Boost gauge moving during regen

Fordracer · March 12, 2014

I have a 2008 F-250 6.4 with 88,000 miles on it. Here's what I wrote into the hotline:

No codes and couldn't duplicate problem. I checked the bearings on both turbos because he thought the turbos were going out. The truck had a very old calibration so I reprogramed the modules and let the customer have the truck. He brought in a video today on his phone of the gauges when it acted up today and the boost gauge jerks around as it goes down to 0 psi and then it goes back up smoothly to around 15 psi and it keeps going up and down while in regen but he has the cruise on and the rpm and speed don't drop at all. When the boost is going down the truck makes a grinding noise he said sounds like dragging a rake in the gravel and the truck surges a little but it doesn't loose power and the sound gets louder the longer it's in regen. When the boost is on the way up the noise goes away.

The owner says when the "drive to regen" comes on he gets on the highway and drives it until it's done. He has the cruise set between 70 and 80 mph and it doesn't loose any speed. The hotine has never heard of it and they said they will be watching for my reply because they want to know what's going on.

I can't believe the boost is actually going to 0 psi or it would loose power. I was talking to another customer yesterday about his 6.4 and he has a DPF delete on it and he said his truck did the same thing until he deleted the DPF and hasn't done it since.

The shop foreman has been driving the truck for the past week trying to get it to go into regen so we can make some recordings and see what's going on.

Has anyone ever heard of this?

Keith Browning · March 12, 2014

Have you ever heard the sound a 6.4L turbo makes when the wheels are scraping the housing? Makes a distinct sound but any failed turbo I have "driven" either worked or it didn't. I agree that if boost falls to zero you would think there wouild be a notable loss of power but it does have two turbos. How much power do you need to cruise at 70? Definately keep us posted too!

Fordracer · March 12, 2014

I did check both turbos for end play and they were tight. When I talked to the hotline he recomended " If the noise is isolated to the turbocharger(s) then it is recommended that the compressor wheels be side loaded and rotated to check for any rotational sticking or binding. This can be done by careully grasping the compressor wheel and pushing it into the housing in different directions and the wheel rotated. If there is any rotational sticking/binding when performing this inspection then it is recommended to replace that turbocharger." He also said that maybe during regen that the exhaust makes the turbos hotter and maybe the bearings are causing a problem at that time.

Keith Browning · March 12, 2014

Makes sense.

amailloux · March 12, 2014

I have seen a couple with a very bad surge that follows the throttle plate and really never completed a good regen. They would regen every 50 miles and boost was low, and power was low. They both had excessive blowby and low compression. Would be 5 or more percent low on relative compression only after a regen.

Matt Saunoras · March 14, 2014

I'm not an international guy but I do have a maxxforce 7 coffee table book. International says they use the ETB to restrict air flow for regeneration strategies (help increase EGTs by restricting intake air). I always thought the throttle body was used to help promote EGR flow (like an 04 6.0) but I'm not so sure now, I've never had one cause problems or had any reason to pull up the PIDs to watch it's activity during regen.