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04.5 and 05 LLY issues

295K views 233 replies 109 participants last post by  04cateyedirtymax 
#1 · (Edited by Moderator)
In light of some of the headgasket and overheating threads here on DF lately, I figured we could have a little discussion on what is going on with the LLY's in general that causes some of the failures we are seeing.

Turbo issues and turbo vanes "sticking" seem to be a problem. I can't count how many issues I've become aware of with problems with the vane sensor going crazy and over-boost or under-boost codes being set. GM really needed to have a drive pressure sensor monitoring drive pressure versus vane position. Drive pressure can hurt a motor fast. If the turbo vanes stay in a higher position than desired, exhaust air is trapped in the cylinder and causes the motor to loose power fast and it holds in a lot of exhaust heat! The turbo vanes in a lly are not very functional below 30%. 100% vane position equals closed, 0% equals open. A closed vane allows faster spool, but creates drive pressure. An open vane allows air to flow through the exhaust side of the turbo easier, but creates slower spool up.

An LBZ will make boost and maintain boost at sea level and 0% vane position. An LLY will not. As I stated above, the LLY needs 30% or more vane position to build boost or maintain boost. In general, the operating range of the vane in a LBZ is from 0% to 95%. 95% and above don't aid in spool up and only increases drive pressure. The range of a LLY is 30% to 95%. 0%-29% vane postion will loose boost on a LLY at sea level.

For efficient operation, the vane position typically is used between 30% and 75% for daily driving and towing on an LLY. Low load and low rpm usage of the vanes above 75% is okay, but there is a drastic increase in drive pressure vs. boost pressure when going above 75%. The same can be said for a LBZ when speaking of high vane position operating characteristics. The difference is that an LBZ can go as low as 0% to maintain boost. So now when comparing efficient vane position operation between an LBZ and an LLY you can see that the LLY uses 60% less of the vane position tables when compared to the LBZ. Because of this, there is less room for error on an LLY when choosing the correct vane position value to get the proper boost value, even in stock form.

The most important thing to realize if you own an LLY, is not all those technical aspects about how you turbo works, but that it was all designed to work with proper maintenance. You can see that a LLY turbo is at a disadvantage to a LBZ turbo right out of the box when it comes down to efficient operating characteristics. Drive pressure kills motors and vane position creates drive pressure.

A clogged or iced up air filter causes a restriction on the amount of air the turbo can suck in to make a desired boost number. Guess what happens when it don't get enough air to make the desired boost number? ECM calls for more vane position to get the boost up! Fail!

A bad MAF or MAP reading makes the truck think it's not getting enough air, guess what? ECM calls for more vane position to get the boost up. Fail

Fuel pressure bleeds off because your fuel pressure relief valve is weak(known problem). Truck has low power and don't make proper boost, so guess what? ECM calls for more vane position to get the boost up. Fail

You have a leaking intercooler or a torn intercooler boot that bleeds off your boost to atmosphere, so guess what? ECM calls for more vane position to get more boost. Fail

Your EGR is struck open and bleeding of boost pressure into the exhaust or sucking in hot exhaust air. Boost readings seem low so guess what? ECM calls for more vane position to get more boost. Fail

Your vane position sensor reads lower than the actual vane postion. The truck thinks it's at 70% vane position but it is actualy at 90%. The ECM don't know there is a problem so you have more boost and drive pressure than you need. Fail

You can see that this is not a perfect system. Your LLY truck doesn't always code or protect itself from self destruction. Your LLY was not designed perfect from the get go, so do yourself a favor and properly maintain it. If you have the means to go above and beyond the proper maintenance, get some gauges and monitor boost and drive pressure. Find a way to watch the vane position desired and actual values and get used to how it changes your boost and drive pressure readings. Stop driving the truck when you see a problem.

The 04.5 LLY and 05 LLY are known to have weak rail pressure relief valves in them. Watch your rail pressure if you don't have yours shimmed or plugged. [Can be tested by "Bottle test"]

The 04.5 LLY and 05 LLY are known to have an extremely restrictive factory turbo inlet mouthpiece and most owners upgrade this piece. If you do an intake upgrade, don't leave the stock mouthpiece on the turbo.

Clean your engine bay and keep an eye on your intercooler, boots, and clamps. Try to eliminate any boost leaks by removing and cleaning the silicone boots when you check them for cracks or holes. When in doubt, replace them with new boots and clamps.

WATCH YOUR COOLANT TEMP WHILE TOWING! Yes, LLY's overheat. Do whatever you can to prevent this. Pay attention to your coolant temp at all times while towing. It's not your fault your truck overheats, but you are the only one that can stop it from happening. You are the one paying to fix it when it overheats, so try to prevent it. Assume it is going to overheat all the time. Better safe than sorry.

Water pumps are known to fail. A big problem has been the impeller falling off the shaft of the pump. If you have a high mileage truck, replace the water pump with one that has been upgraded to keep this from happening. If you are having your head gaskets fixed and your water pump is old or high mileage, replace it with an upgraded one.

It's easy to point fingers at your EGR, a weak factory gasket, your tuner of choice, weak factory studs, or GM when you have a headgasket problem on your LLY. I think the finger pointing should start with the owner/driver of the truck before it ever gets pointed in any other direction. I'm not saying there are things GM could or should have done better. I'm only stating that we know of a lot of these problems already, and you should be informed enough to prevent them before they happen to your LLY.:drink

I also think its important to keep an open discussion of what is failing and under what circumstances. If you have a failure or an opinion/finding on how you could have prevented a failure, let us know! I think we can all help each other make these last longer. I'm sure the info people have shared over the years has extended the life of these trucks a lot already.
 
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#35 ·
Well Bob once again you have made the new lly or at least the mechanically novice owners job alot easier and balled just about everything into one "plain english"thread thank you for throwing down another STICKY!!!!!!
 
#37 ·
Alright I'll try them. Also I have an airdog2 lift pump, if you get below a 1/4 tank it will run out do I need to try and push the suction line down on the tank further?
 
#38 ·
#40 ·
after reading all this i am kind of scared to buy one... i mean i know everything has/ or had problems of some sort.. im looking at a 2005 ccsb with almost 200k that is bone stock and a pretty good deal.. is there any way to check any of this stuff while just on a test drive? any advise will be greatly appreciated
 
#41 ·
Best thing I can suggest is to buy an Edge Insight CS or CTS and connect it for the test drive. Then you can look at the state of most of the engine management systems and make a very informed decision about whether or not to buy that particular truck.
 
#43 ·
They will both monitor the same things so for $100 more you basically get backup camera capability, larger screen and touchscreen navigation. Later if you decide to get EFI, they can both be used to change power levels for a DSP5 setup. That being said, if I were going to keep the truck a long time, I would pay a little extra to get the bigger screen.
 
#45 ·
I would skip the HGs unless they are blown already. Best mods right away would be to install a full LBZ intake (intake and turbo mouthpiece), 4" full turbo back exhaust, PCV reroute, EGR delete, shim your FPRV and then get an EFI DSP5 setup.
 
#47 ·
im looking at a GMC 04 slt how can i tell if its a lb7 or lly . i cant see the engine yet only pics and VIN.
 
#53 ·
great info, have own my LLY since 04 and didn't know some of those things. Thanks!!!
 
#54 ·
So maybe this is an incorrect assumption but coming from a 6.0 powerstroke I'm well aware of how stringent the maintenance schedule must be. Is it fair to assume that the lly is similar? I also have been looking into getting a duramax and am stuck deciding between an lb7 and lly. I'm assuming most problems with this motor can be avoided by doing some simple mods (ie. lbz mouthpiece, gauges, things along those lines) and paying close attention to my gauges/maintenance schedules, correct?
 
#56 ·
Although both are good trucks and not to upset the LB7 guys, but I'd take the LLY any day over the LB7. Just change one set of injectors on both motors and you'll see what I mean. The LLY is a solid performer and the head gasket issue is WAY overrated IMHO. Follow a good maintenance schedule and you'll have your truck for a very long time.
 
#55 ·
Yes sir ^^.

The LLY's get a bad rap, which is not rightfully so, because they are almost like the LMM. A bandaid fix.

The LLY's were the first generation to have EGR, DOC, VVT and other STANDARD emmission control systems. The LB7 had no EGR or DOC, well except for the Cali. models. It is going to have some MINOR issues because it seems as though GM didn't really take into account the LLY has ALOT more going on with it than the much more simple LB7 (operation wise of course). As Bob has said, the LLY's are great trucks but get a bad rap. Not because of a few, again MINOR issues, but more along the lines of owner neglect.

I love my LLY and it has been a great truck for me. Again, read this thread and you will be able to diagnose almost every issue that may arise with your LLY truck. It is unlikely, but it could happen.

One more thing, sorry for the ramble, but don't assume that because you read on a forum that a guy popped his headgaskets that it is immediately going to happen to you. Thousands of people roam all forums, so chances are there may be a few blown headgasket threads. Don't get your panties all wound up because you have stumbled across some head gasket issue threads. You will be fine. Promise.
 
#57 ·
wow, thanks for the right up. that is some awesome info.

to the guys wondering about purchasing an LLY, do it, you will not be sorry. I say this after owning mine for 1.5 years and being told yesterday i need 1 possibly 2 injectors and a fuel pressure regulator. the shop said that wih 260,000 miles i should look into the cp3 not just the fuel pressure regulator. quoted about $2500-3000 and i still say purchase it. also do the egr delete and the pcv reroute. he quoted about a $1000 for the cp3 and 480 for each injector and the rest labor. im going to do the work myself because of it being an LLY.

yes, get the lly, you will not be disappointed, I love my truck. i have literally pulled a house with it, lol. 44' park model mobile home. hope there arent any DOT officers on here, if so, sorry.
 
#60 ·
Maybe i didn't see it while reading but has anyone mentioned the #2 and #7 injector connectors getting lose? The connectors rattle lose and the truck loses power and sounds like a powerstroke. But the simple fix with just unplugging the injector and ice picking the injector connectors back to where they make a good connection again fixes it, about a 10 minute task. I know i ran into that on my LLY.
 
#61 ·
so i think i am having major turbo problems... my vane position is most always between 85% and 95%. i think there is an oil seal shot on my turbo because there is a butt load of oil from the turbo on in all the tubes. wouldnt that be what it would have to be??? and would something be causing the ECM to call for more boost and thats why the vane position is all messed up?
 
#62 ·
So even at cruise on the highway your vanes are at 85%?

I know Rob usually sets up his tunes with a hiss at idle so it should be around 88% then but after you get going it should drop. If you still have the PCV hooked up or if it had been hooked up for a while your oil in the boost tubes was likely from your crankcase. If you have oil in your downpipe too, that is definitely an issue worth looking into.
 
#66 ·
In light of some of the headgasket and overheating threads here on DF lately, I figured we could have a little discussion on what is going on with the LLY's in general that causes some of the failures we are seeing.

Turbo issues and turbo vanes "sticking" seem to be a problem. I can't count how many issues I've become aware of with problems with the vane sensor going crazy and over-boost or under-boost codes being set. GM really needed to have a drive pressure sensor monitoring drive pressure versus vane position. Drive pressure can hurt a motor fast. If the turbo vanes stay in a higher position than desired, exhaust air is trapped in the cylinder and causes the motor to loose power fast and it holds in a lot of exhaust heat! The turbo vanes in a lly are not very functional below 30%. 100% vane position equals closed, 0% equals open. A closed vane allows faster spool, but creates drive pressure. An open vane allows air to flow through the exhaust side of the turbo easier, but creates slower spool up.

An LBZ will make boost and maintain boost at sea level and 0% vane position. An LLY will not. As I stated above, the LLY needs 30% or more vane position to build boost or maintain boost. In general, the operating range of the vane in a LBZ is from 0% to 95%. 95% and above don't aid in spool up and only increases drive pressure. The range of a LLY is 30% to 95%. 0%-29% vane postion will loose boost on a LLY at sea level.

For efficient operation, the vane position typically is used between 30% and 75% for daily driving and towing on an LLY. Low load and low rpm usage of the vanes above 75% is okay, but there is a drastic increase in drive pressure vs. boost pressure when going above 75%. The same can be said for a LBZ when speaking of high vane position operating characteristics. The difference is that an LBZ can go as low as 0% to maintain boost. So now when comparing efficient vane position operation between an LBZ and an LLY you can see that the LLY uses 60% less of the vane position tables when compared to the LBZ. Because of this, there is less room for error on an LLY when choosing the correct vane position value to get the proper boost value, even in stock form.

The most important thing to realize if you own an LLY, is not all those technical aspects about how you turbo works, but that it was all designed to work with proper maintenance. You can see that a LLY turbo is at a disadvantage to a LBZ turbo right out of the box when it comes down to efficient operating characteristics. Drive pressure kills motors and vane position creates drive pressure.

A clogged or iced up air filter causes a restriction on the amount of air the turbo can suck in to make a desired boost number. Guess what happens when it don't get enough air to make the desired boost number? ECM calls for more vane position to get the boost up! Fail!

A bad MAF or MAP reading makes the truck think it's not getting enough air, guess what? ECM calls for more vane position to get the boost up. Fail

Fuel pressure bleeds off because your fuel pressure relief valve is weak(known problem). Truck has low power and don't make proper boost, so guess what? ECM calls for more vane position to get the boost up. Fail

You have a leaking intercooler or a torn intercooler boot that bleeds off your boost to atmosphere, so guess what? ECM calls for more vane position to get more boost. Fail

Your EGR is struck open and bleeding of boost pressure into the exhaust or sucking in hot exhaust air. Boost readings seem low so guess what? ECM calls for more vane position to get more boost. Fail

Your vane position sensor reads lower than the actual vane postion. The truck thinks it's at 70% vane position but it is actualy at 90%. The ECM don't know there is a problem so you have more boost and drive pressure than you need. Fail

You can see that this is not a perfect system. Your LLY truck doesn't always code or protect itself from self destruction. Your LLY was not designed perfect from the get go, so do yourself a favor and properly maintain it. If you have the means to go above and beyond the proper maintenance, get some gauges and monitor boost and drive pressure. Find a way to watch the vane position desired and actual values and get used to how it changes your boost and drive pressure readings. Stop driving the truck when you see a problem.

The 04.5 LLY and 05 LLY are known to have weak rail pressure relief valves in them. Watch your rail pressure if you don't have yours shimmed or plugged.

The 04.5 LLY and 05 LLY are known to have an extremely restrictive factory turbo inlet mouthpiece and most owners upgrade this piece. If you do an intake upgrade, don't leave the stock mouthpiece on the turbo.

Clean your engine bay and keep an eye on your intercooler, boots, and clamps. Try to eliminate any boost leaks by removing and cleaning the silicone boots when you check them for cracks or holes. When in doubt, replace them with new boots and clamps.

WATCH YOUR COOLANT TEMP WHILE TOWING! Yes, LLY's overheat. Do whatever you can to prevent this. Pay attention to your coolant temp at all times while towing. It's not your fault your truck overheats, but you are the only one that can stop it from happening. You are the one paying to fix it when it overheats, so try to prevent it. Assume it is going to overheat all the time. Better safe than sorry.

Water pumps are known to fail. A big problem has been the impeller falling off the shaft of the pump. If you have a high mileage truck, replace the water pump with one that has been upgraded to keep this from happening. If you are having your head gaskets fixed and your water pump is old or high mileage, replace it with an upgraded one.

It's easy to point fingers at your EGR, a weak factory gasket, your tuner of choice, weak factory studs, or GM when you have a headgasket problem on your LLY. I think the finger pointing should start with the owner/driver of the truck before it ever gets pointed in any other direction. I'm not saying there are things GM could or should have done better. I'm only stating that we know of a lot of these problems already, and you should be informed enough to prevent them before they happen to your LLY.:drink

I also think its important to keep an open discussion of what is failing and under what circumstances. If you have a failure or an opinion/finding on how you could have prevented a failure, let us know! I think we can all help each other make these last longer. I'm sure the info people have shared over the years has extended the life of these trucks a lot already.
I read this and first thing that came to mind is that would it be at all possible for you to post a mateninance list of thing to look out for, including pictures and tips and all that. I bought a cc/sb lly back in april and never ever sat in it, drove it or anything. I bought it because i got a smoking good deal at $17k with 126K miles on it. My father also has a lb7 so the trucks arent anything new to me. Upgraded exhaust, efi, downpipe, but have the egr blocker plate and stage 2 afe intake to install along with the lbz mouth piece and ppe fuel pressure relieve valve screw thing yet not a clue how to do it. My father is bring my truck down to me in 3 weeks and when it gets here i want to spend a saturday going through it making sure everything is istalled right, no leaks or problems, change filters, instal new parts, oil ect. but im just hesitant on not know exactly what to look for or what to expect. i want this truck to last me the next 4 years and i enjoy doing mateniance and stuff on my vehicles. and advice or suggestions?:help
 
#67 ·
Just had my FICM Harness rub through near the alternator. Shut down four of my injectors and threw the same codes as a loose fuel injector connector. It may look ok from the outside but you have to remove the tape and carefully inspect the wires. The amperage is high enough on this circut to jump through worn wire shielding and tape. I will be re-taping and covering with heater hose.
 
#68 ·
Is this the location that most LLY's are having issues? I have only had mine for about 3 months or so. I will check the area you had problems and see if it is wearing any. Thanks.
 
#70 ·
Wow, glad. I read this thread! Great information!
 
#71 ·
I m considering buying a 2005 LLY, but it is a donor for my Yukon 2500. I was pretty firm on an LBZ, but some good options opened up and I m considering this route. Do the LLYs lack power in comparison to the LBZs? I m a little nervous after reading, but head gaskets aren't scary as I do all my own work regardless. My main goals for this vehicle are fuel economy and dependability.
 
#72 ·
an lly can be very dependable, as long as you keep proper maintenence, if you have a problem like a boost leak or low fuel rail preassure, fix it! dont wait to fix it
 
#73 ·
X2^^
 
#76 ·
They sell the injector connector at Rock Auto for around $20 each, try that first.
 
#77 ·
Great thread guys! I'm one of those that refuses to take a vehicle to a shop to do something I should/could do myself...really picking up alot of great info! Thanks!
 
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