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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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#4 ·
Id start with intercoolers, more people than not would be surprised how many factory ic leak at the seams, fixed vane charger, thats not gonna hurt much, lbzs and up have better/different IC's, llys will make up for the lost boost, causing high drive pressure, high heat and so on, even high engine heat:help
 
#5 ·
WHOOAAHH! Excellent read and info apppreciated!
 
#6 ·
Bob if i may add, the wiring harness under the seat chaffing against the railing when the seat slides has been a problem on llys that i have seen, my own and at work. While it may not be JUST LLY but if you have the rpo code in your glovebox of AN3, i would check the harness under the seat. It will make crazy electrical things happen
 
#7 ·
Guess I need to read this now lol.....and sticky.

Good write up Bob.
 
#8 ·
Great post Bob, very informative...........

Don't leave out the injector harness and the FICM harness chaffing issue................
 
#15 ·
I am haveing a huge issue with my lly but ill never trade it for any othwr truck
 
#16 ·
New owner of 05

Bob, I just purchased a 05 with 74000 on it. It has a banks kit with the 6 gun. I love the truck and the power it has but i get a check engine light with the following codes.
P0101-Mass air flow sensor performance
P0299-Turbocharger Engine Underboost
P0700-Trans control module requested MIL illumination.
I was kind of righting this off to aftermarket mod's but after reading your write-up of the 05 I'm a little concerned. I have a 2 year warrantee from the stealer on it so i want to make sure it is right. The power seems great but then I was driving a mid 90's ford powersmoke, so anything is a improvement. Please help or if someone else has an idea please chime in.
 
#21 · (Edited)
Awesome writeup and great info as usual Bob!

I have 220K miles on mine and it pulls like a champ now so LLY's are definitely a very solid motor once you address a few things.

Bob, I just purchased a 05 with 74000 on it. It has a banks kit with the 6 gun. I love the truck and the power it has but i get a check engine light with the following codes.
P0101-Mass air flow sensor performance
P0299-Turbocharger Engine Underboost
P0700-Trans control module requested MIL illumination.
I was kind of righting this off to aftermarket mod's but after reading your write-up of the 05 I'm a little concerned. I have a 2 year warrantee from the stealer on it so i want to make sure it is right. The power seems great but then I was driving a mid 90's ford powersmoke, so anything is a improvement. Please help or if someone else has an idea please chime in.
The P0700 likely means that someone limped the tranny on that truck already.

The P0101 and P0299 tie directly into Bob's sticky above.......I suggest you read it carefully.
 
#17 ·
The one biggest issues I found on my LLY was a wire harness rub through that caused all kinds of odd codes to pop up. This issue could affect more than just the LLY but I'm not positive. The location of the rub through was on the lowest of the two main harness connections located on the front left side of the engine just above the valve cover. If you unbolt the quick connect couplers and look at the lowest coupler where it sits on the support bracket you will find that the harness might be rubbing against the support bracket it's self. It doesn't look like much but it can truly make life hell trying to figure out the problem. I would suggest that everyone with an LLY check for this issue, it could prevent the headache I went through trying to figure it out.


Sent from my Autoguide iPhone app
 
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#19 ·
Great write up! Thanks Bob. This is why I spend way to much time on here, just to get good info like this.

:drink
 
#24 ·
BOB you are the MAN! My buddy is a GM mechanic that sole purpose is to work on D-maxs his stealership basically knows less and less about the evolution of problems in our trucks. This is why he and I pay attention when the Vets on this site post these things. So form myself and everyone that you've helped THANK YOU!
 
#26 ·
Is there any actual maintenance on the turbo itself? Besides keeping the air filter clean and the intake track unobstructed, is there something else to be done?
 
#27 ·
Previously owned by an older fella who did sales all over the province, 394,000kms on my 04.5 LLY and still no issues other than the 2 h20 pumps in 5 yrs, BUT also to be 100% honest, absolutely nothing else has been needed for this unit at all. All hwy miles and only just put a single mod atm on it which is a programmer. AND of course plenty more to come.

ps: awesome post and again GREAT site!
 
#28 ·
I've overheated mine so many times I cant count on my fingers and toes, what kills them is big tunes and lead feet. Great write up BTW.
 
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#30 ·
Bob,

Thanks for the good information. I have a few questions for my 2005 C4500 dump truck, everything on the engine is stock so far.

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.

What kind of gauges and where do i get them? How do I monitor the vane position?

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.

I already had to have my FPRV replaced about 5K miles ago. How do I watch the rail pressure?

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.

Is this true for the 2005 Chevrolet C4500 MD trucks also, or just the 2500s? If so, where do i get the new turbo MP?

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.

Is there a post somewhere on how check the intercooler and clean the boots?

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.

Do you recommend another gauge, or just the stock gauge?

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.

I have 57K on my 2005 C4500, what mileage do you recommend replacing the water pump?
 
#31 · (Edited)
Bob,

What kind of gauges and where do i get them? How do I monitor the vane position?

Best investment you can do IMHO to monitor just about any sensor on your truck is to get an Edge Insight CTS. You can see turbo boost, vane position, pedal position and so many more. You can even monitor/display up to 8 parameters at once. Extremely helpful for DIY diagnosis as well.

I already had to have my FPRV replaced about 5K miles ago. How do I watch the rail pressure?

Again Edge CTS will do this. You'll want to set it up to watch both the actual and demand rail pressures. A bottle test will tell you if your FPRV is holding and if not you'll need to shim it.

Is this true for the 2005 Chevrolet C4500 MD trucks also, or just the 2500s? If so, where do i get the new turbo MP?

A C4500 MD is a Kodiak topkick truck which has a different turbo mouthpiece than 3/4 and 1-ton LLY trucks came with (you can tell because the Kodiak mouthpiece has no resonator hookup). In your case you should be fine with that setup IMHO.

This explains the different mouthpieces:
LLY to LBZ Mouth Piece Modification DIY - Dmax Central

Is there a post somewhere on how check the intercooler and clean the boots?

Obviously you'll need to reroute your PCV first or any cleaning will be in vain as more oil is sucked into the intake. The boost tubes and boots can be cleaned by removing them and spraying with brake cleaner. Any oil in the bottom of the intercooler can be soaked up with paper towels with the vehicle on an incline (side-to-side). The EGR should also be blocked or removed at this point as well.

Do you recommend another gauge, or just the stock gauge?

To monitor engine temp it will be ALOT more accurate to view it on the Edge CTS than on the stock gauge......when you see them side-by-side you'll know what I mean.

I have 57K on my 2005 C4500, what mileage do you recommend replacing the water pump?

The water pump is geared so they tend to last quite a long time provided you change the coolant every 5 years (Dexcool is rated for 7 years, but it's cheap insurance to change early IMHO) to keep the bearings/seals in good shape. Beyond that I would just run it until it begins to weep (doesn't usually fail catastrophically unless the impeller comes off). Make sure any replacement has a TIG welded impeller to prevent this in the future.

See above for suggestions.
 
#32 ·
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#33 ·
Great information, Bob!! A question: what does "overheat" mean?? I have been in situations where I was towing my fifth wheel up steep, long grades over 12,000 ft elevation on hot days and I have seen temps of 225*-235* or more on the gauge, even though I gear down when EGTs get over 1250* or ECT goes over 210*. I've never set off the overtemp alarm. Is 225-235 considered "overheating"?
 
#34 ·
I've read about lly's having fuel knocks I have a lly and it has a fuel knock just wondering what it could be from efi maybe causing too high or low rail pressures or maybe timing issues? Just wanting some feed back on what to do.
 
#36 ·
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