8.1L Chevy engine

[larryjb2]

Originally Posted by harleyjt

I've read several horror stories here about 8.1L engines failing. I realize that its just a few, but I'm really wondering how many high mileage 8.1s are out there that haven't experienced any problems. I currently have only about 19k on mine, and it performs well except in heavy rain when it appears some water is getting to the MAF sensor. So far all I've done other than normal maintenance is I replaced the plug wires just because of the age of the wires.
So, lets hear from some of you with some miles on your rigs.
jt

80,000 miles on mine.

[lrsses]

Have 2004 Sea Breeze 95312 problems for the 8.1 none has new wires and plugs. New hoses installed and knock sensors new MAF no problems to power anytime

[harleyjt]

Originally Posted by Forkyfork

What should the fuel trim be at?

Not sure how the ScanGauge2 displays fuel trim. We used to call it the adaptive fuel factor and it was displayed in %. You want to see low numbers. We always taught techs that it should be single digits. Once you got over plus or minus 10% there may be something going on such as low or high fuel pressure, an exhaust leak, a leaky EGR valve, dirty injectors, or any number of other endless possibilities.

Next time I go over to the coach, I need to play with the SG2 and look at the documentation to see what it actually displays.
jt

[CJ7365]

Originally Posted by harleyjt

Not sure how the ScanGauge2 displays fuel trim. We used to call it the adaptive fuel factor and it was displayed in %. You want to see low numbers. We always taught techs that it should be single digits. Once you got over plus or minus 10% there may be something going on such as low or high fuel pressure, an exhaust leak, a leaky EGR valve, dirty injectors, or any number of other endless possibilities.

Next time I go over to the coach, I need to play with the SG2 and look at the documentation to see what it actually displays.
jt

It displays Percentage

https://www.autoserviceprofessional....for-you?Page=1

[harleyjt]

Originally Posted by CJ7365

It displays Percentage

https://www.autoserviceprofessional....for-you?Page=1

Thanks! I'll have to add that to my display. I currently display, engine coolant temp, trans temp, charging voltage, and intake air temp. I may change the charging voltage to fuel trim. Of course fuel trim doesn't have to be constantly monitored like ECT or voltage. I could just cycle through and check it occasionally.
jt

[garyspang]

Mine has 172,000 miles and runs like new. Installed ceramic booted spark plug wires (ACCEL 9065C). Had to retorque intake manifold with 8 new bolts to reseal the relaxed elastomeric gasket (only on 2002 engine). Have separate post on it. Oil mist went past gasket and fouled plugs and also caused backfiring into intake manifold.
Installed an Amsoil submicron by-pass filter and pre-oiler when engine was new.
Mobil 1 10W30 every 8-10,000 miles. Techron in gas tank once in a while. Toured Alaska with no issues.
Cruise at 60-62 mph. GM 3 speed transmission with full synthetic fluid still runs great. Run generator to cool house with roof AC. Use dash air only as supplement when needed.
Just bought a well maintained 2004 Sightseer 35N with 43,000 miles on a W22 chassis. More room and 5 speed transmission. Will miss the wide-track independent front suspension with retrofitted KONI shocks of the P32.
Finally a real wardrobe and a shower I can move in.

[terry735001]

well here is my story . i had a knocking sound show up and no shop around me that can take a 40 foot RV

spent around 500$ for all new sensor and did not fix it
pulled the motor out my self and send it in for a full reman and with all new parts to go back into the motor it only cost me 1250$ and i know have all most a 100% new motor


i can tell you i am not upset at all as some fuel pumps around here can cost more then that or a turbo go bad



the cost to work on this motor is really low

[Forkyfork]

Originally Posted by terry735001

well here is my story . i had a knocking sound show up and no shop around me that can take a 40 foot RV

spent around 500$ for all new sensor and did not fix it
pulled the motor out my self and send it in for a full reman and with all new parts to go back into the motor it only cost me 1250$ and i know have all most a 100% new motor


i can tell you i am not upset at all as some fuel pumps around here can cost more then that or a turbo go bad



the cost to work on this motor is really low

Who did the rebuild? Was it an upper and lower rebuild? Did they give you an idea of what the knock was?

[VanDiemen23]

145,000 in a K2500HD with the allison. Mobil 1 5W30 every 5K. Replacing the bolts gave you bolts with sealant on the threads. thought was that the oil was eating sucked through the threads during times of high manifold vacuum.

I can tell you that probably 30% of the time between changes my "low oil level" message pops up and I have to add two quarts. It almost always happens at 2500 miles from the last change. There is a minor correlation with load. there is a minor correlation with low temps in the morning. Other than that you might as well use a Ouija board to predict when it is going to happen next.

Changed plugs at 90 thou, crank position sensor crapped out at about 35K. Other than that, no engine issues or maintenance required.

[Forkyfork]

Originally Posted by VanDiemen23

145,000 in a K2500HD with the allison. Mobil 1 5W30 every 5K. Replacing the bolts gave you bolts with sealant on the threads. thought was that the oil was eating sucked through the threads during times of high manifold vacuum.

I can tell you that probably 30% of the time between changes my "low oil level" message pops up and I have to add two quarts. It almost always happens at 2500 miles from the last change. There is a minor correlation with load. there is a minor correlation with low temps in the morning. Other than that you might as well use a Ouija board to predict when it is going to happen next.

Changed plugs at 90 thou, crank position sensor crapped out at about 35K. Other than that, no engine issues or maintenance required.

It’s expected on these engines to use a Qt every other tank. I personally would top off more frequent. They don’t hold a lot in the first place. 2 Qts low is just under 1/3 the total volume. Adding only when it says low oil is risky. There is a reason they call them idiot lights.

[akpd]

Gee I have put over 2000 miles on since I purchased my 2004 Monaco 8.1 and the oil level is still on the full mark.

[Arch Hoagland]

Originally Posted by akpd

Gee I have put over 2000 miles on since I purchased my 2004 Monaco 8.1 and the oil level is still on the full mark.

Interesting.

[Forkyfork]

Its a thing and addressed in the service manual. If it doesn't use oil cool, if it does no biggie. Just keep an eye on it because it might not and then depending on load could surprise you buy burning a Qt on one tank.

From the manual Measurement of Oil consumption: Engines require a period of time to BREAK IN so that moving parts are properly seated. erefore, oil economy should not be tested until the vehicle
has accumulated at least 8000 km (5000 mi) and the oil has been changed for the rst time. Manufacturers of piston rings state that piston rings in today’s engines, control oil very e ectively. For example, if 1/10th of a drop of oil would be consumed per explosion when driving at 60 MPH, an eight-cylinder vehicle would use about 90 quarts of oil on a 600-mile trip. e actual average consumption of oil per explosion in today’s engines is from 1/1,000th to 2/1,000th of a drop.
Oil consumption is often more related to duty cycle than mileage. A good GM guideline is one quart per 100 gallons of fuel used.

[VanDiemen23]

Originally Posted by Forkyfork

It’s expected on these engines to use a Qt every other tank. I personally would top off more frequent. They don’t hold a lot in the first place. 2 Qts low is just under 1/3 the total volume. Adding only when it says low oil is risky. There is a reason they call them idiot lights.

As long as you have 10 psi for every 1000 RPM you are okay. Note: I've had this thing for 18 years and been through all the fixes - when they first came to light.

One interesting thing was taking the vehicle in back in 2002 with a complaint on oil usage, so the service department runs a "test" You have to pay to have them change the oil and then bring it in periodically to have them verify the oil level. First thing I did was take it home and pull the dipstick. They had overfilled it by a whole quart, I suppose to make the test come out in GMs favor.

By the way - the quote you have above is completely incorrect. Today's rings don't actually do much to prevent oil consumption. Manufacturers have been reducing oil control ring tension for a couple of decades chasing more fuel economy. As a result, the rings don't seal as well and with the lower vis oils, more gets by. That's why most of the ZDDP has been removed from today's oils and why the fine print details of the service ratings keep changing. With warranties of 100K mi on emissions equipment, the ZDDP in the blow by was poisoning the converters while in warranty, so the manufacturers lobbied the oil suppliers to remove it and create new service grades.

1 qt per 100 gal (2500-3000mi) would be high for anything other than a big block, even running dino oil with all the detergent in it. The bigger the bore, the bigger the problem.