251 cid radiator cap rate?

[Fernando Mendes]

Need help about 251 cid radiator cap rate please.

[1949 Wraith]

I would think around 4 psi. 

[Fernando Mendes]

I bought a 15 psi.

[Plymouthy Adams]

first off is your radiator a pressure type?  you did not list an application but maybe wrong assuming your 52 Dodge...these were at that time of production at most 4lb caps...while the engine block with properly installed core plugs can withstand more pressure, you have to allow for the radiator construction along with the heater core and at the same time added consideration to their age and possible thinning process since original manufacture.  I personally would not use the 15 lb cap 

[Charlie Stephenson]

10-04 A.L.F.  Charlie Stephenson

[dmartin_egroup]

Good afternoon:

The water pump shaft seals may not hold up if pressure cap is too high a value.  It may be hard to research what water pump seals you have.  Just sayin'....

In my opinion, the next weak spot would be the so-called freeze plugs.

[Fernando Mendes]

On 12/11/2019 at 12:29 PM, Charlie Stephenson said:

10-04 A.L.F.  Charlie Stephenson

10-04 ?

[Fernando Mendes]

It is a shame.There is no 4 psi radiator caps here in Brazil.

[1949 Wraith]

1 hour ago, Fernando Mendes said:

It is a shame.There is no 4 psi radiator caps here in Brazil.

Ebay

[Radarsonwheels]

My heater core never leaked until I hooked it up to a modern (‘70s) cooling system

[9 foot box]

   Stant sells a 10308, with a lever to release pressure and a 10208, that is a regular cap. Both 4 lb. Or a 10203, that is a non-pressure cap. As an edit. The earlier radiators with the larger flange, use an R-4 cap. 

Edited December 17, 2019 by 9 foot box

[bkahler]

12 hours ago, Radarsonwheels said:

My heater core never leaked until I hooked it up to a modern (‘70s) cooling system

 

If I remember right my 51 is a non pressurized system so I assuming the heaters sold during that time frame were designed for no pressure.  I can see where a modern cooling system would cause it to leak.  How did you resolve the problem?

 

 

 

[Dodgeb4ya]

I have always had zero pressure caps or leave them slightly loose.

This to help prevent future core pressure damage. Never have had a boil over.

I think in 1951 4lbs was the start of pressure caps.

[Radarsonwheels]

4 hours ago, bkahler said:

 

If I remember right my 51 is a non pressurized system so I assuming the heaters sold during that time frame were designed for no pressure.  I can see where a modern cooling system would cause it to leak.  How did you resolve the problem?

 

 

 

It held for a few hundred miles then started weeping. I pulled the whole heater and covered the holes in the firewall with blue painter’s tape ? 

 

The big motor keeps it warm enough in there with the windows up despite all my insulating for now. The long term plan is to resto-mod the stock heater box with a 12v fan and either a new core or new tubes and fins furnace brazed to the original tanks. I do want a defroster hose to the windshield and a working heater would be spiffy too.

[bkahler]

1 hour ago, Radarsonwheels said:

It held for a few hundred miles then started weeping. I pulled the whole heater and covered the holes in the firewall with blue painter’s tape ? 

 

The big motor keeps it warm enough in there with the windows up despite all my insulating for now. The long term plan is to resto-mod the stock heater box with a 12v fan and either a new core or new tubes and fins furnace brazed to the original tanks. I do want a defroster hose to the windshield and a working heater would be spiffy too.

 

Hmm, now you have me wondering what cap I should have for my 51.  Time for some research!

 

Brad

[Plymouthy Adams]

I have a note in my book that the pressure system was introduced to PLYMOUTH in mid 1950 and was rated at 4lbs through the 1952 model year....the 53/54 was rated 7lbs...I do not have a truck manual for these same years....I therefore default to the Plymouth car for my recommendations.

[JBNeal]

from what I can glean from my parts book, there are two radiators listed:  one for Bs & Cs, and another for Cs & Ds, for B-1, B-2, B-3 and B-4 trucks.

There are also two radiator caps specified:  one for B-1 & B-2 (usually a galvanized cap with a non-rubber gasket), and another for B-3 & B-4 (modern style cap with rubber gasket).

The radiators listed in the parts book both specify the B-3 & B-4 radiator cap...so it appears the truck cooling systems from '48-'53 are not pressurized...

 

See Radiator Identification for Non-Pressurized Systems

Edited December 18, 2019 by JBNeal
added link

[Fernando Mendes]

Today a radiator technic withdrew three leaks on my pu radiator.

[Dodgeb4ya]

Aren't B1 B2 the larget non pressurized rad caps?

B3 and 4 being smaller and hold low pressure?

Edited December 19, 2019 by Dodgeb4ya
Spell check

[bkahler]

2 minutes ago, Dodgeb4ya said:

Aren't B1 B2 the larger mon mlm pressurized rad caps?

B3 and 4 being smaller and can hold pressure?

 

When I got my 51 B3 back in 1996 it had a non-pressurized cap on it.  Also the radiator has the little dome or cap on the top that has a tube running down to the ground.  I believe that also indicates a zero pressure system.

 

Brad

 

[Dodgeb4ya]

I have a 1272446..yes a 1272446 in my 52 pu...

I cannot find that Odd number ...it has the small cap no dome and can be pressurized though I don't pressure it as it has a tiny seep leak.

I hopefully will be putting a NOS 1272945 radiator in it soon that a friend has located.

 

Edited December 17, 2019 by Dodgeb4ya
Wrong part number... corrected

[bkahler]

3 minutes ago, Dodgeb4ya said:

I have a 1372446..yes a 1272446 in my 52 pu...

I cannot find that Odd number ...it has the small cap no dome and can be pressurized though I don't pressure it as it has a tiny seep leak.

I hopefully will be putting a NOS 1272945 radiator in it soon that a friend has located.

 

 

Now you have me wondering, where'd you find the part number on the radiator?!

 

Edited December 17, 2019 by bkahler

[Dodgeb4ya]

Right on the rear passenger side of the tank in 1/2" raised  numbers.

#1272446.

Edited December 17, 2019 by Dodgeb4ya

[ggdad1951]

if memory serves, the rad weep line is BELOW the seal area of the cap....making it a non-pressurized system regardless of the cap you put on it.

[bkahler]

10 hours ago, Dodgeb4ya said:

Right on the rear passenger side of the tank in 1/2" raised  numbers.

#1272446.

 

Now you have me curious.  I'll have to look at mine this evening......