Supply Tank Cap

[Leif A.]

Is there supposed to be a secondary gasket on the inside lid of this radiator cap or just the one on the bottom that seals to the supply tank lower? '67 L79 w A/C. Thanks.

[Edward J.]

Re: Supply Tank Cap

Leif, there should be a gasket on the lid part of the gasket.

[Leif A.]

Re: Supply Tank Cap

Leif, there should be a gasket on the lid part of the gasket.

Thanks, Ed...I had thought that maybe that was the case. This is a new "Made in USA" cap with NO gasket. Should the gasket be rubber or cork type material. I have an RC15 15# used on a BB that has a rubber gasket on the lid part.

[Edward J.]

Re: Supply Tank Cap

Leif, I believe its a fiber type gasket, I would think one of the venders would carry a replacement gasket.

[Paul O.]

Re: Supply Tank Cap

Here are a few photos of an RC-26 and an RC-15 and the differences. Ed not aware of any vender selling the fibrous gasket.

[Joe L.]

Re: Supply Tank Cap

Is there supposed to be a secondary gasket on the inside lid of this radiator cap or just the one on the bottom that seals to the supply tank lower? '67 L79 w A/C. Thanks.

Leif------


This cap looks like it has a gasket. However, it does not appear to be a "loose" type gasket (as-original) but, rather, a "formed-in-place" type gasket. Note the thin, brown material covering the surface usually covered by the gasket. It looks like this material also extends into the "ears". This is certainly not as-original but it should be equally functional---maybe even better than original. I don't think the cap is removed for judging, so no one will ever know.

However, while it may be just how it appears in the photo, the center rivet appears to be brass. If so, that's not correct for an RC-26. The center rivet should be aluminum.

[William M.]

Re: Supply Tank Cap

Pictures are of a NOS RC26 radiator cap that I purchased at my local ChevroletMVC-015S.JPGMVC-013S.JPGMVC-014S.JPG Parts Dept. in the early 1970's. Bill Mock #93

[Leif A.]

Re: Supply Tank Cap

Paul and Bill,

Your pictures show a fibrous type gasket against the top of the lid. The new RC26 that I have has a very thin metal "gasket" where your fiber one is. I'm mostly concerned that this cap will hold the 15# it is supposed to.

Joe,

The pics aren't that great and for that I apologize. What appears to be an inner gasket is that thin metal "gasket". The rivet appears to be brass but is, in fact, aluminium. Again, my concern lies in functionality.

Thanks, guys, I always appreciate your knowledgeable input.

Leif

[Joe L.]

Re: Supply Tank Cap

Paul and Bill,

Your pictures show a fibrous type gasket against the top of the lid. The new RC26 that I have has a very thin metal "gasket" where your fiber one is. I'm mostly concerned that this cap will hold the 15# it is supposed to.

Joe,

The pics aren't that great and for that I apologize. What appears to be an inner gasket is that thin metal "gasket". The rivet appears to be brass but is, in fact, aluminium. Again, my concern lies in functionality.

Thanks, guys, I always appreciate your knowledgeable input.

Leif

Leif------


The pressure seal is at the rubber gasket. The gasket in question simply prevents coolant which may be expelled when the cap pressure-relieves from "over-flowing" the cap and, thus, forces it to discharge through the overflow nipple. I expect the "gasket" you have on this cap will function just fine in this role.

[Leif A.]

Re: Supply Tank Cap

Leif------


The pressure seal is at the rubber gasket. The gasket in question simply prevents coolant which may be expelled when the cap pressure-relieves from "over-flowing" the cap and, thus, forces it to discharge through the overflow nipple. I expect the "gasket" you have on this cap will function just fine in this role.

Joe,

Thanks for the reassurance. I'll drive her for awhile. It will be a good test as it's going to be over 100 degrees here in Dallas for the next several days.

[John H.]

Re: Supply Tank Cap

Your pictures show a fibrous type gasket against the top of the lid. The new RC26 that I have has a very thin metal "gasket" where your fiber one is. I'm mostly concerned that this cap will hold the 15# it is supposed to.

Joe,

The pics aren't that great and for that I apologize. What appears to be an inner gasket is that thin metal "gasket". The rivet appears to be brass but is, in fact, aluminium. Again, my concern lies in functionality.

Thanks, guys, I always appreciate your knowledgeable input.

Leif

Leif -

Other cap designs also used the metal upper gasket to seal to the bottom side of the cap - photos attached are of the known-original RC-15 cap on my '69 Z/28, which also used the metal gasket (earlier RC-15's used an indented rivet, but by '69 it changed to a flat rivet).


RC15Bottom.JPGRC-15RadCap800.JPG

[Joe C.]

Re: Supply Tank Cap

Most of the open style systems used caps without a rubber/fibrous gasket seal at the neck. The more important seal is the pressure seal at the bottom and this is always rubber.

Rubber/fibrous seals were used later on when the upper seal became vital in order to maintain vacuum during cooling process in SEALED recovery systems.

[Leif A.]

Re: Supply Tank Cap

John and Joe,

Thanks for the additional information. I'm going to go with what I have and just watch it for awhile...sounds like I should be OK.

Leif