Leaky coolant brass tap on engine block

[Owlsman]

The story so far.....I had to remove the brass tap in the first place to unblock the drainage channel - a long saga in itself but suffice to say I managed it.

Ever since the tap was replaced water has been weeping from the point where the tap meets the block....or so I thought. I've tried a variety of fibre washers and/or use of PTFE tape but nothing seemed to work. Then I noticed that fluid was seeping from the actual tap itself (possibly still from the block as well). Time for a new brass tap then, I thought.

3 days later (today) fitting said new tap - complete with copper washer and of course, having drained coolant yet again, I screwed it in hand tight as far as I could and just as I applied the spanner to finish off.....the tap sheered off completely leaving the 'stud' screwed into the engine block and about 2mm of jagged brass proud. Insert your favourite expletive here 'cos I can assure you, I used it too!! What to do? I don't have a tap and die set.

Fortunately, VERY, VERY FORTUNATELY, I tried to unscrew what was left in the block with my fingers and it worked! Phew! Needless to say, I've not held back on my comments to the Fleabay vendor. The fact that I could unscrew with my bare fingers gives you some idea of how much pressure I applied with the spanner.

To get me mobile again I've refitted the original brass tap which still 'weeps' slightly - I'm guessing, only when the engine is cold as, presumably when hot, everything expands and tightens up. I'm not losing copious amounts of coolant.

My questions now are - Do I abandon the tap idea and just replace it with a blanking drain plug? If so, it could well be made of the same quality of 'monkey metal'. If I were doing this in winter would it be brass monkey metal ?
- Can I use any sealant or washer types that will guarantee a watertight seal with the block? If I do go down the blanking plug only route, I don't want any sealer to be too 'permanent' as I will need to remove it from time to time.

IMG_20190804_114613155.jpg (1.91 MiB) Viewed 1064 times

As you can perhaps see from the photo (which I've sent to the vendor) it looks like there is a flaw in the casting which I think just emphasises the oft repeated mantra that the quality of replacement parts today is nowhere near the original quality. By just holding the 'old' and the 'new' taps, one in each hand, the new one seemed heavier and more solid.

As ever, any tips or advice will be much appreciated. Thanks.

[philthehill]

Sorry to hear about your woes.

If the taper of your original tap is leaking you can always dismantle the tap and lap the swivel part of the tap into the body with Brasso or similar.

If your original tap is a BMC item I would suggest lapping the two parts together is a better way to go than replacing with new.

If you fit the copper sealing washer (Pt No: 6K638 (MOSS) you should have no problems and there is no need for sealer.
I would suggest purchasing two washers just in case you have to fit the extra washer to get the tap vertical.

Best of luck.

[Owlsman]

Many thanks for your prompt response, Phil.

Sorry, I might be a bit dim here (err...not for the first time in my life!!) but what do you mean by 'lapping the swivel part with Brasso'? Do you mean removing the split pin, the washer and spring to release the lever and then cleaning it all out with Brasso before reassembly?

[philthehill]

Lapping in involves turning the swivel part in the tap body to get the swivel and body perfectly aligned as regards the two contact surfaces so that there is no leak.
It is a bit like lapping in the inlet and exhaust valves. Valve grinding past is a bit coarse for this type of lapping
The spring is there to pull the swivel part into the body which helps the sealing.

[Owlsman]

Message received and understood. Thanks for that, Phil.

I've just 'splashed the cash' and ordered some crush copper washers @ 30p each. I'll let you know how I get on both with my leaky tap and my Fleabay vendor.

PS: As it happens I do have some Brasso but I'm thinking that a bit of paint scratch remover paste may be Ok. It's like polish of course but just slightly more abrasive. I could always use that first and then just finish off with Brasso for a nice smooth/tight fit.

Thanks again

[Owlsman]

Update....well, sort of:-

Existing tap repair - I followed your suggestion Phil and lapped in the tap/lever part to the main body of the tap, firstly with scratch remover paste then Brasso but there was no real improvement. Coolant still weeping out.
I then re-did it using fine wet 'n dry paper, so that both surfaces had a satin-type finish. When I reassembled the tap it seemed really tight but back on the car it still allowed coolant to seep through:(.
The good news is that there was no sign of leakage from the block using the copper crush washer.....but I couldn't resist winding a bit of PTFE tape around the end of the thread as well.
Not that I'm looking for an explanation but I'm really surprised that this coolant leakage (and it really is only minute) is from a static stone cold engine. I know that when the engine is running and the coolant is circulating, it does so under slight pressure, so notwithstanding heat expansion and all that, I could better see that any 'weak points' would be found then.

eBay vendor response - I was asked to return the faulty brass tap amidst surprise that 'of 1,000's of items already sold without failure', mine seemed to be the one exception! Without any other acknowledgement or comment, this afternoon I got a message that 'my purchase had been despatched'. It seems that another tap is winging its way to me.

I would have preferred to have repaired and retained the original item but 2 failed attempts suggests that I'll have to fit a replacement after all.

[Owlsman]

Just to round things off...….
The replacement tap arrived this morning and to be fair to the vendor, it was accompanied by a nice letter of apology and detailed instructions how to fit it. A bit of PTFE tape had already been put round the thread and the copper crush washer.

Fitted it just now. No sign of any seepage either from the block or the tap:) . I'll keep the original as an emergency spare, although I can't imagine for a minute, that there could be a sudden and catastrophic failure of the replacement tap now.

Happy days...….until the next problem arrives! That's what keeps you on your toes though when you decide to run a classic car, eh?

Thanks again for the advice and tips received.