Coolant refusing to return to header tank

Update on the cooling project. We had a good, solid week of cold weather and the new system performed flawlessly. Then it got hot. Not mid-summer 108 degrees hot, but still, into the nineties. The car didn't overheat, or even get all that warm, but we did lose coolant from the new header tank, and the overflow bottle started to fill up. Worse, the header tank wouldn't suck up the overflow when it cooled down the way cooling systems in real cars do, so each morning we had to transfer coolant back to the header tank manually with a turkey baster.

This was a little bit of a mystery, because the old cooling system worked perfectly, or not perfectly but at least it didn't give up a lot of coolant. Every couple of weeks we'd check the level at the thermostat housing, and never had to add more than a cup or two of Prestone 50/50, even during the aforementioned 108 degree summer months. But the new system was losing a pint of coolant in a single balmy day. There wasn't any reason for that. We were using the same radiator, the same water pump, the same hoses. The new system wasn't any different from the old.

Original MGB cap replaced by cheap imitation  

Except for the one thing that was different. Radiator caps. The new system used the same three caps, but the old system had only two of them under pressure—the 15 pound cap that came with our new aluminum radiator, and the 22 pound cap that came with our Speedway filler tube. The 10 pound cap from our MGB donor was on the header tank, which at the time was only serving as an overflow tank for the radiator, which never overflowed. So our lowest pressure cap was 15 pounds. Which means that even on the hottest days, pressure never got over 15 psi.

It did get over 10 psi, however. The 10 pound cap on the header tank was obviously overwhelmed by the full pressure of the hot coolant, spilling its guts into the overflow bottle every chance it got. This forced us to replace yet another original M.G. part with a generic 15 pound cap from O'Rielly Auto Parts, but at least the new cap appears to be doing the job. The overflow bottle has remained empty ever since, although we haven't seen a lot of 108 degree days yet. Or any 108 degree days. Or any 90 degree days. But we're hopeful.

  Engine bay still looks good in photos. Sort of.

The Bay Area Maker Faire is upon us, and we still have much to do to get ready. Okay not really. But we do want to get the car cleaned up, in particular the engine bay. The car draws a lot more attention with the bonnet off, but exposing the engine is embarrassing. We've been okay with how it looks in photographs, but real life is different. We know the mess around the pedal box can't be cleaned up without taking it all apart, and removing all of the oil and grease from the engine and frame could be a rust hazard. Still, there's a few things we can do.

We're also hoping to have a new exhibit this year, which should help to draw attention away from the Locost. At last year's event, about a thousand kids climbed all over the car, tearing up the carpets, scuffing the upholstery, and trying to break every switch, lever, and control in the cockpit. Eventually we had to put up signs and yellow crime scene tape to keep people out, which was disappointing. The Maker Faire is as much for the kids as anyone. We would've liked to have something the kids could play with but not break. As easily.

Junior Locost makes cat look huge  

So what we came up with was a kid-sized Locost, about half the size of a regular Locost. Naturally we didn't come anywhere close to building the thing, but we did put together a wooden mock-up, just as we did ten years ago for our full-scale Locost. The junior frame is virtually identical to a book frame, except for its size, and the fact that it only seats one fairly short person. We still need to add a few pieces to it, get the steering working, and get it painted, but we think it'll make a fine exhibit next to our Locost. Although we will have to keep the kids away from it.

It took us only two years to figure this out, but we learned something recently about our Locost's excessive oil usage. When we drive to work, we hardly use any oil at all. It's a 25-mile round trip, and even after a week of commuting we're barely down half a quart. That's unusual. Take the car on the freeway and we'll go through a quart of oil in less than 50 miles. So on the one hand it appears our tired old M.G. engine is not quite as worn out as we thought, and on the other hand buzzing along the Interstate at 4000+ RPMs seems to burn a lot of oil.

To test this out, we took a drive last Saturday along California's Garden Highway, a scenic route that follows the meandering curves of the Sacramento river for about 50 miles. We started out with a crankcase full of oil, and drove a total of 110 miles, never exceeding 50 mph, at least not on purpose. When we got back, the oil was only a quarter inch down from full, a little more than a cup low. Incredible. We're not sure why we never noticed this before, and we certainly can't imagine how the information could possibly be of any use to us now, but there it is.