why so many crd throw rods?

jamesdart · **Joined:** Wed Oct 06, 2010 4:41 pm **Posts:** 53

just looking around at engines, ive seen more for sale listed with a hole in block for parts, than actual good running ones. what is failing in them? has anyone taken one apart before it self destructed? mine has a rod hanging out of the block, it looks like the rod bolts failed. do they take a torque to yield bolt? do they just use poor quality bolts? or does the bearing go bad and with some play the bolts just get shocked till they fail?

jlgail4309 · **Posted:** Mon Jan 21, 2013 9:54 pm

0-40 oil for years and years and 10000 mile oil changes with lots of soot from a EGR. Some cheap bolts didn't help!! just my two cents

DOC4444 · **Posted:** Tue Jan 22, 2013 12:29 am

I blame it mostly on the soot the US version is stuck with w/o mods. Ours goes about 3K after an oil change before the oil develops any real color to it. Usually change every 5K. M1 5-40 in spring, summer, fall, 00-40 in the dead of winter. Motor has about 115K on it.

DOC

geordi · **Posted:** Tue Jan 22, 2013 12:49 am

DOC4444 wrote:

I blame it mostly on the soot the US version is stuck with w/o mods. Ours goes about 3K after an oil change before the oil develops any real color to it. Usually change every 5K. M1 5-40 in spring, summer, fall, 00-40 in the dead of winter. Motor has about 115K on it.

DOC

My EGR system "fell apart" at 30k miles... Never worked again. I never had the clean oil like others here report, even after many changes and some as low as 3k miles. Never more than 6k mile oil changes, always with Mobil 1 TDT 5w-40 or Shell Rotella T6 Synth 5w-40...

And 2 engines both died in exactly the same way. One with 60k on it, the other with 130k.

If the other engine failures are also rod bolt failures... That REALLY makes me question the build quality. That is a SERIOUS design flaw, and potential for a class action suit and recall... Oh wait - they are immune from lawsuits because of the bankruptcy. That was Daimler-Chrysler, not Fiat-Chrysler, a completely different and blameless group of exactly the same people. I forgot how the corporate world works for a second there.

We are on our own, and they like it like that.

crd260 · **Joined:** Mon Oct 29, 2012 2:28 pm **Posts:** 103

jamesdart wrote:

or does the bearing go bad and with some play the bolts just get shocked till they fail?

just because something "looks" like the rod bolts failed doesn't mean that was the cause.....

remember... these are 4 cylinder's revving out to 4 grand.....

yes I know they have a long stroke, but still

*math*
http://www.csgnetwork.com/pistonspeedcalc.html

our motors have a 94mm stroke and a 92mm bore

That means our pistons are moving at 41 feet per second at 4000 rpms....

to put things in perspective.... how about a chev small block..... let's say the 5.3
it has a 92 MM stroke and a 5500 rpm redline....

that works out to 55 feet per second

and on the extreme end of the spectrum how about an s2000
84.4mm stroke and an 8,800 rpms redline

works out to 81 feet per second

also remember that engine wear is equal to the square of the rpms.....

in the grand scheme of things, these rod bearings have a pretty easy job.... I highly doubt they're under-designed or poorly assembled...

we all know from experience that the EGR system destroys the oil in these motors..... First to go is usually the valve-train, followed by the turbo's..... it would make sense that if it was a worst case scenario, the rod bearings would go too... (which is bad news for me because my valve just went)

one way to know for certain, have the bearings on the rods that didn't break apart and fly through the side of the block analyzed... if they were all "sloppy" than you know it's not the rods or the bolts.... ANY rod will fail if the bearing is sloppy enough......

What was this engine's history? was the EGR deleted? if so how many miles into the engine's life? what about oil changes? what about oil and filter brands?

woodtick · **Posted:** Tue Jan 22, 2013 8:27 am

I would also suspect that type of service may play into the equation as well. These engines are made to push a load at 1600 to 2100 rpm. Those engines that regularly get revved to 4000 rpm + are likely to fail sooner, and catastrophically too. Just because maintenance and mods have been done, does not necessarily equate to longevity.

My :2cents:

flash7210 · **Posted:** Tue Jan 22, 2013 9:18 am

Just because the tachometer goes to 4K doesnt mean you should go there.
I rarely let mine get above 2500.
Of course its been well documented here that a blown turbo will cause the bottom
end to loose oil pressure. If you are pulling 3000 rpm and your turbo takes a dump
the rest of the motor will go with it.
I think a lot of original buyers bought this Jeep and drove it just like it were any other
gasser. I was talking to one of the parts guys at the local dodge dealer who said he
owned a CRD for about a year. He said he didn't like it because once he got
above 50mph it seemed to not have any more power. I was confused by his statement
because to me, the opposite is true. I really don't feel any power until the TC lock
up clutch is applied. To get that feeling of power below 50mph he must have really
been revving that motor.

kjjet · **Posted:** Tue Jan 22, 2013 9:46 am

I TOTALLY agree that it depends on how you drive and maintain your engine, along with EGR removal.

These little engines were not made to handle high RPM and the soot the EGR puts into them. Oil changes should be 5k or 6 months whichever comes first. Clean air filters and fuel filters. Its not a race car, drive it like a Jeep! Not a Mustang.

crd260 · **Joined:** Mon Oct 29, 2012 2:28 pm **Posts:** 103

kjjet wrote:

These little engines were not made to handle high RPM and the soot the EGR puts into them.

Actually Kjjet, I would respectfully disagree...

These motors were originally developed as a marine engine. Anyone who's ever owned an inboard/outboard boat knows...... rpm and speed have pretty much a linear relationship..... you want to cruise at a higher speed? you need more RPMS.....

in a 19' boat, it wouldn't be uncommon for this motor to see something like 3200 rpms steady-state for 15-20 minutes if the boat operator wanted to get somewhere quickly (weekend fisherman usually like to get from the boat launch to their favorite "fishing hole" as quickly as possible)

if the lubrication system is doing it's job, rpms will NOT hurt a motor like this (within reason, of course)

The turbo's letting the oil pressure drop also make sense.... but at the beginning of all the scenarios of engine failure, you will find contaminated / sub-standard oil....

you want to solve that problem permanently, you delete your EGR and add a by-pass filter...

kjjet · **Posted:** Tue Jan 22, 2013 12:50 pm

I beleve what your saying....But 3200 steady RPM in a boat is not nearly as bad as 4000+ rpm when shifting thru gears or passing. Those quick RPM tops are the bad ones for the Rods.

LMWatBullRun · **Posted:** Tue Jan 22, 2013 1:39 pm

To refine the question a bit, what is the exact failure mechanism? Is this a failure of the rod bolt, failure of the rod itself, or some other problem ( bolt untorquing, etc.)? If it is the bolt, then there are aftermarket suppliers of higher strength rod bolts. SAAB used to sell a high performance kit for the 4 cylinder V4 engine used in the 96 that included high strength rod bolts to raise the redline; the rod could take the added stress but the bolt needed to be stronger.

When I disassemble Geordi's old motor I will look at that and see.

crd260 · **Joined:** Mon Oct 29, 2012 2:28 pm **Posts:** 103

the mechanism is this:

poor quality oil causes the rod bearing to wear....

as the rod bearings wear the clearance increases....

Where there is supposed to be a few thousands of an inch, filled by a film of oil, there is now a "relatively" huge gap....

As the rotating assembly changes direction (piston reaches the top and starts coming down, or reaches the bottom and starts going up), the crank-shaft journal "hammers" the connecting rod... in one direction the rod itself, in the other direction the rod cap (and bolts).

At some point, the rod bolts can no longer take the abuse and they simply fail..... which results in chaos and well holes in blocks.....

If the bearing clearances were in spec, the bolts would never fail.... (that's my bet anyway, when you tear the motors down, you will see for certain)

The math for the tensile strength of a con-rod connector is well known.... I simply don't accept the notion that in this day and age anyone could under-design a fastener like that..... especially on a low revving motor like ours.....and especially in a marine environment....

flash7210 · **Posted:** Tue Jan 22, 2013 3:26 pm

Or lack of lubrication causes the bearing to seize to the crankshaft :roll:

kjjet · **Posted:** Tue Jan 22, 2013 4:26 pm

From what I have been reading. A connecting rod knock noise develops. Then before long it breaks and you have ventlation. X two for geordi.

The rod knock is a gap form worn bearings? or bad attachment hardware? This is what i would like to know?

crd260 · **Joined:** Mon Oct 29, 2012 2:28 pm **Posts:** 103

it's NOT a "bad attachment hardware"

no way, no how.....

not in this day and age, not with a 4K rpm redline....

failure of head bolts on a modern engine? sure, I could believe that, designing head bolts is tricky.... sometimes manufactures cheap out.......

but no way no how is a 4000 rpm redline motor going to suffer from rod fastener failure....

If dragsters can take an old Chrysler big block to 7,000 rpms, than VM can darn well build a con rod that can handle 4,000 rpms....

geordi · **Posted:** Tue Jan 22, 2013 8:37 pm

crd260 wrote:

the mechanism is this:

poor quality oil causes the rod bearing to wear....
as the rod bearings wear the clearance increases....
Where there is supposed to be a few thousands of an inch, filled by a film of oil, there is now a "relatively" huge gap....
As the rotating assembly changes direction (piston reaches the top and starts coming down, or reaches the bottom and starts going up), the crank-shaft journal "hammers" the connecting rod... in one direction the rod itself, in the other direction the rod cap (and bolts).
At some point, the rod bolts can no longer take the abuse and they simply fail..... which results in chaos and well holes in blocks.....
If the bearing clearances were in spec, the bolts would never fail.... (that's my bet anyway, when you tear the motors down, you will see for certain)
The math for the tensile strength of a con-rod connector is well known.... I simply don't accept the notion that in this day and age anyone could under-design a fastener like that..... especially on a low revving motor like ours.....and especially in a marine environment....

This fits with my thinking, because when I tore down motor #1, the bearing on rod #1 (the one that the piston broke up and the rod / piston / sleeve were reduced to shrapnel)... The bearing was not to be found. Cylinder #2's rod bearing was --in the process-- of "leaking" out to the sides of where it had been mounted.

I describe it as leaking, because if you visualize the curved bearing by itself... The edges were thinned out paper thin and at a 90 degree angle to the flat curvature of the bearing itself... As if it was peanut butter being squeezed out from between two crackers. This seems to indicate that (on engine #1) the bearing experienced EXTREME heating from lack of oil or oil flow, and was melting out of place.

I still have them, as well as a couple of the rods from that engine. #3 seemed to be a little thinner than it should have been, but not like #2... #4 was the thickest of the bunch and what I would guess a correct bearing to appear as.

Since engine #2 ate itself on cylinder #4, without EVER running low on oil or oil pressure... I am extremely interested in what is discovered down there. I'll try to get pictures of the bearings next time I'm into that bucket of parts.

crd260 · **Joined:** Mon Oct 29, 2012 2:28 pm **Posts:** 103

geordi wrote:

I describe it as leaking, because if you visualize the curved bearing by itself... The edges were thinned out paper thin and at a 90 degree angle to the flat curvature of the bearing itself... As if it was peanut butter being squeezed out from between two crackers. This seems to indicate that (on engine #1) the bearing experienced EXTREME heating from lack of oil or oil flow, and was melting out of place.

This "squeezing out" of the bearing material could also be caused by the "hammering" effect of the crankshaft journal.........

pistons change direction awfully fast.... if there's big clearances in the rod bearings, the "impact" of the journal on the bearing could easily cause it to mushroom and "ooze" out.......

The guy I talked to in the UK said these motors go about 500,000 kms in (their version of) grand caravans consistently....

I quickly searched youtube... not our motor, but just imagine this "click" happening twice per revolution (one up, one down)..... (the worse being the exhaust stroke... the piston is "thrown" up, and then "yanked" back down, with no resistance (on compression, there is some resistance)

at idle, that's 800 rpms, 1600 times a minute or 27 times per second.....

http://www.youtube.com/watch?v=hxmb6WBClDI

moral of the story: EGR is the devil

flash7210 · **Posted:** Tue Jan 22, 2013 9:50 pm

The only defense any engine has against that "hammering" is oil pressure.

geordi · **Posted:** Tue Jan 22, 2013 9:52 pm

How is EGR the reason for the failures? Engine #1 had an egr for less than 30k miles, because the original owner had it replaced TWICE during the 30k he owned the thing. I disabled it in the first week I owned the Jeep, electrically. It never opened again, and I further disabled it when I blocked the pipes after engine #1 failed at 60k miles.

Engine #2 was installed with unknown prior EGR usage at 60k miles, with 60k miles on it. So for the sake of argument, lets assume that it had a fully functional EGR until it was installed in my engine bay. Engine #2 then ran without any EGR at all for another 60k miles, to a total of 134k miles on the chassis... And bang.

Something else is happening here. I was religious about the oil changes, doing them MORE than was needed. The top of the engine was spotless when I pulled it apart, no sludge anywhere. There is another reason for this to keep happening, and I believe dirty oil isn't it either.

crd260 · **Joined:** Mon Oct 29, 2012 2:28 pm **Posts:** 103

whoa...

you're a gear head and you've got 2 blown motors with EGR deleted, eh?

huh... that's a stumper....

let's see... what's in common with those 2 motors.....

- The driver : you bag on this thing or what?
- The turbo: did you re-use the same turbo by chance..... ever look into how much pressure is dropping across it?
- The Trans,flex plate and TC... not sure how it could be the cause..... but.. hey it's most likely a common link (unless you changed those too)......

what about the oil cooler? did you swap it out with the motor?

And when you said you "blocked off" the EGR.. you mean you physically blocked off the pipes? Keith @ GDE and I Talked about this, and he suggested it was a bad idea.... even with the ECO tune, the EGR valve is used as a waste-gate to prevent turbo surging...... Disabling the EGR that way would wear the thrust bearing in the turbo pretty quick (at least in theory).... What's the side to side movement like in you're turbocharger?

if your thrust bearing is worn, and you re-used the turbo on both motors (or the thrust bearing on both turbo's was bad) you may have found your problem....

why so many crd throw rods?

Who is online