Perkins 4-108 "radiator" cap question

[SvenG]

We've just developed a slight leak between the cap and the top of the filler collar. When I investigated I found out that the top of the filler collar and the cap is just aluminum to aluminum (?), no gasket of any kind. There's no real pressure at that seal as it just helps direct the overflow water into the overflow tank, but I wonder if there really shouldn't be some kind of thin cork or rubber gasket ?

In case anyone happens to know

Thanks,



-Sven

[svHyLyte]

Originally Posted by SvenG

We've just developed a slight leak between the cap and the top of the filler collar. When I investigated I found out that the top of the filler collar and the cap is just aluminum to aluminum (?), no gasket of any kind. There's no real pressure at that seal as it just helps direct the overflow water into the overflow tank, but I wonder if there really shouldn't be some kind of thin cork or rubber gasket ?

In case anyone happens to know

Thanks,



-Sven

Sven--

Our coolant cap has a thin gasket. That is the only way a tight seal can be developed for the cooling system which has to pressurize to roughly 10 psi.

FWIW...

[Redcoat]

Put a 7 lb cap on it you can buy one anywhere.

[Dynamo1181]

7LB cap and I added a reservoir tank so that I seldom open the cap to ck the fluid level. As stated you need a sealing 7 lb cap for pressuring the system.
A

[SvenG]

Thanks for the replies, useful as almost always !

As I may not have stated clearly, it is not the pressurized two-way spring loaded seal that leaks, but the one at the top neck of the filler collar.

It is the upper seal in the image below that is just metal to metal in our cap.



As far as I know the two-way spring loaded rubber seal works well.

I'll see if I can find a 7lb cap that will fit here in La Paz, Mx. A great place but with a bewildering assortment of you-can't-get-that-here items.

Thanks again.



-Sven

[Redcoat]

Go to auto zone in La Paz. They have one.

[SvenG]

Originally Posted by Redcoat

Go to auto zone in La Paz. They have one.

Thanks, we'll give them a try.



-Sven

[Cheechako]

Correct me if I'm wrong, but isnt there an upper seal that is rubber also?

[SvenG]

Originally Posted by Cheechako

Correct me if I'm wrong, but isnt there an upper seal that is rubber also?

That was my original question as it seemed strange that we have none. I think there is supposed to be one and I was going to just make one until I found out (in this thread) that the caps apparently are quite standard and we can buy a new one here.



-Sven

[SvenG]

We found the cap today and it is an exact replacement. Autozone didn't have anything like it but for once the directions to a place that would have it was spot on and right across the street !

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(Thanks to Google Earth for the picture)

It's become a joke with us that whenever a store doesn't have something they don't want to be rude and leave you hanging so they always suggest who will have it, even if is very unlikely. Likewise if you ask for directions you'll get helpful suggestions even if they have no idea where it is. It's a different kind of politeness and it's put quite a lot of wear on our shoes but we're not complaining, it gives us lots of exercise.

The new cap is as I said an identical replacement, including having a metal to metal seal and no gasket at the filler throat. The metal in the cap looks and feels like thin soft bronze or brass.



I'll make sure to really clean off the mating surface and will cross my fingers.

Thanks again for all the comments and suggestions.



-Sven

[Cheechako]

So.... upper gasket or no?

"...they don't want to be rude and leave you hanging so they always suggest who will have it, even if is very unlikely. Likewise if you ask for directions you'll get helpful suggestions even if they have no idea where it is.."

Yeah. Manana can mean never sometimes... I've got directions in Mexico before that had nothing to do with where it was at!

[SvenG]

Originally Posted by Cheechako

So.... upper gasket or no?

Just the soft bronze-brass "thingy". No rubber or cork.



-Sven

[Dynamo1181]

You need a spring pluger seal AND an upper rubber seal that is against the inside of the cap top. If yoiu dont have the latter, then you could leak around the neck as well as out the overflow tube.
A

[justlearnin]

the only seal is the rubber the metal is just a springy guide ( no sealing ability) so if it was leaking it was the rubber or the seat the rubber sits on.

[FishyBiz]

I have a 1978 Perkins 4-108 low line style that needed a new header tank cap found it at NAPA PART NUMBER 703-1418 fits great about $7.00 it's a 7 psi. It was tough to find a good part number.