Back again!

I've fitted a Polo rad and plumbed it in using a selection of hoses and tubes from CBS (brilliant next-day service again).
It all seems to work fine as far as I can tell - BUT the engine is introducing a lot of air into the cooling circuit. I bleed it, run the engine for a few minutes, then bleed it again and loads more air comes out.
Is there a simple way of determining whether it's the head gasket or a cracked block? I don't have a compression tester.
(Thinks....) Take the head off or not?
If it is a failed gasket it will hopefully be evident when the head is removed, so replace the gasket and all should be well.
Second possibility is that the gasket is found to be OK when the head comes off - in which case the block or head is cracked and the engine is scrap.
If I don't take the head off, I don't advance in solving this.
Therefore the head has to come off. As they say, 'Simples!'

I've just fitted a 'new-to-me' auto box. It works well and must say that I like the auto. There's £300 invested in the exhaust manifold, so I have no option but to stick with Pinto.
There may be a '2L Pinto wanted' ad appearing soon...

Have you tried with the thermostat removed and have you got the hose to the inlet manifold from the pump to complete the water circuit ?

Exhaust gas analyser waved around inside the neck of the header tank will tell you if it's coming from the cylinders.

Looking at your photos have you a header tank? i can't see one

Pete,
I haven't disturbed the thermostat as it appears to do its job properly. The housing warms up gradually over a couple of minutes then suddenly gets hot, and as time passes I can feel the rad itself warm up as expected.
If I keep bleeding the rad almost continuously it reaches the point where the thermo-switch on the rad operates and the fan comes on, then later switches off.
So I'm pretty sure the cooling system itself is functioning OK and the system is being gasified rather than boiling.
It's looking fairly certain that the gasket's gone or the head/block is cracked.
Rgds,
John.

@grazzledazzle: if I only had a gas analyser...!

@graham: It's now very different from the archive pics. I've fitted a Sierra header tank at the back of the engine, just under the bonnet line so it's the highest point. The (one) hose from that tees into the bottom hose; the manifold outlet (still the original) loops to the pump.
I have a screw tapped directly into the bleed port of the radiator as the clearance from rad to nosecone is too tight to accommodate a hose.
John.

...and the engine oil level is constant, so no water is going into the sump.

If you run the engine up with the header tank cap off, then do you see air bubbles in there?

Another possible test (but only is its really bad) - get it up to temp, pull the plugs out, and turn it over on the starter. If you get water out of the cylinders then, then its getting in there somehow.

You could really do with trying to get that bleed screw replaced with a hose connection of some sort and fed into the header tank bleed point - even if only as a temporary measure to test it.

Is the tank like mine?
the top pipe comes from the manifold
the bottom pipe goes to the 5/8 pipe on the water pump, the tank separators the air out of the water

engine 2

@ss1turbo: There's no bubbles in the header tank but the overflow bottle filled up so I guess the gas is displacing the water downwards into the engine and up the hose to the header (teed into the bottom main hose)
I think you're spot on about connecting the bleed to the header - must try that. Then the air should escape up that pipe and the level should sustain itself better. It would let me check out the general integrity of everything else and even get a few more miles on it! I've only done about 15 miles since 3 April

@graham: The header tank is like yours (same number of ports), but the bigger hose tees to the bottom hose between radiator bottom/cold end and the water pump. The small/overflow currently leads to an overflow bottle, but I'll try connecting to the radiator bleed port (as suggested by ss1turbo)
Manifold loops to the pump - this hose stays quite cool

Cheers guys,
John.

I take it there's no chance there's a leaky hose or something? It's always worth double checking the simple stuff
Also are you getting mayo on the oil filler cap?

Oil filler is as clean as the proverbial whistle and there's no leaks in the coolant hoses.
I've put a few pics in my archive under 'New Radiator'



Front without nosecone

There's about half an inch clearance between the bleed stub (top right in the ^^^ pic) and the nosecone so I need a zero radius right angle 8mm ID pipe to connect it to the header (and get the nosecone on as well)

quote:

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I need a zero radius right angle 8mm ID pipe to connect it to the header (and get the nosecone on as well)

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Good thinking, that man!

So obvious once the right answer is given!

quote:

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Originally posted by MautoK
Good thinking, that man!

So obvious once the right answer is given!

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A little experiment today.

The radiator bleed port is now connected to the header tank overflow:


Rad bleed to header

and I modified a 3 litre squash bottle to fit in the header tank neck:


Inverted bottle

Filled up so the bottle was about 1/3 full. Now the whole system should be full of water with the bottle being open to atmosphere. There's about 6 inches extra head of water on the system, so that's only +1/4 psi above atmospheric.

OK, started engine and ran fast tickover. It warmed up as expected - the stat housing got warrm, then hot as the stat opened; radiator got progressively warmer; temp gauge got up to the 'O' of NORM (i.e. fractionally above halfway); fan switched on, then off after a couple of minutes.
All the hoses got nice and warm, including the manifold-to-pump loop and the bleed-to-header overflow pipe.

When the system was fully warm there were a few small bubble streams seen in the header-header as if little air pockets were being displaced.
If the gasket had failed or if the block/head were cracked I would expect a fairly steady stream of bubbles, surely?

The curious thing was that the level in the header extension rose and fell by an inch or so with a period of 5 to 8 seconds - and no bubbles while this happened.
A couple of times the level rose significantly - by about 1 to 1 1/2 litres - and then fell back to its previous level; again no bubbles while this happened.

Anyone got any ideas, cos I'm running out of them!