the noise ie eminating from the timing chain and or the oil pump assemblies.

FWIW, I replaced the head gaskets on our 1998 last summer as well (incorrectly thinking that I had a coolant leak from one of the gaskets), so I'm pretty familiar with the job you've just taken on.
 
#4 ·
Geez, I wish you'd found us before you tore your motor down. The fact of life is that pretty much all of these motors knock to a certain extent, our 1998 3.8 is no exception. This issue has been discussed a time or three around here and if I remember correctly the popular consensus is that the noise ie eminating from the timing chain and or the oil pump assemblies.

FWIW, I replaced the head gaskets on our 1998 last summer as well (incorrectly thinking that I had a coolant leak from one of the gaskets), so I'm pretty familiar with the job you've just taken on.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++

This motor had KNOCK, I've never heard a knock like that and not find a smoking gun inside... I'm really exasperated at this point not finding anything.
I'm sure if I put it all back together it will knock like I never touched it...
How can a timing chain make a knocking noise>?
Another thing; no debris in the oil pan, no metal, no parts, or broken parts... no shavings...

Thanks for you reply, let me know about the chain and pump, how do they knock?

:cool:
 
#3 ·
Wow, your ambitious my 3.0 liter had a little tick to it - I added some "Kendall High mileage oil" to it and viola Noise gone!!!:biggrin: I do not know that much about the 3.8 L although they are supposed to be a much better engine than my 3.0L I was told that the noise in mine was a collapsed lifter and apparently all the 3.0 do it. Good luck I am sure someone here knows how to help you!
 
#5 ·
I concur with the timing chain noise issue. My van has a little bit of timing chain noise at idle. An older 3.3L I worked on last fall had a lot of timing chain noise. I think the chain just beats against the metal chain guide once even a tiny amount of slack develops. The chain has no damper to take up slack.

- G
 
#6 ·
tommcmullen - are you sure it isn't just piston slap?
 
#7 ·
Check to see if your torque plate is cracked. This problem is actually more common than you would think. Remove the tin plate on the bottom of the bellhousing (I think it is held in with three small bolts) If you can move the torque converter any distance back and fourth with no resistance -rotation, not fore and aft... you have a cracked torque plate. If cracked, you will not be able to see the cracks until you remove the transmission. They crack arround the crank shaft bolts. Quick and easy to check. The torque converter should move, but have no "free play".
These engines are bullet proof, it is unusual to find problems with them.0
 
#24 ·
:angry1:i just found out that i have the same problem. i took your advice and took look at my torque plate. lone behold 2 of the bolts were completely out and the rest were loose. when i first heard the noise i thought it was the engine. this is another reason why I will never buy a dodge.:mad:
 
#8 ·
I don't think it's piston slap, as best I could see everything with the pistons looks a-ok... I'm not taking them out if I don't need to.

The flex plate... I was thinking about that too, it seems tight...
The knock is real pronounced when the engine is cold, like a collapsed lifter, but with no skip, then when the rpms are brought up to 2500 or so holding there the sound is like a bad rattle, but no scraps in the pan.

I'm going to check the flex plate again... the timing chain is loose, i can feel it and see it, can't imagine how it would make that noise but, I'm so close now there is no backing up.
:cool:
 
#9 ·
When my flex plate went it was worse for some reason when the A/C was on. After looking and looking I thought it may be the torque converter. I called my local dealer (Goss Dodge in South Burlington, VT, Great folks) They said from my discription they were sure it was the torque plate. When I asked them if this was common, the service manager told me that they had just done three of them...
I could easily turn the ring gear back and forth about 3/8', then it started to hit some resistance. The frustrating thing for me was there was no way to see the problem to be sure it was the problem until after I removed the transmission. The good news, it was the torque plate and I really did have to remove the transmission. The bad news, my torque plate was shattered.
 
#13 ·
I have a similar 'chuck, chuck, chuck' knocking noise at idle, worse with the A/C on. Little revs and the noise totally disappears. Feeling the sump area tells me it is low down, not top end rattle (lifters, cams, etc).
I think my flex plate may have cracked, I'll see if I can check by removing that cover plate. Any tips diagnosing?
 
#14 ·
A tip for diagnosing a cracked flex plate that I have used, is to take of the inspection plate which means removing the starter. Then remove the tc bolts and slide the tc towards the tranny. Then try to move the flex plate away from the engine, working it back and forth, and then try turning it. If it moves on its own it is cracked around the bolts that hold it to the engine. There should be no loose play or rotation. I had one where it cracked all the way around the bolt area and spun on its counter part.
 
#16 ·
I once tore down the top end of a 3.3 based on a rapping noise that occurred anywhere above idle. The noise seemed to be coming from the intake valley so my first assumption was that a lifter had gone bad. After inspection they all seemed to be fine. I still replaced the lifters along with the pushrods, rocker arms, rocker arm shafts, valve springs, valve seals, and valves, after I found that the number five cylinder and everything in that cylinders vicinity looked yellowed. That cylinder apparently lost either the intake or exhaust, don't know which. After putting everything back together again the noise disappeared, plus, there was no more noise coming from the lifters when starting up cold. Maybe that could have been the source of your van's noise.
 
#18 ·
Pulled the tin and viewed the engine side of the flywheel/starter ring. All 4 bolts were 1/3-1/2 turn loose. Don't see how I could remove the 4 bolts and then slide the tc - it's on the other side of the starter ring/flywheel ? Anyway, would 1/3 turn loose cause noise?
 
#20 ·
What was I thinking:ask_wsign I done that after I had backed the tranny away from the engine, but if I hadn't told you to remove the tc bolts you might have not have discovered they were loose. Loose is bad especially in there, now take the time to take the bolts out one at a time, put the red locktite on them and put them back so they will not loosen up again.:thumb:
 
#21 ·
Definitely was those four tc bolts - thanks for the suggestion! Easy to tighten after pulling the tin, 2 x 10mm bolts + single larger bolt. Didn't venture locktite yet. Purrs along now, can hear all the other squeaks and rattles non-engine related!
 
#22 ·
I would not use locktite. Just torque the bolts up tight and they will stay tight. Think about the millions and millions of vehicles on the road today that do not have locktite on the converter bots with no issues. If the transmission was ever replaced, the mechanic may have not tightened them enough.
 
#25 ·
I got the problem with the flexplate and the dealer replaced it. THe funny part of all is that they left the old flexplate in the back of the minivan. Until today I still dont know where the **** the darn plate it is cracked. In a matter of fact it looks ok, i could sell it w/o any problem i guess. My simptoms where a click noise similar to the valve rockers noise but it stopped after 10 minutes. The dealer guy said that the flezplate gets warm or hot then expand and then the noise stopped... it is true? Who knows.

Regarding the valve rockers noise what i did was to use Sea foam for a couple of days then do a super dupper oil change. I add to it the ford oil filter that people mentioned. THat stopped the noise for a few months and then it comes back.

With the time i have noticed that putting more oil in the crank case it will stop the nosie almost right away. For example i did the oil change last month... and today i get the noise.. i just add like half of a quart to the crank case and thats it... no more noise for a while. What i'm thinking is that i have a little tiny oil leak somewhere, maybe the head gasket... so i need to over top the oil maybe each month and a half to 2 months.

THanks...
 
#26 ·
The timing chain doesn't really knock in my opinion. It's slaps and rattles and clunks. There is a difference in describing sounds when it comes to engines. A knock and clunk can be 2 different things.
 
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