Post by: TopNotch on March 18, 2020, 10:23:52 pm
In this picture notice that there is a gap between the outer seal on the oil cap and the center.
For this fix, you need an O-ring the same size, or slightly smaller than, that gap, as shown above.
Place the O-ring over the gap as shown in this picture.
Press the O-ring into the gap.
Now replace the oil cap. That's all there is to it. You may have to hold the O-ring in place when you replace the cap, but after it's been exposed to engine heat, it will stay put.
I did mine before last year's Run For The Hills, and it hasn't leaked a drop since.
Post by: GTRS Fiero on March 18, 2020, 10:42:10 pm
Post by: MikeMac on March 18, 2020, 11:10:47 pm
Great writezup. Only 1 thing missing: the size or part number for the o-ring.
I guess you could take the cap off the car and let it cool some before taking it into NAPA or another parts store and look through the o-ring assortment. Remember the let it cool some part!
Post by: GTRS Fiero on March 18, 2020, 11:16:19 pm
I guess you could take the cap off the car and let it cool some before taking it into NAPA or another parts store and look through the o-ring assortment. Remember the let it cool some part!
Sure, assuming they have the correct size. Of course, I could also re-invent the wheel. There are plenty of suitable boards at the store. ???
I am curious about the cooling part. The cap only leaks when it's hot, not while the engine is off. Whatever temperature changes the cap undergoes, the seal will also have to undergo. Why let the cap cool off? If I can take it off with my bare hand, how hot can it be?
Post by: TopNotch on March 18, 2020, 11:18:47 pm
Post by: GTRS Fiero on March 18, 2020, 11:24:41 pm
I guess the dial calipers will have to do. Still, good idea.
Post by: TopNotch on March 18, 2020, 11:30:11 pm
Post by: scottb on March 19, 2020, 04:14:43 pm
Post by: GTRS Fiero on March 19, 2020, 06:25:48 pm
Go to Amazon and search for O-ring kit. Anyone who works on cars should have one. I even fixed a friend's medical oxygen concentrator with one of my O-rings.
Ordered.
Post by: GTRS Fiero on March 19, 2020, 06:26:39 pm
The oil cap leaks while the car is running due to the pressure being built up and the thermal expansion of aluminum; i.e. the hole in the valve cover gets bigger. You want the cap cold so that it is at its smallest dimension so the oring fits tighter.
Good explanation, thanks. I'm going to test with a spare cap and valve cover.
Post by: scottb on March 19, 2020, 07:09:14 pm
Post by: GTRS Fiero on March 19, 2020, 07:35:28 pm
Post by: TopNotch on March 19, 2020, 09:50:12 pm
(And I wonder why people have to make some things so complicated?)
Post by: GTRS Fiero on March 22, 2020, 05:02:49 pm
(And I wonder why people have to make some things so complicated?)
I guess that would be me. My intent was understanding for both myself and future readers.
And I'm not the only one. When I say things in technical terms for my area of expertise, people often ask for clarity. This is not my area of expertise.
For example, stating that the local and remote network IDs must differ for successful communication over a VPN. That is generally a true statement, although there are ways around it.
I did not know about the O-ring kit. Additionally, if the hole gets bigger, it would have seemed that I would want the cap to be tight when the hole was at its largest. Usually metals expand when heated, which should make the hole smaller, in my mind. But not my area of expertise. Either way, the seal would be small, because it was cool. Usually, plastic would deform to the aluminum hole when heated, making the plastic cap smaller. I would think that, if this makes a big difference, the cap should be frozen, and a slightly smaller (heated) seal used. I suspect that the seal just needs to be the same temp as the cap.
Post by: scottb on March 22, 2020, 05:23:48 pm
(And I wonder why people have to make some things so complicated?)
Usually metals expand when heated, which should make the hole smaller, in my mind.
Curious as to why you think the hole would get smaller as the metal expands?
Post by: GTRS Fiero on March 22, 2020, 05:29:47 pm
Post by: Slyp on March 22, 2020, 05:48:47 pm
Post by: GTRS Fiero on March 22, 2020, 05:50:58 pm
Post by: GTRS Fiero on March 22, 2020, 06:23:29 pm
Post by: scottb on March 22, 2020, 07:36:40 pm
Post by: GTRS Fiero on March 22, 2020, 07:39:22 pm
The oil cap leaks while the car is running due to the pressure being built up and the thermal expansion of aluminum; i.e. the hole in the valve cover gets bigger. You want the cap cold so that it is at its smallest dimension so the oring fits tighter.
Um...
Post by: scottb on March 22, 2020, 07:40:04 pm
Post by: GTRS Fiero on March 22, 2020, 07:51:39 pm
You then posted that it didn't sound right that temperature changes would affect the size of the hole. There is the contradiction.
My theory is that, when heat is applied to a bolt, the bolt expands (molecules further apart). As the bolt cools, it contracts, creating a small gap, just like heat forcing the spikes out of the rails.
Also my theory, when freon is applied to the head, the hole expands (molecules contract).
Post by: scottb on March 22, 2020, 08:21:48 pm
Temperature does affect the size. As metals heat up and expand a hope will become larger. Case in point: one Saturday at Northlake I spent some removing a broken stud out an exhaust manifold on the AeroDon car. Applying heat to the flange caused it expand (along with the threaded hole) and the stud was removed.
At work there are parts that I make that consist of an Aluminum tube and a lead puck that fits inside the tube. The engineers have called out on interference fit. The only way that i can get them assembled is to heat soak the aluminum to around 160F and cool the lead to around 30F. Even then I only have a few seconds to get it assembled before temperatures equalize and they are stuck
Post by: TopNotch on March 22, 2020, 08:28:38 pm
There are no sizes given in this kit, so I just had to pick one that fit for my oil cap fix
Post by: GTRS Fiero on March 22, 2020, 08:29:38 pm
Post by: GTRS Fiero on March 22, 2020, 08:30:55 pm
Post by: Fierofool on March 22, 2020, 09:22:58 pm
As far as a hole getting larger or smaller. I can tell you from experience that I installed many a large bearing set onto an electric motor shaft or pump shaft. I'm talking about bearings with an outside diameter of 8 to 10 inches. In order to get the inner race to go onto the shaft it was put on a bearing heater which heated the inner race. The inner diameter of the race would expand and the bearing would drop onto the shaft and as it cooled, it would shrink and be considered an interference fit.
We also heated parts of machinery in order to extract a shaft or broken bolt or stud. By heating the surrounding metal, the threaded hole would enlarge, loosening its grip on the bolt. Sometimes when it wasn't feasible to use heat, we would use dry ice or freon to super cool a shaft, rod, or bolt. An interference dowel pin laid on a block of dry ice for an hour will usually drop right into it's hole.
Post by: GTRS Fiero on March 22, 2020, 09:44:15 pm
Heated metal expands in 3D.
Post by: Fierofool on March 22, 2020, 10:49:25 pm
Answer: Metals expand when you heat them, so the circle should expand. There's no real difference between the circle and a hole (of the same size) cut out of it. The circle is, in effect, the circumference of the hole you put into it. So the hole will get larger.
If the hole didn't enlarge when heated, there could be no explanation as to why the bearing would only go on the motor shaft after being heated.
Post by: GTRS Fiero on March 22, 2020, 11:10:27 pm
Post by: MikeMac on March 23, 2020, 08:41:02 pm
Post by: TopNotch on March 23, 2020, 09:06:02 pm
Post by: MikeMac on March 23, 2020, 10:07:28 pm
I must say, my simple fix for the leaking oil cap has elicited quite a discussion of holes. Try this experiment. Insert the oil cap into the valve cover hole, but do not turn it tight. Try wiggling it back and forth. You'll see that the hole is quite roomy. It's not the size of the hole that affects leaking, but the seal on the cap outside the hole. After inserting the O-ring, you'll find the cap harder to close, because of the additional seal.
Pat, I think we are all getting stir crazy. But we will all be experts on expansion and contraction of metals!
Post by: Fierofool on March 23, 2020, 11:05:20 pm
Give this some thought. If you heat a sheet of metal with a hole in it and the sheet expands but the hole gets smaller, wouldn't it cause the hole to break out of the sheet of metal making a progressively larger hole as each hole shrunk away from the plate?
Post by: GTRS Fiero on March 23, 2020, 11:24:15 pm
Give this some thought. If you heat a sheet of metal with a hole in it and the sheet expands but the hole gets smaller, wouldn't it cause the hole to break out of the sheet of metal making a progressively larger hole as each hole shrunk away from the plate?
In my mind, no, but it does sound familiar from grade school. I thought I dropped this.
If I heat a metal ruler, it expands in all directions: height, width, and length. If i hold it in the middle, when heated, the ruler will expand away from the center. If two rulers are placed near each other, and both rulers are heated equally, they will expand toward each other. If the ends of 4 rulers are arranged such that their ends touch in a square, then heated equally, the ends will expand toward each other. So far, so good? Now, connect the corners of those 4 rulers, making a square hole. Now heat the 4 rulers. What happens? According to google, the hole will now grow in size. One of the problems with thermal expansion is that the objects tend to heat unequally, resulting in warping. In my mind, when the metal expands, it should expand anywhere it can. If you think on it, having a hole is easier than not. To illustrate my point, have people line up, shoulder to shoulder. Then, have them move to an arm's length from each other. The further from the center they are, the further they will have to move. Now, suppose that the original line of people had a gap. Obviously, the expanded line wouldn't have to expand as much in this area. Now, try this in 2D. A grid of people. For your point, the metal would warp slightly around holes when heated.
Post by: TopNotch on March 24, 2020, 05:20:56 pm
If i hold it in the middle, when heatedYikes! I hope you're wearing an "Ove glove".
Post by: GTRS Fiero on April 06, 2020, 06:58:06 pm
If you have a stock V6 Fiero (or one with stock valve covers), you probably know about the leaking oil cap. Here is a way to stop it leaking for good.
In this picture notice that there is a gap between the outer seal on the oil cap and the center.
For this fix, you need an O-ring the same size, or slightly smaller than, that gap, as shown above.
Place the O-ring over the gap as shown in this picture.
Press the O-ring into the gap.
Now replace the oil cap. That's all there is to it. You may have to hold the O-ring in place when you replace the cap, but after it's been exposed to engine heat, it will stay put.
I did mine before last year's Run For The Hills, and it hasn't leaked a drop since.
I've been looking at my oil cap. I wonder if there are different designs. The gap betwen the outer rubber piece and the inner plastic piece seems to be narrower, on my cap.
Post by: GTRS Fiero on May 06, 2020, 05:43:35 pm
Go to Amazon and search for O-ring kit. Anyone who works on cars should have one. I even fixed a friend's medical oxygen concentrator with one of my O-rings.
Ordered.
It (they) arrived today. I ordered one in SAE and one in metric. Neither one has a size that fits, but there does not seem to be a groove there.