BLOWING OUT

[missfixit70]

about 1 cm from cold to hot. Also if the pressure cap was not sealing you would in fact be constantly loseing coolant when running and the level would drop.

Eventually, or once you stopped surely?

[haydn callow]

You will only lose coolant via a loose pressure cap whilst the system is hot and pressurized.

[haydn callow]

If the trapped air isn't actually escaping but caught in an air lock, it's going to push up the level in the header & keep it there/cause overflow & coolant loss which will then be picked up when the engine cools down by the low level alarm, but possible damage - localised or otherwise already caused?

If, because you get a airlock in the system and the level in the tank neither goes up or down...what can we do ?? But how did this air get in if it wasn't by a massive hose failure or som such thing. I don't think air could be introduced via a pinhole on cooling...Having trouble getting my head round this.!!

[francophile1947]

I don't think air could be introduced via a pinhole on cooling...Having trouble getting my head round this.!!

No expert here but, as the system is effectively sealed (unless too much pressure builds up), when the air and coolant expands when hot, some coolant could be lost through a pin hole leak. When the system cools down again, this will create a sort of vacuum and, because there is less coolant than before, it will draw air in to replace it(I think!! )

[missfixit70]

about 1 cm from cold to hot. Also if the pressure cap was not sealing you would in fact be constantly loseing coolant when running and the level would drop.

Eventually, or once you stopped surely?

I meant the level would drop eventually or once stopped if the pressure cap was not sealing, the level wouldnt show as dropping if you were losing coolant out of the pressure cap as it would be reading as full I'd have thought?

[lizard]

Veg-Ian....good point...thats the sort of feedback I'm looking for.

If I argue against any suggestions please don't anyone take offence....argue back and we will come to a conclusion. The above is a example of this .

Argue? On this forum? Surely not

You're very welcome.

Now Now then, I have been told to go to the naughty step for this sort of comment

Discussion and debate thats what the forum is about. Something else that the Romans gave to us.

[haydn callow]

You would lose coolant out of the faulty pressure cap in the form of steam/vapour...it would not be because the level has raised.

[bigdaddycain]

Something else that the Romans gave to us.

..... And the roads..... And the viaduct.....

[mikeonb4c]

return hose to the rad is the "top hose" this is a big hose and I don't see that getting blocked.

But, what if the flow through the radiator is poor due to chronic clogging, and the system backs up?

[haydn callow]

In that case I think it would have overheated long ago.

[spout]

So if a blockage would cause overheating and a raising in the expansion chamber, then a high level alarm would be worth fitting.
Suppose it's just a question of timing though as to whether it would save the situation.

[mikeonb4c]

In that case I think it would have overheated long ago.

Not sure I can agree with that I'm afraid. Peeps and Bongos both can have partially clogged systems that only spill over into crisis when the system is stressed. Look at the recent thread about overheating when towing. But if this is the case, the question then is - what is the mechanism by which this happens.

The only other clue I can offer to all this, in case it is linked, are the reports of header tanks suddenly boiling over (sometimes after stopping) . Why is this happening? Is it perhaps because the coolant system is so close to failing to cope that something small tips it over the edge (steep hill? loss of airflow cooling upon stopping? radiator fans not kicking in when they should due to aged/faulty sensors?). A 'high tide' sensor may offer early warning of such an event, although I suspect by the time the coolant has started to move as a result of internal boiling, then you are only a few seconds from being advised anyway by the issue of steam coming out from under the bonnet.

[haydn callow]

Fair points indeed...What I'm trying to determin is, if having a "high" level sensor is going to help prevent anything!! Telling you that somthing has already failed is not a lot of good. I see the value of it if it warns of impending head gasket failure due to a "boil up" and so perhaps preventing that.
I think on balance it would do no harm to incorparate a high level sensor and it could under some circumstances prevent expensive damage. We will now look into the tecnical problems involved and let you know.
Can I suggest that peeps do not put off fitting a alarm whilst waiting for the outcome of this or even the "proposed" factsheets which we are waiting for and have been for some time now. I understand they are on hold due to other pressures.

[haydn callow]

A high level alarm may well be a good thing but it will not replace a Low Coolant Alarm. This will detect any drop of level in the header tank which in most cases leads to overheating shortly after. The high level alarm would only sound as I understand it if...trapped air was suddenly ejected into the tank (shortly after this the level would drop by about the same volume).....overheating/boiling occured for some reason other than coolant loss)....head gasket failure (combustion gases exiting via the tank)
Have I got this more or less right ??

[Simon Jones]

Just a quick reply:

1) I've been delayed in preparing the coolant alarm factsheet due to a whole pile of things getting in the way. By the sounds of things, there have been further developments recently with the Haydn & TM2 alarm, so we'll be able to incorporate these in there too.

2) I had the problem referred to in Poland with coolant overflowing from the header tank. This was traced to a pin hole in the bleed pipe which must have let air into the system. The unanswered questions are: why did the leak allow air in rather that coolant out (especially under pressure) & why did it happen after about 6 hours of driving, rather than shortly after start up. After cutting out the damaged section & thoroughly bleeding it, we successfully made it make across Europe with no further incidents.

3) Having previously suffered from head gasket failure which was only discovered when I noticed coolant escaping from the header tank; I developed my own 'coolant overflow alarm'. It is this device which allowed me to stop the van & deal with the problem in Poland straight away. At the time I had a Haydn alarm, Mason alarm & a TM2, but none of these told me there was a problem caused by the airlock. They would have only have indicated a problem once significant coolant loss had occurred & the engine temperature had started to rise. Think of it like this:

You fill a bath with water, to just below the brim. Then some fat bloater comes along & gets in the bath. The water level rises as he displaces the water (as does the airlock) & it will escape over the top of the bath. At no point will he think that he needs to turn on the tap to put more water in the bath because it is already full to the brim. However, when he steps out of the bath, you will then see that the level has dropped considerably. At that point you have a very wet bathroom floor & the damage is done. You’ve also got a large naked gentleman in your bathroom, but that is where we should leave that analogy

4) I’ve since produced several more of these alarms & currently have a few on trial as part of their ongoing development. If all goes well, I would expect to make these available to forum members at a discounted price early in the New Year.