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MG MGB Technical - No water round cylinder 4

Head off and no water round rear cylinder on my B. Car starts 1st time and runs well on the road but overheats and cuts out in traffic. Have elec fan, new hoses etc. How can I clean out the block? And yes, I have tried all the flushing products I can find.
J I Jones

You may need to remove the head so you can rod (drill) the muck in the bottom of the block out the block brain. See mgaguru web site for details
Mike
Mike Ellsmore

You seem to have more casting sand left in there than most, the usual complaint is that it blocks the drain tap.

I don't know how the passages run, but as you already have the head off I'd be looking at the front pair with a view to the rear pair being similar.

However while I can understand that would cause the rear cylinder to overheat, possibly affecting the plug or even warping the head, I can't really see it causing cutting out.

Overheating maybe - depending on what you mean by that term. I can imagine an uncooled cylinder causing localised boiling of the coolant round the adjacent cylinder, but whether that would affect the temp gauge sensor at the other end of the engine, or cause coolant loss as only three cylinders are heating the coolant, I don't know. Likewise cutting-out. Even if the back plug packs up the engine will still run on just three cylinders.

Also *no* water round the rear cylinder doesn't sound right either. I'm assuming there are passages between head and block for all four cylinders, I would have expected that to allow water into the jacket around No.4, even if it didn't circulate properly.
Paul Hunt

the engine block drain is often forgotten about when changing coolant and when cleaning and flushing the cooling system

often the engine block drain needs scraping out with thick wire when being drained and flushed even if this work has been done before

I think on the B engine it gets so bad with neglect that the drain can get blocked solid

the engine drain is on the r/h/s of the engine near the dissy and heater valve, a drain plug on later cars and probably a non-working drain tap on early cars

I always recommend after cleaning the cooling (and heating) system with something like Bars Flush Cooling System Cleaner that the block and radiator (and heater matrix) are flushed/back flushed/flushed again

(better still if you can take the radiator and heater matrix out of the car to give them a good shake at the same time as flushing and back flushing)

also important to refill coolant steadily and as per Driver's Handbook instructions to prevent 'hotspots'

the cutting out in traffic might be another issue but the overheating certainly wont help once the full circulation of coolant around the system is sorted then other possible issues can be addressed
Nigel Atkins

Knock out the rear O/S core plug. It is not uncommon to find large amounts of sand and rust blocking the water ways between 3 and 4 and particularly round the back of No 4. I have often found that the rear drain plug is not drilled thru to the water way.
jim soutar

I had the same problem and there was an inch of solid muck at the back of the block. It took a hammer and screwdriver to eventually remove it all. Long screwdriver through the water holes in the block and also removed all the welch plugs. The drain for the block must have been blocked for years as 10 bar of air did nothing. I doubt if any cleaning fluid would have made any difference.

Ronnie
RA Potter

as many owners don't buy, read or refer to the Driver's Handbook for their car they don't even know there is a engine drain that can be drained and flushed from

or many other details about the car they can find in the DH

http://www.mgocshop.co.uk/catalog/Online_Catalogue_Handbooks_5.html

ETA: I was still typing my last post when Paul posted so a bit of duplication on my part
Nigel Atkins

With the head off mine I found a similar build-up of gunk all around the back of that rear cylinder. In my case it was evidently wet gunk but reasonably thick/solid.

I worked at it through all of the nearby coolant holes in the block with stout wire (coathanger cut to purpose) and also lengths of that clear fuel line stuff, which holds a reasonably stout form on the thickness of the tube section.

I attached a suction pump to the tubing and cycled a draw/push action with the tube end well down in the mush. That eventually got the bulk of the mass shifted.

Of course, protect the cylinders and oil run holes in the top of the block to prevent any 'popping' mess running where you don't want it. Also, loop the end of the wire to prevent a section from slipping in to the cavity.

I also worked on the drain hole, with some success but probably not getting to all of the crud inside that block section. When doing that spot be sure not to damage the somewhat shallow thread area you will need to insert the plug.

Regards
Roger
R Taylor

Hi and thanks for the interest. Have any of you (especially our Aussie friends)ever tried the Liquid Intelligence flushing product? If so, with what results?
Regards, Ian
J I Jones

G'day Ian,

No, I've not used that product. I'm not a great fan of flushing products. Did use something years ago on a Holden Torana I had at the time but found it difficult to flush all of it from block recesses. That worried me in regard to any traces affecting anti boil/freeze.

Regards
Roger
R Taylor

Flushing compounds carry a risk of their own. A friend of mine decided to flush out the cooling system of his two year old pickup truck. After finishing the flushing, according to the instructions, his heater core developed a leak. RAY
rjm RAY

I hope he didn't then use Barr's Leaks, and completely block his rad ...
Paul Hunt

Nope. The leak was so bad that the heater core had to be replaced. This required the removal of the complete dashboard assembly and the AC evaporator. Needless to say, he wasn't very happy about the whole situation. RAY
rjm RAY

People moan about the MGB heater, but like your pal's pickup The Garage showed a high-end Mercedes with a heater matrix leak, and the whole dash had to come out for that as well.
Paul Hunt

I owned a '75 MB 300D that had a heating problem. They used a double matrix system, one for the driver's side and one for the passenger's side. To repair it, the console, front seats and entire dashboard had to be removed. I did this job in February with a foot of snow on the ground. Not a lot of fun. When my B eventually started to leak a very small amount of coolant, I pulled the heater box out. An easy job compared to the Benz. When I went to order a new matrix, nobody had any in stock. Everyone had them on backorder. I was forced to use one of my spares. I pressured tested them and they all held 15 psi. I simply chose the one that looked the best. That was over twenty years ago and the used matrix, that I installed, has held up just fine. Try to do this job on a Ford Taurus. The dealer book time is thirteen hours! Most of these cars were scrapped if their heater cores were leaking as the cost of repairing them was so prohibitive. RAY
rjm RAY

This is why I always want the block to be properly cleaned out when getting an engine rebuilt. A good caustic clean makes a huge difference to the cool running of the engine. Just doing a replacement of all the mechanical bits doesn't get rid of all the crud that is hiding deep within waterways and oil ways.
Dominic Clancy

Even a caustic clean won't shift some of the debris - over the years it settles and hardens around the rear of number 4 cylinder and in the drain drillings particularly.

I have a selection of "special" tools that I use with electric drill and air needle gun through the various openings in the block to loosen the sediment and often chunks of cast iron flashing from the casting process, sometimes casting sand too!

After the mechanical clean, I flush with high pressure water and then leave overnight soaking in a deoxidising bath followed by another high pressure flush and dry with compressed air.

Finally a thin coat of red lead primer will retard further corrosion - especially if antifreeze coolant is used all year.
Chris at Octarine Services

This thread was discussed between 13/01/2014 and 06/02/2014

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