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It’s been a busy past couple of weeks! Victoria visited me for a week, then the same day she left my sister and her friend arrived for another five days. Lots of running around and heavy eating. I’m glad to have had visitors, it’s a welcome change. Weather has finally settled down and it’s sunny out.

Between all of them we went to Fredericksberg, Lady Bird Johnson Wildflower Center, Congress ave bats, the capitol, UT tower, and many eating establishments in between.

I finally took my truck to the mechanic again to work on my mystery coolant leak and my usual basket of other problems. It’s to the point I’m putting in a half gallon every couple of weeks. I would think it’d be fairly obvious where it’s at, but no luck today. Really, I’m not any better off than I was. I need to have them fill it full of dye, put it in neutral, put a brick on the gas pedal and run it at 3 K RPM for a couple of hours.

He did point me to a TSB on that engine that describes a casting defect on cylinder heads built by Castech which is known to cause coolant leaks with no evidence. It claims in the oil drain holes a porous crack can develop, letting coolant weep out. To verify, it involves getting inside the valve covers. Once inside it should be pretty obvious from what I can tell. The telltale manufacturer’s name should be on the top, and there should be clean/shiny spots around the crack while the rest of the head is oil-stained. There could also be coalesced oil+coolant “butterscotch” everywhere.

There’s a few obvious problems with this. It’ll take a couple of hours of labor just to get into it to see if it’s even made by Castech. It may not even be the cylinder head, it could be a head gasket or intake manifold gasket. Any of these could be weeping at high temperatures and it burns off without a trace. Once in there, if it is identified to be a leaking head, that means new heads. Worse, the vented coolant could’ve corroded my rods and lifters.

From a previous estimate, I know replacing a head gasket would be 10 hours of labor+parts at $1100. Fine. New GM Goodwrench cylinder heads are $344 each, so that’s at least $1100+$688+gaskets+oil+more labor. If it involves rods and lifters, it gets ridicuously expensive. It takes 16 lifters, OEM are $11 each, AC Delco are $44 each. By my estimate, the worst case is around $4k in parts and labor.

The upside to the visit, he’s very convinced my lingering P0135 code is caused by a flaky replacement Bosch O2 sensor I put in. As soon as I walked into the parts store and said I wanted a new sensor, the guy said “you must’ve just failed an inspection.” I mentioned I was replacing a Bosch, and both of them audibly tsk’ed. So, one expensive new O2 sensor later, we’ll see what happens.

Two other interesting notes from today. They inspected my brakes, my pads were at 60% wear — and they’re original parts, 160k miles on them. I clearly don’t stop much. The other, I discovered GM actually makes coolant seal tablets. More interesting, they’re made from ginger root and walnut shells. There’s a couple of tech notes where they recommend this, they’re designed for DEXCOOL and aluminium engines. The only problem I can find is that they also recommend draining the coolant every 24k miles to help maintain the pH balance.

I’m certainly not a fan of cutting corners, but I’m very tempted to try the tabs for now. I’m still angry about my financing deal on this truck. I don’t want to give up on it yet by trading it in. The rest of the truck is in great condition. I may have to get my Maserati coupe sooner than I expected.

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