This week, we have encountered a few questions regarding the original-style temperature gauges and how they are installed. A properly functioning water temperature gauge is a very helpful tool, so its important to know the best way to install yours!

All Sprites and Midgets until 1977 used some variation of a combination water temperature/oil pressure gauge. Bugeyes used one like you see pictured below, with water temperature on the bottom and oil pressure on the top. These gauges are fully mechanical; the oil pressure gauge is something that requires its own post, so today, we are focusing on the temperature gauge and how to properly hook it up.

Bugeye and Spridget water temperature gauges use a thin metal tube filled with ether connected to a capillary tube that sits in a coolant passage. When the coolant heats up, the ether expands and the temperature needle moves.

From the factory, Bugeyes had their temperature probe installed into a bung off of the side of the top tank of the radiator, underneath the upper radiator hose.

The radiator isn’t the ideal location for the temp probe in the radiator because the temperature doesnt increase until the thermostat opens when the engine reaches temperature. This means if the thermostat sticks closed, for example, you wouldn’t know there’s an issue until it was too late.

It’s much better to put the temperature probe somewhere in the engine for more accurate and immediate readings. Unfortunately, if your Bugeye still has a 948 engine with its original 948 head attached, you are stuck with the original placement in the radiator. There is no alternative location present on 948 engines.

However, on 1098 and 1275 engines, there is a perfect alternative mounting location built into the cylinder head!

In front of the foremost spark plug on 1098 and 1275 engines lies a port that has been cast and drilled into the cylinder head, for the temperature probe. Later Sprites and Midgets sometimes had a different style of radiator fitted, known as a cross-flow radiator, that didn’t allow for a temperature port to be installed, so they relocated the port to the cylinder head, which is a better place anyways. However, you can’t just move the probe straight into the head, as the probe is too long and will foul on the casting, as shown below.

To avoid this, all you need (when you relocate the probe) is our temperature probe adapter and a copper sealing washer. These two components will help you relocate your temperature port correctly and avoid leaks and damage to your temperature gauge.

Should you be installing an aluminum radiator in a 948-equipped Bugeye (with no port on the head), you will need to keep the probe in the radiator. Most of the time, the probe will screw in directly without issue. However, occasionally we have found that even when tight the probe can leak through the threads; when this happens, you will need to install the probe adapter in the bung on the radiator top tank first. This will prevent leaks.

If you are looking to upgrade your cooling system or replace your combo gauge, click on the links below for some of the parts we offer, or click here for our full catalog!

We’ve made plenty of posts about radius arms, but once again here’s one that defies all prior worn out pieces. This one is so badly worn that both the front and rear bushings are flopping all over the place, as you should be able to see in the video below.

Because of the design of the rear suspension on Bugeyes and Sprite Mark II’s with quarter-elliptical springs, the radius arm bushings are critical to locate the axle and stop it from clunking on acceleration and deceleration. Once those bushings tear, the rear axle is banging all over the place. This is a critical repair if you want your drivetrain to function properly.

There are rigid radius arms available that employ Heim joints in lieu of rubber bushings, but we don’t recommend those because we find that they make the rear suspension very jarring under load. While you’ll never have to deal with a failed radius arm bushing again with this setup, you lose a lot of the comfort that the original design provides for your rear end.

Take a look at your bushings by leaning into your rear wheel arches. You will be able to see if the front bushing is cracked and needing replacement.

Almost every car that comes through our workshop gets a set of brand new radius arms with new bushings installed, which we sell in our catalog. We also sell the radius arm bushings if you want to change them yourself with a press; in general, however, we recommend simply changing the entire radius arm, as the new ones come with new bushings ready installed as well as a nice paint job.

Keep in mind when installing new radius arms that you cannot tighten the fasteners for them with the car in the air. Tightening the radius arm bolts with the wheel off of the ground adds rotational torque to the rubber bushings, cracking them before you’ve even driven a mile and making them susceptible to early failure. Click the photos below for our radius arm-related parts offerings, or click here for our full catalog!