Huston, we have a problem....

[Dragsled]

first off, let me say that I've been a member of this web site since 2001 when I bought my beloved duramax.

last month @76,000 miles if developed its first problem. a "low coolant" light. no big deal, top off the system. Next day, 70 miles later, another low coolant light. hmm... no drips, no smell of burning coolant, kind of odd, it couldn't possible be going into the engine... or could it?

topped it off again (3/4 gallon each time), drove to work 30 miles, checked it out, there was cooling ****ing past every hose clamp in the cooling system. not good. when i cracked the coolant system cap, instead of the slight "whoosh" of pressure bleeding off, the cap damn new blew out of my hand and coolant blasted out everywhere. There was way too much pressure in the system.

turned out that combustion pressure was leaking past the head gasket into the coolant, super pressurizing the system and blowing coolant out of every fitting.

dealer fixed it but....

since they gave me the truck back...

milage has dropped from rock steady 19 to 15

the truck takes .4-.5 miles to go from 0 to 70 *yawn*. previously the truck would get to 70 in about .2 miles or a little less.

at 70 on flat roads the truck will downshift into 4th just to hold 70mph. it used to go right to 99 in overdrive no problem.

towing a 4000lb trailer on flat roads the truck will not get past 60-65, in 4th, running at 2800 rpm. it used to haul that same trailer up hill, 75-80 and never even have to down shift.

did they forget to hook up the turbo?

my dealer is lost. he has not clue what to do.

they are replacing the injectors under the special bulletin. I don't see any logical reason why that should be a problem. the problem seems more fundemental than that. this truck can no longer get out of its own way. mashing the throttle won't even spin the tires in the snow anymore. thats pathetic.

anyone ever hear of anything like this????

oh, the truck is a 2001 2500 crew cab duramax/allison, 76,000 miles roughly 1600 hours

[Kennedy]

If you find out,please let us know!

I spoke with a guy from TX who had a similar power loss after head service.

[Jim Brzozowski]

Do you hear any strange noises, like maybe it's leaking compression somewhere else, just not in the water jackets. Does it run as smooth as it used to? I'm thinking lower compression, assuming they actually did replace head gasket, or was it a problem with the head allowing the compression into the cooling system?

[01max]

i do know that there are 3 different head gasket thickness availible for the duramax and when you go to replace one, you have to remove the head to make sure you get the right thickness. if they installed too thick of one it might have lowered the compression.

[duning chevy]

I dont think that a slightly lowered compression would make that much of a difference. Also, if thye had forgotten to hook up the turbo you would have a ton of smoke and no turbo whistle. That seems VERY unlikely to me. Have you tried to read if there are any codes being set with a code reader that might be a good start.

[More Power]

Assuming there is a genuine drop of 4-mpg and a very noticeable loss in power, something definitely changed.

With a head replacement, I would first suspect some other engine component, wiring or sensor was inadvertently affected during the service work.

MAF and rail pressure sensors come to mind. If either of these were damaged or altered in some way (but not so much as to set a code), it could affect performance.

If you had a Predator or some other tuner, you could collect some real-time info about the mentioned sensors. Your dealer could also do this using a Tech II scan tool. This is the direction I'd go...

MP

[Dragsled]

thanks for the replys..

to answer a few questions.......

the engine runs smooth, no missing, skipping or erratic running.

I cannot hear the turbo whine like i used to on highway runs, but then again, with all the other noise in the truck, who knows. I would expect that if the turbo wasn't working, it should set the SES light, which has not come on.

There does appear to be a lot more smoke than there used to be under hard acceleration.

Another thing I noticed is the change in pitch of the engine. It used to have a more rattling sound that came on around 2500 rpm +/- a few, under hard acceleration. If I remember right, on this forum back when I bought the truck in 01 there was discussion about some pre-injection of fuel that either comes on or off (don't remember which) at that rpm to prevent detonation. It was very distinct, and it no longer does it.

Yes, its true, that truck now gets 4mpg less than it used to. It accelerates like a slug. Power is way down. at times when driving 65-70 on flat roads it will down shift to 4th just to maintain 65. Towing my trailer (4-4.5k lbs) at speeds over 60-65 just doesn't happen any more. last weekend I towed my trailer 60 miles on flat highway (NY State thruway), no head wind, the truck would not get over 65, and it stayed in 4th gear @ 2800 rpm the entire trip. no amount of mashing the pedal into the floormat would make it go any faster. It lost speed going up the slightest grade.

the dealer is going to replace the injectors but i'm very skeptical that they are the problem. To me it seems like something more fundemental didn't get reconnected when they had it all apart, or the timing is off, or low compression. All of which should be easy enough to verify, yet they are stumped.

meanwhile, i'm getting passed on the highway by nuns driving minivans and its really pi$$ing me off lOl !

[DMAXED]

Did they check the turbo waste gate ?

[More Power]

I really doubt you have an injector problem, based on your reports.

Generally, the less someone works on your engine/truck, the better off you'll be.

I'd "request" that they first perform a system-wide evaluation of all engine sensors and fuel management systems using the Tech II scan tool. Locating another dealer might be an option....

MP