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BOOST TOO HIGH ON ENGINE DECEL?

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STROKER_T
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STROKER_T

STROKER_T

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I've got an '05 F350 in for what seems to be head gaskets... pressure and vacuum tests pass,funny thing is that when on road test for leaking head gaskets and pid monitor checks the coolant pressure jumps to 18psi on decel and vents (new cap installed for s&g's)....anyone failed the head gaskets because of decel pressure readings are higher than at WOT?.... Posted Image

ECT/EOT variation never exceed 8 degrees....has a 5th wheel hook up(of course)....

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Bruce Amacker

Bruce Amacker

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No, I've never seen it but am interested in why. I think I'd go do another RT and take control the VGT on decel to see if it made a difference in the colling system pressure on decel. If so, I might take a closer look at the EGR cooler. I have seen leaking EGR coolers that mimicked bad head gaskets by pressurizing the cooling system.

 

Good Luck!

 

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Fordracer

Fordracer

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I have one right now doing the exact same thing. It came in for no boost and the turbo unison ring was stuck. I noticed some coolant stain on the degas bottle but we just did an egr cooler 10,000 miles ago so I thought it was left over residue from that. When I test drove it the degas bottle cap would whistle on decell. I went back to the shop and put a pressure gauge on it and the pressure would go to 13 psi on accell and then spike to 16 on decell. The egr cooler passed the vacuum test so I'm in the process of pulling the cab right now to do head gaskets. I did notice that the radiator fins are completely packed with dirt and grass but the coolant temp never got above 195 so I don't know if that has anything to do with it.

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STROKER_T

STROKER_T

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Ok,got ESP approval for head gaskets...the egr cooler has been submerged in the sink for a half hour now w/30psi of pressure attached...i got NO bubbles,this truck had an oil cooler put on 20,000 miles ago,the egr cooler tested good then as well,according to the tech notes...the head gaskets definitely look like they have been leaking... Posted Image

Never had one jump up pressure on decel before...something new learned every day,will know for sure if it's fixed tommorrow... Posted Image

Edited to say EGR cooler did pass vacuum test...

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