Unblocking engine coolant drain tap passage

[Owlsman]

I know there are already a number of historic threads on the seemingly not uncommon problem of unblocking the water coolant drain passage located at the rear of the engine block. Whilst all those threads have been very useful to me......I still haven't managed to, as yet, clear all the sediment out. Or, at least, what I mean is I cannot get water to pour out of the tap when I turn it on.

The story so far:- I've invested in a re-cored radiator (but not yet fitted), put in an 88 degree thermostat (when I discovered there was NO THERMOSTAT at all), replaced all the hoses (incl. by-pass) with good quality 'standard' rubber ones. I've yet to flush through the heater/hoses. All this, to get the heating/engine cooling system as reliable and efficient as reasonably possible. The only 'little job' was to check engine drain tap was working.

After unscrewing the drain tap, I could fairly easily insert a long narrow screwdriver (about twice the diameter of a typical narrow 'electrical' screwdriver) 4 or 5 inches and some black sludgy watery sediment trickled out. Subsequent poking with a straight length of 'coat-hanger' wire got me a bit further in. Some more sludge came out, but not a lot more.

Fast forward 90 minutes and several cups of tea later and the screwdriver easily goes in 5 inches and appears to sound as though it's hitting solid metal...…..and this is the bit that really puzzles me, the wire easily also goes in for 5 inches then with a bit more wiggling seems to go in a further half inch or so but that last bit is quite a tight fit as if it's just gone into a very narrow cavity. Again, it feels and sounds as if I'm hitting solid metal.

As I've got a 90 degree flexible Karcher pressure washer attachment I even manged to give the passage a couple of blasts with that. Tip: don't try this wearing your best dinner shirt if you want to go out later to a posh 'do

The passage seems to be clear of any sludge now but after I refitted tap and ran the engine nothing comes out. I've seen the very useful 'slice' picture of the back of the block (on a previous thread) and it looks as though the passage is a long tapered 'V' shape but this doesn't seem to be what I can feel with the screwdriver and my coat-hanger wire.

What actual shape is the passage as it enters the water jacket?

Is 5.5 inches as far in as I'm going to get before hitting solid metal? If so, why is water not freely running out?

I'd prefer a physical resolution rather than resorting to chemical descalers/crud removers, but I will if I must. I just feel that I am so close to unblocking everything. Am I missing something?

Thanks, as ever guys 'n gals for any help you can offer.

[ianmack]

If you’ve used a straight screwdriver have you tried using something curved? You may have made a straight hole through a mass of muck and the coolant may be held back by the remainder.

[philthehill]

The floor of the water jacket at the rear of the engine does rise upwards from the drain tap and goes around the back of No: 4 cylinder wall.
It also goes to the left along the camshaft side of the engine and upwards to and through the top of the block via the transfer passages.

If you are not getting anything through the drain plug you must have a serious blockage at the rear of the engine water jacket.

I had this occur recently and had to take out the rear core plug and poke around to clear the sludge.

You could fill the block with food grade Citrus Acid mixture and leave for 48 hrs and then flush. It has worked well for me, it also helps get rid of the rust in the water jacket.

https://www.ebay.co.uk/itm/CITRIC-ACID- ... rkP_VvrDqA

I mixed 10 table spoons of Citric Acid / 600ml of hot water and poured it into the block.

I upended the bottom hose after blocking the heater connection so as to keep the Citric Acid mixture just within the block.

5.5" of screw driver into the block drain hole is about right - I have just tried it.

Phil

[myoldjalopy]

Mine is blocked the same but has caused no problems over the last 19 years. It would be nice to have the tap working properly though. Next time I drain it I might have another go at clearing it....

[Owlsman]

Thanks all. I've just ordered some citric acid...….I'll 'claim' it as household expenses as the kettle and the teapot need descaling .

Sorry, if a daft question now:- How to I get the citric acid into where it's most needed i.e. in the back of the engine block, if I can't drain the block 'cos the drain plug orifice is bunged up? Do I remove the thermostat cover and pour as much as I can in there? The engine is in situ, of course.

As much for my curiosity as anything, can anyone confirm what shape the drain passage actually is please. It 'feels' as if it's like a parallel sided tube (apart from the small tight bit right at the end where I can only get my coat-hanger wire in) but the picture on the historic thread clearly shows it to be tapered towards the main water jacket.

Many thanks again everyone. Really much appreciated.

[philthehill]

Drain the block by removing the bottom hose.

Refit the bottom hose but with the radiator end facing upwards. Make sure that you have blocked the heater pipe take off in the bottom hose, I used a bolt and a jubilee clip.

Remove the top hose.

Pour the Citric Acid mixture into the upside down bottom hose until it starts to flow out of the thermostat housing.

Leave for 48 hrs and drain and flush.

You may have to do the operation a couple of times but you will get there in the end.

The bottom of the water jacket at the rear of the block has to slope upwards as it has to pass over the rear main.
Once the threaded drain plug stub casting is passed through the water jacket opens out upwards, forwards and across the block.

For general information:-
The water flow in the rear of the block is determined by the size of water pump impellor and the thermostat being in place. At times the water flow at the rear of the block can be very poor.
Poor water flow to the rear of the block can cause overheating around cylinders Nos: 3 & 4.
Racing Minis can have the block to head passages sealed and a transfer pipe fitted at the rear of the head to ensure that water has to pass via the rear of the block/head. Unfortunately not possible on a Minor without modification to the cross member behind the head
The 1275cc Cooper S had a deeper impeller to increase the water flow and relieving the water jacket casting to the right of the water pump increases the flow around the block.
If fitting the deeper 1275cc water pump to a small bore block the clearance to the rear of the impellor may have to be increased.
Water pumps with the deep cast impellor are best for shifting water around the block.
To overcome cavitation around the water pump impellor BL on the 'A' Plus engine fitted a larger water pump pulley to slow down the rotations of the pump. The Cooper S water pump had an option to fit a larger cast steel pulley.
Phil

[RobThomas]

Citric acid becomes much more vigorous if the water is hot. Maybe run the engine with the filler cap off (no pressure) and then pour in the crystals just before switching off?
The down side is that it might attack the radiator tubes if they are already a bit thinned down.

[philthehill]

Rob
Disconnecting the radiator top and bottom hoses as suggested in my post above keeps the Citric Acid contained in just the block and alleviates any possibility of the radiator being attacked.

Phil

[Owlsman]

Many thanks chaps. Fantastic detailed response Phil. I'll let you know how I get on...…..and give you an update on the kettle and the teapot!

[Owlsman]

Sorry for slight delay chaps in bringing you the final episode...….well, it's not quite really. More of that in a mo!

The engine drain blockage was actually shifted by a couple of blasts of compressed air!! Someone who has been very kind and helpful to me at my local MMOC group very generously offered to help me fit an Accuspark electronic ignition kit at his place. Actually, he fitted it while I just stood and watched and passed the occasional spanner.

Whilst there, he asked if there was anything else I would like help with. 2 minutes later his compressor was fired up, the drain plug/tap removed and after 2 quick blasts water was pouring out of the orifice like Niagara Falls. We took the opportunity to flush everything through and this morning I've just finished fitting my newly re-cored radiator and fresh 'blue' antifreeze.....which brings me on to my minor query.

As you will see from the photos (hopefully) the gubbins of the 'old' radiator is very much narrower than my 'new' one. The new one is one that was given to me and I've had re-cored at a local rad specialist and I think it was narrow just like my 'old' one before I took it in for the re-core. (I've painted it and generally smartened it up). From the photos, does it look like I've now got a rad with a double/twin core? If so, does it matter? As you will probably gather, I'm not sure what a twin core rad looks like anyway!

……..Just in case you were wondering...….because I didn't need the citric acid to unblock my drain plug, I haven't tackled the kettle and the teapot yet. That'll be my 'summer project

Thanks again all, for your help and advice.

[geoberni]

As you will see from the photos (hopefully) the gubbins of the 'old' radiator is very much narrower than my 'new' one. The new one is one that was given to me and I've had re-cored at a local rad specialist and I think it was narrow just like my 'old' one before I took it in for the re-core. (I've painted it and generally smartened it up). From the photos, does it look like I've now got a rad with a double/twin core? If so, does it matter? As you will probably gather, I'm not sure what a twin core rad looks like anyway!

Well what I understand as a 'Twin Core' (and I may be wrong) is having a double row of pipework running top to bottom, rather than a single row. So it you look at the bottom where there's a bit of a gap in the vanes, you should see two rows of vertical pipes.

So this image is just a single core. http://www.instantradiatorokc.com/uploa ... 2_orig.jpg

[philthehill]

Practically - having a twin core or single core radiator is of little consequence as the Minor is way over cooled. It is the thermostat that controls the engine block temperature - therefore so long as you have the right temp thermostat in the head and your water pump is working all will be alright.

The most important thing is that you have a radiator that does not leak and is crud free.

Whatever core the new radiator is - just enjoy.

[Owlsman]

BREAKING NEWS...…...Citric acid works a treat getting rid of tea stains in a metal teapot!!

More seriously, I went for a half decent run today in my '62 saloon fresh with its unblocked water jacket drain tap and re-cored radiator and the temp gauge maintained a constant 88 degrees (it does have an 88 deg. stat). Perfick.

That radiator in geoberni's link will need at least 2 tins of Radweld, methinks, to stand any chance......