Coolant loss and sludge in oil

[J Mac]

I'm afraid I know the answer to this but want some more opinions on the issue please.

Started about a year ago after pulling our camper on a 4 hour trip. Yukon ran great, no issues. Next morning I start it up and there is a horrible tapping sound...ended up being lifters. Once engine warmed up, noise stopped and after cold start the next day, noise was there but no where near as loud. Got better throughout the week. Pull camper home with no issues, next day crazy lifter noise again. I did notice that oil pressure was lower than normal when lifters were noisy. Changed the oil and had some sludge come out...no metal shavings. Added Marvel Mystery Oil to help clean the sludge. This same scenario played out after any interstate trip over an hour. Kept changing oil and adding MMO. I use Mobil 1 and Wix filter. Thought issue was o-ring on oil pickup tube. Pulled pan...sludge was CRAZY and pickup tube was almost totally clogged. O-ring was fine. Put in new pickup tube and o-ring. Engine was much quieter after cleaning out sludge. All was good until this past weekend and a good interstate trip. Next morning...lifter noise. Oil pressure is great now...even when lifters are tapping. Another issue I've been having is disappearing coolant. No leaks anywhere I can find so I'm guessing at this point head gaskets. I read that good ol' Dex Cool mixed with oil creates sludge and not the chocolate milk looking oil like the green coolant does. My thought is the sludge in the pan and pickup is stopping oil from getting to top of engine until it warms up. So before I dive into head gasket replacements...any other ideas what I could have going on? Any input is greatly appreciated!

 

[iamdub]

I'm afraid I know the answer to this but want some more opinions on the issue please.

Started about a year ago after pulling our camper on a 4 hour trip. Yukon ran great, no issues. Next morning I start it up and there is a horrible tapping sound...ended up being lifters. Once engine warmed up, noise stopped and after cold start the next day, noise was there but no where near as loud. Got better throughout the week. Pull camper home with no issues, next day crazy lifter noise again. I did notice that oil pressure was lower than normal when lifters were noisy. Changed the oil and had some sludge come out...no metal shavings. Added Marvel Mystery Oil to help clean the sludge. This same scenario played out after any interstate trip over an hour. Kept changing oil and adding MMO. I use Mobil 1 and Wix filter. Thought issue was o-ring on oil pickup tube. Pulled pan...sludge was CRAZY and pickup tube was almost totally clogged. O-ring was fine. Put in new pickup tube and o-ring. Engine was much quieter after cleaning out sludge. All was good until this past weekend and a good interstate trip. Next morning...lifter noise. Oil pressure is great now...even when lifters are tapping. Another issue I've been having is disappearing coolant. No leaks anywhere I can find so I'm guessing at this point head gaskets. I read that good ol' Dex Cool mixed with oil creates sludge and not the chocolate milk looking oil like the green coolant does. My thought is the sludge in the pan and pickup is stopping oil from getting to top of engine until it warms up. So before I dive into head gasket replacements...any other ideas what I could have going on? Any input is greatly appreciated!

Castech head failure? My brother's 181K-mile '05 Sierra gradually lost oil pressure and I found the inside to be really sludged. It had Castech 706 heads and the driver side had the puddled coolant in the telltale locations. I pulled the motor and found the pickup tube completely clogged. Scrubbed the entire inside of the engine by hand and replaced the heads with some low-mile 317s from a 2010, GM lifters, HV Melling oil pump, GM timing set, push rods, rocker arms and all gaskets/seals. It's been chugging along great ever since with great oil pressure.

If the coolant that mixes with the oil is small enough amount, the liquid part of the coolant will steam off so just the "hard" chemicals remain and that's what makes the sludge. You'll never see a milkshake in the oil and you'd be lucky to notice any steam from the exhaust pipe. Pop off the valve covers and look for coolant.

 

[Larryjb]

It's not only the Castech heads that can fail. Mine weren't Castech and it failed.

Get a coolant pressure tester. Then pull the valve covers and look for any "clean" spots in the head. Wipe dry and pressurize the cooling system and look for any weeping. This confirmed my cracked head. Take a look, especially at my pictures in Post #31.

https://www.tahoeyukonforum.com/threads/latest-oil-change-oil-filters.99646/page-4

 

[J Mac]

I talked to my mechanic about the issue and he's not 100% sure it's the head gaskets. That is based solely on the fact he believes the heads have been off the engine before based on how the head gaskets look from the outside and grease pencil markings on the engine. Yukon had 186k miles on it when I got it and I know nothing on the history of it. I ordered an oil analysis kit and will do a pressure test on the cooling system this weekend. Today was day 3 after the interstate drive and no lifter noise at all when starting this morning. In the past, once the noise clears up it won't happen again until the next cold start after a long interstate drive. I'll do an oil change for the analysis and see how much sludge comes out. The oil pan was completely cleaned less than 1k miles so hopefully none!

I'm hoping to get this straightened out before pulling camper 4 hours to Martinsville in May for the race! That's when this all started...Martinsville spring race last year but I wasn't pulling the camper. Just that 4 hour drive...next morning 'tap tap tap tap....'. I initially thought I lost a header gasket it was so loud. After changing those 2 times I realized that wasn't the issue and took it to my mechanic. He said lifters as soon as he heard it and after a few oil changes with MMO and all the sludge...here we are.