Radiator Pressure Cap

[MRG1965]

HI all, silly question time again.

Was topping up the coolant, engine oil etc on Saturday, and noticed that the pressure cap has a 10 on it. I'm assuming this is 10psi, which seems a little high to me.

It does not seem to be causing any issues, but I was wondering if this is the correct pressure cap for a standard (as far as I know)1964 TR4.

 

Any help, as always gratefully received.

 

Mark

[peejay4A]

7 is normal iirc.

[stuart]

Should be 4lb Im afraid for all 4 cylinder cars.

Stuart.

[RogerH]

Hi Stuart,

Moss show 7lbs for the 4A - is this not right then.

 

Roger

[tim hunt]

I've had a 7psi cap on my 4A ever since acquisition in 1970. I always thought this was the received wisdom for the 4A. I note that Rimmers list a 4lb cap of 1" depth for 2,3 and 3A and a 7lb cap of 1" depth as an option on 2,3 and 3A and apparently standard on TR4 with filler neck. For the TR4 without filler neck a 7lb cap of 3/4" depth is standard with the option of a 13lb cap of 3/4" depth. For the 4A Rimmers list a 7lb cap of 3/4" depth as standard and a 13lb cap as option.

 

Make of that lot what you will!

 

Tim

[stuart]

Workshop manual lists 4lb for TR4 with no revision for 4a.You can run what you like but thats factory recommendations. FWIW it probably was the difficulty of getting 4lb short reach caps that is why most supply a 7lb.

Stuart.

Edited September 26, 2016 by stuart

[Richardtr3a]

Anything over 4 lbs can cause leaks. i had that problem on my 3A

 

Stuart is usually right.

 

Richard & H.

[MRG1965]

Hi, as always, much appreciated, I think :-)

So anything from 4 to 13lbs.

4 sounds a little light, but the 10 I have on it sounds too much, god knows where the pressure would go with a 13lbs cap on it.

7lbs cap sounds like a good compromise. I'llget one to see what if anything happens to the temperature or the overflow.

 

Cheers

Mark

[BlueTR3A-5EKT]

Hi Stuart,

Moss show 7lbs for the 4A - is this not right then.

 

Roger

According to the parts lists.....

 

137691 (GRC112) is listed for TR4/4A/250/5/ & early 6 which is a 7 lb cap. (TR6 went over to 13 lb later in its life) It is a 3/4" reach cap with 7 lb pressure release. This I believe fits the radiator without the extended header that a sidescreen car has.

 

The earlier one for TR4 is a 1" reach cap with 7 lb release.

 

Sidescreen cars had the 1' 1" reach 4 lb cap.

 

Peter W

 

Reach symbol corrected - Thanks Brian

Edited September 27, 2016 by BlueTR3A-5EKT

[peejay4A]

I've posted this before but here goes again. Don't go above 7psi if you have a sleeve/bellows thermostat or it won't open.

Edited September 27, 2016 by peejay4A

[BlueTR3A-5EKT]

I've posted this before but here goes again. Don't go above 7psi if you have a sleeve/bellows thermostat or it won't open.

Thanks for that reminder.

Peter W

[BrianC]

Sidescreen cars had the 1' reach 4 lb cap.

 

Peter W

That will be to the bottom of the rad then

[RogerH]