Sludge In Oil From What?

[govener71]

Hey guys,

 

I have a 99 GMC Sierra 1500, 5.3l, with 186,000 miles on it and recently I have been losing a little coolant somewhere. I have zero exterior leaks and assume it must then be going internal. So I brought it to the local dealership and had them do a pressure check and a block check. After two hours with the pressure checker they said it had no loss of pressure and no signs of a head leak with the block check. Also the last two times I have changed my oil I have been finding some "sludge" in the oil. All it is is chunky and sticky black stuff that comes out along with the oil. I run penzoil platnum and have zero loss of oil. I am just very confused about where the coolant could be going.

 

My primary concern is that 2 months ago I had the lower intake manifold replaced after getting banks 1 and 2 lean ses light came on and I had it fixed at the dealership. Its losing enough that I go from the cold mark to Low Coolant in about 1.5-2 months.

 

What do you think I should check/do next? Asside from selling .

[SouthCo]

If coolant leak started around time of intake manifold, maybe look there 1st? Did same dealer do the intake work that is checking for low coolant? What did they say could be cause?

 

As far as sludge, should have nothing to do with coolant. I have a '03 Tahoe with 182,000 miles that I use Penzoil Platnium in too. It uses no oil but has no sludge either. Since new it has always had regular oil changes. Sludge is usually associated with not changing oil often enough. how long have you owned the truck? Again oil sludge and coolant loss is not related most likely.

[dlstewart01]

The intake manifold on a 5.3 is dry. there is no coolant going through it.

[SouthCo]

He said lower intake manifold, I thought there was only an intake manifold (not lower and upper)? But coolant loss ain't causing his sludge issue.

[jro909]

coolant in the oil sump can cause sludge

[gapost]

coolant in the oil sump can cause sludge

 

 

Yes, and especially the Dex-cool will cause black sludge. The 5.3's around 03-05 (?) had some issues with defective Castech heads. They would develop small cracks around the valve holes and leak coolant into the oil. I had them and mysteriously lost coolant and found it when I went to change the oil and no oil came out the drain hole because of the sludge in the bottom of the oil pan. I don't think the Castech problem was that early, but it sure seems like some coolant leak. You could pull your lifter covers and see if there is "chocolate pudding" anywhere in there.

[govener71]

Thanks guys for the input. I have had all of the work done at the same dealership. They have done what they said was the, lower intake manifold gasket, and the pressure and block test. I have had truck for about 20,000 miles and on the car fax it had oil changes every 5 thousand miles and I have run PP and changed the oil every 4 thousand miles. I am very meticulous when it comes to the engine especially with this many miles on it.

 

I have not had enough sludge yet to cause the oil to not come out but I can find it sitting on top of the oil catch pan I use when I change the oil. When I brought the truck in for the pressure check and block check I asked them to check the intake manifold bolts again because of their previous work. When they called me back they said everything check out but.......it may not be bad enough yet that they can find the leak and we may need to wait longer inorder to find it. I hate that solution because by the time it gets bad enough I dont want , the possible, oil in the coolant to ruin any bearings.

 

Also thank you for the confirmation that oil can cause "sludge" in the bottom on my oil pan. I had explained this to a mechanic friend and he looked at me like I was an idiot.

[SouthCo]

I thought coolant in the oil just made it milky brown? Oh well. Goood luck with it. Hopefully you don't end up dropping more into it than it's worth.

[gapost]

I thought coolant in the oil just made it milky brown? Oh well. Goood luck with it. Hopefully you don't end up dropping more into it than it's worth.

 

 

I've read that unlike the green coolant, the Dexcool forms a black sludge versus the more milky chocolate. However, in my case, the sludge in the oil pan (about an 1" thick) was black, but the real indicator was the "chocolate pudding" type deposits under my rocker covers and on top of the heads. And unlike the older coolant leaks, there was NO indication of coolant on the oil dipstick

 

 

Really, if you are loosing coolant, and none is leaking out, it has to be some internal leak and should be checked/fixed. At least pull the rocker covers.

[txab]

You can test your oil for traces of coolant

[LAGA]

You had work done 2 months ago with no external leaks and now you are losing coolant. Sounds like you had air in the cooling system from an improper refill and now it is purging out and lowering the coolant level. Refill to proper level and keep an eye on it for an another couple of months. As far as the sludge, if you are finding chunks when you drain, remove your oil filter and cut it open to make sure it is not being clogged up. A clogged filter can cause big problems even with a by pass valve in the filter. If there is visible crap on the filter, start doing short oil change intervals with conventional oil and see what happens. If it runs clean, maybe a piece of sludge has just broken off from somewhere in the engine and is getting filtered out. If it continues, maybe it is time for a new truck.

[govener71]

When a chunk of sludge breaks free from within the engine can it take several oil changes for all the sludge to be completley filtered out? I did notice that this time when chainging the oil there was not as much as last time and the oil filter did feel fairly heavy. But when inspecting the inside of it I could still see the shiney metal grate on the sides and a little on the bottom. But the bottom of the filter had sludge in it. I mean Im glad its going there instead of back in the engine but preferriable no sludge is best. Maybe the PP is begining to clean some stuff out.

 

Also I know I have see it on here before but I cant find it back. Could someone post the proper refill for the cooling system, or how to purge an air from the system.

[Black02Silverado]

I'm with Darral, have the oil analyzed. It will tell you what is going on. If the engine was taken care of like stated it just doesn't start to sludge up. My bet is coolant leak.

[dlstewart01]

Check your PCV system. A clogged PCV valve can cause sludge.

[govener71]

Sounds good I just found an oil testing place on line and sent in for the kit. All the help and ideas are really appreciated guys. I have tryed using another website you had to pay for, for car advise before its junk compared to this. If youve got any more ideas keep them coming.