Check for a stuck thermostat.

 

Thanks, Gearloose

That's my next project. Already have a new T-stat, VC-9, 20 gallons of Albertson's finest distilled spirits (and also 20 gallons of distilled water) and 3 gallons of Ford Gold.

Ordered dieselsite's coolant filter as well, just waiting to see if Santa leaves it under the tree.

Watched videos and have read Coolant Change 101, as well as every relevant post here and on other sites. Seems time consuming, potentially messy but pretty straightforward to me.

Expect more questions, guys! But I'll start a new thread for that project.

 

I had a stuck thermostat that caused it to "overcool" then the temp gauge would swing wildly as it stuck / unstuck itself.

At the end of the day, it freed itself, putting off the inevitable (coolant change, hose change, flush, new thermostat) for another season.

 

Well, I thought I had these codes fixed. I towed my 8000 lb trailer about 200 miles, stopped after an hour of highway driving, checked the codes, and all was good. The last hour of the drive was mostly two lane hills. Got to the campsite and though there was no CEL showing, I rechecked the codes.

P0404 again. No P0405 though.

Before this trip I replaced the EGR valve with a new one from Ford and cleaned as much carbon as I could, which was not much at all.

So now I'm wondering, is there a step I missed? Or is it time to go to the dealer?

 

You are getting no CEL but a code?

Ha!

You discovered the "relearn" procedure.

There is a huge controversy over this, because it is an undocumented feature --- software writers never give away all their trade secrets.

If you are really ****, I can show you a way to mitigate it.

If you are like the rest of us --- just ignore it unless the CEL light comes on again.

If it does, clear it, and see if it comes back.

It has to do with how the software relearns / figure out the mini-maxi, possibility of carbon bits clogging things a bit.. etc.

But... I don't want to get into a discussion in public with the non-believers on here.

There are certain benefits I have from being at a major center of Engineering excellence...

 

It doesn't have to look too bad to have a electrical / electronic failure inside the valve.


Mark ---- Notice the rash of clean EGR valves we are seeing --- ever since people started routinely taking them out, and cleaning them.


This is adding weight to my hypothesis that;

A) There was a lot of bad fuel (low cetane) in the early 2000s that created a lot of soot / deposits.

B) Once cleaned (and if there are no other problems like fueling, etc.) the soot has not come back --- e.g. on your vehicle.

C) It could be that carbon builds from too much short trip driving, not enough WOT... but I am wondering....



This is leading me to think.. on any older 6.0 that someone just bought, it should be routine to pull the EGR and clean carbon / plenum / verify operation.

I haven't pulled my EGR a 3rd time, but I suspect I no longer have a carbon problem.