1937 Radiator pressure - new cap needed

[SteveR]

My Radiator cap is kaput and I need a replacement. The problem is here in England there are not many places to go for a replacement cap.I have talked to several people and they are asking me what pressure cap do I need.

I assumed that this is a non-pressured system. But in thinking there must be some pressure in the cooling system. Does anyone know how much pressure there might be?

[Ivan_B]

Do you still have the OEM cooling system and the 201 motor? If so, there is no pressure. Just make sure that the new cap fits the rad and you have a gasket to prevent spills.

What's wrong with the old cap? Rusted away? 🤨

If you want, someone from over the old colonies way can probably mail you another one.

[SteveR]

The engine is a 230 now. What radiator I have I have no idea.

The clip to secure it is rusted away

I am finding a replacement here is about as easy as a one-legged man in a butt-kicking contest.

Getting one from America might be my only hope. I usually find the shipping is more than the part.

I did think I could possibly drill out the broken retainer and make a new one and rivet it in.

[desoto1939]

You are correct that you DO NOT use a pressure cap on the radiator.  The radiator should have an overflow tube and these older systems are self leveling. Fill the rad with water and then run the car until it gets up to temperature.  The rad will burb out the excess water and it seeks its own level which willbe approx 1 inch down from the top, just keep it maintained at that level, sorry, we are not metric here in the states, and we drive on the right and not left side of the road, just kidding 

[desoto1939]

You will use an r-1 radiator cap if you still have the original radiator.

 

here is a picture of the cap.

Rich hartung

desoto1939@aol.com

 

[Ivan_B]

19 minutes ago, desoto1939 said:

You will use an r-1 radiator cap if you still have the original radiator.

Or, you can stick a large cork plug in there. That'll sure look fancy, and be a great conversation starter 😁

[SteveR]

2 minutes ago, desoto1939 said:

we are not metric here in the states, and we drive on the right and not left side of the road, just kidding 

LOL I'm from Minnesota but living in Limmy Land and that aint always easy.

[SteveR]

1 hour ago, desoto1939 said:

You will use an r-1 radiator cap if you still have the original radiator.

Moparpro has one for $39 + $37:26 shipping. $76.26 for a radiator cap?! Gulp!!!   I like the cork idea.

[Young Ed]

Come back to visit MN I'll give you one 😁

[Ivan_B]

How about something like that? https://www.ebay.com/itm/126578045722

[Sniper]

Tell you what I will mail you a radiator cap at my expense if you hook me up with a headlight for my Jaguar

[andyd]

I could be wrong here but generally the old non pressure radiators use a cap that is either deeper or not as deep between the cap and the rubber seal.......can't remember which it is but I'd think that I'd try a cap for an English car from the 30's or 40's....isn't there a radiator shop anywhere close that you could contact..........surely the Pommies can't be that backward that if you say you need a non pressurised cap they should know what you mean..............lol.......andyd

[SteveR]

6 hours ago, Ivan_B said:

How about something like that? https://www.ebay.com/itm/126578045722

This one can't be used. The securing tabs are on the outside. Mine is on the inside of the neck.

[SteveR]

10 hours ago, Young Ed said:

Come back to visit MN I'll give you one

I just checked cheap flights to MPLS. Take a guess. It's over $1500 + car + lodging + food. I knew there was a reason I had not been back in 28 years.

 

If you have one (a R1) I will pay the postage.

[Ivan_B]

https://www.ebay.com/itm/267086047070 Would this fit?

[SteveR]

16 minutes ago, Ivan_B said:

https://www.ebay.com/itm/267086047070 Would this fit?

Not sure. According to Desoto39 I need a R1. This one is a R2. I need dimensions to see if it will fit.

[38plymouth]

I don't have the time right now or maybe even the ability to go back and look through my old posts but if someone wants to give it a try a couple years ago I found a cap at Tractor Supply that fit just like the original but it was for a tractor I think. I took pictures of the part number and posted them here. The only problem is it does rust on the inside so I probably will have to replace it every couple years. But so far it works perfect. And it was very cheap compared to the original cap.

[38plymouth]

This is what it looks like. My car is a 38 I think the 37 is the same.

[SteveR]

4 hours ago, 38plymouth said:

I don't have the time right now or maybe even the ability to go back and look through my old posts

Your post was on February 10, 2023. I have ordered one similar here in the UK for £9.11. The dimensions are correct so we will see if it fits when it arrives. Thanks for the tip.

Edited March 12, 2025 by SteveR

[38plymouth]

2 hours ago, SteveR said:

Your post was on February 10, 2023. I have ordered one similar here in the UK for £9.11. The dimensions are correct so we will see if it fits when it arrives. Thanks for the tip.

Only two negative things is if this makes sense when you twist it on the inside can spin so it can make it a little hard to get off and like I said it will start to rust. But it fit perfect on my car and you cannot beat the price. I thought I saved the package so I had the part number in the future maybe it's in the glove box I can't remember.

[SteveR]

15 hours ago, 38plymouth said:

Only two negative things is if this makes sense when you twist it on the inside can spin so it can make it a little hard to get off

I suppose I could drill an offset hole and put in a pop rivet to secure it.

Rust? That is a daily occurrence on these old cars.

I should get this in the next couple of days.

[SteveR]

I've got the new cap but as 38plymouth said, the middle will rotate when installing it. I will either drill a small hole in the inner piece and install a screw or pop rivet or maybe file down the tabs. I also bought some 1mm spring steel to make the tabs for my old cap.

[SteveR]

The rubber gasket that came with the cap was .117" (3mm) and was too thick. I had some gasket material that was .062" (1.5mm) and that fits great. I'm back in the saddle again. Thanks to all who helped, especially 38plymouth!