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MG MGA - Engine block drain tap

My engine block drain tap has never worked and I have no intention of trying to get it working at this time. My ’59 roadster has plenty of more pressing problems. When I had the dizzy off recently I noticed that the drain cock handle was sticking straight out from the block. Intuitively to this shade tree mechanic, that position indicated that the drain was open. My manual also indicated that it was open. So I “closed” the valve, see the attached picture.

About the same time Barney put out his thread that he had updated his list Confidential Service Memoranda. Looking through the list I noticed that MG291 is for the Cylinder Block Drain Tap, http://mgaguru.com/mgtech/care/csm/mg291.pdf. The memo indicates that the drain cock is closed when pointing out and away from the engine.

Not that any coolant is coming out regardless of the position I have the valve handle, but I would hate to have some sediment or rust break free at an inopportune moment and I suddenly have a dry engine block because I didn’t have the valve closed.

Could someone give me a definitive answer on the position of the drain tap valve handle?

PS – I would like to add my big thank you to Barney for his site and advise!

John



jjb Backman

John

Your post had me scurrying under the bonnet to see what position my tap is in, only to find I don't have one! Instead I have a blanking plug. Mine is an 1800 engine and, looking in the parts list, a blanking plug is offered as an alternative to the tap.

If you are in any way feeling uneasy about your tap, an interim fix could be to fit the blanking plug.

Steve
Steve Gyles

Yes my tap has the handle pointing out with it closed as you described. This had me fooled for a while as this goes against all our engineering practices in the UK and I assume the rest of Europe. Normally on a valve the direction of the handle would indicate the action. For example across the valve (parallel to the engine) would indicate close, therefore exactly opposite to what we have on an MGA.
Bob (robert) Midget Turbo

Yes, the handle is pointing out when in the off position. It is opposite of conventional reasoning. I just assumed it was a British thing.
Ed Bell

I have the same tap on the bottom of my radiator too.
dominic clancy

Dear jjb.I have to tell you that your posted image looks like a close-up photo of the creature from the dark lagoon.Hope you get your tap query sorted.
MR Blencowe

I recently installed a new reproduction drain valve on mine and had a devil of a time getting it correctly oriented. Using the supplied fiber washer, there was just no way to get it clocked correctly; I had to make a new washer out of thinner material in order to make it fit straight up and down.
Del Rawlins

Even with the tap open you may not be in dire risk of spraying coolant all over the place.

In typical engines, the sediment and rust flakes have drifted to the bottom of the water jacket and formed a fairly solid block there. In many cases you would need to use a drillbit through the tap or with the tap removed to excavate you way to water again.
Bill Spohn

MR,
I have to say that the posted image looks pretty good to me. Are you actually having trouble viewing or just being humorus?
Cheers,
GTF
G T Foster

Bill's point is well taken about removing the crud to restore flow to the drain. My first "A" was plugged so badly that I couldn't get it clean with only the drain removed; I had to remove the head to clean out the water passage. And that was in 1966 on a 1600 that hadn't have been out of the factory but a few years. There seems to be a tendency for rust to settle there; all the more reason for good antifreeze.

Ken
k v morton

If the crud settles at the drain it shows good design. When the engine was new, or after you loosen up the crud, a regular draining of some coolant should clear the passages quite well.
If the tap was situated where the crud does not deposit it would not work properly.
Good antifreeze (one with rust inhibitors) will help and should be used even in hot countries.

Mick
Mick Anderson

Steve
I rushed out to look at mine to. A 1957 1500cc engine. No tap and no blanking plate...just a hole. I assume it is a blind hole but I refrained from poking it! The parts book shows the tap followed by "selective" so presumably only fitted on some versions/markets
David
David Marklew

David,

No, it is a hole, and blocked with casting sand, rust and other crud.

What might selective is whether a tap or a plug screw is fitted (I thought all initially came with a tap).

There does need to be a way of draining the block without removing the engine and tipping it on end.

I would recommend fitting a plug as there might come a day when the blockage gets dislodged and drains your coolant out on the road.

FWIW I have a tap fitted, but whenever I have drained the block I have unscrewed it as the flow rate is so slow.

cheers

dan
Dan Smithers

When I acquired my present "A" ten years ago now, the engine drain valve was well and truly blocked. On removing the valve - nothing stirred. Eventually I wound a 3/8" (10mm ish) dia drill in about 2" before I got coolant to run out. At least I could drain it then.

Subsequently, when the head got "unleaded" I had the head and block waterways cleared out by the garage and have since changed the anti-freeze annually, using distilled water as the dilluent. This way any remaining scale gets gradually dissolved, keeping the passages clean and the anti-corrosion side of things up to scratch.

The two drain valves are always clear now. Perfect!
Pete
Pete Tipping

Thank goodness I still have something original amongst all my bits and pieces. Just had a look at my old 1500 (1958) engine in the corner of the garage. Pristine drain tap with the handle in line! hurray!

Steve
Steve Gyles

I looked at my block drain tap after first reading this thread and found my drain did not have a handle. It has two short "wings" that are used to rotate the drain about its axis to open. Another bodge fix by a PO I thought, I'll start looking for an original (there's one on e-bay now). Looked at my spare engine last night, as it came out of the donor car. It has the same winged drain tap. Maybe MG used both types, does anyone else have this variation?
George
G Goeppner

I've got one like that on my ZB on the engine and the radiator.
I'd assumed it was a replacement.
Dan Smithers

You don't need to pay ebay proces for replacements. They are available new at a very reasonable price
dominic clancy

MG used both types of tap. I have attached a scan of the winged type from the factory edition of the mga twin cam Workshop Manual.


Mick


Mick Anderson

Following on from the earlier post with a scan of the "winged" type tap on the engine block, I have loaded a scan of the same tap on the radiator.
MG used them in both places.
This is also from the factory edition of the MGA Twin Cam Workshop Manual.
Note the oil fittings pointing down on the steering rack. This one of the two things that makes a Twin Cam rack different from a pushrod rack, the other being that the pinion shaft is 1" longer.

Mick


Mick Anderson

Mick, the funny thing is I haven't ever actually seen a drain tap on a twin cam radiator (including mine) anyway!

Andrew
A Buick

Hi Andrew,

I suppose after 50 years it is difficult to know what is original and what is not.
I have found a Twin Cam with a radiator drain tap in your city. The Twin Cam of Garry K has the winged type drain tap.
A strange thing is the variations in factory documentation. The Workshop Manual and Driver's Handbook show a winged type drain tap. The Service Parts List shows the right angle handle type tap.
The Engineering Technical Data Book, which was used by the factory when building the cars, says "Drain Tap L.H.S of vehicle projecting downwards 1/4" B.S.P."

Mick
Mick Anderson

I don't want to beat this subject to death, but the winged tap shown in Mick's image is a stamped metal wing. I have this type on my radiator. The block drain tap on my two engines has a cast brass wing, so maybe now we have 3 variants used by MG....?
George

G Goeppner

This is the place that sells the taps and a whole load of other interesting bits too

http://www.vintagesupplies.com/
dominic clancy

It appears that two of the variants are available from Vintage Car Parts. See www.vintagecarparts.co.uk/en/list+taps,+pipe+and+fittings~taps~drain/

However one (537 butterfly [winged] type drain tap) has a 1/4" BSP taper thread and the other (339 brass straight drain tap) has a 1/4" BSP thread (straight?).

Anyone know whether or not the radiator and block ports are straight or tapered threads? Or does it matter any more?

Thanks

Larry
58A
Larry Hallanger

My 1500 has a straight thread, and as mentioned above, the sealing is accomplished by the fiber washer.
Del Rawlins

This thread was discussed between 25/11/2007 and 06/12/2007

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