Reader Scott pointed us to his blog where he asks the following:
What are these little blue and grey caps called? What do they do? Are they part of the cooling system? What happens if they are not there?
Ellen’s 2001 Eclipse is overheating now and then. Her coolant reservoir is empty, we filled it. The radiator seemed to still be full of coolant. Near the coolant reservoir there is a metal pipe/line that looks like it has one of these little caps missing. There is also a short hose coming out of the reservoir that is not attached to anything but we assume this is an overflow hose, are we right?
Before I launch into some possible explanations, I’d like to point out that I’m not going to make fun of Scott. And I’d like to ask that you don’t either. Some of us were lucky enough to have parents or friends (or just plain situation) that gave us an understanding of basic automotive troubleshooting before we were old enough to drink legally. But some didn’t.
Our job as Toolmongers isn’t to deride them but to pass on that knowledge — to remind our less-experienced friends that they can figure it out by using the same reasoning they apply to other problems in life.
As I point out in my recent jackass project post, having a manual for your car — even a cheap-ass crappy manual — makes troubleshooting a lot easier. The manual will show, for example, what parts comprise the Eclipse’s cooling system and how they work together. From that point you can make some reasonable guesses as to the problem based on the symptoms with a little imagination and logic.
Personally, I know nothing at all about the Eclipse. And I’m too poor to shell out for a manual (even a subscription one) just to take a stab at this question. But anyone who’s messed with cars much will know the basics: There’s an upper and lower connection on the engine which connects to the radiator via hoses, usually soft hoses but sometimes a combination of soft and metal. Somewhere in the system you’ll also find a thermostat which closes off coolant flow from the radiator until the coolant reaches a specific temperature. This helps get the coolant to its proper operating temperature more quickly and reduces overall system wear.
Let’s start with a little imagination. What if the thermostat sticks closed for a bit sometimes before letting go and doing it’s job? That’d cause Scott’s reported symptoms — the Eclipse only overheating “every now and then” and not appearing to leak a lot — wouldn’t it?
Now let’s apply a little logic: Automotive thermostats contain a cylinder with a bit of wax inside that melts at a given temperature, allowing a spring-loaded plunger to depress and open a valve. (If you’d like to know more, HowStuffWorks.com has a great, detailed explanation of the process.)
In fact, thermostats often become corroded and fail in the closed position either temporarily or permanently. Thankfully they’re also relatively easy to remove (at least on non-Porsches), and you can test them by placing them in a pot of water over a stove burner set on high. Place a thermometer in the water and note the temperature at which the thermostat opens. If it’s above the specified temperature — or it doesn’t open at all — it’s boned.
Or better yet, if you’ve gone to the trouble of removing a thermostat, just replace it. They usually cost less than $20, so why bother?
Other issues can reduce cooling efficiency without leaking coolant as well. The radiator depends on pushing coolant through lots of tiny tubes to effectively sap heat from the coolant and radiate it safely away. If gunk or corrosion build up within the radiator, some of these tubes can get sealed off reducing the radiator’s capacity or effectiveness. Rocks and road debris can also damage radiators, closing them off without puncturing them. Sometimes a simple radiator flush can clear out the mess and get you going again, but if the radiator is too far gone, you’ll have to replace it.
But my point is this: If you’re going to try and troubleshoot car problems on your own, this is the procedure you’ll follow.
- Read and understand (at least in simple terms) the vehicle’s systems.
- Simulate in your mind what would happen if a given system failed.
- When you find one that matches your symptoms, read up on the system and how it can fail.
- Follow the manual’s procedures for testing the system and replacing it if necessary.
Or if you’ve dumped the dosh for a dealer’s maintenance manual you can just follow the step-by-step troubleshooting and decision charts within. Either way, you’ll get there, though probably not without getting some grease under your nails first.
And Scott, regarding the little blue cap: Remember that I don’t know squat about the Eclipse. But I’ll bet you a quarter that your missing cap covers a Schraeder valve on a freon line for the car’s air conditioning system. I’m certain that the gray cap does. I’d also bet that removing the cap won’t affect the system at all — except for allowing the valve to corrode over time or collect crap from the engine compartment.
PS: Even if you’re not willing to dive in, you can always roll the dice with Google. For kicks I plugged in “2001 Eclipse overheating” and got the following advice:
- Bleed the cooling system (first result)
- Blown head gasket (second result, though not applicable to you because you don’t have coolant in your oil and the car runs)
- Thermostat, radiator flush (fourth result, though spelled atrociously)
- Cooling fan/relay (seventh result, from a Diamond-Star Motors forum with lots of helpful responses)
Just keep in mind that car enthusiasts will probably jump right in to help you solve your problem — as long as you’re willing to help yourself.
Scott’s Blog Post [ApertureQuiet]