I am fast losing patience with

[Mad Mart]

I wonder; could the face of the block be distorted?

I was wondering that also, or has the head been skimmed too much? What is the distance from the skimmed surface to the bottom of the camshaft journal? (I can't remember the minimum thickness).

[tinweevil]

Are the bubbles a sign of head gasket issues still ?. I have re-torqued once after it last ran.

How many bubbles are we talking and how long has it been sitting? Did the bubbles tail off or was it a steady stream? It takes a few heat cycles to get all the dissolved air out of water after a fresh fill and more to get rid of any that gathers at high points within the system. The design of the system is such that it will expel a bit of air that has gathered at the highest point each time the engine warms.

If the head comes off again for a block check then I'll send you a gasket set and you'll get a refund if it fails.

[JPB]

I'd also consider having further testing done on the head since it's possible that there's a very clean crack which doesn't open up on the table but would when the engine's running and hotter than [the head] would be during pressure testing.

I've found exactly that with a few of my Reliant heads over the years. They're aluminium too and, in some cases, where refaced ones have been pressure tested, they've held up well on the table but subsequently failed to seal around the tops of the liners, a phenomenon eventually traced to fine cracks running from the combustion chambers on the inside of each liner, over the fire ring and directly into the water jacket.
We discovered this courtesy of a 750mc member whose partner worked in a hospital emergency department and had access to "suitable" test equipment.

[80Sprint]

Thanks for the offer Julian , i may well take you up on this. It's a good point there may still be air escaping after re-filling but would that also cause the overheating ?

I will push it a bit more at the weekend and see if the bubbles stay the same , stop or get worse. If they get worse i would think this may be a gap opening further. If i manage to get hold of a hydrocarbon tester i will also use this but if all else fails it will be off with the head again.

[80Sprint]

Had another go today. Started by checking the water level. I opened the thermostat plug and it took about 2fl oz. I then noticed the expansion tank was a little low so i opened the top up and this released pressure ( it had been standing a week ) and the thermostat housing dropped some more. It took another 2 Fl Oz and then i topped up the expansion tank.

Got the car started and the timing is set to 12 deg. Spits a lot through the carbs at idle and i think they may need richening up a bit but improved as it got warmer. Ran it at 1500rpm approx for 5 mins. Dash gauge read 70deg after 5 mins from stone cold but all was well. Hoses felt soft still and no bubbles in the tank. I did notice however when i topped it up there was bit of a film over the water in the tank.

7 mins and i could just about leave my hand on the top of the rocker cover before it got too hot. Hoses soft , fan has kicked in and gauge at 85 deg. No bubbles. Some white vapour from the breather now but not too bad.

10 mins and all hoses and rad are hot . Hoses still soft. Vapur a little worse but again not drastic.
Temp now hitting 90 deg and start to see a bubble or two in the expansion tank. Fan still blowing and dropped the revs to 1200.

11 mins and nearing 95 degs. Other symptoms the same except bubbles seem to be on the increase. Shut her down....

Realised i can't test the heater as i don't have the blower on in case the head comes off again. Vertical hoses to the heater were both hot though so assume flow is ok.

I think the head is sealing ok when cold but something opens up at approx 85 deg creating a leak and bubbles in the tank. The more it runs the more it heats up and opens up. I have got my eyes on a gas tester at work but not sure if it picks up hydrocarbon. Looks like it could well be a head off job again though...

[JPB]

That certainly sounds as though there's gas leaking into the coolant, especially as the system was still holding pressure after a week.

Do you have access to another head that you could try? I'm still thinking that either there's a crack in yours or that the block isn't flat.

[Stag76]

If you heat water in a saucepan, it will start to form bubbles at 85 degrees, and by 95 degrees is nearly boiling, so bubbles may not be an indication of HGF etc. In most cases where compression is getting into the water, water will also be getting into the cylinders, making the plugs look as though they have been steam cleaned. The only sure method is to use a tester. 95 Degrees after only 11 minutes idling in cold weather would seem to suggest that the water is not circulating properly.

[80Sprint]

These always looked suspicious to me but i had the head pressured tested after i spotted them and it was given the all clear.

[JPB]

If you heat water in a saucepan, it will start to form bubbles at 85 degrees, and by 95 degrees is nearly boiling, so bubbles may not be an indication of HGF etc.

Yes, but presumably your pan is on earth at atmospheric pressure, the 13psi cap will allow water to reach a higher temperature before it boils, that's why it's there.

In most cases where compression is getting into the water, water will also be getting into the cylinders,

I've only done head gaskets on around a dozen slants and a couple of V8s and the most common failure mode - combustion gases escaping into the coolant - will tend to work in one direction as, unless the engine's completely had it, compression pressure is vastly higher than the coolant pressure.

The only sure method is to use a tester.

Agree with that.

95 Degrees after only 11 minutes idling in cold weather would seem to suggest that the water is not circulating properly.

Perhaps, but it wouldn't explain the bubbles as the coolant is well below boiling point under 13psi at 95 degrees.

[Stag76]

Sorry..my mistake. I presumed you had removed the cap in order to see the bubbles.

[80Sprint]

I pulled the head off this morning. I first noticed all the head studs had a lot of oil around them when i pulled them out. When i took the head off and baled out the water that falls in a couple of the bores i found the pistons also seemed oily. You can see the piston as it should be below and then as i found it after only half a dozen runs on the drive up to temp or a bit beyond. The block is a good condition second hand one and the old pistons were fitted with new rings. Could something be wrong with the rings to get this or fitted incorrectly ? Could oil be trying to lift the head and causing the overheating.

I don't think i could even contemplate having to take the engine out and strip it again ...

[Mad Mart]

Mike, sorry if I'm covering old ground but what torque did you tighten the head bolts to? After the initial warm up after replacing the head, did you leave it until at least the next day & then re-torque the head? If you drain the block (3/4" brass bolt on L/H side of block), you won't get water in the bores.

[80Sprint]

Martin

I ran it once up to about 90deg as i wanted to see if the temperature held where it should but shut it down when it did not stabilise. I then left it to cool over a day or so and then re-torqued the head although they bolts did not really move any more. ( 55lb)

How can i tell where the oil came from. I did not get clouds of smoke whilst it was running. Do you think this was pushed up the oil ways and leaked from the gasket into the cylinders or do you think this could be a rings issue ?

I can live with having to sort out the head with a replacement but i was not planning to have the block out again any time soon.

[timinder]

Had another go today. Started by checking the water level. I opened the thermostat plug and it took about 2fl oz. I then noticed the expansion tank was a little low so i opened the top up and this released pressure ( it had been standing a week ) and the thermostat housing dropped some more. It took another 2 Fl Oz and then i topped up the expansion tank.

Am I reading this right?
You say that you opened up the top fill plug over the thermostat (at the top of the engine) and topped it up. If you then opened the expansion tank cap, which sits lower than the fill plug, of course you'd get a drop in the water level, and a little 'hiss' as you open the cap, as the water sitting higher up in the system pushes the air out of the expansion tank.
If you keep opening the fill plug and the expansion cap, you'll never get rid of the excess air in the system...
Just fill it as per the book, then run it up to temp a few times, without opening anything up in between.
(obviously too late now, and may not be the cause of your troubles anyway, but it won't help the diagnosis)

[Stag76]

Did you hone or de-glaze the bores when you fitted the new rings? Were there any tell-tale signs of coolant leakage on the gasket when you took it apart?