Just completed a 2004 LB7 repair for a friend. Had lots of advice/help from 2004LB7 on this forum. Thank You 2004LB7. A little background, this truck A friend has had this truck since new, new injectors were installed at 90K and up to say 130,000 miles the GMC Sierra 2500HD had been getting an easy 20 MPG freeway travel and running pretty good.. Around 130K it was acting up, bad injector discovered, just wanting this truck back to stock performance and reliability 8 new injectors were installed again, truck never ran quite right and MPG was down by 5. He kept taking it back to a shop asking why, a few times the shop said it had a bad injector and would install one new injector. They kept the truck for 3 weeks and installed a new #6 injector, gave the truck back with the same problem. The truck started using coolant at around 130,000 miles and smoking on start up, had trouble passing the smog test for DMV. This truck has been back in the shop for warranty repair several times, they claimed to have replaced injectors on both banks in this period of time and the truck kept getting worse. Shop charged $9200 to repair the truck, MPG dropped by "5" mpg and the shop says nothing is wrong. Truck runs pretty good other than the morning smoke and using coolant which keeps increasing in amount as time goes on. About a year ago he is talked into installing a tune to fix his MPG and help with Towing power, he tows a 12,500 LB trailer frequently. The Tune is one of the 5 step tunes available, install cost $605. Truck still is down on MPG and power is a little better. He is a friend and asks if we can tear it down for repair. Says he does not care what parts we need to buy he just wants it RIGHT again. So as many of you know this tear down is not for the faint of heart. There is an amazing amount of stuff bolted to the Duramax to make it work correctly. I am old and work slow so I think I had 4 full days into getting the heads off. I don't have a lift and had limited ceiling height, just under 8' in the garage so I decided to pull the heads in the truck. I do have a Top Creeper, they are really nice when you work on tall trucks, save a lot of wear and tear on your back. The Tear down had several eye openers. Several of the valve cover bolts were stripped, the allen head not the bolt threads. Some of the banjo return line bolts were stripped. Got them all out. One injector, #7 of course was extremely tight and hard to remove from the head, the injector bolt I should say not the actual injector. First this #7 bolt had a 10MM allen head not the 8mm allen head like the other 7 cylinders? Every turn of the wrench was a battle on this bolt. Lots of lock tite I presume. When removed this one injector bolt was much larger and shorter than the other 7. Hmm. The injector hold down bracket in #7 had been modified. Drilled out to receive a larger bolt. Same bracket had been modified with a grinder to make it have more clearance around the valve springs???
This injector in #7 when removed came out with the injector cup and showed huge carbon build up? OK, now the heads were removed and taken to the Machine Shop to have them checked out, Surfaced, Pressure checked and new valve stem seals installed, truck is 18 years old, seals age and new seals are in the Fel Pro Head Set so we installed them. Machine shop looks at the now clean head and sees a Heli Coil in that #7 injector bolt hole, it is not straight and off center, explains why the bracket was ground on for clearance. Further checking with the heli coil pulled out finds a broken off drill bit or easy out down under this heli coil hole. The Hole depth is only .600 not the 1 inch of the other 7 injector bracket bolt holes. So now we know the shop had a problem with this bracket hold down bolt, being #7 it is very hard to get to for repairs under the AC unit and against the fire wall. They tried to drill it out, failed, compromised and installed a heli coil but put it in off center and crooked, not deep enough. Holy Crap, we pay for this type work at shops charging $150 per hour? OK, now my machine shop uses a needle point high speed grinding tool to go down in that hole and grind out the bit or easy out that is broken off in there. Now with this out and the head in the Petersen they were able to properly drill out the hole and insert a Time Sert that allows the OEM bolt to be used and gives full depth for strength. They fly cut this insert back down to exact factory height so it is very straight, it is slightly off center from the factory bolt because so much aluminum was removed by the bad shop repair but Motor Machine in Fair Oaks CA was able to save the head. They had to flex a little off of perfect but a new head was $1100 and both heads checked with this repair was only $800. It is very close and works perfectly with a new Injector bracket in place, so the bad repair caused sidways pressure on the injector, that injector cup started leaking due to improper hold down torque and the twisted hold down bracket. Examination shows the head gaskets were not leaking so the problem was in the heads. Surfacing the heads showed they were straight, cleaned nice with a .004 cut. Final step they went to install the valve stem seals. Remove the #7 valve springs and guess what? 2 springs the ones closest to the #7 hold down bracket for that injector are collapsed, the shop had used a torch trying to remove the broken bolt or stripped bolt head. They heated it enough to cause the lower coils on the 2 valve springs to collapse. Assembled it was invisible. Removed it was obvious. The springs are about 1/4" short of factory height and lean like the Leaning Tower of Pisa. We installed all new Valve Springs, could have done just the 2 but a whole set was only $140 so they are all new.
So the engine is all assembled, added a Lift Pump, All new Injectors, Used the Fel Pro Head Gasket Set, all new Injector Cups, new Factory Head Bolts, New ARP Valve Cover Bolts, they are really nice to work with. All new Hoses etc. Engine Runs like a Top, has great power, zero smoke now. Should last a very long time. Installed new Bosch injectors, looked at SAC but the owner wanted it quiet, I have read reports that Mahle are the only head gaskets to choose. I did some reading and even spoke with the Fel Pro Engineering Team, great guys by the way. The Fel Pro Gasket is using the latest Laser welded fire rings so they are state of the art. Fel Pro has been a rock solid provider of high quality gaskets for at least 70 years. I trust what they provide. I also trust the Mahle design both companies can supply a very high quality gasket.
Remember that $605 tune install? On the first test drives watching the scan tool to make sure everything is working as designed the Timing on this engine stayed at 1* or 2* on steady cruise or Wide open throttle pulling a steep long freeway hill??? 1 or 2* No wonder this truck had lousy MPG. The Fuel Pressure did jump with every turn of the 5 step dial, 1 being the lowest fuel pressure and 5 showing the highest fuel pressure. We chose to go back to the factory tune and leave it alone. The owner said he was never wishing the truck had more power, he always wanted it to just run and be reliable. Even towing his 12,500 pound trailer he said it always had plenty of power. The Balance Rates are fantastic with the new injectors, most times when checked they are around 1 plus or minus and it sounds so smooth at idle and on the road. We test towed with it, only had a 7,500 pound trailer to test tow with but we do have some very steep grades and it goes up those at 70 MPH towing with no issue at all. Uses zero coolant, has near zero smoke at any time even on cold start up. So there you have it, I was pretty worked up about the damage caused by a shop that took $9,200 and not only did not fix the truck but screwed it up. I guess I write this for therapy. I think so much time has gone by that he does not really have a case against the shop, I will not say the name in case he does take this to court. Great Truck now, runs very strong and I really like the LB7 engine. He has kept it in very good shape for an 18 year old truck. Now it runs and looks like new. You never know what will be found on a tear down.
Mark
This injector in #7 when removed came out with the injector cup and showed huge carbon build up? OK, now the heads were removed and taken to the Machine Shop to have them checked out, Surfaced, Pressure checked and new valve stem seals installed, truck is 18 years old, seals age and new seals are in the Fel Pro Head Set so we installed them. Machine shop looks at the now clean head and sees a Heli Coil in that #7 injector bolt hole, it is not straight and off center, explains why the bracket was ground on for clearance. Further checking with the heli coil pulled out finds a broken off drill bit or easy out down under this heli coil hole. The Hole depth is only .600 not the 1 inch of the other 7 injector bracket bolt holes. So now we know the shop had a problem with this bracket hold down bolt, being #7 it is very hard to get to for repairs under the AC unit and against the fire wall. They tried to drill it out, failed, compromised and installed a heli coil but put it in off center and crooked, not deep enough. Holy Crap, we pay for this type work at shops charging $150 per hour? OK, now my machine shop uses a needle point high speed grinding tool to go down in that hole and grind out the bit or easy out that is broken off in there. Now with this out and the head in the Petersen they were able to properly drill out the hole and insert a Time Sert that allows the OEM bolt to be used and gives full depth for strength. They fly cut this insert back down to exact factory height so it is very straight, it is slightly off center from the factory bolt because so much aluminum was removed by the bad shop repair but Motor Machine in Fair Oaks CA was able to save the head. They had to flex a little off of perfect but a new head was $1100 and both heads checked with this repair was only $800. It is very close and works perfectly with a new Injector bracket in place, so the bad repair caused sidways pressure on the injector, that injector cup started leaking due to improper hold down torque and the twisted hold down bracket. Examination shows the head gaskets were not leaking so the problem was in the heads. Surfacing the heads showed they were straight, cleaned nice with a .004 cut. Final step they went to install the valve stem seals. Remove the #7 valve springs and guess what? 2 springs the ones closest to the #7 hold down bracket for that injector are collapsed, the shop had used a torch trying to remove the broken bolt or stripped bolt head. They heated it enough to cause the lower coils on the 2 valve springs to collapse. Assembled it was invisible. Removed it was obvious. The springs are about 1/4" short of factory height and lean like the Leaning Tower of Pisa. We installed all new Valve Springs, could have done just the 2 but a whole set was only $140 so they are all new.
So the engine is all assembled, added a Lift Pump, All new Injectors, Used the Fel Pro Head Gasket Set, all new Injector Cups, new Factory Head Bolts, New ARP Valve Cover Bolts, they are really nice to work with. All new Hoses etc. Engine Runs like a Top, has great power, zero smoke now. Should last a very long time. Installed new Bosch injectors, looked at SAC but the owner wanted it quiet, I have read reports that Mahle are the only head gaskets to choose. I did some reading and even spoke with the Fel Pro Engineering Team, great guys by the way. The Fel Pro Gasket is using the latest Laser welded fire rings so they are state of the art. Fel Pro has been a rock solid provider of high quality gaskets for at least 70 years. I trust what they provide. I also trust the Mahle design both companies can supply a very high quality gasket.
Remember that $605 tune install? On the first test drives watching the scan tool to make sure everything is working as designed the Timing on this engine stayed at 1* or 2* on steady cruise or Wide open throttle pulling a steep long freeway hill??? 1 or 2* No wonder this truck had lousy MPG. The Fuel Pressure did jump with every turn of the 5 step dial, 1 being the lowest fuel pressure and 5 showing the highest fuel pressure. We chose to go back to the factory tune and leave it alone. The owner said he was never wishing the truck had more power, he always wanted it to just run and be reliable. Even towing his 12,500 pound trailer he said it always had plenty of power. The Balance Rates are fantastic with the new injectors, most times when checked they are around 1 plus or minus and it sounds so smooth at idle and on the road. We test towed with it, only had a 7,500 pound trailer to test tow with but we do have some very steep grades and it goes up those at 70 MPH towing with no issue at all. Uses zero coolant, has near zero smoke at any time even on cold start up. So there you have it, I was pretty worked up about the damage caused by a shop that took $9,200 and not only did not fix the truck but screwed it up. I guess I write this for therapy. I think so much time has gone by that he does not really have a case against the shop, I will not say the name in case he does take this to court. Great Truck now, runs very strong and I really like the LB7 engine. He has kept it in very good shape for an 18 year old truck. Now it runs and looks like new. You never know what will be found on a tear down.
Mark
