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Diesel Tech Questions and Answers

Top Tech

Bruce W. Smith
Jun 12, 2017
Photographers: Bruce W. Smith

Blow-by Issues

We’ve had a ’95 Dodge Ram 2500 in the family since it was new. It is used mostly to tow our travel trailer and toy hauler. Last fall, my dad gave me the keys. I’m 17 years old, and it’s my first diesel-powered truck. It has 285,000 miles, and Dad is very direct about me keeping it maintained, which I plan on staying on top of and doing as much as I can on my own. The valve-cover gasket pushed out and was replaced. But it’s leaking again. Dad says it’s from too much blow-by and it may need a rebuild. Is there anything I can do as a temporary fix? For now, I just want to stop the constant oil drips.
Brandon Davis
via email
Photo 2/5   |   Blow-by (oil getting past the piston rings during an engine’s compression stroke) can create a lot of oil-leak concerns on older, high-mileage 5.9L Cummins engines, including blowing out the tappet gasket and letting an excessive amount of oil drip from the breather hose. A solution that averts a complete overhaul is installing a valve-cover breather from the Cummins I-4 engines that power tractors or other equipment.
Your dad is right. Too much blow-by (oil getting past the piston rings due to cylinder compression) will cause oil leak issues and the 5.9L Cummins engine’s valve-cover gasket to squirt out, which is what happens when diesels start racking up miles. There are many 12-valve engines with 250,000-plus miles that are experiencing the same issues. First, address the general oily mess by giving your engine and undercarriage a good pressure wash or steam cleaning. That will help you track down the source(s) of oil leaks in addition to the blown gasket.
Regarding the remedy for the tappet-cover gasket, the solution is to install a breather in one or two covers. Doing so reduces the pressure in the oil pan by giving that blow-by an avenue of escape other than through the vent tube at the tappet cover, which eventually ends up with nasty diesel oil dripping on the ground—or misting all over the undercarriage when driving down the road.
We address this topic in a technical article written by Bruce Smith, who followed Mobile Diesel Service technicians as they installed a dual valve cover and breather setup on a customer’s ’96 Dodge Ram 2500. The combination is normally used on the Cummins diesel engines found in Case IH/New Holland farm tractors. It’s an easy job that you can do yourself, for less than $125 for the cover and breather. The new breather should cut blow-by pressure in the crankcase by more than half. There’s less pressure, less chance of the side-cover gasket blowing out, and it reduces the amount of oil consumption caused by crude pouring out on the ground.

Ford Death Wobble Revisited

The information printed in the April 2017 “Top Tech” section regarding this issue is incorrect. Death wobble is more prevalent on the ’05-and-up Ford Super Duty, mainly due to a front-coil-spring change for those vehicles. Typically, wobble is caused by a worn track bar bushing or loose drag links or tie-rod ends. Obviously, oversized tires magnify such worn components. When those are ruled out, adding 1-degree caster shims will do the trick. I have worked on nothing but diesel-powered Super Duty trucks since 2003 and worked at Ford for eight years as a Ford Master Certified diesel technician before opening my shop more than six years ago. I hope this helps.
Kenneth Tripp
via email
Photo 3/5   |   One of the best steering upgrades for ’01-to-’10 GM pickup trucks is to replace their pivot assembly with a heavy-duty version. This Super Steer kit from Cognito Motorsports includes a gusset that helps eliminate flex in the stock mounting bracket. That bending, along with worn steering components, is the main cause for wander and other steering ills.

Putting an End to Steering Play

The steering of my ’09 Chevrolet Silverado 2500HD has gotten to the point where I need to get it repaired. There’s a few inches of play in the steering wheel, it wanders instead of driving straight like it used to when I bought it, and when I put it in four-wheel drive, the front shakes a little when the tires spin. Before I take it to a shop, I wanted to see if you guys have any suggestions on what else can be done, other than just replacing the tie-rod ends and ball joints. It has 163,000 miles, a 4-inch lift, and 35-inch tires.
Bernard Michalke
Chicago, Illinios
Worn steering parts are a very common issue with that era (’01-to-’10) fullsize GM pickups. Excessive, abnormal wear in the tie-rod ends, ball joints, steering damper, idler-pivot assembly, and idler all are contributors to loose steering. Engaging four-wheel drive puts more load on those components, which is typically what causes shaking when the front tires lose grip. Replacing all those parts will tighten up that steering.
However, one thing we suggest to anyone running a four-wheel-drive GMC or Chevrolet truck with bigger tires is to step up to stronger, more durable components. The aftermarket part that makes the biggest difference in providing more responsive steering is Cognito Motorsports’ Idler-Pivot assembly, a kit that uses a heavy-duty, cast-aluminum pivot with roller bearings and a weld-in gusset to stop any flex in the unit’s mounting bracket.
If you drag race or play a lot in the sand or mud, we also suggest upgrading to beefier tie-rod assemblies. Cognito offers those as well. We’ve seen more than one rig bend the stock tie rods and split the tie-rod ends apart during a good romp off-pavement. That won’t happen if you use heavier-duty components. You should also install a good aftermarket steering stabilizer.

Testing Glow Plugs

A couple of years ago, I bought a ’99 Ford F-250 with a 7.3L Power Stroke engine. Shortly after purchasing the truck, I had the injectors and glow plugs replaced, and a few other things were done on the top end to stop some oil leaks. Now it has 260,000 miles and is a wonderful tow rig and a great workhorse around the ranch. But last winter the engine started acting up, being hard to start when cold. I think there might be a problem with the glow plugs. Is there an easy way to check them without pulling the valve covers and taking them out?
Lance Cooter
via email
Photo 4/5   |   To test glow plugs on 7.3L Ford Power Stroke engines, unplug the connector to the valve-cover-gasket harness and use a test light to touch the exposed outer two pins that feed power to each bank’s glow plugs. If the test light comes on, that plug is working.
Your hunch is good. A hard-start condition during winter could be caused by the glow plugs or the glow-plug relay, according to Ruben Villalobos, a technician at Mobile Diesel Service. There is a very easy way to see if the glow plugs are working on a 7.3L Power Stroke, and, if they’re not, determining which one is the culprit.
Unplug the connector for the wiring harness located under each valve cover. The two outer pins on each side of that connector energize the glow plugs. Glow plugs ground to the engine block, so they only need a source of power to become instantly red hot. This makes testing the plugs while they’re in the truck easy.
Clip one end of a test light to the battery’s positive terminal and then carefully, individually, touch each one of those two outside pins on that bank’s valve-cover-harness connector. If the glow plug is working, the test light will illuminate.
If the glow plug is bad or there’s a problem with the wiring harness under the valve cover, the light will not illuminate. Doing this also lets you know which plugs are not getting power: The pin closest to the front of the engine attaches to the forward-most glow plug/cylinder in that bank, the next pin back connects with the second, and the rear two pins are affixed to those respective plugs.
If you determine there is a problem, remove the valve cover. Check the wiring harness closely, making sure the connector is fully plugged into the harness and hasn’t rocked itself loose. Then check to ensure each glow plug’s wiring clip is tight. Finally, test each glow plug by placing the test-light probe directly on top of a plug. If the tester lights up, the glow plug is fine. If there’s no light, the plug is bad.

Low-Buck Turbo Rebuild

A buddy is helping me overhaul the 7.3L engine in an ’01 Ford Super Duty that has 317,000 miles. We were looking at the turbocharger and wondered if that’s something we can pull apart and safely rebuild ourselves, instead of buying a remanufactured turbo. It’s just a work truck, and we are trying to keep the overall rebuild cost down.
Warren Spears
via email
Photo 5/5   |   Rebuilding Garrett GTP-38/38R turbochargers isn’t difficult. Basic refurbishing kits cost less than $75, and complete centersections sell for around $500. Time to rebuild is less than an hour, with no special tools required.
Those older turbochargers are relatively simple in design and very easy to disassemble. The critical area is the centersection, where all the work happens. The Garrett GTP-38 (the stock turbocharger on ’95-to-’02 7.3L Power Stroke engine) spins to almost 110,000 rpm, so everything in the assembly must be in perfect balance and well oiled to protect it from suffering catastrophic damage.
Rebuilding one is easy, and kits for doing it are available for less than $75. Use a kit that includes a 360-degree thrust bearing. The stock bearing is 27 degrees and doesn’t oil and disperse the huge forces inside the turbo like the upgraded piece.
We also highly recommend replacing the compressor wheel while you have the turbo on the bench. The stock piece is known for surging and taking forever to spool up. Basic aftermarket performance wheels prevent surging. The best bang for the buck is to replace the stock compressor wheel with one that has a “5/5” blade design (Whistlin' Wheel, Anti-Surge Wheel, Banks Wheel, and such) or the new 4/4 billet wheel from Riffraff Diesel.
If you find damaged turbine or compressor wheels or there are signs that something went through the turbo, its entire centersection can be replaced with a Garrett assembly for about $500. Aftermarket suppliers can usually install an upgraded turbine wheel before sending the unit to you. When it arrives, just bolt on the ends and you’re good to go. Either way, doing your own rebuild on a Garrett GTP-38 will save money.

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