Technical Head gasket blown - again!

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Technical Head gasket blown - again!

UnoMia

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Hi All,
I've owned my Uno 1100 since 2005.
In the time I've owned her I've replaced the head gasket four times and now I'm about to do it for a fifth time! Every time I get the head off I find the water passages have been eaten away by the coolant, even though I always use a 50/50 mix of water and antifreeze.
I'm wondering if the alloy that the head is made of is exceptionally soft and this is why it gets eaten so quickly.
Anyone else found a similar thing?
 
Very strange. The most likely culprit has to be the coolant. Do you mix up your own antifreeze from concentrate? If so do you use distilled or, less effective, deionized water? or are you just using tap water? Tap water is never a very good idea, although in some areas - like where I live in Scotland - the tap water is pretty uncontaminated with minerals. Personally I like to use either distilled water or deionized if I can't get distilled when mixing with concentrate. Of late though I'm coming round to the idea that ready mixed may be the best way to go as most producers use distilled water. - check the labeling.

I'm also wondering if there could be combustion gasses leaking into the coolant which would combine chemically to create Carbonic acid which might contribute to the corrosion. Are you reusing the same corroded head each time? Are you having it surfaced for flatness and also checking the block face is flat? Once you get serious corrosion of the waterways the gasket has a much tougher job to do due to the decrease in sealing area so flatness of both faces becomes even more critical.
 
The anti-corrosion properties of the coolant do wear out, the main reason to change it regularly, as its anti-freeze properties do not change.
Older ethylene glycol coolants should be changed every two years, and if left in do become corrosive. The newer OAT coolants have longer change intervals, but if left in longer, become more corrosive than the older type.
If you are changing the coolant every two years, then combustion gas contamination is the most likely cause, as this will turn coolant corrosive.
 
Very strange. The most likely culprit has to be the coolant. Do you mix up your own antifreeze from concentrate? If so do you use distilled or, less effective, deionized water? or are you just using tap water? Tap water is never a very good idea, although in some areas - like where I live in Scotland - the tap water is pretty uncontaminated with minerals. Personally I like to use either distilled water or deionized if I can't get distilled when mixing with concentrate. Of late though I'm coming round to the idea that ready mixed may be the best way to go as most producers use distilled water. - check the labeling.

I'm also wondering if there could be combustion gasses leaking into the coolant which would combine chemically to create Carbonic acid which might contribute to the corrosion. Are you reusing the same corroded head each time? Are you having it surfaced for flatness and also checking the block face is flat? Once you get serious corrosion of the waterways the gasket has a much tougher job to do due to the decrease in sealing area so flatness of both faces becomes even more critical.
I use green antifreeze concentrate and mix it 50/50 with distilled water. I'm also convinced it's the type of coolant that I've always used. I've now removed the head and the water galleries have again been eaten away around the edges in places and breached the head gasket. I'm definitely going to change to a different colour/type of coolant when I put it back together. In the past I've had the head checked and skimmed if necessary and I'll do the same this time depending on whether the corroded water ways can be repaired.

What coolant would you recommend I use?
 
The green is usually ethylene glycol, fine for two years life. If you are changing it around the two year mark, that should not be the issue.
Have you still got the stuff that came out, or can you find some in the engine block? Get some litmus paper and check its acidity.
Garages often have a kit to tell if the coolant contains combustion gases, if you can find enough, see if any local garage will test it for you.
There's a limit to any skimming, before you break through, or increase the compression beyond what it can cope with, if skimmed before, you may have reached the limit.
Are you sure the corrosion has caused the gasket breach? The opposite could be true, a gasket breach will introduce combustion gases to the coolant, which can then lead to corrosion.
Gaskets for current engines are coated with a polymer sealant. It is likely that replacements for older engines will be too. The gasket MUST be left in its sealed bag until ready to fit, then once dropped on, the head should be fitted and torqued down without delay. Once opened, the sealant starts to harden. If left too long, it will no longer seal properly. Leaving a gasket unsealed, then fitting it, has led to many short timescale failures.
 
As PB says above, green is usually the good old standard Ethylene Glycol type which needs to be changed every 2 years or so. There's no reason why you shouldn't use it but I prefer the more modern "brews" which incorporate Organic Acid Technology and can safely be left in the system for up to 5 years. Most usually these are called "Red" antifreezes and can be used in most post 1998 vehicles but it's maybe a bit dangerous to buy antifreeze by colour because it's no real guarantee of content - better to read the label. Prestone do an antifreeze which they claim can be mixed with anything without reacting adversely but I'd rather buy the exact right one for my vehicle. It's not difficult to find out just go to a trusted supplier's website and look it up using your reg no or vehicle details. With the problems you've been having I'd be doing a really good flush through before refilling with coolant. The big thing is not to mix types of antifreeze.
 
As PB says above, green is usually the good old standard Ethylene Glycol type which needs to be changed every 2 years or so. There's no reason why you shouldn't use it but I prefer the more modern "brews" which incorporate Organic Acid Technology and can safely be left in the system for up to 5 years. Most usually these are called "Red" antifreezes and can be used in most post 1998 vehicles but it's maybe a bit dangerous to buy antifreeze by colour because it's no real guarantee of content - better to read the label. Prestone do an antifreeze which they claim can be mixed with anything without reacting adversely but I'd rather buy the exact right one for my vehicle. It's not difficult to find out just go to a trusted supplier's website and look it up using your reg no or vehicle details. With the problems you've been having I'd be doing a really good flush through before refilling with coolant. The big thing is not to mix types of antifreeze.
Thanks for the reply. I've removed the head and found, just as in the previous four times, the water passages in the head have corroded and breached the gasket. Once I've had the head repaired, (hopefully), I'm changing the type of antifreeze that I've been using as clearly it's not preventing the alloy head from being eaten! I've already flushed the rad and block thoroughly, so will try the red stuff next time around.

One question I do have, does the engine really need to have water flowing through the inlet manifold? I live in a hot climate, so cold weather is not a concern. I've been thinking of blanking off the water inlet to the manifold while the head is in for repair thus doing away with a lot of external pipework. The heater has been disconnected for years, by the way.

Thanks again for taking time to reply.
 

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Thanks for the reply. I've removed the head and found, just as in the previous four times, the water passages in the head have corroded and breached the gasket. Once I've had the head repaired, (hopefully), I'm changing the type of antifreeze that I've been using as clearly it's not preventing the alloy head from being eaten! I've already flushed the rad and block thoroughly, so will try the red stuff next time around.

One question I do have, does the engine really need to have water flowing through the inlet manifold? I live in a hot climate, so cold weather is not a concern. I've been thinking of blanking off the water inlet to the manifold while the head is in for repair thus doing away with a lot of external pipework. The heater has been disconnected for years, by the way.

Thanks again for taking time to reply.
Ooh! The heater being disconnected could be significant.
As a general rule, when the engine is cold, and the thermostat is closed, the only way water circulates is through the heater and back to the engine. As it warms, the thermostat opens and allows some of the hot water to pass to the radiator to be cooled. There is no water valve on the heater, it will be a full flow system, relying on the flaps inside to determine whether you get heat or not. Earlier designs, before the mid/late seventies used water valves, but needed a separate part of the circuit that allowed the water to circulate within the engine until the thermostat opened.
With the heater disconnected, if you have joined the two hoses together, then water will still circulate, but with a shorter distance, so should not be a problem.
But if you have blocked off the heater inlet and outlet from the engine, the coolant will not circulate until the thermostat opens. This can create two problems. First the coolant is not moving, so the hottest part of the system, at the head, will get significantly hotter than designed before the stat opens, as it will be relying on heat transfer rather than the hot water movement. (I wonder if the hotter spots might accelerate the deterioration of the coolant.) The head will run hotter which can lead to earlier failure of the gasket. (Gasket failure might be the cause of the head deterioration, not the result. The second problem is that with the water pump running, but little circulation, you may get 'cavitation', where the coolant aroound the pump impeller bubbles up, like being whisked. Free oxygen in the water escapes, creating bubbles and potential airlocks and hot spots.

Lots of theory, difficult to prove if any or all of that might be happening, even if at the car, but you should consider reinstating the heater circuit to standard. If the internal flaps in the heater box are good, this should not cause any heat issues in the car.
 
Hi, sorry for the late reply, I’ve been busy reassembling the Uno and just got it running today.
I took my time as I have another car to use meanwhile.
The good news was that the machine shop was able to repair the head.
I understand where you’re coming from regarding the heater but the water flow that supplied the heater hasn’t been blocked off, I just rerouted the supply hose directly to the inlet manifold where the heater return would have connected to, so basically water still flows through the head, it just doesn’t go through the heater core anymore. As a matter of interest I did this mod after the last head gasket failure four years ago, so on the previous three failures the heater was still part of the cooling circuit.
I was talking to the spares shop owner about which type of coolant additive I should try this time and he asked if I normally buy the concentrated type and mix it myself or do I use the premixed? When I said I mixed it myself 50/50 he said that I should try the premixed, (which I now have), as it’s possible my mix was too strong and the additive itself was damaging the alloy head.
The car is now running although I now have two noisy cam followers…. I’m now going to be hunting for cam shims!
 
I've never heard of antifreeze eating away headgaskets like that.

Are you sure it's all torqued down properly, checked to be flat or skimmed, and not the gas in the cylinder pushing the gasket?

If you had doubts over the coolant, you could try just water given you are in durban, 10°C is a cold winter day in SA
 
If you had doubts over the coolant, you could try just water given you are in durban, 10°C is a cold winter day in SA
NO!

Whilst in the UK we often refer to coolant as 'anti-freeze', that has not been its primary function for decades. Its most important function is as a corrosion inhibitor, very important with any engine containing aluminium.
The reason to change coolant regularly, is because the corrosion inhibitors wear out. The anti-freeze properties are hardly affected by age, as this is simple chemistry of adding stuff will change its boiling/freezing points.

Years ago, working for an international parts organisation, we had a radiator returned from Dubai as a warranty claim for having restricted flow. It had been used on a car with an iron block, alloy head engine, and the radiator was full of aluminium from the head. It weighed 3 times its new weight. All that extra weight was from the cylinder head.
 
Not as a long term fix, just to rule out the coolant since some believe it's corroding the headgasket
 
I've never heard of antifreeze eating away headgaskets like that.

Are you sure it's all torqued down properly, checked to be flat or skimmed, and not the gas in the cylinder pushing the gasket?

If you had doubts over the coolant, you could try just water given you are in durban, 10°C is a cold winter day in SA
It's not the head gasket that was eroded but the edges of aluminum cylinder head water passages that contact the head gasket. Each time it has happened the head has always been sent to an automotive machine shop for checking to make sure it's flat and have the eaten aluminum repaired and skimmed.
 
You can only skim a head about twice before it's aproblem with thinkness. And it's the aluminium is eroded away, was it a new head each time?
 
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