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Discussion Starter · #1 · (Edited)
Not really sure if this is urgent but...\P
Put on an S&B drop in filter about a week ago and today I started getting a nasty knocking sound and pulled a p0101 code for the Mass Air Circuit?

Any suggestions? Do I need to pull the S&B and clean the MAS? Is cleaning it possible without damage?

Cleaned the MAF sensor no change. Knocking sound seems to be coming from the Vacuum Pump...Any ideas out there?
 

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I have a 2003 4X4 GMC 2500HD Duramax Crew Cab, I was driving and all of a sudden I started hearing this new ticking like my fan was hitting the shroud or something. I looked and it wasnt the fan but the noise was coming from the vacuum pump I drove it and after about 25 more miles the eng light came on. Got the codes of P0101(MAF) and P0404(EGR).
took it to the dealer and told them, got call back and he said it was the vacuum pump, and he tried saying I need to replace my MAF also, I told him just replace the pumpm and I will clear the codes and it should be good. So now I'm waiting for the pump to come in so they can install it. I hope they dont try and do something to my MAF in the mean time, while it sits at the dealer. I will let you know if this works when I get my truck back, I'm pretty sure this is the problem, since you just described the same thing.
 

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Discussion Starter · #3 ·
When this happened to me, I went to Kragen and bought a pump for about $125. I think there was a core charge in there so it was probably a little cheaper than that.

It probably took 30-45 minutes to take the old one out and put the new one in plus the time at the machinists to get the flywheel changed. I cleaned the MAF also but I don't think you'll need to change it out.

It's annoying but not urgent even though it sounds like it's urgent.

I haven't had any issues with it since.
 

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jaybird and RAIN,

Thank you very much for posting this issue on this forum. Your stories helped me fix this myself and stay away from the dealerships.

While I'm at it, I'd also like to thank all the guys who post on all of the Duramax forums as well. I've been lurking around since 2003 when I first got the truck and threads from wherever have helped me do a couple things that cost very little but made big differences. First... OverDrive Lockout button install. Can't remember exactly where I got the very detailed instructions, but I sort of remember it being Kenedys. The other was the mods to allow the high beams, low beams, and fog lights to all be on at once. Could have done another mod to keep the daytime runners on at night too, but I think that's pushing it a little too far and asking a little too brightly to have a conversation with law enforcement. That came from GM-diesel or DieselPlace I think.

Anyway, here is my overdue contribution to the Duramax knowledge base. It may be elementary to some, but I made a misstep before reading this thread and it cost me the price of a new tensioner pulley to replace a perfectly good one. After reading this thread I was able to pinpoint the issue from the given clues and make the fix correctly.

This is my first post to any forum and I most likely won't be checking in so I'll try to be as thrurough as possible.

My California LB7 just started rattling at idle one day and I didn't think much about it. After a couple days and 100 or so miles it started to be quiet at idle and sound around 1200rpm and increase frequency with rpms. The more I thought about it, the more I thought it sounded like one of those really expensive and BAD sounds. All of a sudden I thought the SuperChip turned up all the time might not have been a good idea for the last six years and the last 100k mi of the 150k+ it has.

Pulling up to a retired GM mechanic buddy's house with the truck rattling, he pulled out the stethescope. He and I agreed that the loudest rattling was coming from the bolt that holds on the belt tensioner. Belt tensioner replaced and dry wobbling idler pulleys while I was at it... same rattle still there.

Ironically the alternator went three days later so I replaced that away from home under a freeway overpass in a rain storm. OK, now I'm at least narrowing things down outside the engine.

Talking to another mechanic buddy who listened to the rattle scared the ..it out of me when he said it could be a connecting rod. He had me lined up to have one of his diesel mechanic buddies look at it when I finally found this thread and read it 5 times.

With this thread in mind and another buddy (The Swedish Mechanic) listening with me, he said "hey, just pull the belt and you'll know if it's inside or outside the engine." Well cool. Belt off sound gone. Now, the only thing left on the passenger side front of the engine is the vacuum pump. And hey, I just read this thread so it seemed clear to me now what it was.

Off to Kragen to order the new vacuum pump. $109 for the new Cardone with a 50 cent core charge vs $129 for the remanufactured Cardone with a $32 core charge. Don't ask me their logic, but I think I passed the IQ test by getting the new one.

Old vacuum pump out... The inlet tube simply broke off where it mounts to the pump. The weakest link theory proves true here. When you look at the pump, the cheesiest part is the tube. When I was figuring out how to get the big chunker of pump and pulley set up out of such a tight space, I was peaking through the plastic inner fender well and could see the little tube hanging from the vacuum hose. That's what must have been rattling I guess.

So, old one with pulley in hand and new one without pulley... Off to Kragen again where they have the pulley puller to pull the pulley off the old and the nut/bolt/washer setup to press the pulley onto the new one - thanks guys at Kragen on Cherokee Lane in Lodi, CA. Oh, if you can get a ride, do. Driving without the vac pump means driving without the belt thus no power brakes or power steering - a little nerve racking in an 8000lb truck on 35's. New vac pump in and MAF code cleared with the SuperChip DTC clearing feature - sweet. 25 miles and 8 or so starts later, no engine light, no code, no rattling, and no cleaning or replacing of the MAF sensor.

Thanks again to all. I've been lurking for years.

I know this is a long post, but I probably won't be checking in to answer questions so I wanted to spew it all out.

The next post will be for the P0540 code that I've been getting for 2 years. No worries until now, but since we are now smogging diesels here in California, I guess I better get around to figuring out if it is the Intake Air Heater or the Intake Air Heater Relay, or both. It's a little different here in California so I'll put up what I know when I know.

I hope this helps at least one late night internet searcher like myself.

Peace,

Doug
 
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