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Old 12-26-2016, 05:00 PM   #1
V
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Sediment buildup in water jacket???

I've been working on a 1998 Cadillac STS.
It has the infamous front wheel drive 4.6L 32Valve Northstar V8.

The car is in decent shape and has just over 95k miles on it. I bought it with the main issue that it overheats. Having had a Northstar in the past and knowing a lot of the issues with them, basically the headgaskets will all fail eventually, I decided to fix this one with a set of aftermarket head studs.

The repair job is a pain to put it nicely. But I wanted to do it anyway.
I dropped the front cradle and the motor and trans last week or so. Then I started some of the tear down to actually get the heads off. That's where I dealt with the y pipe issue I had talked about in the other thread in the fabrication forum.

Today I pulled both heads. The new head studs arrived Friday so I was hoping to get the block drilled tapped and studded tonight. Once I had both heads off, I noticed something odd in the water jacket of the number 2 cylinder. It looked almost like granular sand had accumulated around the cylinder(3/4 of the way around and about 1/2 way up the water jacket at the outer side). Number 4 cylinder had some but much less build up, number 6 and 8 water jackets were 100% clear down to the bottom. All the water jackets are interconnected and the flow looks like it enters the bloack by #8 cylinder. I then looked at the other side of the engine and noticed buildup as well around #1 cylinder. It wasn't as much as by #7 but still enough.

The debris has the appearance of sand(different colors and granular), but with a softer rubbery texture, not hard and grainy. My cell phone died so I couldn't get a picture of it tonight. I looked at the opening for the water pump/thermostat and i saw a trace inside that area of a few grains of whatever that stuff is.

I'm trying to figure out what the sediment is. I have two thoughts. One is that it is the left over residue of some type of leak stop product. It ran through the coolant system and built up where the flow was decreased. If that is the case, then it is though the whole coolant system, radiator, heater core etc, and makes fixing the car now financially pointless. If it was leak stop it could have clogged things up so bad that could be why the motor was overheating. They could have used the leak stop the try to battle a headgasket issue. My other thought is that it is pieces of the head gasket that broke away and built up. The gaskets looked ok though and the only issue was that the stock head bolts were all sorts of tightness. Some were a pain to break free others practically had the washers lose before i even touched them.
Either case, I think the car now needs too much additional work and I should cut my losses now. I'm just still curious as to what it could be from.

Last edited by V; 12-26-2016 at 05:03 PM.
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