Losing Boost Presure
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New User
Joined: Mar 2009
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From: Colorado Springs
Losing Boost Presure
Hey All, I have a 2004 6.0 – I was towing my 5’er up about a 5-7% grade this weekend – about ¾ of the way up I started hearing a loud fan (not sure if it was the engine fan or the turbo spinning like crazy) and then I watched my boost steadily drop from 25, 20, 15 and then settle at about 11. I had my foot to the floor trying to get up the hill doing about 30mph.. Once I made it to the top and was going downhill for a bit, the fan noise stopped and I felt the pressure come back. Any thoughts on what might cause this?? Mods I’ve made to my truck are:<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com
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4” exhaust<o></o>
EGR blocked off (not removed)<o></o>
Head studs<o></o>
Bullydog Powerhound<o></o>
<o></o>
Thanks for any ideas you all might have..<o></o>
fficeffice" /><o></o>4” exhaust<o
></o>EGR blocked off (not removed)<o
></o>Head studs<o
></o>Bullydog Powerhound<o
></o><o
></o>Thanks for any ideas you all might have..<o
></o>
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Joined: Jun 2006
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The noise you were hearing was most likely your engine fan. I had the exact issue last summer and I too originally thought it was my turbo going south. How did you block the EGR? Did you just block the exhaust from entering the cooler, or did you re-route the coolant flow around the cooler? When you did the EGR work, did you rebuild the oil cooler? Any idea what your coolant and oil temps were when you were hearing the fan run? If you have head studs and the work was done properly, i.e flat surfaces, that should not be the issue. In my case, the fan was coming on due to the high oil temp while towing. I rebuilt the oil cooler and all is good now.
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From: Colorado Springs
Yup - once I got to the top of the hill and was able to let off the gas a bit, the "fan" noise went away and the boost returned to normal.. This isn't the first time it's done this, but the last time I thought it had gone into "limp mode" because I had the EGR unplugged - since then I've had the EGR block off kit installed.
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From: Colorado Springs
Based on the stock gauges all the temps looked to be in the normal range.. I had the EGR valve blocked and the back of the EGR cooler blocked - this was due to a coolant leak in the EGR cooler - that took care of the coolant smell under a heavy load.. I didn't have anything re-routed. I haven't done anything to oil cooler.
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Joined: Aug 2007
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From: Lakewood, Ca.
Could be the pcm started commanding less fuel due to very high temps. By chance do you have aftermarket gauges? If so, what kind of temps were you seeing?
I don't know anything about Bullydog, but what kind of setting was it on?
I don't know anything about Bullydog, but what kind of setting was it on?
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From: Colorado Springs
I do have a pyro gauge that's installed in the downpipe - it was reaching about 8, which is about normal for my truck when I'm towing. My 5'er is 12K dry and I was pulling it full of water..
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FTE Leadership Emeritus
Joined: Aug 2007
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From: Lakewood, Ca.
I don't know if the pcm will pull fuel based on EGT...even if it does, 800 degrees post-turbo doesn't sound too terribly high.
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Joined: Aug 2007
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From: Lakewood, Ca.
I missed this earlier
If that's the case I would suspect that you have a clogged oil cooler....to confirm this you need to monitor the oil/coolant temps to see that they are within 15 degrees of one another. If they aren't the oil cooler is shot.
If I'm not mistaken the pcm will begin to pull fuel out if oil temps get too high.
If I'm not mistaken the pcm will begin to pull fuel out if oil temps get too high.
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Maybe I am an idiot here, but can you explain your EGR cooler blockoff in more detail. If it was already leaking, you would have had to either re-route the coolant and go directly to the oil cooler, of replace with a new EGR cooler an then block exhaust flow. Unless I am not thinking very well today, you can not just block off coolant flow. Anyway, I suspect your oil cooler is toast.
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From: Colorado Springs
hndacr: I wish I could explain it better -lol... I know they blocked off the exhaust on the back of the cooler and then put a plate under the EGR valve to block that off.. As far as I know there was nothing in the work that rerouted the coolant - it was just the exhaust that was blocked off.
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No code. You can monitor the oil temp vs coolant temp with the right software. Or, if you know someone who has a scangauge II, that will read it. I put a scangauge in my truck after my cooler went bad.
I wish I knew how they stopped your EGR cooler from leaking without replacing it or bypassing it. Anyhow, if you can't find a way to get the readings yourself, the dealer can monitor those sensors for you. Let us know how it turns out.
I wish I knew how they stopped your EGR cooler from leaking without replacing it or bypassing it. Anyhow, if you can't find a way to get the readings yourself, the dealer can monitor those sensors for you. Let us know how it turns out.
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From: Colorado Springs
Installed the new Bullydog Tripledog GT Tuner on Thursday.. LOVE IT.. I was able to narrow down my problem to the oil cooler (Thanks hadacr).. Had the oil cooler replaced, fan clutch, coolant and oil changed as well as the thermostat.. Pulled the 5'er home on a 2 1/2 hour trip and it pulled like a dream..
Thanks again for all the help fellas...
Thanks again for all the help fellas...