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3.5L start up rap only

4K views 25 replies 8 participants last post by  ncfrc 
#1 ·
I'm new here and I appologize if this has been discussed many times.

I just picked up the 3rd Dodge Intrepid we've owned , a 2002 ES 3.5L
with 172,000 miles.

The car is rock solid with NO rust and drives great.

The only slight negative I found when I tried it out was that for maybe a few seconds
on start up , it seems to have a low end slight rap. The car it self is in such great shape that
I bought it anyway.

I've changed the oil and only driven the car maybe a 1000 miles. It's mostly noticeable on
the first start of the day and barely there the rest of the day. I'm on the road most of the day
and it gets started a lot.

There's zero noise when accelerating from a stop light as I've heard some 3.2's with
bad rod bearings do that.

My question is ------ Should I pull the oil pan and check the rod bearings with this high
a mileage or would they make noise after it's up to temp also?

I'm leaning towards rolling a set of bearings in it just because of the mileage but then
I hate to spend a weekend on a creeper , on my back tearing it apart in the garage.

Thanks for any feedback , as it's greatly appreciated !!

I've been thru the 2.7 engine deal and had a 3.2 that I did put bearings in and sell ,
making the new owner fully aware of the scared up crank. I'm crossing my fingers
that this 3.5L engine has many more miles in it.
 
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#3 · (Edited)
I've heard about the rocker arm update but this really sounds much deeper in
the engine. I've even tried fluttering the throttle from under the hood but can't
duplicate it. I even unplugged one coil at a time and reved it between 2 and 3 thousand
rpm's with no change in motor noise.
 
#4 ·
There've been lots of posts over the years about people just replacing the bearings without properly machining or replacing the cranksahft, and the overwhelming majority of them turn out to be a disaster - within days or weeks of the work being done.
 
#7 ·
So you think it's a bearing starting to go ?
There are some people here that are much more qualified than I am to answer that. I was only responding to your indicating that you might replace the bearings with no proper crank work.

I'm going to pull the oil pan today and see what's happening.

I picked up a set of std. rod bearings that I'll put in , hopefully the

crank is not all scared up .
I repeat: That is almost never successful on these engines, even when there does not appear to be significant crank damage.
 
#9 · (Edited)
I pulled the pan and the rod bearings looked good for the mileage.
Very little scaring on the crank journals. I reinstalled a set of std. bearings
since I was there , especially for the minor cost of $35 . The pan gasket you
have to buy anyway.

The start up noise when cold is still there so I had an A level Chrysler tech " someone who
was recommended to me " listen to the motor and his immediate response was that this
is a short skirt piston engine and that's very common. Run it and Have a good day.

One thing I'd forgotten to mention on doing this job " in the car " is when you get the pan
off and are cleaning it up , grind a 1/6" off the backside so you don't have to fight with
reinstalling it. It also helps to remove the two 6mm studs on the front of the block and replace
with 6mm bolts when bolting the pan up.
 
#11 ·
I wonder if anyone is close to someone at a machine shop and can ask them if it is a shorter skirt than average... The thing that I find as a problem is that if it was a case of short skirts, ALL 3.5 engines should make the same sound for the same number of hours run, IMO...
 
#12 · (Edited)
Good question. It is a fact that the industry in general got obsessed with shortening the pistons 10 or 15 years ago, and often went too far. Piston slap was a common thing in brand new samples of several makes of cars while they were experimenting at the consumer's expense. Subaru even had a recall over it, IIRC. And noises are very common in the 3.2/3.5 LH engines at various stages of warm up/cool down cycling. Piston slap can be *very* much oil (viscosity, temperature, and age) dependent.

On the other hand, some people like short skirts. :D
 
#14 ·
I've done a little home work on these pistons and wish I had a picture to post.
The picture that I found of a 2002 3.5L piston really didn't have a short skirt but
it had NO side skirts at all. The wrist pin area on the piston is very narrow and
that area has zero side material all the way up to the lower oil ring land.
I wish I was better at describing it but from being into the rod bearings and seeing
a picture of the piston , it appears to me , just my opinion , that Chrysler was after
some lower rotating friction and sacrificed engine durability.
There's no reason that the rod bearings in this engine couldn't have been made .80
to .100 wider to at least fill the bearing caps but again I'm sure that on paper a narrow
bearing surface causes less drag.
Sorry, got off track , but I'm assuming for now that this less skirted piston is the noise
I'm hearing.
 
#15 ·
...it appears to me , just my opinion , that Chrysler was after
some lower rotating friction and sacrificed engine durability....
Less reciprocating mass has synergistic effects: Lower forces on connecting rods and bearings, other things can be slimmed down, everything gets lighter. With lighter rotating and reciprocating parts, spinup inertia (flywheel effect) is lower, so snappier response.
 
#16 ·
Knock on wood , it's been 21,000 miles since installing new rod bearings and so far so good.
I may be wrong or just my opinion , but if I had any Intrepid 3.2 or 3.5 engine with over 150,000
miles , I'd suggest to roll a set of rod bearings in it. A little time consuming but worth it in the end.
Chrysler should have designed the bottom end a little stronger.
 
#17 ·
When I swapped out my oil pan 29,000 miles ago I checked and changed my rod bearings. They were at the high end of the range for clearance before and about middle range after the change out. All has been OK. Perhaps the big difference with my car is that the rods hadn't gotten "bad" or noisy, so the crank was still in pretty good shape.
 
#18 · (Edited)
Yes , thats what I was trying to say , change them before their noisy.

We just did a 2.7 to 3.5 swap and the 3.5 on the engine stand got new bearings and
complete timing kit before installing it. It had 120 and the bearings looked decent .
 
#22 ·
The 3.5 has been around for I believe almost twenty years. Seen many revisions and tweaks, from block material changes (Iron to Alunumum) to intake and accessory configuration changes. It's definitely one of the most reliable engines Chrysler has put out, especially next to the 2.7 by comparison. Been in nearly every class car they make, from the Prowler to the Charger or even a Sebring.

I have roughly 220K KM on my engine (had 200K KM off a Canadian Intrepid). I've experienced odd little noises with the motor myself that raises an eye-brow. As said, when cooling down and warming up it's a normal time for the sounds to happen, beyond that and I would be concerned.

Mine will top-end rattle/tap for a few seconds on statup only, now the oil is half-through it's life-span (1500miles) it's lightened up on start up it's just a faint rattle for 2-4 seconds. When the nights were extremely cold, and my oil was fresh (has 1L of Lucas in it) it would tap for 10-30 seconds if the engine isn't primed before starting. After that statup's are prompt and smooth and driving it's smooth and peppy as hell.

The idea of throwing in new bearings to keep things solid sounds great, but the horror stories people have told from just throwing bearings in and calling it a day, scare the hell out of me. Have you driven it hard, or rev'd it high or we talking very calm driving (old lady style) since the work?

I'm keen, just very skeptical.
 
#23 ·
I hear what your saying 100% . If I hadn't caught this engine with only a start up rap then I wouldn't have
put bearings in it. The upper half of the bearing was the most worn with a few spots showing very small areas
of the copper backing. This motor was very poorly maintained as I spent an hour scraping and cleaning
all the bluild up in the oil pan. I use this car for business everyday and it rarely see's anything above 3500 rpms.

IF AN ENGINE IS KNOCKING WHEN RUNNING , EVEN LIGHTLY , I'D NEVER RECOMMEND TO
ANYONE TO JUST INSTALL BEARINGS ,, YOU "NEED" A CRANK KIT OR EVEN BETTER A
REPLACEMENT ENGINE.
 
#24 ·
The best test to see if a bearing change is in order? Do it! If it lasts, you're golden. If it doesn't then perhaps it's time to change your thinking about what a "good" rod journal looks like. Or your skills with a caliper and/or plastigage. Or whether a little oil film will do for engine assembly lube. Or if your work should be clean.

BTW, if your rods start making noise, I'd say it's too late. :glum:

If you think that this car (the '98) has made it 29,000 mile is because I drive it like a diesel, you'd be mistaken. :hit1: On the other hand, I've only once had it do the "survival shift" because it was left autostick, I neither bog nor flog my engine; I want it to last. :D
 
#25 ·
If you think that this car (the '98) has made it 29,000 mile is because I drive it like a diesel, you'd be mistaken. :hit1: On the other hand, I've only once had it do the "survival shift" because it was left autostick, I neither bog nor flog my engine; I want it to last. :D
I drive mine like it's a 69 Charger off the Duke's of Hazard set. :baller:

Nothing is more fun than cursing along at about 2K rpm in autostick and than dumping the peddle half way and watching everyone sink into the seat's like I got a 578 Supercharged Hemi under the hood.

Has been through that childish behavior for years and never let me down, it's just all the more fun with the 3.5 and gearing changes. If it blows, I got another 3.5 out of another police interceptor at the yard I can snag for $100. But that is suppose to be my Stroker build.

A good variation of hard and light driving is the best thing for a motor. I wouldn't want one that was strictly babied or "piss" driven out of it non-stop. Like the good old book says, nothing within moderation is bad.
 
#26 · (Edited)


I rolled a set of rod bearings in as the stock ones were showing copper on the upper half.

I just sold the car today with 233,000 miles and still running strong.

I won't get in to testimonials of Lubricants but this car had been run off oil of which
price was not a concern. You do get what you pay for. :)

Yes , I told the new owners the service history.
 
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