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MG Midget and Sprite Technical - radiator cap

My 64 midget has been having a few issues (mostly due to lack of use! only managed 390 miles in in over the last 12 months)

Anyway, its losing water and has overheated once due to lack of water. Its not head gasket as done compression test - and it runs way to well for that, but it is losing water out of the overflow pipe on top of rad. (its the early style radiator as my car is a 1098cc engined car)

It seems that once warm, the cap doesnt hold pressure and lets water out of the overflow - hence the water loss, when driving along, it leaves a water trail.

I've looked at the cap and it seems to be too short so as not to seal against the neck of rad - I've measured it and it is 27mm from the top of rad cap down to the rubber seal.

No one near me stocks any longer ones, is there a longer one available or am I barking up the wrong tree?

John Collins

There are certainly different length caps, but I can't remember specs off the top of my head.
Dave O'Neill2

Lawrence done a thread on this for the Archives so it's in there, if I find it I'll post the title as links don't work
Nigel Atkins

the thread is called

7lb longneck Radiator Cap, part No's

in this forum (MG Midget and Sprite Technical)

just an example of where you might be able to buy it but I don't know if they are a good supplier or if the part quality is good as I've never dealt with them
Nigel Atkins

If it's a standard Mini item, you could try Min-its at Coleshill.
Dave O'Neill2

Save you searching the archives.

Sounds like you have the wrong cap. There are 2 lengths for Spridgets. Short and long.

Short neck(wrong for your car) is just about the measurement you have. 25mm.

Long neck (correct for your car) is 34mm.

You need a 7lb long neck cap.

QH part number FC41A (fits a range of car makes as well as pre-crossflow rad Spridgets).

Some equivalent part numbers to the QH FC41A are:

GRC101. Not to be confused with GRC110, which is the 15lb cap for the expansion tanks on the later 1275 and 1500 x-flow radiator setups.

FRC64. This is made by First Line who claim OE quality. I bought one. Its well made.

CHT105 From AH spares.

Lawrence Slater

The one Nigel has linked you to are charging too much for post. Total of 9.11

This one will do you too, and will cost a total of 6.48.

According to the website it's genuine QH. But I would call them first to confirm the details, just to be certain.

Or there are loads on Ebay.
Lawrence Slater

Yeah I just put that supplier up as an example I didn't check out post but I think there was a scrolling postage banner that said something like 57 to somewhere

I did think about copy and paste of info but it's a short thread and it's sometimes useful to read the whole thread, plus giving a bit more practice and joy of using the Archive search
Nigel Atkins

Try Leacy's John, they may have them


Thanks for all above comments

Especially the part numbers, my local shop ordered me a couple of new QH caps, hopefully these will do the job!?!

John Collins

I seem to recall that some suppliers (Moss, maybe?) had the part numbers mixed. Or used the same part number for both versions of cap. Maybe my memory is wrong with this, but worth checking.


Moss have a habit of doing that, like supplying the same clutch release bearing for 948, 1098 and 1275!
Dave O'Neill2

or mixing up uprated front road springs and then denying it - :(
Nigel Atkins

This thread was discussed between 30/05/2012 and 02/06/2012

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.