Silicone hoses and OAT.

[SD1too]

Originally Posted by Mike Noc

.... when I had to replace the top hose connection to the cylinder head because the seal had degraded and was leaking.

I'm not familiar with the diesel Mike. Why does this connection require a seal and was it the same part we are discussing (CDU 3858)?

What form did the degradation take; flattening (as in my experience), severe erosion (as in Brian's) or something different?

Simon

[marinabrian]

Originally Posted by SD1too

Brian; by not making any corrections, thank you for confirming your belief that OAT is the cause of both the flattening of the KV6 O ring and the severe erosion of the M47R O ring.

1. So, why would the failure mode be different simply due to the way the O ring is mounted?
2. Why don't KV6 O rings suffer the same severe erosion seen on your photograph from a diesel?
3. Why isn't the 4 cylinder K series engine affected to the same degree, if at all?

Simon

Simon, the O ring I pictured is not a KV6 one, however the chemical attack pattern is similar, although the mounting method has a lot to do with the way the O ring degradation is manifested.

In a flange joint the o ring is not contained in the same way as it is in a groove joint, allowing the elastomer to swell in a much less controlled fashion, eventually leading breakdown of the O ring structure.

The joint Mike was talking of is the top hose junction on the cylinder head, where an EPDM gasket seal shaped to match a face to face joint between the head and the plastic pipe extension.

It is fairly common for this gasket to soften and swell and indeed the PA66 Nylon pipework to become embrittled, and further to that, the outlet pipework which has a quick coupling similar in design to that of the 1800 turbo top hose, and contains a gland O ring seal which are also prone to swell and leak.

Photos courtesy of Arctic.........









The four cylinder K series engine thermostat housing O rings are affected in exactly the same way as the KV6, I have noted this on countless occasions now, and on post 1998 cars only.

The point being that prior to widespread introduction of OAT, there was no occurrences of compression set in the housing O rings, and indeed in the case of my own 1995 car which has covered 397000 miles when I removed the 'stat housing, a car which has never had OAT in the cooling system ever, the O rings were in perfect condition.

So yes I believe there to be a direct correlation between OAT antifreeze and damage to fluorosilicone and EPDM seal types in the cooling systems of our cars.

Brian

[Mike Noc]

Originally Posted by SD1too

I'm not familiar with the diesel Mike. Why does this connection require a seal and was it the same part we are discussing (CDU 3858)?

What form did the degradation take; flattening (as in my experience), severe erosion (as in Brian's) or something different?

Simon

Here is the connection from my scrapper Simon with the seal removed.






It is actually in better condition than the one I replaced on my own car, but the seal material has degraded and lost its 'springiness'. It also has a slightly sticky feel to it. These are the symptoms of a material breaking down and so the ony question is what has caused this degradation. It can of course happen with some materials over time, or it can be due to another agent, in this case OAT.

[SD1too]

Originally Posted by marinabrian

... however the chemical attack pattern is similar.

It is clear from your picture (diesel) and mine (KV6) that the end results couldn't be more different so I disagree with your view. I remain to be convinced that a mounting method can cause the same O ring to flatten (with no erosion) on one car and severely disintegrate on another.

Originally Posted by marinabrian

It is fairly common for this gasket to soften and swell ...

My KV6 sourced ring has not softened or swollen, quite the opposite!

Originally Posted by marinabrian

The four cylinder K series engine thermostat housing O rings are affected in exactly the same way ... I have noted this on countless occasions now ...

You seem to be the only one with that experience Brian. I would have thought we'd have at least heard about this from a handful of forum members, but no. Doesn't that strike you as strange?

Here's another set of interesting facts concerning my KV6.

It was ten years and 50,000 miles before the first coolant leak occurred. At that stage, MGR had modified the curved elbow pipe with a more substantial mounting boss and consequently a longer screw. Why did they do this? It's an odd decision if the cause was OAT.

Subsequent leaks happened much more frequently, after three and five years and less than half the original mileage interval. So why did your alleged chemical reaction slow down significantly?

At the third failure, antifreeze deposits were found only at the base of the thermostat housing yet all four O rings had flattened. Leakage had occurred only at a joint which the Chinese had addressed by adding three stabilising feet to the thermostat housing. I fitted one of these parts (supplied by your friend Nick Daldry). Why did the Chinese do that if the cause is OAT?

Have the resources and expertise of both MGR and SAIC/Nanjing failed to diagnose the problem correctly, but you have?

Simon

[SD1too]

Originally Posted by Mike Noc

... the ony question is what has caused this degradation. It can of course happen with some materials over time, or it can be due to another agent, in this case OAT.

Thanks for the picture Mike. This seal is, of course, not the O ring CDU 3858 and so, whatever the problem is, it won't further the discussion we're currently having.

I would caution against looking at any seal in less than good condition and speculating that OAT is responsible on the basis that it's in the minds of us all. For example, the old cork gaskets have a limited life sealing rocker covers and sumps but we don't blame changes in engine oil formulation do we.

Simon

[Mike Noc]

Well I'm happy to agree to disagree on this Simon.

From my own experience, and from what I have read on the subject, I have concluded that the OAT antifreeze degraded the various original silicone rubber seals in my car, and since I changed over to an inorganic anti-freeze I haven't had any further problems.

Of course an alternative would have been to replace the seals with ones resistant to OAT and then carry on using it, but I find it easy and cheap enough to replace the coolant every couple of years.

[VVC-Geeza]

Are there different grades of silicone?


Or are "O" rings and hoses made of precisely the same material?

[marinabrian]

Originally Posted by VVC-Geeza

Are there different grades of silicone?


Or are "O" rings and hoses made of precisely the same material?

No, there are countless different grades of silicone Mick, the hose manufacturer I linked to line their hoses with a different material to make them resilient to OAT.

Ignore Simon, he should start his own thread if he wishes to argue the toss about O ring failure, and his hijack of your thread is rather irritating to say the least, but that's the measure of the man

He is absolutely wrong in his conclusions, and he is making himself appear rather foolish in insisting the failures he is experiencing are due to abrasion caused by movement, especially given his own photograph clearly shows an O ring suffering from compression set, and not one that has suffered the effects of abrasion, but heh ho

Vroom Tish !!

Brian

[Neil1]

This is worth reading https://www.viperperformance.co.uk/p...one-hoses.html

I think I asked about this a couple years or so ago, but it was the cost of changing every hose that put me off.

Now I can pay for it and we have lock down.

[marinabrian]

Originally Posted by SD1too

My KV6 sourced ring has not softened or swollen, quite the opposite!

You seem to be the only one with that experience Brian. I would have thought we'd have at least heard about this from a handful of forum members, but no. Doesn't that strike you as strange?



Simon

Simon the O ring in your picture has clearly suffered from compression set, do you honestly think that there is sufficient movement to abrade the O ring flat by reciprocating action, while simultaneously depositing the abraded material and allowing that material to reform elsewhere on the body of the O ring as if by magic??

If so you are even more blinkered and ignorant of the facts staring you in the face than I gave you credit for.

Anyway, just for balance, here is a picture MGJohn posted up of an 1800 turbo K series thermostat housing, and unlike yourself I do not find the failure mode of an O ring fitted to a four cylinder K series thermostat housing employing the same O ring as the KV6 surprising.

What is much more pertinent to your "theory" is this assembly employing the exact O ring as fitted to your car, is bolted rigidly to the engine block and as a result cannot move axially or radially at all, and yet it has suffered the same failure of compression set, how can this be if the failure is caused by movement?



Just look at that lovely droplet of water, and it's beautiful meniscus, I've seen this myself on many occasions, and simply because you dislike me Simon, doesn't make the facts any less factual

Now if you wish to start your own thread debating nonsensical O ring failure, versus factual ones, please do so, I'm sure the rest of the members simply cannot wait for the next thrilling chapter of Enid Blyton's "Magic O-ringaway Tree"

Brian