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Cummins' Fatal Flaws

There Are Two Things That Could Be Killing Your 5.9L Right Now - Here's How To Fix Both

Text By , Photography by Cory Dow, ,

Cummins engines are thought to be completely indestructible. In practice, however, there are two fatal flaws that not only damage these engines but can ruin them beyond repair.

Fatal Flaw 1: The Killer Dowel Pin
The first such weakness affects 5.9L Cummins engines manufactured between 1988 and 1998 (in other words, 12-valve Cummins engines used in Dodge Rams). These engines feature a steel dowel pin that locates the front timing gearcase. Over time, this steel dowel pin can wobble out due to the constant heat cycles and vibrations of the engine. If (or when) the dowel pin works its way completely out, it falls into the timing gearcase.

When the dowel pin falls, a few things can happen. If you're lucky, the pin will miss everything and just fall straight into the oil pan. If you're not so lucky, it will hit one of the timing gears and shoot out the side of the timing case, creating a BP-sized oil spill in your driveway. In the third and most unfortunate scenario, the steel pin will jam between the timing gears. This typically causes the cam to break, the valves to hit the pistons, and the engine to internally self-destruct. While this last scenario is rare (a hole in the timing gearcase and a big puddle of oil is most likely), it has happened to many unfortunate enthusiasts, which is how it got its name-the killer dowel pin (KDP).

Fatal Flaw 2: The Weak 53 Block
The second potentially deadly flaw occurs in '99 to '02 5.9L Cummins 24-valve engines. It's known as the 53 block problem, because these engine blocks have the number 53 cast into the side of the crankcase. After years of use, the 53 blocks tend to crack until coolant starts to pour out the side of the block. This is an issue that many people kid themselves about. While it's something you can live with for a while, eventually the leak will get so severe that you'll be refilling your cooling system on your commute to work. Sooner or later, the truck will need a new engine if it's not repaired.

Tackling the Killer Dowel Pin
For a KDP repair, most of the front of the engine needs to be disassembled to gain access to the timing gearcase. The fan, shroud, overflow bottles, balancer, and lower pulley all need to be removed. With the front of the engine stripped, you can install a small metal tab over the dowel pin to keep it from rattling out. While you're in there, make sure to tighten up all the gearcase bolts. These bolts loosen over time and will do just as much damage (or more) if they fall into the front geartrain. Many diesel companies (such as TST Products and Source Automotive) sell killer dowel pin kits for about $60 and include a tab, timing cover gasket, and front crank seal to put the engine back together. After performing this repair (or getting a shop to do it for you) you'll feel much better knowing you're not driving a ticking time bomb down the highway.

The 53 Block-An Impossible Fix?
While other Cummins blocks have been known to crack, the 53 blocks are by far the most common. To identify a 53 block, look for the casting numbers on the front driver side of the engine.

We might as well break it to you right off the bat. The best way to fix a cracked 53 block is to replace it. That repair can cost $5,000 to $10,000 if you have a shop perform the work.

A lot of people try to fix a cracked 53 block by other means-with varying degrees of success. Temporary fixes include block stitching, stitch welding, and J-B Weld. These temporary fixes can hold you over until you can find a replacement engine from a junked truck, or let you save your pennies and dimes until you can buy a new engine.

The real problem with these temporary fixes is the wall thickness in that area of the block. That's why drilling out the ends of the crack, V-notching the wound, and welding don't permanently fix the problem. The block will just simply re-crack.

Brad Ponci at Ponci's Diesel Center said he charges $500 to weld the block. His repair gets the truck back on the road and gives the owner time to decide what he or she wants to do with the engine. Ponci said the average lifespan for a welded block is usually a year or two before cracks start to form again, but there's no guarantee.

If you happen to be a professional welder (or know a friend who is), then there is a very labor-intensive process that involves welding the block. Some say this repair will last the life of the engine. It involves using an extreme amount of filler rod to basically rebuild and reinforce the weak area of the block. This welding procedure can be found at: www.muggyweld.com/53block.html.

Buying A Flawed Vehicle
So the real question is: Should these problems keep you from owning or buying an '89 to '02 Dodge? Our answer is no, they shouldn't. In the case of the '89 to '98 trucks, just get the KDP fixed as soon as possible. On the '99 to '02 Dodges, our advice would be to stay away from the 53-block trucks, because not all '99 to '02 Dodges used the 53 blocks. If you do find a 53-block Cummins-powered truck, we'd negotiate heavily on price. We'd offer $2,000 to $3,000 less than what you think the truck is worth.

SOURCES
Source Automotive
16805 SE 130th Ave.
Clackmas
OR  97015
503-654-9004
www.sourceautomotive.biz
TST Products Inc.
7440 S International Dr
Columbus
IN  47201
812-342-6741
www.tstproducts.com
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94 comments
Braden Hiller
Braden Hiller

What? Laugh at the fact they now have to pull the cab off....again

Troy Suddaby
Troy Suddaby

I go to work everyday with my Cummins and pull fords and chev's out of the ditch!

Eddie Byron
Eddie Byron

Goin strong at 3,000 miles that's pretty impressive for a 6.7

Nic Bergounous
Nic Bergounous

Iil stick to my 6.7. 408 cummins. Almost 3000 miles and goin strong. Lol. Bone stock

Brian St Dennis
Brian St Dennis

The 5.9 is the best engine ever put in a pickup truck!

William May
William May

Can be fixed in the truck, I've done multiple. welding won't do it will weaken the cast iron and create spider cracks and then you have ruined it. Can fix a 7"crack for about a grand and can reinforce to prevent further issues for about $400 to $1100 for extreme usage.

Eddy Tamez
Eddy Tamez

lo tipico de siempre block reventado

John Spindler
John Spindler

Ill stick to my d-max....330k and goin strong on a COMPLETELY stock and all original....gott say somethin

Justin Sellers
Justin Sellers

Jason sands your information is always a bit invalid. The kdp effects any cummins 4bt, 6bt, or ISB all the way up to the 02' model year. When they switched to commonrail they changed the design. Iv had a 02 at my shop with a kdp failure. And you second misinformed thing is that the 53 block was infact present from 97.5-02 iv got a early 98 12v with a 53 block. In 97.5 cummins switched to whats called an "encore" style block they went from 14mm main bolts to 12mm main bolt. They recieved weaker rods then the pre 97.5 motors and they had provisions for a second oil drain if you ever wanted to do twins.

Ryan Smith
Ryan Smith

Know what kills your 7.3 my 5.9 and 6.9

Paul Harrop
Paul Harrop

I hope that's true! I have 225K on my O1!

Ramiro Garcia
Ramiro Garcia

Natividad Guerra Jr stop cummin on engines wey haha

Rock Stronggo
Rock Stronggo

Not me I just had to worry about the killer dowell pin!

Corey Simonetta
Corey Simonetta

I've welded one of these up. Best way is to remove the battery, fender, and turbo. Grind like crazy, drill the end of the cracks, pound in studs, fill weld the rest, then grind flat, then add a 1/4" plate abd weld that from the lip to just before the indents kind of like the tappet cover is on the other side.

Staggs Josh
Staggs Josh

Put that hole block in a vacume and then weld it shut sucking the slag in the hole might work idonno

Staggs Josh
Staggs Josh

Or whoever put that freeze plug in pounded the hwck out of it weekining the block

Staggs Josh
Staggs Josh

Ive watched cloged oil pipes to the valves on one side crack a block beform my eyes after running just 10 min motor hunny will promote that

Staggs Josh
Staggs Josh

It cracked because you have to run straight antifreeze in and q special kind helps diesels should be stored in warm garage in the winter and from the look of the muck that can out when they drained it oil prolly wasnt gettin to the intire motor and just part of the block a small part not gettin oil will crack a block

Trey Lane
Trey Lane

Called a 53 block a very prone for it. If you make it past 120k your good

Collin Reveley
Collin Reveley

That's not a 53 block, they're just replacing a broken freeze plug.

Ryan Johnson
Ryan Johnson

Good thing I don't have a 53block and have already removed the KDP

Martinez Lalo
Martinez Lalo

I got a 2000 5.9 sport model with 55 block airdog lift pump vp44 heads studded and oringed 6 sped doble disc clutch ats elbow and intake cuadzilla adrenaline 254000 miles running like champ

Mark Fernandes
Mark Fernandes

Almost 300k on my 53 block and no problems yet... Fingers crossed

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