The MGA With An Attitude
Radiator PRESSURE CAP and Interchange Parts List - CO-126
ARH1022 Cap [4-psi] for radiator block [1500 + early Twin Cam + early 1600]
ARH1039 Cap [7-psi] Com. (C) 71832 - [mid 1600]- Always supply AEH1542
AEH1542 Cap [7-psi] Com, (C) 88192 - [late 1600 + 1622] - retrofit to all MGA
Original radiator pressure cap for MGA has 1-1/8-inch reach to fit 1-inch deep filler neck. I like to call this the "long reach cap" for the "deep filler neck". The MGB and other later model cars commonly have a shorter filler neck requiring a 7/8-inch reach cap for 3/4-inch deep filler neck. Please do not confuse these different configurations. The long reach cap cannot be installed in the shallow (3/4" deep) filler neck. If you install a short reach cap in the deeper (1" deep) filler neck it will not hold pressure, same as having no cap at all.
Please review article CO-101 on Keeping your cool", and article CO-204 on Coolant recovery system". Early production MGA pressure cap had 4-psi relief pressure rating. In July 1959 at Car Number 71832 this was changed to 7-psi, and it is highly recommended that earlier cars should be retrofit with the 7-psi cap. This should not deduct points in a concours car show, as it is to be considered original by the factory design change and Confidential Service Memorandum CSM_MG/289 noting the upgrade to earlier cars.
At the inside top of the pressure cap there is a wide flange, actually a springy diaphragm, that covers the top of the filler neck. This generally prevents fluid from spilling over the top of the neck and directs the fluid to flow out through a small pipe on the side of the filler neck. That pipe is originally routed to a point low on the side of the radiator where any escaping fluid can drain on the ground. The diaphragm in the top of the pressure cap does not (originally) have to be absolutely pressure tight, just good enough to direct most of the overflow into the drain tube, and not allow much fluid to dribble out the top of the filler neck. As such, the original cap design used a bare metal diaphragm with metal to metal contact between the diaphragm and the top of the filler neck.
For the purpose of installing the coolant recovery system, the pressure cap DOES need to have an absolute seal at the top of the filler neck, because it has to be able to create a slight vacuum to draw fluid back into the radiator when the system cools down. You will notice in the picture at right that the top diaphragm in the cap has a thin rubber seal around the edge. This is not included on the original MGA radiator cap. It was not used much prior to 1968 (when radiators had shorter necks), so the demand is only for aftermarket conversions on older cars.
The radiator cap in this picture is the long reach cap with the top seal, one of those very rare items. This one is NAPA-Balkamp part number 703-1411, but ordering this part number does not guarantee that you will get what you need. In past years this same part number was used for the original type cap with no rubber seal at the top. Around 2001 or (thereabout) the cap design was changed to include the top seal. Since the new design works equally well in older applications, the new part supersedes the old one, and the same part number is still used. With demand being so low, and sales slow, it is possible that there may still be some of the older parts still in stock on the shelves for years to come. As recently as summer 2003 my local NAPA dealer had an older part on the shelf in Illinois, while a friend found this newer one for me at a NAPA dealer in North Carolina. So if you're buying one of these parts, open the box and check it before you walk out of the store.
Stant 10206 recovery type long reach cap with top seal
Pressure caps, 7-psi with 1-inch reach, as pictured above that will work for coolant recovery:
| Manufacturer | Part No. |
| Balkamp | 7031411 |
| Mini Spares | GRC101 (same as NTG part) |
| Motorad (Taiwan) | T-6 (UPC 055644000060) |
| NAPA | 703-1411 |
| NTG | B350A |
| Stant (Mexico) | 10206 (UPC 00333420010602) |
| Summit Racing | SNN-10206 (Stant) |
| Tridon | CA0750 (Australian origin) |
Check Amazon and Ebay for the good part numbers.
NTG part number B350A coolant recovery cap appears to be a standard pressure cap with a thin rubber washer added and left loose (not bonded). Otherwise it appears to be original style in all respects, including original stamping of the lettering on top.
Pressure caps, 7-psi with 1-inch reach that will NOT work for coolant recovery:
(This list could ultimately get to be very long).
| Manufacturer | Part No. |
| Stant | R-6 |
Cross reference numbers for the MOTORAD T-6 and STANT 10206 pressure caps. Check to be sure if these will or will not have the top seal to work for coolant recovery.
| Manufacturer | Part No. |
| ACDelco Aftermarket | 12R31 |
| ACDelco Aftermarket | RC-3 |
| Badger | BR-6 |
| Beck Arnley | 133-801 |
| Berkson | P-6 |
| BMC-Rover | GRC101 |
| Borg & Beck | FRC 64 |
| Bowes | 77-505 |
| Bowes | 7BC-6 |
| Bowes | 7BC-6 |
| Bradex | TCL7 |
| CarQuest | 33003 |
| Dole | DR-6 |
| Eaton Corp. | ER-6 |
| Firstline | FRC 64 |
| Ford | 240E 8100 A |
| Ford | 240E 8100 A1 |
| Ford | 240E 8100 A2 |
| Ford | 240E 8100 A3 |
| Ford | 1506245 |
| Ford | 1508306 |
| Ford | 1515128 |
| Ford | 1517588 |
| Ford | 1517589 |
| Ford | 1519321 |
| Ford | 1521874 |
| Ford | A710X 8100 AJA |
| Ford | A710X 8100 BA |
| Ford | A710X 8100 HA |
| Ford | A710X 8100 NA |
| Ford | B2AZ 8100 E |
| Gates | 31306 |
| Gates | 33003 |
| Gates | 7031411 |
| Gates | RAD6 |
| Gates, Canada | 31306 |
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| Manufacturer | Part No. |
| General Motors | 255300 |
| General Motors | 850797 |
| Ideal Aftermarket | 46004 |
| John Deere | AT29054 |
| Lazorlite | U95-4128 |
| Lucas | KRB211 |
| Lucas | LC3 |
| Lucas | LC3 |
| MGOC | GRC101 |
| Moss Europe | GRC101 |
| Moss USA | 583-004 |
| Motaquip | VCR207 |
| Motorcraft | RS-6 |
| Motorcraft | ERS 6 |
| Motorcraft | ERS 11 |
| Murray Temp. Control | M-6 |
| MQ | VCR207 |
| Powertrain | PCRC7L |
| Purolator | RC-6 |
| Robertshaw | RR-6 |
| Rover Group | ARH1039 |
| Rover Group | ARH1542 |
| Rover Group | ARH1662 |
| Talbot | 1-221-765 |
| Talbot | K21765 |
| Unipart | GRC101 |
| Vera | 53-10629 |
| Victoria British | 2-301 |
| Wayne | WA-6 |
| Wayne | WC-6 |
| Wayne | WR-6 |
| Wipac | S5300 |
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Vehicles this part fits:
Make Model Engine Year
Austin A60 1962-1964
Austin Cambridge 1962-1964
Austin Mini 1960-1964
Austin Princess 1962-1964
Austin Westminster 1960-1961
Auston Healey Sprite 1958-1970
Austin Healey 100-6 1958-1959
Austin Healey 3000 1959-1967
Buick Roadmaster 1942-1947
Daimler SP250 1960-1963
Fiat 850 1969-1970
Fiat Strada 1979-1981
Ford Anglia 1962-1966
Ford Anglia II 1.0 1959-1964
Ford Capri 1962-1963
Ford Consul 1960-1963
Ford Cortina 1963-1965
Ford Country Sedan 1952
Ford Crestline 1952
Ford Customline 1952
Ford Prefect 1.0 1959-1961
Ford Victoria 1952
Ford Zephyr 1960-1961
Hudson Commodore Series 1950-1952
Hudson Hornet 1951-1953
Hudson Pacemaker 1951-1952
Hudson Super Custom 1951
Hudson Super Jet 1953
Hudson Super Series 195
Hudson Super Wasp 1953
Hudson Wasp 1952-1953
Mercury Monterey 1951-1953
MG MGA 1955-1962
MG MGB 1963-1964
MG Magnette 1963
MG Midget 1963-1964
Morris Minor 1960-1966
Packard Deluxe Eight 1948-1950
Packard Standard Eight 1948-1950
Packard Super Deluxe Eight 1949-1950
Packard Super Eight 1948-1950
Rover Group (Austin) AH Sprite II 1.1 1960-1962
Rover Group (Austin) AH Sprite III 1.1 1963-1966
Rover Group (Austin) AH Sprite IV 1.3 1966-1974
Rover Group (Austin) Mini 848cc 1961-1969
Rover Group (MG) MG Magnette 1.6 1961-1968
Rover Group (MG) MG Midget 1.1 1961-1966
Rover Group (MG) MG Midget 1.3 1966-1974
Rover Group (MG) MG Midget 1.5 1974-1980
Rover Group (MG) MGA 1600 1955-1962
Rover Group (Morris) Oxford 1.6 1962-1970
Rover Group (Riley) Elf 848cc 1959-1969
Rover Group (Wolseley) Hornet 848cc 1959-1962
Skoda 105 1.0 1976-1989
Skoda 120 1.2 1976-1989
Skoda 130 1.3 1984-1989
Studebaker Champion 1952-1955
Studebaker Commander 1952-1955
Studebaker Truck E5, E7, E10, E1 1955-1960
Sunbeam Alpine 1960-1967
Addendum November 23, 2016:
The long neck recovery type pressure cap is Motorad T-6 or NAPA 703-1411 or Stant 10206. I have been trying to cross reference this to other suppliers but always end up with non-recovery type caps, because the original applications were non-recovery type. Some years ago Motorad and NAPA and Stant upgraded this part number cap to be recovery type but apparently no one else has. Nearly every NAPA store has one in stock. It is possible that Motorad or Stant may make it for other suppliers, but I haven't found them yet. Check Amazon and Ebay for the good part numbers.
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