An M.G. Locost Build
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March 31, 2016
Cool Systems

For all those who noticed, and as usual all those who didn't, we've been away for the past several weeks, to various points around the globe, all of them within the continental U.S. however. Most of our travel was work-related, but some of it wasn't, and in either case none of it allowed us to enjoy tinkering with and/or driving our Locost, and reporting on it here. But all of that changed last Saturday morning when we woke up in our own bed, went out to the garage, climbed in the car, and fired it up after just half a dozen tries.

  Hiding in the parking lot at work
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Since then, the car has started easily on the first try, and we've gotten back to our regular commute, the weather cooperating beautifully, and recent distributor and valve repairs apparently holding forth after five weeks sitting around unused in a cold garage. The car needs a tune-up, as it usually does, and it's still pretty loud, and it goes through a quart of oil as fast as it ever did, but none of that detracts from the driving experience, or the joy of seeing the Locost nestled among the giant SUVs and pick-up trucks in the company parking lot.

Shift knob missing functional Lotus badge  
click to enlarge

As a further treat, we've also gotten back to tinkering with the car. We replaced a broken pedal spring, installed a new fuel filter, and fixed our fancy wooden Lotus shift knob. A few months ago we somehow lost the miniature Lotus badge that came with it. The missing badge had little effect on shifting, but the knob looked kind of sad with a hole in the middle. Searching online, we found the source of these badges, a company on eBay that sells automotive-themed tie tacks. After clipping the pin off the back, the tie tack pressed in easily with a handy bench vise.

  Lotus tie-tack a perfect press-fit
click to enlarge

The other bit of tinkering involved our Locost cooling system. For awhile now we've been thinking that two burnt exhaust valves in two years might be trying to tell us something, and not something good. We've long believed that our makeshift cooling system has not been providing a lot of relief for our cylinder head, due in large part to the radiator sitting lower than the engine. We've explained the problem in the past, and mostly ignored it, or ignored it altogether, but now, two crispy valves later, we had to start thinking about what we might do to fix it.

The highest point in virtually all automotive cooling systems is the radiator header tank. Air in the system, which can be hundreds of degrees hotter than the coolant itself, or maybe not hundreds but certainly hot enough to allow valves to burn, will rise up through the cooling system and find its way to the header tank. This air (a.k.a. steam) can't do any harm there, because the radiator is designed to take it. If the header tank pressure gets too high as a result of the heat, the radiator cap, conveniently located nearby, has a built-in relief valve.

Moroso tank in its old useles configuration  
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In our Locost, the radiator is lower than the engine, because the car doesn't have any places higher than the engine, at least for a radiator. When we first built the car, we mounted a Moroso catch tank on the firewall, slightly above the engine, and tried to make it work as a header tank, but coolant kept spewing out of it, and so we had to demote it back to a catch tank. Of course the spewing wasn't due to using the catch tank as a header tank, but rather to our limited knowledge of MGB cooling systems, which we've hopefully improved upon since then. Hopefully.

After considerable thought, we eventually realized the mistake we made with our early header tank attempt, and decided what we really needed was a simulated heater. The heater in an MGB sits high up on a shelf at the back of the engine bay. Coolant is routed to the heater from the side of the cylinder head, and exits from the heater to a branch in the lower radiator hose. This seems to work just fine in an MGB, with minimal effects on engine cooling, and unfortunately also minimal effects on cockpit temperatures, although that's not a concern for us.

  Giant heater installation in an actual MGB
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The heater from our donor car is far too big to fit in the Locost, but our Moroso catch tank, dented last year by an exploding intake manifold plug but still serviceable, is much smaller. It also has hose fittings similar to those on an MGB heater. So all we needed to implement our plan was a couple of parts, an MGB radiator hose with a heater hose branch, and a fitting for the hole in the side of our cylinder head. We actually had a fitting like that two years ago for our header tank attempt, but then we took it off and stashed it somewhere. And then we moved.

MGB heater valve normally goes here  
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Fortunately we never throw anything away, and after a lengthy search we eventually found the fitting in a box labeled 'M.G. parts', of all places. As soon as our new radiator hose arrived, we installed everything in less than eight hours, most of that spent cleaning spilled coolant off the garage floor. We routed a new hose from the cylinder head to the smaller NPT fitting on the Moroso tank, a second hose from the larger NPT fitting to our new radiator hose, and as far as the cooling system is concerned, the Moroso tank is now just another ineffective British heater.

  Pipe mounting clips slightly longer than stock
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We wanted to use the original MGB heater pipe between the header tank and radiator hose, because a fixed metal pipe in this location seems like one of the rare things M.G. got right. But the pipe bolts to the valve cover, and trying to fit the hood (bonnet) over the installed pipe was an unpleasant reminder of the many similar clearance issues that plagued us during the build. In this case, fortunately, it turned out to be only a minor impediment, way down on Locost clearance issue scale, and all we had to do was extend the mounting clips a bit, or slightly more than a bit, and we were good to go.

Our new cooling system allows us to add coolant through the cap on our simulated heater, a.k.a. Moroso coolant tank. This is a vast improvement over our previous system, and it let us eliminate our old and unloved filler pipe that extended from the thermostat housing and threatened to break loose every time we removed the cap. Of course you don't fill the cooling system in a real MGB through the heater, but so far it's working, and whenever we check the coolant level, the header tank is always close to the top, and more importantly, higher than the top of the cylinder head.

Heater hose plumbed to new radiator hose branch  
click to enlarge

Of course the Moroso tank is now under quite a bit of pressure whenever the coolant is hot, something it hasn't really experienced before, but it seems to be handling it okay, and may have even been designed for it. The filler relief valve dumps into a plastic overflow tank, which doesn't appear to be in immediate danger of overflowing, and actually is empty right now. With all of these changes we're not sure our cooling system cools any better than it did before, but the temperature gauge reads about the same, and we no longer worry about the valves, although we probably should.

Right now we're just happy that everything on the Locost appears to be working, even if it only means the car is momentarily between repairs, and could fall apart at any moment. We'll see how it does this summer, and how cool it runs in the Sacramento heat. We have many exciting events planned for the coming months, including several drives with the local British car club, a trip or two to Monterey, and the Bay Area Maker Faire again in May. We'd like the car to be running for most of these.


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posted December 20, 2018 at 15:41:41  
pretty handy stuff, overall I believe this is worth a bookmark, thanks