Diesel Mech advice needed

[jcmseven]

Robbie,

I am a certified diesel gearhead but not a diesel mechanic. I believe Greg H or Donnie could offer some opinions on the "official" end of this topic--you may wish to PM one of them for the official word, but I am unaware of any way the 46 psi would be an accurate reading for boost. As for EGT, it is a little like business overhead calculation--it is all about where you check it. Location of the sensor etc. can have a real impact on your numbers. A few months ago there was a post about pre-or-post turbo numbers and how they differed. The diesel websites are filled with lengthy and heated arguments about where the best place to check is. A 600 degree reading post turbo housing is really not hot at all, as 1000+ is the norm here for a high reading. A 600 degree pre-turbo reading is moderate but not outrageous. Due to packaging under the hood, my sensor is located post-turbo and I drive around at 300-450 and get to 600 climbing a hill--unloaded. The guys at Banks say the EGT of 600 is the sweet spot for a Ford PSD with the sensor mounted post-turbo. This seems to be the temp where the 7.3L is when things are harmonious. With an aggressive programmer and no exhaust, which some do, 800+ could occur unloaded. These guys (or gals) are destined for readings of 1500+ if they are pulling heavy. So, first the numbers you mention about that are not that high so I doubt heat was a primary factor--BUT--the scenario minus the 46 psi could be seen if your EGT was really higher than you were seeing.

John M

 

[JESSE1]

Since you have an '04, you have the 6.0 Powerstroke. It does not have a wastegated turbo. You have a VGT (variable geometry turbo) with movable vanes on the turbo. The vanes probably stuck open temporarily and caused the overboost. It will set a code. You're lucky it didn't blow an intercooler boot off.

 

[KICK]

let me put it this way... if you truly had a condition where you had 46 psi of boost you were probably overspeeding the turbo so bad that it will fail at some point in the future. and then your engine will be full of shrapnel.

I don't know enuf about Ford to say exactly how they do things on the Power Stroke but most Diesle engines that are running EGR have what is called a VNT or a VGT ( both the same thing, variable nozzle/geometry turbo).

they use these turbos as a way of controlling boost and exhaust backpressures for when they need to force exhaust to flow into the intake during EGR mode.

if the turbo isn't being controlled, boost psi can go over the top of its limit.

it is possible that the controls weren't working or the turbo vanes are sticking inside the turbo.

 

[Robbie Hegwood]

Jesse, I think were closing in on what happened. That sure sounds like the most fisable explaination. I knew the instant it did it, weird sound. I pay very close attention to my truck for the weight I pull.

Now, what if the check engine light didn't come on. Does the light always come on with a code?? Mine did not, I lifted a little as soon as I heard the difference.

Also, enteresting enough I did have a intercooler boot fail recently. They repaired under warranty and metal piped the intercooler return. Sure fits into your explaination. That's when the mech told me not to put a programmer on it. Head gasket theory.

Also why I have you here it will surge while idling. I had the EGR tube replaced and it fixed it for a while but it's back. Does this have anything to do with the stuck vain issue???

Just for clarification it is a 6.0, I have the fuel filters replaced every 15k as suggested. It is also the 6.0 without the extra air sensor in the intake tube.

And yes my EGT temp probe is right behind the turbo.

Thanks tremendously for the input. I'm sure it will have to go to the shop for a check up but i like knowing what's going on before i turn them loose. Now I know what to look for to make sure they fixed it. Again, thanks TBN'ers.

 

[JESSE1]

I have an '04 F-350 Dually with the 6.0 and Torqueshift trans. It's been an excellent running truck with more than enough power. I have had the EGR valve replaced once. Truck would become very quiet at idle then start making the normal sound. Replaced under warranty but easy to replace if you had to do it yourself. Using the Motorcraft Premium Fuel Supplement and Cetane increaser will help with the EGR valve. Using the truck hard, putting the engine under load and changing the oil often helps with the EGR problems, too.

I was pulling a large load of hay last summer when one of the intercooler boots partially slipped off. Loud hissing sound when you put your foot in the throttle. Took it to the shop and the computer had set a code of high boost pressure. Mechanic said the turbo vanes probably temporarily stuck open and high boost pressure blew the intercooler boot off. I never got a check engine light. A good site for Ford Diesels is TheDieselStop.Com - www.thedieselstop.com and check out the forums. Lots of good info and knowledgable people there.