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MG MGB Technical - Engine rebuild problem. Next chapter

Hi Chaps,
Many thanks for your replies to my 1st posting ‘Engine Rebuild Problem’.

I have now put a new Head Gasket on making sure it is the right way round, although the 1st one was ok, also put another new Water Pump, Thermostat and Gasket on just in case the 1st ones were dodgy and I’ve changed the Temperature Gauge.

When I took the thermostat off and opened the drain tap on the block there was no water coming out of the tap. Took tap out and checked that it and the hole were not blocked (they weren’t)

It seems there is no water getting round to the block, so is this the reason for the overheating? If it is, I am now stumped as to why it is not getting round.

Any ideas?


J Fowle

John I have found that the water path to the tap is not direct and it sometimes takes a good wiggle and poke around with a wire to get a flow. It seems to be a bit of a sediment trap. Mine was always blocking but on an engine build last year with all the welsh plugs out it was very good in the water jacket, I had the block hot tanked anyway. If you are worried about this its nor hard to pull a welsh plug to get a look in, the rear one near the distributor would be the best place to look as its close to the tap and the most likely place for gunk to settle. Denis

ETA: Denis posted as I was typing but what I've put stands

perhaps it's an airlock, sh*t/crud/muck/foreign body(s) - blocking passages

did you test the new stat for opening and closing before you installed it

did you pre-mix the coolant (or bought pre-mixed) so that you could measure the quantity you were putting in compared to capacity required - that way you also know you have the correct ratio - refills rarely take the full dry fill quantity - and refill slowly to avoid air getting in

I'd also try getting a stout wire and scraping out the drain tap hole and removing the heater valve to do the same with the heater valve and the hole to it as the blockage may be further back in any of them

then I'd (now) with the rad, engine and heater matrix - flush each of the three until water runs out thoroughly clean
- reverse flush each of the three until water runs out thoroughly clean
- final flush through each of the three until water runs out thoroughly clean

whilst draining and flushing I'd be scraping out the engine drain tap hole particularly - you'd be amazed how much crud could be around or on its way there in the flushing water

did you also follow the refill instructions in the relevant Driver's Handbook (which will also give you the capacities, don't forget to allow for the heater)

talking of which did you check the heater valve was fully open by looking at the valve rather than the dial on the dash

there's a few 'tricks' you can do to encourage the air out but I've only ever followed the Driver's Handbook instructions with my midget and had no problems the many times I've had to deal with the coolant

Driver's Handbooks -
Nigel Atkins

This thread was discussed between 20/06/2014 and 21/06/2014

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