BD Diesel • Troubleshooting Guide

6.7L Cummins Issues: 10 Common Problems & Proven Fixes

Real-world symptoms, root causes, and the BD solutions that keep Ram 2500/3500 (and Cab & Chassis) trucks working. From grid-heater electrical failures and VGT actuator faults to manifold leaks and 68RFE shudder—diagnose, prevent, and upgrade smartly without compromising emissions.

Ram 6.7L Cummins long block on stand — BD/Precision Plus Ready Run engine
Ram 6.7L Cummins Turbo Diesel — proven workhorse, but not without quirks.
Quick Summary: Watch for grid-heater fastener failure (BD Killer Grid Heater), VGT actuator/soot-stuck vanes (BD VGT/Screamer), manifold cracks/leaks (BD pulse-divided manifolds), and 68RFE converter shudder/heat (BD thermostat bypass & Stock-Plus package). Add smart maintenance: boost-leak tests, CCV filter service, and healthy regens.

On this page: Grid Heater • VGT Turbo & Actuator • Exhaust Manifold • 68RFE Heat/Shudder • EGR/DPF/DEF • High-Pressure Fuel • Boost/Charge-Air Leaks • CCV Filter & Blow-by • Cooling Hotspots • Head Gasket/Clamping

1) Grid-Heater Fastener Failure (The “Killer” Fix)

Heavy current through small internal fasteners can arc and break off inside the intake. Best case you lose heat; worst case hardware goes through the engine. There’s rarely a warning beyond weak cold starts or a code.

  • Symptoms: poor cold starts, intermittent intake electrical DTCs.
  • Fix: BD Killer Grid Heater — direct-to-busbar, self-locking threads, retains full OE heat, emissions compliant.
ElectricalCold Start
BD Killer Grid Heater vs OEM internal connection
Direct-busbar connection removes the failure-prone internal nuts.

2) VGT Turbo: Actuator Faults & Soot-Stuck Vanes

Heat/soot slow the vanes; actuators age out. You’ll feel lazy spool, erratic exhaust brake, or turbine speed/position codes. After basic checks (boost leaks, regen health), many trucks wake up with a fresh, calibrated turbo.

Pro tip: After turbo work, pressure-test the charge-air system. Tiny leaks masquerade as “lag.”

3) Cracked / Warped Exhaust Manifolds (Drive Pressure Creep)

Regen cycles and towing heat-soak thin castings. A faint tick becomes soot at the flange, sluggish spool, and higher drive pressure. Doing it twice is common with thin replacements.

  • Fix: BD thick-wall, pulse-divided manifolds with slip-joint expansion control, pre-drilled pyro port, hardware & gaskets.
  • Pickup: 6.7L Manifold Kit • Cab & Chassis: C&C Manifold Kit
ExhaustEGTs
Uniform wall thickness + slip joint = fewer cracks, steadier clamp load.

4) 68RFE Heat & Converter Shudder (35–55 MPH “Rumble”)

Light-throttle shudder plus rising temps points to converter clutch glazing and marginal cooler flow. Fluid alone won’t hold if pressure/lockup are unstable.

Service cadence: Towing often? Inspect fluid/filter ~20–30k mi. Heat kills ATF—treat it like consumable under heavy use.

5) EGR/DPF/DEF Strategy: Frequent Regens & Doser Build-Up

Short-trip cycles and idle-heavy use load the DPF quickly and can crystallize DEF at the doser. You’ll see frequent regens, higher EGTs, and sometimes reduced-power messages.

  • What to do: Ensure healthy regens (avoid repeated short trips), keep the system stock & serviced, and verify no boost or exhaust leaks that inflate soot production.
  • Upgrade synergy: A responsive VGT (or Screamer) plus sealed manifolds keeps EGTs and drive pressure in check, which helps emissions systems work as intended.
EmissionsDriveability

6) High-Pressure Fuel Wear (Pump & Injector Return)

Age, contaminated fuel, or aeration show up as hard starts, white haze, rough idle, or excessive return flow. Chasing one injector on a tired system is false economy.

  • Shop fix: Address pump & injectors together when return rates are out of spec. BD’s Ready Run engines include a reman CP3 (with new metering unit) and matched injectors tested on a Bosch bench.
  • See Ready Run packages: 2007.5–2012 • 2013–2018
Fuel System

7) Charge-Air Leaks (Boots, Clamps, Intercooler Pinholes)

A tiny boost leak feels exactly like turbo “lag.” You’ll chase power and EGTs until you pressure-test. After turbo/manifold service, re-seat and re-torque everything.

  • Checklist: Cold pressure test to ~20–25 psi, inspect boots for oil soak & micro-tears, verify clamp quality and orientation.
  • Why it matters: Leaks skew fuel/air balance, increase soot, and stress the emissions system.
BoostDiagnostics

8) CCV Filter Saturation & Blow-by (Service Item)

A saturated crankcase filter raises crankcase pressure, oils up the charge tract, and can trigger service messages. It’s a maintenance item many owners miss.

  • Do this: Replace on schedule (sooner for tow/short-trip cycles), inspect for oil in the CAC tubes, and reset the service minder if applicable.
Maintenance

9) Cooling Hotspots (Water Pump, Thermostat, Radiator)

Heavy tow + summer grades = marginal margins. Aging pumps/thermostats and partially blocked fins nudge temps up, which snowballs into EGT and trans-heat issues.

  • Basics first: Clean condenser/radiator stack, verify fan clutch behavior, and replace tired pumps/thermostats.
  • Note: BD Ready Run engines ship with a new water pump & thermostat to reset the baseline.
Cooling

10) Head Gasket & Clamp Load (Tuned/Heavy Use)

While stout in stock form, prolonged high drive pressure/EGT or aggressive tuning can stress the seal. Early wisps at cold start or pressurizing coolant are red flags.

  • Prevention: Keep EGTs in check (pyro in BD manifold port), fix boost/exhaust leaks, and avoid lugging under heavy load.
  • Build path: BD/Precision Plus long blocks are assembled with ARP 2000 head studs for reliable clamp load.
Engine Build
Related BD upgrades (emissions-compliant):

FAQ

Do Screamer turbos require tuning?
No. They’re designed as drop-in, 50-state-legal upgrades with calibrated actuators. Proper airflow and healthy fueling help you realize the gains.

Will a manifold leak hurt performance?
Yes—exhaust leaks raise drive pressure, slow spool, and tick loudly at cold start. BD’s thick-wall, slip-joint design helps the joint survive heat-cycle abuse.

My truck shudders at ~40–50 mph—engine or transmission?
Usually the 68RFE converter clutch. Improve cooler flow first, then address converter/pressure control if shudder persists.

Fix it once—properly. Shop the parts above or talk with a BD specialist about your use case (tow, work, or mixed-use). Small changes—cooler flow, thicker manifolds, a smarter grid heater—add up to thousands of miles of trouble-free work.

Notes: Always follow torque specs and procedures in BD installation manuals for your exact year/trim. Emissions compliance varies by SKU and location; confirm on each product page.