Boiling like a kettle.

[sidecar]

In the last few days my Minor (un-modified 1964 model) has taken to blowing steam and water from the radiator cap after 2 or three miles. A change of cap makes no difference. The engine is a reconditioned one fitted around 5000 miles ago, a compression test shows three cylinders at 175 psi and one at 180 psi, so pretty good there.

I now notice water spluttering from the exhaust on a hot engine at tickover. Looks like head gasket, what do you think ?

[MarkyB]

A small amount of water from the tailpipe is normal.
As the compressions seem good I wonder if the head might be cracked?
Unusual but not unheard of apparently.
Another thought, could the thermostat be stuck shut?

[bmcecosse]

Compressions are VERY good! Has this come on suddenly ? I'm assuming the fan belt is ok/water pump turning ok? If you start up from cold - with the rad cap off and the water topped up - do lots of bubbles come up through the water? You could try rad flush etc - but it does rather point to a gasket failure or something cracked. Was there plenty of anti-freeze in it over winter? Stat stuck is certainly worth checking - although in my experience they stick open - not shut.

[sidecar]

Thanks for prompt replies, but oh dear cracked head is a possibility. I bought the car at the end of October, just before it got very cold , I checked the coolant after the initial cold spell. It is kept in a unheated garage..

Of with his head tomorrow , will let you know what i find.

[simmitc]

Is performance OK? Any strange odours? Binding brakes could cause overheating, but unlikely to be as severe as you describe. Do you have access to a cooling system tester or block testing fluid - this changes colour if combustion gases are present in the cooling system.

By "checking the coolant", does that include making sure that it had anti-freeze in it?

[bmcecosse]

I did wonder about the slightly evasive answer there !

[sidecar]

Cylinder head is now off and stripped down. Unfortunately, strange thing to say, but everything looks perfect. Pistons all uniform, head gasket perfect, all the valves as one would expect, no obvious differences. Only the inlet valves looked a little oilier than I would have expected, but it has been many years since I looked into a minor engine.
All the combustion chambers look uniform, no sign of water in one or two. Inspected for crack with magnifing glass and torch, nothing.
About two weeks into the big freeze, I remembered the minor, checked the radiator, nothing frozen, left it at that. Not very good should have drained it at the start. Thats why I think the crack theory may be correct.

[MarkyB]

Actual crack detection looks a bit technical;
http://www.ehow.com/list_6947342_ways-c ... racks.html

I wonder if a wipe with engineers Blue might show something?

I think the common place is between the valves but I'd go over the whole surface with a magnifying glass.

As it's only pressure leaking out, I'm not surprised that there isn't much to see.

Is there much scale in the waterways?

[Dean]

I have an earlier Minor, so the later ones may be different. I found it is really easy to think the engine, rad and heater are full of water but without realising it you have a huge air bubble sat in the heater matrix and the pipework from the bulkhead back. This can shift and cause the car to overheat.

[chrisd87]

Was the cylinder head torqued down properly after the recon engine had been run up to temperature a few times? I've tended to find the head bolts need re-torquing before the commonly reccommended 500 miles. Ages ago I had the head off one of my cars and after only a few trips it started boiling over pretty badly, blowing steam out of the radiator cap. On inspection the head bolts were quite loose, and after tightening them down the car was fine.

[bmcecosse]

The head should always be retorqued after the first heat cycle - I wouldn't go back to it 500 miles later! Never ever agreed with the 'air lock' theory - it clears itself as soon as you start the engine.....

[charlie_morris_minor]

The head should always be retorqued after the first heat cycle - I wouldn't go back to it 500 miles later!

but you do not feel it necessary to use a torque wrench on the head either do you

[bmcecosse]

I advise others to do so! But for many many years I worked on A series engines without having access to a torque wrench - I just tightened up until I felt the stud 'yield' slightly - and didn't have any problems with head gaskets. But officially I have to say - use a good torque wrench, tighten in sequence going round and round increasing the torque up to 44 ft lbf.

[MarkyB]

Some thread drift going on here.
How about some pictures?

[bmcecosse]

It's all part of trying to ensure the gasket doesn't leak - but i suspect a good reverse flush of the rad may be the best way to go forward.

[katy]

Have you checked/tested the thermostat?

[sidecar]

Latest update. Head off and stripped down, every thing looks perfect, see pictures. While I did not expect to see a crack, I thought I might see evidence of one, ie, some discolouration but nothing.
All waterways and rad clear, however on testing the thermostat (Katy) it did seem a little tardy in operation. Thinking about it, a faulty thermostat would give those symptons, as gases expanding in the head would force water back up the radiator, and that force would be considerable.
Thanks all for your help. Next step refit head without thermostat, and look out for a cheap spare head. Will keep people posted as its annoying when people post problems, but never come back on to say how they solved them.[frame][/frame]

[sidecar]

Another picture[frame][/frame]

[MarkyB]

I don't think I've ever seen such scale free waterways!

Have you tried a flat edge across it?

The inlet valve guides look very shiny too, it may be an optical illusion but they seem to stick out a lot more than the exhaust ones, are all the guides level on the other side?

[bmcecosse]

Stats are always 'tardy' to open when tested in a pan of water (I have found) - but as long as it does open, it should be fine. It's possible (but unlikely) that the vanes of the water pump have been damaged/rotted away. You shouldn't run without a stat for any length of time - ok for a 'test'.