Saturn Update

It's been a while since I've done an update on the Project Saturn. About two weeks ago the "Low Coolant" idiot light came on. This car has a sealed system, which means there is no "overflow" tank, it is actually in the loop and all the hot coolant flows through it. I knew that the coolant level was perfect a few weeks before so I had a leak somewhere.

A quick look under the hood showed a small leak from a crack (see above) on one of the plastic end caps on the radiator. Time for a new radiator. While I'm in there with everything drained it's also a good time to change the thermostat, which I had already purchased because I suspected it was running cooler than it should. More on that later. Here's what the old radiator looked like after 6 years/148K miles (below). And this is the side facing the engine! You can tell that only the bottom 1/3 gets direct air/debris. Also remember that the A/C condenser sits in front of this, so it is even worse. While the radiator was out I took my handy air compressor and blew as many bugs, pebbles, etc. out of the condenser as possible from the back side.

The new radiator cost me right at $100 including tax. Note to other DIY types: awesome prices on most car parts at Amazon.com. The exact same radiator was $150 at Advance, $90 on Amazon.com. Another Note to other DIY types: Advance will "Price Match" competitors, including websites, for the same item. So my total investment in the Saturn is now about $650, not bad, huh?

And about that thermostat... Here's how the car almost always ran before...

And it seemed to take too long to warm up when cold. Now here's where it is when it's warmed up...

And it warms up quickly now. Yup, the thermostat was bad. You normally expect a bad thermostat to stay shut and cause the car to overheat, but many times the spring just gets weak and it never closes enough to keep the car warm enough. Most cooling systems are over-engineered and will cool a car too much without a thermostat there to control the temperature. That's why it's not a good idea to just remove the thermostat.

This difference doesn't look like much on the gauge, but is probably around 10 degrees. So what's the problem? Today's cars are designed for the engine computer to deliver exactly the right amount of fuel to the engine to run well and have the cleanest possible emissions. It has sensors for the coolant temperature and intake air temperature and adjusts the fuel amount to match conditions. When the engine (via coolant temp.) is cold it burns slightly more gas because a cold engine needs more fuel to run smooth.

So basically this has been costing a few mpg for a while because the computer always thought the engine wasn't warmed up yet. I haven't been through a full tank of gas yet but after a half tank I can already tell I'm probably going to get about 1-2 mpg in the city and at least 2 mpg on the highway. So the $15 and 15 minutes (because I already had the radiator out) to replace the thermostat will pay off quite a bit at the gas pump. Now I should be able to easily achieve 29/35 instead of 28/33. Since the window sticker shows a 27/37 rating I still have some more room for improvement. I intend to hit that 37 highway rating eventually.