Coolant bottle cap that works

[Stainless]

I have read a couple of threads regarding the cap pressures, but not one about alternative caps that will also work with our coolant bottles. I was going to buy the $20 cap from DMC, but I figured that should be a relatively common part that can be obtained elsewhere.

I understand that the original caps were 15 psi, so ideally I would like to get another 15 psi cap but am unsure about what will fit. I found this stainless cap on ebay for $15, but I don't know if there's much, if any, variance between cap brands.
http://www.ebay.com/itm/AC-DELCO-NOS-STAINLESS-RADIATOR-CAP-15LB-/370522823426#vi-content

Will any 15 psi cap work, or do only certain brands, like the one that DMCH sells, fit? This may be a stupid question, so pardon that.

On a second, but related note, my cooling system never seems to get pressurized, which is what brought me to this question in the first place. When this happened last year in my Jeep, a simple cap replacement fixed the issue, which is why I'm thinking that this is what it is on the DeLorean. I haven't tested the cap, but I'm sure it's time to replace it anyway. I figured I'd start there. Thanks for the help.

[ccurzio]

As someone who had their radiator cap disappear in the middle of a drive, I can tell you it's not easy to find a crossover from Pep Boys or Autozone or what have you.

Just spend the extra couple of bucks and get the correct part from DMC. Also buy a second one to keep as a spare.

[Ron]

I understand that the original caps were 15 psi, so ideally I would like to get another 15 psi cap but am unsure about what will fit. I found this stainless cap on ebay for $15, but I don't know if there's much, if any, variance between cap brands.
http://www.ebay.com/itm/AC-DELCO-NOS-STAINLESS-RADIATOR-CAP-15LB-/370522823426#vi-content

Will any 15 psi cap work, or do only certain brands, like the one that DMCH sells, fit? This may be a stupid question, so pardon that.
They caan check you cap at Autozone etc...There is an attcahment in the radiator testor kits they sell/rent to do it with.

The eBay cap in your post is an AC brand RC26 -- You don't want to use it because it is for a system with an expansion/recovery tank.
You can use any of the older style (they "puke" on the ground) 15psi that fit, or, a crossover for a AC brand RC15.
I'd just get one from DMCMW.

[Bitsyncmaster]

You don't want to use it because it is for a system with an expansion/recovery tank

Isn't our system a expansion/recovery tank?

[David T]

The header tank is part of the pressurized cooling system. An overflow bottle/recovery tank is NOT pressurized. The hose from the radiator cap neck feeds into the bottom of the overflow tank. When the pressurized system pushes excess hot coolant into the tank it sits there till the pressurized system cools. At that time it sucks the overflow bottle and pulls the excess back in. This is good for several reasons. Less air in the pressurized system for corrosion and foaming. Easy to check the level without having to remove the pressure cap, just look at the overflow bottle. All modern cars now have this. Very easy to add to the Delorean.
David Teitelbaum

[Ron]

No. Short of it is- If you can't add coolant while the system is pressurized, it is not a recovery system.

Early radiators had ~zero/low pressure caps and were vertical flow with a large top, or "header", tank to allow for expansion. They vented onto the ground, often via a hose, and required a constant watch on the level. Horizontal or "cross" flow radiators (more efficient) worked similarly except the side tanks did not allow enough room for expansion, so a remote header tank, or "expansion tank", was added. These could have a simple sealing cap (like a D) at the radiator or none at all. A pressure cap, at the tank, had a "vacuum sensing" valve that would allow air to enter the system as it cooled to replace any coolant pushed out (prevents hoses from collapsing...).
Eventually, to protect the environment and reduce the risk and frequency of removing the cap to add/check the level, the overflow hose was routed into the bottom of a "recovery" tank...Unlike the older systems, coolant is kept, any air rises to the top, and when the engine cools, the valve allows coolant to replace the void instead of air.
Another interesting addition (which causes controversy in the D world ;-) was a hose from the top of the radiator joining the larger hose from the bottom of the radiator (forming a venturi) on its way to the remote expansion tank to capture and draw off any air in the system, a self bleeder.
Cool?...lol

EDIT: One of these days I'm going to remember to check for other replies before I post with an answer I write between phone calls and #$%&@ kids revving my supercharged vehicles before they are warmed up....
A lot easier to say, "+1 David T"

There, now I'm vented too! LOL

[Stainless]

I got a new cap from DMCH installed and it is working. System pressurized fine, and even better, I didn't have any leaks.