Cylinder head water manifold (early)

[David.H]

Since putting in antifreeze the inevitable has happened. A leak appears from the top hose where the manifold meets the head, It has a tired looking rubber gasket. I see that new manifolds, stainless studs et al are available. My manifold looks ok, is it worth changing the stud? I have nor disturbed anything yet. I imagine the stud screws into a cross piece in the head (or should do!) The parts list shows a set screw, I have a stud with washers & a nut,. Any advice/pitfalls? I know the side manifold is a bit of a minefield, but that (fingers crossed) is holding out.

[Chris KC]

Hi David,

Is it leaking from the top of the stud or around the base? As long as the bottom of the manifold is sound and flat a new gasket may do the trick (if not, you could replace the manifold, or you could try lapping this face on some abrasive paper on a flat surface). If leaking from the top, perhaps some gasket goo (heat resistant) or a fibre washer. Like the side manifold, I'd be careful of the temptation to tighten the nut, unless you know the stud is screwed into sound metal.

As an aside, I have never used anti-freeze in my car, I simply drain it when not in use. This is partly to avoid getting a faceful of anti-freeze when I brake (recently discussed on the forum) but also because glycol is a less efficient coolant than water and your engine will run hotter; fine if your cooling system is in good shape, less fine if it isn't.

[David.H]

Hi David,

Is it leaking from the top of the stud or around the base? As long as the bottom of the manifold is sound and flat a new gasket may do the trick (if not, you could replace the manifold, or you could try lapping this face on some abrasive paper on a flat surface). If leaking from the top, perhaps some gasket goo (heat resistant) or a fibre washer. Like the side manifold, I'd be careful of the temptation to tighten the nut, unless you know the stud is screwed into sound metal.

As an aside, I have never used anti-freeze in my car, I simply drain it when not in use. This is partly to avoid getting a faceful of anti-freeze when I brake (recently discussed on the forum) but also because glycol is a less efficient coolant than water and your engine will run hotter; fine if your cooling system is in good shape, less fine if it isn't.

Thanks Chris,
the leak is from the rubber gasket (30 years old?) still soft, but splitting. I will get a gasket, dismantle carefully & reassemble even more carefully.
As my aside I always thought glycol raised the boiling point, which is why it was/is used in aircraft engines....
My garage can get quite cold & it is a faff to drain & fill....no drain tap on the radiator... so getting the system in good shape is the aim! The car has had little use since a rebuild in the 80's, so I am getting little bugs out of it. (see my questions on carb overflowing!)

[Chris KC]

In that case I reckon a new gasket sounds like a good idea. I feel sure Jamie at Seven Workshop or one of our other stalwart suppliers can provide. Yes, go easy on the joint at least until you can see how strong it is (and even then...)

You are absolutely right, glycol antifreeze does raise the BP of water (though not as much as it lowers freezing point). However it has a lower specific heat capacity (meaning it takes less energy to raise its temperature) and higher viscosity (meaning it flows less freely) than water (how much of course depends on the dilution). Cooling systems designed for ethylene glycol coolant have to be significantly bigger in capacity to achieve the same result as plain water, which is a surprisingly good coolant. Surface tension may be an issue too - hence 'water wetters' which seek to disperse the film of bubbles which form on the surface to be cooled, which tend to inhibit heat transfer. I guess the imperative in aircraft systems is to prevent freezing at high altitude, where temperatures can be pretty brassy.

Anti-corrosion properties are of course another question, and it's a good idea to have something in your system. Anyway, I digress - there are plenty of A7 owners driving around using glycol antifreeze and there's nothing to worry about as long as your car is not overheating.

[David.H]

In that case I reckon a new gasket sounds like a good idea. I feel sure Jamie at Seven Workshop or one of our other stalwart suppliers can provide. Yes, go easy on the joint at least until you can see how strong it is (and even then...)

You are absolutely right, glycol antifreeze does raise the BP of water (though not as much as it lowers freezing point). However it has a lower specific heat capacity (meaning it takes less energy to raise its temperature) and higher viscosity (meaning it flows less freely) than water (how much of course depends on the dilution). Cooling systems designed for ethylene glycol coolant have to be significantly bigger in capacity to achieve the same result as plain water, which is a surprisingly good coolant. Surface tension may be an issue too - hence 'water wetters' which seek to disperse the film of bubbles which form on the surface to be cooled, which tend to inhibit heat transfer. I guess the imperative in aircraft systems is to prevent freezing at high altitude, where temperatures can be pretty brassy.

Anti-corrosion properties are of course another question, and it's a good idea to have something in your system. Anyway, I digress - there are plenty of A7 owners driving around using glycol antifreeze and there's nothing to worry about as long as your car is not overheating.

Thank you...clearer now! bigger problem is the carb overflowing!
D

[Chris KC]

In that case I reckon a new gasket sounds like a good idea. I feel sure Jamie at Seven Workshop or one of our other stalwart suppliers can provide. Yes, go easy on the joint at least until you can see how strong it is (and even then...)

You are absolutely right, glycol antifreeze does raise the BP of water (though not as much as it lowers freezing point). However it has a lower specific heat capacity (meaning it takes less energy to raise its temperature) and higher viscosity (meaning it flows less freely) than water (how much of course depends on the dilution). Cooling systems designed for ethylene glycol coolant have to be significantly bigger in capacity to achieve the same result as plain water, which is a surprisingly good coolant. Surface tension may be an issue too - hence 'water wetters' which seek to disperse the film of bubbles which form on the surface to be cooled, which tend to inhibit heat transfer. I guess the imperative in aircraft systems is to prevent freezing at high altitude, where temperatures can be pretty brassy.

Anti-corrosion properties are of course another question, and it's a good idea to have something in your system. Anyway, I digress - there are plenty of A7 owners driving around using glycol antifreeze and there's nothing to worry about as long as your car is not overheating.

Thank you...clearer now! bigger problem is the carb overflowing!
D

Good luck with that!

You've got me thinking now - at 20,000 ft (for example) water boils at about 80 degrees C so perhaps you are right about aeroplanes and anti-boil. It's not a big gain though at normal automotive dilutions.

[Bob Culver]

It is getting off the immediate topic, but some sort of anti corrosive is very desirable. The difference in typical car engines post 1970s when additives became common and the typical Seven  is amazing. With Sevens the high loss rate is irksome although a catch bottle will recover much. I suspect corrosion with a drained but moist block accelerates. I don’t know what effect is of additive is in that case.

Here we have available Type B additives which are much less expensive but not anti freeze. Used in competition as retain full specific heat.

[Dave Mann]

I use a 50% antifreeze not just as an antifreeze but also as a corrosion inhibitor. With this I found that the top early manifold joint was prone to weeping, even with flat faces and a new joint, and was only cured by using a sealant on the joint. i don't know it's name as it has long since disappeared from the tube.

[Zetomagneto]

I use Fernox Alphi 11 in my cars and central heating system. available from screwfix and others.
Interesting read here : http://docplayer.net/36781994-Antifreeze...arris.html

[Chris KC]

Completely agree with Bob, having recently rebuilt an engine which has run on plain water for many years, I resolved to use a corrosion inhibitor from now on. I rejected glycol antifreeze on grounds mentioned above. I'm thinking of using Redline's 'Water Wetter' as it offers both anti-corrosion pack and better cooling performance than glycol, while sounding generally less toxic than some of the other offerings (important when it blows off in your face now and then).